DA6 Integra XSi

Our TOVA DA-Integra special series continues by looking at a DA6 Integra XSi Coupe. Lyonel is a Malaysian who has settled down in New Zealand. A friend of Tamati, (whose stock DA8 Integra XSi was the focus of our first article in this DA-Integra series) Lyonel drives a 1991 3-door DA6 Coupe. As the main photo above shows, Lyonel keeps his DA6 in very pristine condition ! But unlike Tamati, Lyonel has done quite a bit to his DA6. In this second article of our DA-Integra series, we study Lyonel's car to see how far bolt-on modifications can take the performance of the DA6 (and DA8) Integra XSi. However Lyonel frequents the race-track so his mods approach leans towards race-usage.

Bolt-on Power

At the moment, all of Lyonel's mods are concentrated on "bolt-ons", i.e. modifications that can be installed by simply removing the existing stock component and replacing the aftermarket one in. Bolt-on ideally also means no need for hacking, sawing, welding, etc. If there are any mounting and fitting, the original stock points and items will be used. The most popular bolt-on items for engine power are the open element air-filter, exhaust and headers, and air-fuel controllers. For handling & ride, bolt-on items entails replacing the stock shocks & springs as well as the re-sizing the wheels. Lyonel's mods are focussed on these items, but because of his leaning towards track-usage, he also did mods which sacrifices certain conveniences for street usage in return for a bit more power.

As described above, modifications to the engine for power increase has gone via the popular route of bolt-on mods. Favoured for their simplicity in installation, bolt-on mods exploits the restriction in air-flow that certain stock components has (in return for practicality and domesticity like noise level, etc) and enhances air-flow into the engine. The ideal complementary mod would be to use an air-fuel controller to adjust the air-fuel ratio for more power. Nevertheless, the stock Honda ECU is able to compensate for this increase in air-flow resonably well so we will see some power increase via this method even without an air-fuel controller. The mods Lyonel has on his car includes :

• - Custom cold air intake with open element filter (short-stack for winter)
• - original JDM 98 Spec ITR 4-1 headers
• - custom 2.5" exhaust with an N1 type muffler
• - PCV ventilation filter (mini K&N type filter)

TOVA readers are probably well aware of the superior air-flow of the open element filter. A 'cold air intake' is typically used to refer to a system of providing cooler outside air to the air-filter. A cold-air intake will use an extra long intake pipe that places the air-filter into the space originally occupied by the resonator. This placement keeps the filter away from the hot air inside the engine bay, thereby allowing it to ingest the cooler outside air. However, during winter where rain is likely, such an arrangement do incur slight risks of water being ingested into the engine so a short-stack is used. A short stake is really just another name for the standard metal-pipe/open-element-filter that is popularly used. A well-designed 'short-stake' will put the air-filter back into the original position occupied by the stock air-filter box just like Lyonel's car. For the DA6/DA8 (and in fact also for the corresponding EF8/EF9 CRX/Civic SiRs), this original position also benefits from the placement of the battery which actually helps to form a sort of heat shield between the filter and the hot engine. This preferable placement between the air-filter, battery, and engine can be clearly seen from the photo of the engine bay above.

The JDM 98 Spec Integra Type-R 4-1 headers are stainless steel items made of individual runner tubes for each cylinder. Indeed the stock item is quite comparable to expensive aftermarket versions ! However after the initial 160ps generation, B16As and B18Cs (including the Spec-Rs) uses a double wired O2 sensor instead of two individual single-wire O2 sensors. Furthermore, the block design for a B18C is different from that of the B16A (the B18C block itself is actually taller). So fitting the 98-Spec ITR headers required some customization work making it not a fully bolt-on item but it did work well.

An N1 type muffler is usually used to refer to a straight-through design. The muffler itself has a straight pipe running through, wrapped in noise damping materials. Nevertheless the exhaust gases flows right through the muffler so this type of exhaust system gives practically no exhaust flow restriction with consequent benefits in power gain. The downside however is noise; with no baffling or materials to directly dampen the noise, N1 type exhausts are very loud, 'extreme' models frequently loud enough to be heard across several blocks or streets ! For domestic requirements, such exhausts are strictly speaking not streetable. Go cruising with one in the car and conversation will be impossible not to mention anti-social too. But for track-use, N1 exhausts are the only way to go because they are able to squeeze every last bit of power from the engine.

Because of his fondness for track-racing and the good weather conditions in New Zealand, Lyonel also removed the entire air-conditioning system from his car. This includes removing the air-cond compressor, the condensor plus all pipings, etc. This not only allows some saving in vehicle weight, the parasitic power loss due to the air-cond compressor, irregardless of whether the air cond is in use or not, also contributes to a power 'gain' (or more accurately, a reduction in parasitic power loss due to auxilliary engine components). The particular mod works for Lyonel of course since New Zealand is famous for its clean atmosphere and year round cool weather. However, the air-cond system is a domestic requirement for street-usage so this mod really works only for race-cars or cars biased towards track-use.

Complementary Performance Mods

The performance of a car is not determined solely by its engine. The rest of the car is also crucial to its overall performance and like all knowledgeable enthusiasts, Lyonel pays equal attention to these parts as well.

First to come under attention is the suspension. Unlike later generation DC-Integra and EG-Civics, the DA-Integra is rather unusual in that it has a suspension that is not compatible with its "smaller" brother the EF-Civic. If fitted with EF or EF-compatible shocks/springs, a DA6 will ride so low that the wheel well rests on the tyres !

Lyonel fell back on properly designed suspension components for his DA6. Shocks are the popular Koni Yellow, adjustable for rebound only. Koni Yellow comes with a choice of spring perches, which allows a few levels of pre-tension of the springs to be set when they are installed into the shocks. Setting the pre-tension allows some mild adjustment of the car's ride height but more importantly allows the suspension compression rates to be adjusted as well. As expected from his track-usage, the springs are Neuspeed racing springs.

The suspension and chassis mods includes:

• - Koni Yellow adjustables
• - Neuspeed Race springs
• - Z-Speed front and rear strut tower bars
• - 16" Daytona Speed / 205/45 Toyo T1S for street use
• - 14" Volk Racing NRS / 195/60 G-Grids for track use

The strut tower bars are not installed in the car when the picture of the engine bay above was taken. Note the use of two separate set of wheels/tyres, one for street use and one for track-use. Stock tyres for DA6 are sized at 195/60 HR 14. This means the Daytona/Toyos street wheels used by Lyonel are a little bit oversized. But 16" rims will contribute significantly to the look of the car.

The cabin/interior of the car is also in immaculate condition and Lyonel have changed both the steering wheel and the gear shifter. The steering is what Lyonel describes as a "sport type", smaller in diameter and contoured for better grip. The shifter is a C's Sports Shifter; the shifting stick is shorter and the pivot point is moved, both leading to a shorter shifting distance. This effectively gives Lyonel a 'short-shift', standard issue for all super-cars and racing cars. The DA6 Integra XSi however does not come with a shifting mechanism designed for short-shifting, so a downside to the C's shifter is that shifting effort is increased. But in return, the shifting efficiency is improved since each gear shift requires less distance. In reality, this sort of mod for the DA6 can also be considered for track-use.

The Dyno Result

Lyonel dyno'ed his car during the same session as his friend Tamati, on the New Zealand designed Dyno-Pack dynanomater as explained in our previous article. So the conditions during the dyno-run will be similar to that for Tamati's car. To re-cap, it was raining at the time of the dyno, with ambient air temperature around 16-17 degrees Celsius. However I do not know if Lyonel dyno'ed his car with the bonnet closed or opened.

As explained in our first article on Tamati's car, the Dyno-Pack measures power through an electrical device mounted to the wheel mounting lugs. Although this method also measures power at the wheels but because the wheels are taken out for the dyno, it will also disregard the effect the wheels have on the measured power. I.e. the power loss due to wheel inertias are not measured in the result. As a result, after some reasoning, I thought it would be more accurate to use Tamati's result - 138ps at the wheel-lugs as the baseline for a stock 1G B16A when measured on a Dyno-Pack dynanometer. 138ps works out to around 14% power loss, so for Lyonel's car, I will use this value as the power loss benchmark instead of the 15% value that we have been using for Dynojet results.

This article is our first look at bolt-on modifications to a B16A engined Honda. As a result we do not have any reference figures to work out some power expectations for Lyonel's engine using theoretical calculations. Rather, Lyonel's car/engine will actually be the basis for us to work out a reference for expectations of power gains from bolt-on mods on a B16A in good working condition. In this case, in my opinion, we will get more of an upper bound for this reference level since Lyonel's engine has some mods that are biased towards racing use and not all owners who uses their car for purely street-use will be willing to adopt them.

The DynoPack result for Lyonel's car comes out to 112.6 kW which translates to 153ps. Using a 138ps baseline reference as explained above, this works out to a 15ps or 11% power gain. Using the 14% power loss value, 153ps now works back to approximately 178ps at the engine, 18ps gain from the 160ps spec'ed stock power of the 1G B16A !

While an ideal situation would be if Lyonel also did some fuel tuning using an air-fuel regulator like HKS' S-AFR or A'PEXi's S-AFC, nevertheless the DA6 PR3 ECU is quite flexible and would have largely compensated for the extra air-flow of the mods, leading to a very good increase in power. The use of the N1 straight-flow exhaust in particular, will really help in air-flow and therefore power increase compared to items which are designed to obey more domestic noise restrictions.

An interesting theoretical consideration will be to try to work out how much power gain removing the air-conditioning system have given. Even when not in use, there would be power drop due to parasitic losses from driving the compressor. How much parasitic power loss will be 'regained' by removing the compressor is an unknown factor. However I have personally witnessed an unusual case where a Malaysian Proton Putra (also sold as the Proton Coupe in the U.K.) was first dyno'ed without knowledge that the belt driving the alternator has snapped. Subsequently a new belt was replaced and the car re-dyno'ed again. On a Dynojet, the difference in power at the wheels was around 2ps. If we take this as representative, removing the air-cond compressor from the engine might probably also allow an extra 2ps gain (or more accurately, regain 2ps of lost power from the engine).

Conclusion

153ps measured on the Dyno-Pack works out to almost 178ps at the engine. All from a 1G B16A that is already 11 years old and with only bolt-on mods. This is a great achievement indeed !!

If we take a close look at all factors, three are particularly significant to Lyonel's very good power gain; the very favourable weather condition, the N1 straight flow muffler, and the removal of the air-conditioning components. These three combined can well attribute for quite a few of the large 15ps gain that Lyonel acheived.

Nevertheless, eventhough there are factors that worked in Lyonel's favour due to his biasness for track-usage, this case have allowed us to set a upper bound for expectations of power gains from a bolt-on mods package to the 1G B16A at 11% over the base reference power, which is a high figure indeed.

Wong KN
February 2002
© Temple of VTEC Asia
Lyonel has a personal web-site dedicated to his car at lyonel.8m.com/projectxsi.