just have a few simple questions, i have been street tuning my gsr for a while now and have some questions. What i'm tuning with is a innovate lc1, crome p72 which was tuned about 6 months ago and a vafc(which i use to tune to find out how much fuel to add or remove before my friend reflashes my crome chip). Now i've added a few things to my car, and been trying to get the afr's straighthen out before i hit the dyno.

first question
Where do you guys position your wideband?
i have mine about 4 inches after the header collector. i have no cat and its just a test pipe is that fine? its at like the 2 o clock position.

would having the wideband too far or too close to the header affect the reading?

second question
My car is n/a i've been trying to smooth out my afr when vtec switches over. before vtec, afr are at about 13.1 then as soon as vtec hits, at about 4800rpm it leans out to 14.5ish and holds it there til 5200ish rpm then drops back down to 13.1-13.2 til redline. i've added up to 20% fuel and still no change in the afr's when vtec crosses over. I can get the afr's to fine everywhere but when vtec crosses over. How do i fix this?

third question
When making corrections with the vafc i notice that when i add more than 20% fuel, it would throw the map sensor code, and throw the car into some safe mode. Just wondering if any of you guys have this same problem? or know what i'm doing wrong?

 

1. The wideband should go in the first bung...usually at the end of the header, close to the collector. Where you have it is fine.

2. so you're tuning with both crome and a VAFC? why? Since you have crome, you should just be using it to tune. To get rid of the lean spike right after vtec, you need to setup breakpoints right where vtec engages, then go into the fuel map and add fuel right when vtec engages/wherever you're getting those lean spikes until it evens out.

 

The VAFC alters the MAP signal, hence the code since it's adjusting the MAP voltage signal to the ECU too high. It does not adjust the fuel output directly... Adjusting Crome based on your VAFC settings is a horrible idea. Altering the MAP signal by 20% via the VAFC does not add 20% fuel to where you currently are on the fuel map. Tune it in Crome alone and leave the VAFC out of it. Also, you'll have to have your VTEC set to the exact same settings as the VAFC in order to have everything work properly. That also means ALL VTEC settings must be the same in Crome as well, not different values based on different loads like it is stock.

I'd remove the VAFC or at least reconnect the VTEC wire to the ECU directly.

 

You have to add fuel right before VTEC to get the right A/F. With S300 I add fuel right at VTEC crossover on both the high and low cam maps and then alittle before and after that. For example, removing fuel at 4k will usually cause a slight lean mixture at 4.5k. This is one of the reason's why you should tune the lower RPM's first. This effect is usually greater at WOT due to fast RPM transitions, or so I've read. On what little street tuning I've done, I factor this in and it seems works.

 

But none of that applies, since the VAFC is controlling VTEC, not the ECU. That may mean in some situations he's actually still on the low cam maps until 5200, since the VAFC is making the switch before the ECU is. Connect the VTEC wire back to the ECU directly and see if it still does the same thing.

 

For smooth AFR transitions from low to high cam, I always tune low cam to 7000 RPM (dissable VTEC and set 7000 Rev limit), then tune the high cam with VTEC point at 3500 RPM. For street tuning, a happy median is 5000 RPM, but a dyno will tell you where the proper transition is for low to high cam.

I agree with the above comments, you should eliminate the VAFC before making any more tuning adjustments.