[home][rumors and news][model release matrix][dealer network][desktop calendar][exhaust notes][tov forums][links][search][sponsors][garage][login]

Tire Rack Upgrade Garage
 Search for a Dealer:
 Canadian Flag US Flag
 Honda Acura
 ZIP  
2019 Honda Civic Type R and Civic Hatchback Accelerate into Dealerships
More.......................
American Honda Reports October Sales
More.......................
Honda Rugged Open Air Vehicle Concept Debuts at 2018 SEMA Show
More.......................
SEMA: Graham Rahal Injects Style, Power and Performance to Custom Acura RDX A-Spec
More.......................
NSX GT3 Evo To Compete Globally in 2019
More.......................
2019 Acura ILX Arrives with Dynamic New Styling, Major Technology Upgrades and New A-Spec Treatment
More.......................
Honda Joins with Cruise and General Motors to Build New Autonomous Vehicle
More.......................
Honda reports September 2018 sales numbers
More.......................
CR-Z --> Re: Honda's Biggest Mistake? Why Now Is The Time To Buy The Misunderstood CR-Z
Join Discussion......
TSX --> Re: TSX Sportwagon - rear washer not squirting
Join Discussion......
CR-V --> Re: 2018 CR-V price experience
Join Discussion......
MDX --> Re: MDX update schedule?
Join Discussion......
IMA/Hybrids --> Re: Check IMA System light is on - what could it mean?
Join Discussion......
Today's Reading Links --> Re: 2019 Mazda CX-5 Turbo
Join Discussion......
CR-V --> Re: Oil Contamination in CRV's and Civic's with the 1.5T
Join Discussion......
CR-V --> Re: 2019 Honda CRV on Honda Canada Website
Join Discussion......
CR-V --> Re: CR-V Hybrid
Join Discussion......
Professional Motorsports --> Re: 2018 Honda F1 PU
Join Discussion......
TLX --> Re: My TLX so far
Join Discussion......
Professional Motorsports --> Re: F1 - 2018 Brazilian Grand Prix - Spoilers
Join Discussion......
Odyssey --> Re: 2018 Odyssey droning noise
Join Discussion......
Odyssey --> Re: Valve adjustment needed?
Join Discussion......
Fuel Cell Technology --> Re: Hydrogen Power coming back into focus?
Join Discussion......
2019 Acura NSX PR Photo Gallery
Read Article....................
First Drive: 2019 Acura ILX
Read Article....................
2019 Acura ILX PR Photo Gallery
Read Article....................
First Drive: 2019 Honda Pilot
Read Article....................
2019 Honda Pilot PR Photo Gallery
Read Article....................
First Drive: 2019 Honda Insight
Read Article....................

[fancy] [flat] [simple]
TOV Forums > General Talk > > Re: Fixing SH-AWD

Go to:

Viewing Threshold (What is this?)

Thread Page - [1]
Author
  Post New Thread
TonyEX
Profile for TonyEX
Fixing SH-AWD    (Score: 1, Normal) 10-10-2018 14:18
Reply to This Message Attach Quote to Reply
One of the biggest drawbacks ( the only one? ) with mechanical SH-AWD is that it needs power to do its torque transferring thing.

SH-AWD works primarily in turns, when wheel rotation speeds are different, specially front and back. Unfortunately, when you combine TURN and STEER you usually also combine BRAKING.

Which means, that going into a turn with SH-AWD you lose torque vectoring if you do not apply power. Think rear engined Porsche, trust the car and God and stay on the power, not the brakes.

Hard, VERY HARD to do. In the controlled environment of a racetrack I'm sure it's OK to do. But, on a real road, and worse, on a real WET, SNOWY, ICY road... who in his/her right mind wants to get around a turn hitting the gas?

So the fix is to put something in the back end that can move torque around without power coming from the front end.

(1) Use a TMU. But then you're looking at eSH-AWD and its full blown cost.

(2) Use a passive torque transfer, similar to what the TMU does already but without the motors. Question is where to put it? The current clutch based SH-AWD looks pretty busy, the gear based SH-AWD might have room for it.

(3) Put a small auxiliary motor at the input of the rear SH-AWD differential, perhaps in parallel with the driveshaft. Will likely need some kind of clutch to decouple the driveshaft, so maybe put the electric motor behind the SH-AWD transfer clutch? Use the computers and accelerators to provide the necessary power to twist the outside rear tire when needed, while the front brakes and the inside rear brake are busy braking. Just don't tell the fuckin' lawyers.

Anyhow, it looks like that short of eSH-AWD or a full blown AWD EV vehicle with either two TMUs or four separate motors, some means needs to be provide some torque to the rear end while the driver is hitting the brakes to slow down the car barreling into a suddenly too tight turn.

The current learning curve for SH-AWD is steep. It does require some counter intuition and faith in the system... and some dry, open spaces to test it out. Or, like me, just take your brand new car into a mountain pass in the middle of a historic Pineapple Express Storm with snow and rain... and by pure chance figure out it works. ( Note: I really don't recommend that... but it worked for me, it HAD to work for me... ).


TonyEX
Profile for TonyEX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-10-2018 14:21
Reply to This Message Attach Quote to Reply
TonyEX wrote:
One of the biggest drawbacks ( the only one? ) with mechanical SH-AWD is that it needs power to do its torque transferring thing.

SH-AWD works primarily in turns, when wheel rotation speeds are different, specially front and back. Unfortunately, when you combine TURN and STEER you usually also combine BRAKING.

Which means, that going into a turn with SH-AWD you lose torque vectoring if you do not apply power. Think rear engined Porsche, trust the car and God and stay on the power, not the brakes.

Hard, VERY HARD to do. In the controlled environment of a racetrack I'm sure it's OK to do. But, on a real road, and worse, on a real WET, SNOWY, ICY road... who in his/her right mind wants to get around a turn hitting the gas?

So the fix is to put something in the back end that can move torque around without power coming from the front end.

(1) Use a TMU. But then you're looking at eSH-AWD and its full blown cost.

(2) Use a passive torque transfer, similar to what the TMU does already but without the motors. Question is where to put it? The current clutch based SH-AWD looks pretty busy, the gear based SH-AWD might have room for it.

(3) Put a small auxiliary motor at the input of the rear SH-AWD differential, perhaps in parallel with the driveshaft. Will likely need some kind of clutch to decouple the driveshaft, so maybe put the electric motor behind the SH-AWD transfer clutch? Use the computers and accelerators to provide the necessary power to twist the outside rear tire when needed, while the front brakes and the inside rear brake are busy braking. Just don't tell the fuckin' lawyers.

Anyhow, it looks like that short of eSH-AWD or a full blown AWD EV vehicle with either two TMUs or four separate motors, some means needs to be provide some torque to the rear end while the driver is hitting the brakes to slow down the car barreling into a suddenly too tight turn.

The current learning curve for SH-AWD is steep. It does require some counter intuition and faith in the system... and some dry, open spaces to test it out. Or, like me, just take your brand new car into a mountain pass in the middle of a historic Pineapple Express Storm with snow and rain... and by pure chance figure out it works. ( Note: I really don't recommend that... but it worked for me, it HAD to work for me... ).




There are lots of places that describe SH-AWD. I believe we got into a long technical discussion at TOV years ago. Here's a short link that describes it...

http://youwheel.com/home/2017/05/07/acura-sh-awd-a-comprehensive-analysis/

sadlerau
Profile for sadlerau
Re: Fixing SH-AWD    (Score: 1, Normal) 10-10-2018 21:28
Reply to This Message Attach Quote to Reply
Tony, Tony, Tony, you are coming at from the wrong end!

There is nothing to "fix" with SH-AWD!

When comparisons are made with "sporty" RWD cars, it's the inherent balance of the RWD chassis that is the trademark missing from the FWD Honda sedans, that seems to be the problem for enthusiast drivers.

A very simple solution is for Honda to actually give their sedans sporty suspension setups in the first place!! Look no further than the venerable CTR for how you can get a fabulously good handling chassis out of a FWD setup. With today's "magic" dampers you can even avoid the uncomfortable ride inherent in the past, with sporty chassis set-ups.

Which just leaves one problem, and the one place, in theory, where the CTR can be improved - understeer when applying power in a FWD chassis. Low and behold, guess where SH-AWD does it's magic.........

I know you guys never believed me, but the Australian Legend that I had the privilege to own, didn't understeer anywhere near what I read for you guys. There was nothing to fix, as where it understeered [taking very tight corners stupidly fast] is where even a good RWD chassis would understeer in all likelihood. I also acknowledge that the Legend's SH-AWD system was a tad more sophisticated than on the lower models.

But that fact doesn't override my argument that it would be very easy for Honda to give us a sports sedan to be very proud of, without "fixing" SH-AWD in any way, if Honda had the will...............

Nick GravesX
Profile for Nick GravesX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-11-2018 04:51
Reply to This Message Attach Quote to Reply
Indeed - most front-engined barges understeer in tight situations, whereas an NSX will simply dart into the turn.

I understood the simpler diff on the TLX can do a limited amount of overrun torque transfer?

And these days, if most cars get a bit ooh shit! understeery, the inner rear brake engages anyway.

But yes, a rear-biased TV system with a conventionally-located powertrain would indeed demonstrate the ultimate capabilities of the system.

But those cars went down the shitter in 2008, so you'll just have to move to a parallel universe somewhere, where Honda is more aggressively-run and electrickery isn't taking over.


Grace141
Profile for Grace141
Re: Fixing SH-AWD    (Score: 1, Normal) 10-11-2018 07:21
Reply to This Message Attach Quote to Reply
TonyEX wrote:
One of the biggest drawbacks ( the only one? ) with mechanical SH-AWD is that it needs power to do its torque transferring thing.

SH-AWD works primarily in turns, when wheel rotation speeds are different, specially front and back. Unfortunately, when you combine TURN and STEER you usually also combine BRAKING.

Which means, that going into a turn with SH-AWD you lose torque vectoring if you do not apply power. Think rear engined Porsche, trust the car and God and stay on the power, not the brakes.

Hard, VERY HARD to do. In the controlled environment of a racetrack I'm sure it's OK to do. But, on a real road, and worse, on a real WET, SNOWY, ICY road... who in his/her right mind wants to get around a turn hitting the gas?

So the fix is to put something in the back end that can move torque around without power coming from the front end.

(1) Use a TMU. But then you're looking at eSH-AWD and its full blown cost.

(2) Use a passive torque transfer, similar to what the TMU does already but without the motors. Question is where to put it? The current clutch based SH-AWD looks pretty busy, the gear based SH-AWD might have room for it.

(3) Put a small auxiliary motor at the input of the rear SH-AWD differential, perhaps in parallel with the driveshaft. Will likely need some kind of clutch to decouple the driveshaft, so maybe put the electric motor behind the SH-AWD transfer clutch? Use the computers and accelerators to provide the necessary power to twist the outside rear tire when needed, while the front brakes and the inside rear brake are busy braking. Just don't tell the fuckin' lawyers.

Anyhow, it looks like that short of eSH-AWD or a full blown AWD EV vehicle with either two TMUs or four separate motors, some means needs to be provide some torque to the rear end while the driver is hitting the brakes to slow down the car barreling into a suddenly too tight turn.

The current learning curve for SH-AWD is steep. It does require some counter intuition and faith in the system... and some dry, open spaces to test it out. Or, like me, just take your brand new car into a mountain pass in the middle of a historic Pineapple Express Storm with snow and rain... and by pure chance figure out it works. ( Note: I really don't recommend that... but it worked for me, it HAD to work for me... ).





Honda claims SH-AWD counters oversteer when the throttle is closed during cornering. They also claim it's a system capable of continuously managing the torque at all four wheels. My experience has been it's impossible to know what the system actually does unless you drive the SH-AWD and FWD versions of the same car under the same conditions back to back. A pair of new MDX's would be a great choice for the test drives.

sadlerau
Profile for sadlerau
Re: Fixing SH-AWD    (Score: 1, Normal) 10-11-2018 09:19
Reply to This Message Attach Quote to Reply
Grace141 wrote:
Honda claims SH-AWD counters oversteer when the throttle is closed during cornering......


Yep, I can vouch for that from first hand experience.

My girlfriend was driving the Legend on my local race track, and approached Turn 1 way way to quickly. Sitting in the passenger seat I'm not sure when she applied the brakes, nor how hard she applied them [she's a woman after all], but I do know the tail started to come around rather dramatically as she applied more steering lock in an effort to make the corner. But in the blink of an eye the car sorted itself out, maintaining the arc through the corner in a very neutral stance. It could have been VSA, or it could have been what Honda claim?

What I do know is she thought us getting around that corner so quickly and smoothly was all down to her driving ability! You try telling her it isn't so...........


Nick GravesX
Profile for Nick GravesX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-11-2018 13:22
Reply to This Message Attach Quote to Reply
I can vouch for the car's ability to catch big oversteers in 2nd gear wet roundabouts drifts.

It lets go almost as abruptly as an S2000, but it makes one think one is a driving god. I'm not...

Grace141
Profile for Grace141
Re: Fixing SH-AWD    (Score: 1, Normal) 10-12-2018 07:19
Reply to This Message Attach Quote to Reply
I'd think a snap correction for oversteer would be due to VSA. With a maximum of 70% of engine braking torque going to the inside rear wheel I wouldn't think the turn in effect would be that aggressive.

I'm sure Honda has a mountain of data compiled for each car with SH-AWD which they would never share with us customers, of course. One factor I don't think people consider is with SH-AWD being completely variable and based on intelligent sensor readings it's difficult even to compare tires without routinely taking a car right up to the limit. It would explain why I might have been the only person on TOV who thought the Michelin MXM tires used on the Acuras for years were decent tires.

sadlerau
Profile for sadlerau
Re: Fixing SH-AWD    (Score: 1, Normal) 10-12-2018 07:51
Reply to This Message Attach Quote to Reply
Hard to say where one stops and the other takes over. On the race track disengaging the VSA allowed some serious attitude on turn-in (the old "backing it in" style) but SH-AWD still worked on throttle application, helping rotate the rear well past the apex.
Nick GravesX
Profile for Nick GravesX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-12-2018 09:43
Reply to This Message Attach Quote to Reply
Grace141 wrote:
I'd think a snap correction for oversteer would be due to VSA. With a maximum of 70% of engine braking torque going to the inside rear wheel I wouldn't think the turn in effect would be that aggressive.

I'm sure Honda has a mountain of data compiled for each car with SH-AWD which they would never share with us customers, of course. One factor I don't think people consider is with SH-AWD being completely variable and based on intelligent sensor readings it's difficult even to compare tires without routinely taking a car right up to the limit. It would explain why I might have been the only person on TOV who thought the Michelin MXM tires used on the Acuras for years were decent tires.



The dash lighting up like a christmas tree and the loss of throttle is a bit of a dead giveaway.

Civicb18
Profile for Civicb18
Re: Fixing SH-AWD    (Score: 1, Normal) 10-12-2018 20:22
Reply to This Message Attach Quote to Reply
If Im not on the throttle during hard cornering, my TL SH will understeer. Throttle on and the cars nose tucks in and no understeer. The key to the system is corner entry or how fast you enter the corner. Apply even light throttle and the car will rotate and maybe even step the rear out if youre aggressive enough. I like it but Id like to see the system in a smaller, lighter package like an ILX-S with at least 300hp.
alpha0
Profile for alpha0
Re: Fixing SH-AWD    (Score: 1, Normal) 10-13-2018 09:30
Reply to This Message Attach Quote to Reply
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?

Grace141
Profile for Grace141
Re: Fixing SH-AWD    (Score: 1, Normal) 10-13-2018 09:46
Reply to This Message Attach Quote to Reply
Nick GravesX wrote:
Grace141 wrote:
I'd think a snap correction for oversteer would be due to VSA. With a maximum of 70% of engine braking torque going to the inside rear wheel I wouldn't think the turn in effect would be that aggressive.

I'm sure Honda has a mountain of data compiled for each car with SH-AWD which they would never share with us customers, of course. One factor I don't think people consider is with SH-AWD being completely variable and based on intelligent sensor readings it's difficult even to compare tires without routinely taking a car right up to the limit. It would explain why I might have been the only person on TOV who thought the Michelin MXM tires used on the Acuras for years were decent tires.



The dash lighting up like a christmas tree and the loss of throttle is a bit of a dead giveaway.


I thought Honda's VSA worked behind the scenes but reading the section in my Accord owner's manual now, yeah, Honda says the warning light flashes when the system is actively working and not just when the full ABS is engaged. So the big step forward with Agile Handling Assist is you don't get the idiot light right away.

Grace141
Profile for Grace141
Re: Fixing SH-AWD    (Score: 1, Normal) 10-13-2018 10:37
Reply to This Message Attach Quote to Reply
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?


Honda has claimed the 3G RDX has a greater RWD bias to the system so there is that.

The SH-AWD system warning flashing telltale more or less means the rear diff temp is too high and the instruction is to park the car until the light turns off. I've never read of anyone seeing damaged clutch packs in an SH-AWD diff so my guess is the system will cook the fluid beyond its service specs before damage occurs. Either way, the system must be torque limited. If the input clutch can be rated high enough I can't imagine the current 250 to 300 lbs-ft of torque the Acuras are rated is anywhere near the SH-AWD limits but then again the new RDX 0-60 wasn't what people expected. The problem with the Honda sales pitch for SH-AWD is the statement the system can transfer "up to" 70% of the torque supplied to the rear diff to one rear wheel. There's no way of knowing exactly what that means.

Our 1G RDX had the SH-AWD warning light as well as a transmission fluid temp light. Even with pushing the car pretty hard through some interesting twisty roads at what I thought were tall CUV scary speeds I never saw those lights. My guess is it's Honda's conservative safety philosophy which sets the tone for their SH-AWD specs.

alpha0
Profile for alpha0
Re: Fixing SH-AWD    (Score: 1, Normal) 10-13-2018 12:18
Reply to This Message Attach Quote to Reply
Grace141 wrote:
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?


Honda has claimed the 3G RDX has a greater RWD bias to the system so there is that.

The SH-AWD system warning flashing telltale more or less means the rear diff temp is too high and the instruction is to park the car until the light turns off. I've never read of anyone seeing damaged clutch packs in an SH-AWD diff so my guess is the system will cook the fluid beyond its service specs before damage occurs. Either way, the system must be torque limited. If the input clutch can be rated high enough I can't imagine the current 250 to 300 lbs-ft of torque the Acuras are rated is anywhere near the SH-AWD limits but then again the new RDX 0-60 wasn't what people expected. The problem with the Honda sales pitch for SH-AWD is the statement the system can transfer "up to" 70% of the torque supplied to the rear diff to one rear wheel. There's no way of knowing exactly what that means.

Our 1G RDX had the SH-AWD warning light as well as a transmission fluid temp light. Even with pushing the car pretty hard through some interesting twisty roads at what I thought were tall CUV scary speeds I never saw those lights. My guess is it's Honda's conservative safety philosophy which sets the tone for their SH-AWD specs.



I suspect that conservative philosophy will not work for Type S models if they want to be taken seriously in performance segment.

owequitit
Profile for owequitit
Re: Fixing SH-AWD    (Score: 1, Normal) 10-14-2018 00:03
Reply to This Message Attach Quote to Reply
alpha0 wrote:
Grace141 wrote:
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?


Honda has claimed the 3G RDX has a greater RWD bias to the system so there is that.

The SH-AWD system warning flashing telltale more or less means the rear diff temp is too high and the instruction is to park the car until the light turns off. I've never read of anyone seeing damaged clutch packs in an SH-AWD diff so my guess is the system will cook the fluid beyond its service specs before damage occurs. Either way, the system must be torque limited. If the input clutch can be rated high enough I can't imagine the current 250 to 300 lbs-ft of torque the Acuras are rated is anywhere near the SH-AWD limits but then again the new RDX 0-60 wasn't what people expected. The problem with the Honda sales pitch for SH-AWD is the statement the system can transfer "up to" 70% of the torque supplied to the rear diff to one rear wheel. There's no way of knowing exactly what that means.

Our 1G RDX had the SH-AWD warning light as well as a transmission fluid temp light. Even with pushing the car pretty hard through some interesting twisty roads at what I thought were tall CUV scary speeds I never saw those lights. My guess is it's Honda's conservative safety philosophy which sets the tone for their SH-AWD specs.



I suspect that conservative philosophy will not work for Type S models if they want to be taken seriously in performance segment.



It has been talked about on here before, but ultimately, it is torque capacity.

Remember that SH-AWD is sending power to the rear off of the differential up front, so it has already been multiplied by the gearing of the transmission. That means that the ~270lb-ft on the 4th gen TL SH-AWD was already well over 1200 ft-lbs in 1st gear.

The only solution to protect the driveline is to limit torque transfer to the rear and/or limit powertrain torque. In the case of the boosted engines, the PCM could dial boost pressure back, etc to lower the torque output of the engine. Of course the downside to this is that you don't get maximum go from the powertrain because you are artificially limiting power in order to not exceed the limits of the AWD system.

The specific issue with SH-AWD is you have multiple clutch packs transferring torque around. They could increase the torque capacity, but that generally means bigger components and more weight. I think the RDX actually did make a meaningful improvement in torque capacity though. It is made worse that you are essentially making the torque make 90* turns through the powertrain as well.

This is why you don't typically see the system cooking itself because the software is designed to keep everything within limits.


People say I am stupid and I am NOT trying to beat a completely dead horse, but that is one of the advantages to a long layout. It would allow up to 100% of the torque to go the rear and then a much reduced amount could be sent forward and side to side. You would end up with an even better balanced system (which the NSX proves) and you would not need to be trying to shuttle massive amounts of torque rearward in order to achieve it. You get the grip, the light(er) weight, the better balance and less limiting of the powertrain in lower gears.

It is sort of what BMW is doing with the new M5, though I don't think they actively move it side to side.

sadlerau
Profile for sadlerau
Re: Fixing SH-AWD    (Score: 1, Normal) 10-14-2018 01:10
Reply to This Message Attach Quote to Reply
I would have thought the NSX proves (much to my surprise) that torque vectoring has limited benefits in a longditudinal layout, which may be why BMW are doing what they're doing with the M5?
Nick GravesX
Profile for Nick GravesX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-14-2018 09:02
Reply to This Message Attach Quote to Reply
owequitit wrote:
alpha0 wrote:
Grace141 wrote:
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?


Honda has claimed the 3G RDX has a greater RWD bias to the system so there is that.

The SH-AWD system warning flashing telltale more or less means the rear diff temp is too high and the instruction is to park the car until the light turns off. I've never read of anyone seeing damaged clutch packs in an SH-AWD diff so my guess is the system will cook the fluid beyond its service specs before damage occurs. Either way, the system must be torque limited. If the input clutch can be rated high enough I can't imagine the current 250 to 300 lbs-ft of torque the Acuras are rated is anywhere near the SH-AWD limits but then again the new RDX 0-60 wasn't what people expected. The problem with the Honda sales pitch for SH-AWD is the statement the system can transfer "up to" 70% of the torque supplied to the rear diff to one rear wheel. There's no way of knowing exactly what that means.

Our 1G RDX had the SH-AWD warning light as well as a transmission fluid temp light. Even with pushing the car pretty hard through some interesting twisty roads at what I thought were tall CUV scary speeds I never saw those lights. My guess is it's Honda's conservative safety philosophy which sets the tone for their SH-AWD specs.



I suspect that conservative philosophy will not work for Type S models if they want to be taken seriously in performance segment.



It has been talked about on here before, but ultimately, it is torque capacity.

Remember that SH-AWD is sending power to the rear off of the differential up front, so it has already been multiplied by the gearing of the transmission. That means that the ~270lb-ft on the 4th gen TL SH-AWD was already well over 1200 ft-lbs in 1st gear.

The only solution to protect the driveline is to limit torque transfer to the rear and/or limit powertrain torque. In the case of the boosted engines, the PCM could dial boost pressure back, etc to lower the torque output of the engine. Of course the downside to this is that you don't get maximum go from the powertrain because you are artificially limiting power in order to not exceed the limits of the AWD system.

The specific issue with SH-AWD is you have multiple clutch packs transferring torque around. They could increase the torque capacity, but that generally means bigger components and more weight. I think the RDX actually did make a meaningful improvement in torque capacity though. It is made worse that you are essentially making the torque make 90* turns through the powertrain as well.

This is why you don't typically see the system cooking itself because the software is designed to keep everything within limits.


People say I am stupid and I am NOT trying to beat a completely dead horse, but that is one of the advantages to a long layout. It would allow up to 100% of the torque to go the rear and then a much reduced amount could be sent forward and side to side. You would end up with an even better balanced system (which the NSX proves) and you would not need to be trying to shuttle massive amounts of torque rearward in order to achieve it. You get the grip, the light(er) weight, the better balance and less limiting of the powertrain in lower gears.

It is sort of what BMW is doing with the new M5, though I don't think they actively move it side to side.



To widen the can of worms further, BMW has reverted to active AWS on the new M5! I've often wondered about a car with both TV-AWD and 4WS....

Also, it depends which SH-AWD you are dealing with; the Leg End does not use clutch packs to transfer the torque - they control the epicyclics as does many a modern farm tractor CVT. You therefore don't get the wear issues associated with Fast Fords and overheated diffs. I should imagine that was the system that the "NB"/"GT5000" utilised for that reason.

owequitit
Profile for owequitit
Re: Fixing SH-AWD    (Score: 1, Normal) 10-15-2018 03:27
Reply to This Message Attach Quote to Reply
sadlerau wrote:
I would have thought the NSX proves (much to my surprise) that torque vectoring has limited benefits in a longditudinal layout, which may be why BMW are doing what they're doing with the M5?


I think the NSX's biggest issue is weight.

The M5 was simply a matter of how to put 600HP+ HP reliably to the ground and still keep the handling balance, which is why they try to limit the amount going forward. Basically, it is just limiting the amount moved to the front axle to whatever the rear can't handle grip wise. They also give you the ability to just turn it off and overpower the front wheels. They also only send up to about 30% to the front, if my memory is serving me correctly. You get a fundamentally balanced car that only send power forward to keep itself sorted out. Add slight torque vectoring to that (like maybe up to 70% of whatever you send forward) and you would probably end up with a pretty balanced car that acts like it has a FWD LSD when you goose it.

The NSX is almost 4,000lbs. Compare that to a similarly powered and probably similarly capable 911 GT3 which barely cracks 3200lbs. You know as well as I do that is going to have a big effect on the total envelope, especially if tire size and performance are similar.

The NSX does magical things in terms of being able to make a capable car easy to drive, but breaking the laws of physics isn't one of them. I found it telling that they admitted that it took them YEARS during the development process to make the hybrid car not slower than the non-hybrid mules.

But in a sedan, you could use it to improve turn in where the weight of the engine is up front (albeit not entirely in front of the axle) while still helping the car maintain safe composure, AWD grip and launch traction.

TonyEX
Profile for TonyEX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-16-2018 18:37
Reply to This Message Attach Quote to Reply
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?




Whatever torque came to the back end kept me consistently about a foot away from the 4 foot high central concrete median barrier on a long right hand sweeper the first time I found it that it worked.

It's just, it's just that I sure would have love to have slowed down at the same time the tail was coming around. And with snow and rain all around me I didn't want too much braking either.

Honestly, I had no issues with my car's FWD bias. As it made it a very good steady cruiser on the open road, for hours and hours and miles and miles and on and on. The SH-AWD control the back end when it was needed, turns, poor traction, cross winds, rain, snow, etc...

What I like about FWD per se is how little effort it requires to drive it. The car pretty much drives itself. The RWD cars are quicker, yes, but also just a little "twitchier" and that piles up when you are driving for hundreds of miles without stopping.

As far as altering torque transfer... I suppose that can easily be done with the Sport Mode "selections".

TonyEX
Profile for TonyEX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-16-2018 20:08
Reply to This Message Attach Quote to Reply
Grace141 wrote:
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?


Honda has claimed the 3G RDX has a greater RWD bias to the system so there is that.

The SH-AWD system warning flashing telltale more or less means the rear diff temp is too high and the instruction is to park the car until the light turns off. I've never read of anyone seeing damaged clutch packs in an SH-AWD diff so my guess is the system will cook the fluid beyond its service specs before damage occurs. Either way, the system must be torque limited. If the input clutch can be rated high enough I can't imagine the current 250 to 300 lbs-ft of torque the Acuras are rated is anywhere near the SH-AWD limits but then again the new RDX 0-60 wasn't what people expected. The problem with the Honda sales pitch for SH-AWD is the statement the system can transfer "up to" 70% of the torque supplied to the rear diff to one rear wheel. There's no way of knowing exactly what that means.

Our 1G RDX had the SH-AWD warning light as well as a transmission fluid temp light. Even with pushing the car pretty hard through some interesting twisty roads at what I thought were tall CUV scary speeds I never saw those lights. My guess is it's Honda's conservative safety philosophy which sets the tone for their SH-AWD specs.




Honestly, I don't think you can ever reach the limits of SH-AWD, in terms of cooking the clutch, on a public road.

And even then, it doesn't take that much power, nor for that long, to keep the tail in place. Using the SH-AWD dash display on the TSX, I did note times when all of the torque was going to a single rear wheel, but at those extremes, I wasn't really going that fast because the turns were quite tight.

The only time I can think that SH-AWD will be on, would be on an icy, slippery road. And even then, I doubt you'd be going too fast. Plus the cold weather and water and ice splashing on the differential housing will help to cook it too, huh?


alpha0
Profile for alpha0
Re: Fixing SH-AWD    (Score: 1, Normal) 10-16-2018 22:34
Reply to This Message Attach Quote to Reply
TonyEX wrote:
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?




Whatever torque came to the back end kept me consistently about a foot away from the 4 foot high central concrete median barrier on a long right hand sweeper the first time I found it that it worked.

It's just, it's just that I sure would have love to have slowed down at the same time the tail was coming around. And with snow and rain all around me I didn't want too much braking either.

Honestly, I had no issues with my car's FWD bias. As it made it a very good steady cruiser on the open road, for hours and hours and miles and miles and on and on. The SH-AWD control the back end when it was needed, turns, poor traction, cross winds, rain, snow, etc...

What I like about FWD per se is how little effort it requires to drive it. The car pretty much drives itself. The RWD cars are quicker, yes, but also just a little "twitchier" and that piles up when you are driving for hundreds of miles without stopping.

As far as altering torque transfer... I suppose that can easily be done with the Sport Mode "selections".



I am not sure whether Acura would want to position Type S sedan as "steady cruiser".

owequitit
Profile for owequitit
Re: Fixing SH-AWD    (Score: 1, Normal) 10-17-2018 01:46
Reply to This Message Attach Quote to Reply
Nick GravesX wrote:
owequitit wrote:
alpha0 wrote:
Grace141 wrote:
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?


Honda has claimed the 3G RDX has a greater RWD bias to the system so there is that.

The SH-AWD system warning flashing telltale more or less means the rear diff temp is too high and the instruction is to park the car until the light turns off. I've never read of anyone seeing damaged clutch packs in an SH-AWD diff so my guess is the system will cook the fluid beyond its service specs before damage occurs. Either way, the system must be torque limited. If the input clutch can be rated high enough I can't imagine the current 250 to 300 lbs-ft of torque the Acuras are rated is anywhere near the SH-AWD limits but then again the new RDX 0-60 wasn't what people expected. The problem with the Honda sales pitch for SH-AWD is the statement the system can transfer "up to" 70% of the torque supplied to the rear diff to one rear wheel. There's no way of knowing exactly what that means.

Our 1G RDX had the SH-AWD warning light as well as a transmission fluid temp light. Even with pushing the car pretty hard through some interesting twisty roads at what I thought were tall CUV scary speeds I never saw those lights. My guess is it's Honda's conservative safety philosophy which sets the tone for their SH-AWD specs.



I suspect that conservative philosophy will not work for Type S models if they want to be taken seriously in performance segment.



It has been talked about on here before, but ultimately, it is torque capacity.

Remember that SH-AWD is sending power to the rear off of the differential up front, so it has already been multiplied by the gearing of the transmission. That means that the ~270lb-ft on the 4th gen TL SH-AWD was already well over 1200 ft-lbs in 1st gear.

The only solution to protect the driveline is to limit torque transfer to the rear and/or limit powertrain torque. In the case of the boosted engines, the PCM could dial boost pressure back, etc to lower the torque output of the engine. Of course the downside to this is that you don't get maximum go from the powertrain because you are artificially limiting power in order to not exceed the limits of the AWD system.

The specific issue with SH-AWD is you have multiple clutch packs transferring torque around. They could increase the torque capacity, but that generally means bigger components and more weight. I think the RDX actually did make a meaningful improvement in torque capacity though. It is made worse that you are essentially making the torque make 90* turns through the powertrain as well.

This is why you don't typically see the system cooking itself because the software is designed to keep everything within limits.


People say I am stupid and I am NOT trying to beat a completely dead horse, but that is one of the advantages to a long layout. It would allow up to 100% of the torque to go the rear and then a much reduced amount could be sent forward and side to side. You would end up with an even better balanced system (which the NSX proves) and you would not need to be trying to shuttle massive amounts of torque rearward in order to achieve it. You get the grip, the light(er) weight, the better balance and less limiting of the powertrain in lower gears.

It is sort of what BMW is doing with the new M5, though I don't think they actively move it side to side.



To widen the can of worms further, BMW has reverted to active AWS on the new M5! I've often wondered about a car with both TV-AWD and 4WS....

Also, it depends which SH-AWD you are dealing with; the Leg End does not use clutch packs to transfer the torque - they control the epicyclics as does many a modern farm tractor CVT. You therefore don't get the wear issues associated with Fast Fords and overheated diffs. I should imagine that was the system that the "NB"/"GT5000" utilised for that reason.



As I recall, the original implementation of SH-AWD used magnetic clutches to control torque transfer. Ultimately, it is going to have a torque capacity.

TonyEX
Profile for TonyEX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-17-2018 15:56
Reply to This Message Attach Quote to Reply
alpha0 wrote:
TonyEX wrote:
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?




Whatever torque came to the back end kept me consistently about a foot away from the 4 foot high central concrete median barrier on a long right hand sweeper the first time I found it that it worked.

It's just, it's just that I sure would have love to have slowed down at the same time the tail was coming around. And with snow and rain all around me I didn't want too much braking either.

Honestly, I had no issues with my car's FWD bias. As it made it a very good steady cruiser on the open road, for hours and hours and miles and miles and on and on. The SH-AWD control the back end when it was needed, turns, poor traction, cross winds, rain, snow, etc...

What I like about FWD per se is how little effort it requires to drive it. The car pretty much drives itself. The RWD cars are quicker, yes, but also just a little "twitchier" and that piles up when you are driving for hundreds of miles without stopping.

As far as altering torque transfer... I suppose that can easily be done with the Sport Mode "selections".



I am not sure whether Acura would want to position Type S sedan as "steady cruiser".



"Grand Tourer".

JeffX
Profile for JeffX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-17-2018 16:46
Reply to This Message Attach Quote to Reply
owequitit wrote:
Nick GravesX wrote:
owequitit wrote:
alpha0 wrote:
Grace141 wrote:
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?


Honda has claimed the 3G RDX has a greater RWD bias to the system so there is that.

The SH-AWD system warning flashing telltale more or less means the rear diff temp is too high and the instruction is to park the car until the light turns off. I've never read of anyone seeing damaged clutch packs in an SH-AWD diff so my guess is the system will cook the fluid beyond its service specs before damage occurs. Either way, the system must be torque limited. If the input clutch can be rated high enough I can't imagine the current 250 to 300 lbs-ft of torque the Acuras are rated is anywhere near the SH-AWD limits but then again the new RDX 0-60 wasn't what people expected. The problem with the Honda sales pitch for SH-AWD is the statement the system can transfer "up to" 70% of the torque supplied to the rear diff to one rear wheel. There's no way of knowing exactly what that means.

Our 1G RDX had the SH-AWD warning light as well as a transmission fluid temp light. Even with pushing the car pretty hard through some interesting twisty roads at what I thought were tall CUV scary speeds I never saw those lights. My guess is it's Honda's conservative safety philosophy which sets the tone for their SH-AWD specs.



I suspect that conservative philosophy will not work for Type S models if they want to be taken seriously in performance segment.



It has been talked about on here before, but ultimately, it is torque capacity.

Remember that SH-AWD is sending power to the rear off of the differential up front, so it has already been multiplied by the gearing of the transmission. That means that the ~270lb-ft on the 4th gen TL SH-AWD was already well over 1200 ft-lbs in 1st gear.

The only solution to protect the driveline is to limit torque transfer to the rear and/or limit powertrain torque. In the case of the boosted engines, the PCM could dial boost pressure back, etc to lower the torque output of the engine. Of course the downside to this is that you don't get maximum go from the powertrain because you are artificially limiting power in order to not exceed the limits of the AWD system.

The specific issue with SH-AWD is you have multiple clutch packs transferring torque around. They could increase the torque capacity, but that generally means bigger components and more weight. I think the RDX actually did make a meaningful improvement in torque capacity though. It is made worse that you are essentially making the torque make 90* turns through the powertrain as well.

This is why you don't typically see the system cooking itself because the software is designed to keep everything within limits.


People say I am stupid and I am NOT trying to beat a completely dead horse, but that is one of the advantages to a long layout. It would allow up to 100% of the torque to go the rear and then a much reduced amount could be sent forward and side to side. You would end up with an even better balanced system (which the NSX proves) and you would not need to be trying to shuttle massive amounts of torque rearward in order to achieve it. You get the grip, the light(er) weight, the better balance and less limiting of the powertrain in lower gears.

It is sort of what BMW is doing with the new M5, though I don't think they actively move it side to side.



To widen the can of worms further, BMW has reverted to active AWS on the new M5! I've often wondered about a car with both TV-AWD and 4WS....

Also, it depends which SH-AWD you are dealing with; the Leg End does not use clutch packs to transfer the torque - they control the epicyclics as does many a modern farm tractor CVT. You therefore don't get the wear issues associated with Fast Fords and overheated diffs. I should imagine that was the system that the "NB"/"GT5000" utilised for that reason.



As I recall, the original implementation of SH-AWD used magnetic clutches to control torque transfer. Ultimately, it is going to have a torque capacity.



As I have mentioned in other threads here, it does in fact have a maximum capacity. One of the cool things about the new RDX is that the capacity is 40% larger now, but it still can't put anything close to all of that multiplied torque to the rear axle until the transmission gets into 3rd gear.

It will be interesting to see how much (if at all) they scale up the SH-AWD diff for the coming V6 Turbo SH-AWD TLX and RDX Type S.

TonyEX
Profile for TonyEX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-17-2018 19:16
Reply to This Message Attach Quote to Reply
JeffX wrote:
...

As I have mentioned in other threads here, it does in fact have a maximum capacity. One of the cool things about the new RDX is that the capacity is 40% larger now, but it still can't put anything close to all of that multiplied torque to the rear axle until the transmission gets into 3rd gear.

It will be interesting to see how much (if at all) they scale up the SH-AWD diff for the coming V6 Turbo SH-AWD TLX and RDX Type S.



My wife is driving me bananas lately.

She now only wants cars with AWD. Under the illusion she'll retire soon.

If only the interior of the RDX weren't so overstyled! :-P

Anyhow, I don't see why you would have to put so much torque to the back end anyhow. In tight turns and slippery conditions you are not going to be going that fast anyhow, so a lower gear and a lower power is what you are going to be doing, so there really is no need for so much torque to that outside rear tire.

On a race track it's different, of course, but SH-AWD is not sold for race cars, it's sold for road cars.

A twin turbo V6 in an RDX, even with SH-AWD, is gonna be nuts, IMHO. Every time I look at a Porsche SUV with those big wide tires I shake my head in disbelief. Why? Lipstick on a pig.

OTH, if the TLX-S SH-AWD ditches that 9AT.. hmm... I might just convince the wife.... but then I won't get my CTR. Or that putative ILX-S4.

My cousin in law just bought a new targa top Miata.... either I get my car or I get my Linn Lingo and Pass amps.



owequitit
Profile for owequitit
Re: Fixing SH-AWD    (Score: 1, Normal) 10-18-2018 01:37
Reply to This Message Attach Quote to Reply
TonyEX wrote:
JeffX wrote:
...

As I have mentioned in other threads here, it does in fact have a maximum capacity. One of the cool things about the new RDX is that the capacity is 40% larger now, but it still can't put anything close to all of that multiplied torque to the rear axle until the transmission gets into 3rd gear.

It will be interesting to see how much (if at all) they scale up the SH-AWD diff for the coming V6 Turbo SH-AWD TLX and RDX Type S.



My wife is driving me bananas lately.

She now only wants cars with AWD. Under the illusion she'll retire soon.

If only the interior of the RDX weren't so overstyled! :-P

Anyhow, I don't see why you would have to put so much torque to the back end anyhow. In tight turns and slippery conditions you are not going to be going that fast anyhow, so a lower gear and a lower power is what you are going to be doing, so there really is no need for so much torque to that outside rear tire.

On a race track it's different, of course, but SH-AWD is not sold for race cars, it's sold for road cars.

A twin turbo V6 in an RDX, even with SH-AWD, is gonna be nuts, IMHO. Every time I look at a Porsche SUV with those big wide tires I shake my head in disbelief. Why? Lipstick on a pig.

OTH, if the TLX-S SH-AWD ditches that 9AT.. hmm... I might just convince the wife.... but then I won't get my CTR. Or that putative ILX-S4.

My cousin in law just bought a new targa top Miata.... either I get my car or I get my Linn Lingo and Pass amps.





Launch traction, handling traction, etc.

Speaking of "lipstick on a pig," been to an Acura showroom lately?

Nick GravesX
Profile for Nick GravesX
Re: Fixing SH-AWD    (Score: 1, Normal) 10-18-2018 05:10
Reply to This Message Attach Quote to Reply
JeffX wrote:
owequitit wrote:
Nick GravesX wrote:
owequitit wrote:
alpha0 wrote:
Grace141 wrote:
alpha0 wrote:
Since current SHAWD can transfer upto 70% power to rear wheels, i assume software limits situations when it transfers power to rear. What is stopping Acura to transfer let's say 30% power to rear all the time and transfer more power to rear even while taking mild turns at 1500 rpm? Turbo engines shoulld have good power at low rpms compared to NA engines.

Or is the fear of wear/tear and enhanced maintanance needs stopping Acura from doing that?


Honda has claimed the 3G RDX has a greater RWD bias to the system so there is that.

The SH-AWD system warning flashing telltale more or less means the rear diff temp is too high and the instruction is to park the car until the light turns off. I've never read of anyone seeing damaged clutch packs in an SH-AWD diff so my guess is the system will cook the fluid beyond its service specs before damage occurs. Either way, the system must be torque limited. If the input clutch can be rated high enough I can't imagine the current 250 to 300 lbs-ft of torque the Acuras are rated is anywhere near the SH-AWD limits but then again the new RDX 0-60 wasn't what people expected. The problem with the Honda sales pitch for SH-AWD is the statement the system can transfer "up to" 70% of the torque supplied to the rear diff to one rear wheel. There's no way of knowing exactly what that means.

Our 1G RDX had the SH-AWD warning light as well as a transmission fluid temp light. Even with pushing the car pretty hard through some interesting twisty roads at what I thought were tall CUV scary speeds I never saw those lights. My guess is it's Honda's conservative safety philosophy which sets the tone for their SH-AWD specs.



I suspect that conservative philosophy will not work for Type S models if they want to be taken seriously in performance segment.



It has been talked about on here before, but ultimately, it is torque capacity.

Remember that SH-AWD is sending power to the rear off of the differential up front, so it has already been multiplied by the gearing of the transmission. That means that the ~270lb-ft on the 4th gen TL SH-AWD was already well over 1200 ft-lbs in 1st gear.

The only solution to protect the driveline is to limit torque transfer to the rear and/or limit powertrain torque. In the case of the boosted engines, the PCM could dial boost pressure back, etc to lower the torque output of the engine. Of course the downside to this is that you don't get maximum go from the powertrain because you are artificially limiting power in order to not exceed the limits of the AWD system.

The specific issue with SH-AWD is you have multiple clutch packs transferring torque around. They could increase the torque capacity, but that generally means bigger components and more weight. I think the RDX actually did make a meaningful improvement in torque capacity though. It is made worse that you are essentially making the torque make 90* turns through the powertrain as well.

This is why you don't typically see the system cooking itself because the software is designed to keep everything within limits.


People say I am stupid and I am NOT trying to beat a completely dead horse, but that is one of the advantages to a long layout. It would allow up to 100% of the torque to go the rear and then a much reduced amount could be sent forward and side to side. You would end up with an even better balanced system (which the NSX proves) and you would not need to be trying to shuttle massive amounts of torque rearward in order to achieve it. You get the grip, the light(er) weight, the better balance and less limiting of the powertrain in lower gears.

It is sort of what BMW is doing with the new M5, though I don't think they actively move it side to side.



To widen the can of worms further, BMW has reverted to active AWS on the new M5! I've often wondered about a car with both TV-AWD and 4WS....

Also, it depends which SH-AWD you are dealing with; the Leg End does not use clutch packs to transfer the torque - they control the epicyclics as does many a modern farm tractor CVT. You therefore don't get the wear issues associated with Fast Fords and overheated diffs. I should imagine that was the system that the "NB"/"GT5000" utilised for that reason.



As I recall, the original implementation of SH-AWD used magnetic clutches to control torque transfer. Ultimately, it is going to have a torque capacity.



As I have mentioned in other threads here, it does in fact have a maximum capacity. One of the cool things about the new RDX is that the capacity is 40% larger now, but it still can't put anything close to all of that multiplied torque to the rear axle until the transmission gets into 3rd gear.

It will be interesting to see how much (if at all) they scale up the SH-AWD diff for the coming V6 Turbo SH-AWD TLX and RDX Type S.



Well, the problem with the Leg End system is with three epicyclics, it was already bloody heavy. I do not know if it's ultimately the gears or the clutch packs that limited it as it was - the latter may easily be upgraded without a full re-design.

But the modern ones use wet clutches for torque transfer, so will be torque-limited inevitably. Though that's less of a problem, if you add PAWS as well to angle-vector. That also works on overrun too.

Since the future seems to be econoboxes and EVs, we'll probably never know Honda's ultimate application. But I fucking wish they'd reveal the GT5000 to us! The engine alone was fascinating and I thank them for releasing what they did. I bet the driveline had some felicitations too.



 
Thread Page - [1]
Go to:
Contact TOV | Submit Your Article | Submit Your Link | Advertise | TOV Shop | Events | Our Sponsors | TOV Archives
Copyright © 2018 Velocitech Inc. All information contained herein remains the property of Velocitech Inc.
The Temple of VTEC is not affiliated with American Honda Motor Co., Inc. TOV Policies and Guidelines - Credits - Privacy Policy
30 mobile: 0