I guess this is for those of you that have dual widebands installed in your cars.I am wondering how many of you out there are having to trim fuel on one bank or the other while in boost?

I find that in the low boost, low RPM's I have to trim up to -5% on bank one to get a nice flat 11.5:1 fuel ratio through out the RPM range. At 10psi and 4500-7000rpm I only have to trim -1.5%.

 

I had to add about 5% to bank 2 for equal A/F at 8psi. This causes idle/part throttle to be off a little more than usual but in closed loop the ECU corrects for it no problem.

I assume this is really only an issue for DE's because of the way the intake wraps around and air favors one set of intake runners.

Another thing to consider is cyl. 1 and 2 get less air than 5 and 6. This means you should also make some front to rear corrections but I haven't had a chance to really dig into that, would take a good plug reader.

 

sasha, you know mine are off because you've seen my logs.

Mine tends to separate during boost building but once i'm at my desired boost level they are usually dead on.

My vac map it seems that i'm about 5-7% different between banks though. I've just left it alone and not tried to mess with it. During the boost thing i just adjust the leanest bank into a safe range and just let the other bank be slightly rich.

Under boost it's bank 2 for me that is lean also.

 

Yeah good think for the Haltech and the ability to adjust banks to avoid disaster. This is why I do't like to run on the edge like some other guys here.

I also just did an exhaust leak test. Pressured up each bank to 40psi and found a leak on the header/engine bank 1 flange. It is a very small leak, but still a leak. Can't hear it under 20psi of pressure, only once it gets up to the 30's. At this point I don't think it is a problem.

 

Uprev can trim banks and individual cylinders as well.

 

How? Did you use a leak down tester with the exhaust valves open? Have you not had a chance to re-snug your headers since you installed them, or is that virtually impossible with the engine in?

 

I plugged the two bolt flange after the two banks merge. Then, I drilled an O2 sensor plug, tapped it to 1/4" NPT, and plugged the compressor hose in. Very simple, and you can easily hear/feel where the air is escaping.

The headers did get re-torqued, but maybe I missed a bolt. It is a PITA but can be done with engine in place, and proper tools.

 

haltech does individual cylinders for fuel and timing. It's pointless unless you have 6 widebands so we only adjust per bank and not cylinder.

Re-torqueing the headers in the car is a PITA. I haven't done mine yet but I did my headers with the engine out and torqued everything properly and i've done the headers a few times and i still have the same results in a/f every time.

 

Not entirely pointless, but perhaps a bit overkill. You can shut down at the top of a boost pull and read the plugs. I just haven't had a chance to do it yet.

 

screw that. we do that on our MX bikes but that's just a single plug. To get a true reading you should start fresh with new plugs each pull which would get expensive in a 6 cylinder. I'd be more inclined to spend the money on 6 widebands than do it the old school way

 

I have never had to adjust the bank trims, FWIW.