So, it seems to make sense to engage VTEC earlier for performance, yes? I've seem that around 4700 seems to give fine results.

To my understanding, you need a fairly complicated system to do this. But wouldn't it be something relatively easy to do on it's own? I'm a layman in this area, so my idea probably won't make sense. Anyway...

The VTEC solenoid needs to see a number of requirements be met before it makes the switch. One of them is RPM (though I assume it's really the ECU that sees this and sends the signal).

RPM should be monitored by a signal which is either a voltage range or a series of pulses, I would imagine. Couldn't something be put in-line that would magnify the signal to make the solenoid think you are at a higher RPM than you really are, therefore engaging VTEC earlier?

The big problem here would be that the info probably goes through the ECU, and tricking the ECU into thinking that you're at the wrong RPM could mean other problems like wrong fuel delivery, fuel cutoff, etc, etc, etc.

So someone please explain why this wouldn't work and how these systems really function if you don't mind - that'd be great! Or maybe explain how the aftermarket systems do it to see if that one function could be emulated in a more simple fashion without the full tuning ability, etc.

Now that I'm thinking... didn't they used to make VTEC controllers for Integras and other cars? Can those be used on the S2000?

 

This is what I believe and is only my opinion. Engineers at Honda designed this engine so that vtec kicks in at a certain rpm for optimal performance for stock configuration. The engine actually performs better without vtec at lower rpm, and where the vtec is configured to kick in is probably the best for stock performance. Setting the vtec to kick in at a lower rpm is kind of like removing the butterflies on the intake manifolds, it takes away low end performance. I could be wrong; maybe they just set it at 5 thousand something, because they do not want it to kick in during normal highway driving. My little brother has a B series engine with a Type R tranny and a modified vtec engagement. His vtec kicks on and off when driving on the freeway at 75-80 mph.

 

Yeah i wanted to do that, but with 4.77s at 80 im at 5 grand. So its a no go here.

 

vafc will work for the s2000, but it will only control Wide Open Throttle scenario's (so set the TPS above 80%), anything below that and the ECU will adapt to your settings for partial throttle so it's useless.

You can lower vtec and lean out fuel. I'm not sure how well it works with lowering vtec but with a Test pipe you can try bring it down 400-500 rpm. I know Ballistic has it around the 5000 rpm mark with thier new Greddy ECU pre-tune.

 

VAFCs work on s2ks...very good mod on an AP1 to lean the car out.

For you though, you won't see as much gain in an AP2 with tuning the afr. But the VAFC will definitely let you lower your VTEC engagement point.

4700 may be too low...it really depends on your car...every car likes a slightly different VTEC engagement point. A couple pulls on a dyno can help find the sweet spot on your car.

Other options are a Greddy eManage Ultimate...which will also let you tune the timing and afr. There is a little headroom left in the AP2 with some timing adjustments. A good tuner might be able to coax another 8-10whp with a eMU or even a full stand-alone like the AEM EMS.

 

All these cars getting the Hondata Toda Reflash seem to be looking pretty good on the dyno with a 4200 VTEC. Even the ones without a header. Maybe Honda only did it to be conservative? To my understanding it won't kick in at highway speeds under its normal engagement unless you are really on the gas?

 

There's no question that even on a dead stock car the VTEC can be lowered about 500 RPMs with very favorable results. I have no idea why Honda put it where they did, but that's the reality of the situation. I think sometimes people give "Honda Engineers" a little too much credit. Sometimes things are done as a business decision and sometimes things are just skipped over for expediency. For example the TSX cam profiles (not the cams themselves just the lobe profiles) were directly copied from the AP1. There's no way you can tell me that they just happened to have the exact same profile to optimize performance and MPG for two motors that are quite a bit different. It was expediency. I'm sure they put thought into where VTEC was set, but it may not have been 100% about peak performance.

 

The only thing a car needs to run the toda reflash is a testpipe. A better flowing exhaust helps to. Nothing else is needed, but some power may be gained from a header and intake.

 

rpm isn't the only factor. you can drive at 6500 rpms and not be in vtec. There are load parameters that need to be met aswell, and throttle position requirements.

 

also, ive personally seen my vtec not engage until 6500ish RPMS at WOT when i was stationed in the mountains in utah. i come back home to sea level, and vtec is back to 6000 RPMS like it was before i moved out to the moutains. no, im not going crazy i studied this happening very closely on numerous occasions.

so. altitude/air pressure may possibly be another factor????????

but. vafc/vafc2 = cheap and easy way to lower your vtec. they are cheap now days.