v00tecsi

I have a 2000 Si, and I just installed my VAFC. Everything seems to be ok, but I'm having a hard time with VTEC.

VTEC always used to engaged on my stock tach at 5500RPM (I know the stock tach is off, but its just a reference point) Now that I have the VAFC, VTEC engages on the stock tach about 200-300rpm late. This worries me.

As of now I have the vafc set at low to high VTEC 5500RPM and high to low VTEC at 5300. I would have to take VTEC down to 5300 on the VAFC to get it to engage at 5500 on the stock tach like it used to???

Can anyone help me out? As of right now I don't have any serious mods, that would cause me to want to change any of the settings. Does anyone know how I can set the VAFC so EVERYTHING is like stock?

Thanks

00MRSi

Don't know man. Like you said, stock tach is not the most accurate. Best bet is getting on a dyno and do some tuning. Make sure all your wiring is correct. Out of curiousity, why did you install a VAFC if you are basically stock?

v00tecsi

I'll be getting CTR cams in about 1 month, and I got a good deal on the vafc so I figured I'd get it a little pre-mature.

tooqwik1

did u solder the connections?

Al Bundy

well...since u got a vafc, set the monitor to the rpm's so u can accurately see your rpms. then cpmpare it with your tach

v00tecsi

Yes we did solder all the connections.

Also I have the VAFC set so I can see the rpms. The stock tach is off by about 1-200rpms from the VAFC.

The thing that bothers me is that before the VAFC VTEC always engaged at 5500 on the stock tach. So even though the stock tach is not 100% accurate, it still engaged at that point everytime. Now with the VAFC set at 5500, when VTEC engages the stock tach is reading just short of 5700.

I guess my real question is then, at what point does VTEC engage in the b16a? It can't be 5500RPM because thats where it is on the stock tach, and we all know the stock tach is off by a little bit. So I guess since the stock tach reads high, VTEC has to be lower then 5500???

Thanks again

CTR94Joes

I have a 99 SI swap and replaced the stock cams with CTR's full drive train, didn't need a VAFC. Vtec still ingages @ stock RPM's and I get a redline of 8100 RPM's. No ECU work done at all. Bone stock ECU, with headers & exhaust. I could see if you was gonna rechip your ECU, but your still running a stock one right. Check all your connections, but I think you should get it dynoed, just my .02!

v00tecsi

I'm going to get it dynoed after I get the cams...

I figured out the VTEC problem the other day.

There is an option on the VAFC that allows you to monitor both the VAFCs VTEC engagment point, as well as the ECUs VTEC engagment point at the same time.

The display looks like this:

VT-i
VT-o

VT-i represents when the VAFC engages VTEC
VT-o represents when the ECU engages VTEC.

Turns out that the ECU engages VTEC at 5300RPM according to the digital tach on the VAFC. After seeing this, I lowered the VTEC on the VAFC to 5300RPM. Now the VAFC, and the ECU engage VTEC at the exact same time.

Also guess what??? With VTEC set at 5300RPM on the VAFC, when VTEC engages, the stock tach reads 5500RPM on the nose...That was the exact same point it engaged before the VAFC was installed.

What does this tell me? It tells me that the STOCK ECU in a 99-00 Si engages VTEC at 5300RPM.

So many people including myself thought that VTEC engaged at 5500RPM (I'm assuming due to the unaccurate stock tach) in the si, but I still to this day have yet to see anything official to verify that.

As of right now, I still have the display on the VAFC showing both the ECUs VTEC engagment point, as well as the VAFC's. As of right now in every gear, and every engine tempature they remain identical at 5300RPM.

CTR94Joes

Glad to see that you found your problem.

EKB18BPR3

maybe stock is right and vafc is wrong...hehe i dunno, good luck dawg!