Ok i went to the dyno the first time and let some tuner tune my car(couple months ago). I felt the gains were minimal and the more i watched him tune my car i felt i could have probably created a better tune(afc tuner not used to tuning vtec). I have some questions. I was wonder what a good starting point is for the low cam to hi cam vtec unmatched fuel is. Also i was wondering what a good way to find the best vtec engagment point is for my car. Lastly whats the best a/f to aim for on a h22 is. I am wondering all this bc i got my skunk2 intake manifold on, and am waiting to get the greddy header then im going straight to the dyno.

 

Run it rich up until VTEC like 4%, then at VTEC progressively lean it out to 20%.

 

20 percent...good lord...you can do that at your own risk is all ill say to that

 

set ur vtec at around 4600-4700, see what worsk best for u on the dyno. dont worry aboutthe vtec unmatched fuel, leave that at 0%.

then tune the hi cam at about 13-13.5:1 AFR. but thats not a golden number, just see where it makes power, but keep the AFRs around there.

Don't worry about trying to lean out too much up top over 7k, cuz the cams run out of steam and the power is droppping off anyway.

 

Do you have aftermarket cams? If so, DO NOT lean out the top end.

As for VTEC engagement, and the two points, keep them close, and keep them at 4800 or higher.

 

on a vafc i had my best crossover at about 4600-4700. but if you got the time what i would do is set up crossover at like 6000, and get a baseline low cam dyno plot, and set your adjsutment points and tune itfromt he peak on teh low cam and below. where the low cam stops making more power is where to set crossover.

anyway without tuning id jsut leave it at 5k and leave it all at 0%.

I had followed someone elses suggestions and when i got on the dyno the first time with it i had SOLID 16:1 or leaner air fuel ratios.

 

you need to go to a dyno to do it right.

To find the best VTEC x-over point:

1) set the VTEC point to come on real late (make it real high RPM) do a run.

2) Set the VTEC point to come on real early (make it real low RPM) do a 2nd run.

3) plot the 2 curves on the same graph, now set the VTEC to were they intersect. This is your best VTEC x-over point.

To tune the fuel you will need a wide band O2 sensor while you do dyno runs. The prelude engine seems to like to run at about 13:1 to 13.5:1 for best power. By looking at the A/F graph during a dyno run you will know were to lean or add fuel as needed to achieve this.

Also if you have 1997+ car, don't tune part throttle, and only make changes for full throttle. Read my post here for why.

https://honda-tech.com/zerothread?id=976718

 

So does anyone mess with the vtec unmatched. I know it takes away or adds fuel right when vtec comes in. By looking at my old dyno plot it seems to get running. Otherwise you guys cleared everything up for me and i think i will create a good tune.