Project: Gen2 JDM Integra XSi Hybrid

In April 1989, Honda introduced the Integra XSi as its very first VTEC engined car. Coded as E-DA6, this model became very popular due to its slim design, generous cabin space, and good handling and ride. Integra XSi/RSi first came with the early B16A generating 160ps and in 1991 was again the first Honda model to get the revised 170ps B16A. Today, there are still many happy owners who are using their Integra XSi/RSi. Having been replaced in April 1993 with the DC-generation, it has become popular for DA6 owners to modify their car to keep up with the level of quality of the DC2 as well as the improving general level of quality of the competition. A suitably modified Integra XSi can be a very potent vehicle and if coupled with a sensibly designed bodykit can give the whole car a fresh new look, enough for it to keep abreast with all of the current cars which it competes with.

The DA6 in this article is a special street-use modification project. The owner wanted the highest possible power but had a requirement that the engine will fit into the engine bay. What he did was basically simply handed the keys to the car over to the tuner, AMOIL MOTORSPORTS. There was also a requirement that the engine must still be naturally aspirated but I was told that there wasn't really a pre-set budget or other big requirements for the project. So this modification project quickly became an exercise in squeezing the maximum amount of power, NA means, from an engine that is based on the 'B'-series.

The approach that Desmond of Amoil did was to do what is popularly known as the 'rojak' in Malaysia. Also known as the 'Frankenstein' in the states, this consists of matching compatible Honda B-series blocks and heads together, and making use of VTEC and racing technology to squeeze maximum power off the combination but yet still making the engine practical to use. To this end, Amoil do have a good amount of experience, backed by racing knowledge for this job since they regularly field race-prepped Civics in many national as well as regional race series.

The approach that Amoil took for this DA6 was to match a B16A head to a block off a selected B20 engine, this effectively upping the displacement to 2000cc (or more). The extra displacement now makes it possible to go for much higher power outputs over a B16A or B18C while still retaining sane revs limits of around 8500 - 9000 rpm. Stock Honda pistons, con rods and crankshafts from various different Honda engines were used in the block (and this may have modified the actual displacement of the engine slightly). The already high-flowing B16A head was further ported and JUN camshafts were used with high-rpm rated valve springs and suitably selected intake/exhaust valves to ensure very good air-flow right up to 8500rpm and beyond.

Nevertheless, due to the DA6's unusually slim design, the overall B16/B20 engine package still ended up slightly too high for the engine bay. So a rather imaginative solution was adopted to raise the hinge points of the bonnet. This effectively made the bonnet sit higher at the hinge-points while keeping the latch properly aligned with the front-end of the car. In practice however, to some eyes, this has the rather unexpected unique effect of making the car look fiercer !

All other items to the engine were also specially matched for optimal high-rpm power output. The intake manifold was a special DC2R version (with a nice 'Integra Type-R' casting on top of the plenum) while the exhaust system is full Mugen header + cat-back (without the cat). Filter is the popular Akimoto style system. To permit proper tuning of the engine, the JUN cams were used with adjustable cam sprockets to allow degreeing. Taking care of the fueling control is a HALTECH computer.

I chanced upon this car while it was being dyno-tuned at Aerotech's Dynojet facility. Being for street-use, the car has a full interior, keeping the original factory steering wheel and semi-bucket seats and also sporting a good sound system ! The car idled properly around 1,000rpm and has a docile character when puttering around at very low speeds. The intention of the dyno-session was to properly set the cams and tune the HALTECH maps.

The initial tuning was to optimally degree the cams. Degree-ing the cams will set the open timing of the intake and exhaust valves to their optimal points. This will achieve two things. The point of opening of the intake valves and the valve open overlap will both be tuned for optimized air-flow into the combustion cylinder. Proper degreeing of the two camshafts can liberate quite a few hp from the engine, since more air-flow allows more fuel to be burnt and hence more power.

Once the cams are properly degreed, the fuel map will need to be tuned to optimize power output. The fuel map tuning ensures that sufficient fuel is delivered to the combustion chamber, optimized for the new VE of the engine. This will ensure the engine is operating at an air-fuel ratio optimized for power delivery. An adjustable fuel pressure regulator was used to set the fuel pressure to ensure that injector duty-cycles do not exceed the recommended maximums. The ignition timing will also need to be set for maximum power output.

The effort required was large. Proper degreeing of the cams took the most part of 1 hour. Fuel map tuning was done with the use of an air-fuel ratio meter mounted in the car which is a tedious process because the tuner needed to look at both the air-fuel ratio meter and the tach-meter at the same time ! Nevertheless, with determined effort, the fuel maps were fine-tuned and the ignition timing was then tuned.

The net result of all this work was extremely impressive. The final power output of the B16A/B20 engine was dynoed at a huge 212ps at the wheels. Using the standard 15% transmission/accessories loss, this works back to 249ps at the crank, F20C (S2000) power levels ! This represents one of the highest known verified dynoed power for an aftermarket modified 2000cc NA Honda engine, especially one that fits into the car's original engine bay.

The car is topped off with a proper EXEDY clutch system while suspension and braking also got attention. The overall cost of the car although extremely high but after considering all factors, was in truth commensurate with the extremely high uplift in performance of the car over the base version. This project represents an very respectable achievement and serves to highlight what can be achieved by good, experienced tuners.

WongKN
© Temple of VTEC Asia
March 2001