S2000 Turbo
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From: You wish
Tanqueray,
Every system is different, but let me describe the mechanisms by which gains could be made with the Comptech system using aftermarket management and an intercooler.
First, on the intercooler - At 6 psi, a typical compressor section will add at least 40-50 degrees of charge temperature (something like an Eaton blower will add closer to 70-80 deg). That means that compared to ambient you're losing 4-5% power. With a good intercooler you could get intake temps back to within 10-20 degrees of ambient. At the flow and boost levels used here, such an intercooler would probably cost less than 0.5 psi in charge pressure. The upside is that you could regear the system to compensate, and in reality run more boost since the cooler temps reduce the possibilities of detonation. But even if you just ran the same boost level, you could expect to see another 10-12 wheel hp peak. Up the boost to 7 psi and you could see an additional 15 hp.
On the engine management, you probably wouldn't see much in the way of peak gains, but you could see significant midrange improvements. I have an Eaton supercharged Honda that made an additional 5 hp peak with engine management, but picked up nearly 20 hp in the midrange with proper tuning. I suspect that most of the engine management gains would be realized pre-VTEC. An additional benefit would be better drivability, more reliable fueling, etc.
This ties into your question of why not more boost sooner? Comptech reps have posted here that they tried running more boost sooner, but ran into detonation issues and didn't pick up any power. This is almost certainly an artifact of a timing curve set up for a normally aspirated engine. Such engines, especially those that use a single path intake manifold, go through some resonance effects at different rpms. One usually occurs in the 4000-5000 rpm range where power will drop off. Because cylinder filling and mixture motion aren't good here (relative to other operating ranges) timing has to be advanced to optimize power. When you add boost, you eliminate a lot of these resonance issues and the timing curve has to be remapped to a much flatter curve (boost dependent).
Oh, and BTW, other VTEC cars with turbos still get a nice hit when VTEC kicks in. It's just that there's a lot more before and after VTEC than stock :-)
UL
Every system is different, but let me describe the mechanisms by which gains could be made with the Comptech system using aftermarket management and an intercooler.
First, on the intercooler - At 6 psi, a typical compressor section will add at least 40-50 degrees of charge temperature (something like an Eaton blower will add closer to 70-80 deg). That means that compared to ambient you're losing 4-5% power. With a good intercooler you could get intake temps back to within 10-20 degrees of ambient. At the flow and boost levels used here, such an intercooler would probably cost less than 0.5 psi in charge pressure. The upside is that you could regear the system to compensate, and in reality run more boost since the cooler temps reduce the possibilities of detonation. But even if you just ran the same boost level, you could expect to see another 10-12 wheel hp peak. Up the boost to 7 psi and you could see an additional 15 hp.
On the engine management, you probably wouldn't see much in the way of peak gains, but you could see significant midrange improvements. I have an Eaton supercharged Honda that made an additional 5 hp peak with engine management, but picked up nearly 20 hp in the midrange with proper tuning. I suspect that most of the engine management gains would be realized pre-VTEC. An additional benefit would be better drivability, more reliable fueling, etc.
This ties into your question of why not more boost sooner? Comptech reps have posted here that they tried running more boost sooner, but ran into detonation issues and didn't pick up any power. This is almost certainly an artifact of a timing curve set up for a normally aspirated engine. Such engines, especially those that use a single path intake manifold, go through some resonance effects at different rpms. One usually occurs in the 4000-5000 rpm range where power will drop off. Because cylinder filling and mixture motion aren't good here (relative to other operating ranges) timing has to be advanced to optimize power. When you add boost, you eliminate a lot of these resonance issues and the timing curve has to be remapped to a much flatter curve (boost dependent).
Oh, and BTW, other VTEC cars with turbos still get a nice hit when VTEC kicks in. It's just that there's a lot more before and after VTEC than stock :-)
UL
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From: El Segundo
Well today I meet the gentleman that owns the Turbo S2000 that Atomic Performance did and it is still not working. He said that it currently is not hooked up and that they are working on it. He also said that it was their first one so I will wait until someone comes up with good kit. All I know is that I did my first 6500 RPM clutch drop and this car is pretty fast. I think for now I am going to lose some weight on the car and myself to get performance gains. Sending my car to Thermal Research in a couple of weeks for the exhaust, I will tell you what it is like when I get it back.
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From: You wish
I'm running a Zdyne on my CRX. Zdyne does make conversion harnesses for OBDII to OBDI, so I need to pull out my ECU and compare it to the connectors they have on their website, maybe I can just swap my Zdyne into my S2K :-)
Also, turbo cars actually don't mind overlap nearly as much as supercharged cars do. In part because the turbo increases pressure at the exhaust while it increases pressure at the intake. Thus, overlap will not necessarily bleed as much charge as you might think. On an SC though, exhaust pressure is no higher while intake pressure is much higher, meaning you can blow charge right through the chamber.
VTEC cars actually do quite well with turbos and stock cams.
UL
Also, turbo cars actually don't mind overlap nearly as much as supercharged cars do. In part because the turbo increases pressure at the exhaust while it increases pressure at the intake. Thus, overlap will not necessarily bleed as much charge as you might think. On an SC though, exhaust pressure is no higher while intake pressure is much higher, meaning you can blow charge right through the chamber.
VTEC cars actually do quite well with turbos and stock cams.
UL
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LB 350Z
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Aug 21, 2003 09:34 PM