Does Apexi build a VAFC for the S2000? What is the factory V-Tech point set for 2000-2 S2?

 

the stock VTEC point is 6k. Lots of people have VAFC in their s2k. check s2ki.com for install pics.

 

wurd!

 

The most effective point is 5600 rpms I believe. Honda just didn't make it like that because VTEC is harder to feel when set at that point. A guy on http://www.s2ki.com did research and found that 5600 was the most effective point for gains in the car.

 

I'll clear a few things up.

VTEC engagement/disengagement on a stock S2000 is variable. The ECU makes a value judgement based upon throttle position, manifold pressure, IAT, and engine speed before sending signal to the VTEC solonoid. For example, some owner have experienced VTEC engagement at 7,000rpm in high altitudes.

The VAFC does not make a value judgement. The VAFC will only use a value you've programmed. Which is pretty neat right?

Actually no.

The VAFC allows you to modify the fuel map for a given RPM, but it does not allow you to modify the ignition maps. If you are following me you see a recipe for disaster.

Remember the ECU will signal the VTEC solonoid to engage at a variable engine speed value AND switch to the VTEC Fuel/Ignition Maps. The VAFC will signal the VTEC solonoid at a preset engine speed. Uhh oh!!!

Why is this bad? How about an example?

5600rpm
VAFC signals the VTEC solonoid. Well at 5600rpm the ECU hasn't decided to switch to the VTEC fuel/ignition map yet so... less fuel, and retarded spark. (Leaner Fuel map, and mismatched iginition timing)

6000rpm
VTEC solonoid is still engaged. Throttle Positon looks good ECU switches to the proper maps.

7000rpm
looking good but there is a slow car in front of you so you ease off the gas.

5900rpm
Still above the preprogrammed 5600rpm value for the VAFC: VTEC still engaged. Given the throttle posistion though, the ECU has swithed back to the non-VTEC fuel/ignition map. Less fuel, incorrect timing again.

Will this blow up your engine? Probably not, but I'm not saying it won't either. While you could run the mixture richer for a safety margin, you'd be obviating the whole reason you installed the VAFC. You have no way to modify the ignition maps becuase those are still under the control of the ECU.

Forced induction S2000's are at even greater risk in these mismatch conditions because they tend to be more prone to detonation because of the inherent modifications.

 

I see this arguement alot but don't quite understand where it is actually coming from. Looking at an actual ignition timing map there's little to no difference between the non-VTEC and VTEC range at WOT. It mainly goes up gradually by RPM and then stays at a specific value below VTEC and then stays pretty much the same after VTEC. At least it's like this on Integras, does anyone have a map of the S2000 ECU?

Less fuel isn't a problem, that's what the AFC in VAFC is for. Add fuel until stock VTEC engagement, pretty basic stuff. You'd want to tune the corrections on a dyno with a wideband to get the best settings.