Hey guys,

I'm new here as you can see. Anyway, I have a 2001 4Runner that I have supercharged w/ the 7th injector kit. She runs great for the most part. I have a AEM Wideband so I know exactly whats going on as far as AFR. This is where my "problems" begin. Under normal driving and moderate acceleration (without much load) it stays within 14.4-15, so basically ideal. However, when driving at low RPM ≈2250 and higher speed ≈45mph and I give it enough gas to go into boost, the ARF drops to the low 13's sometimes even into the 12's. After letting off the gas, the AFR spikes all the way to 16+ and sits there until the ECU figures out what is going on, at least 5-10 seconds. My theory is that, in boost, the 7th injector starts firing, causing the AFR to drop, then the existing injectors fire less to compensate for the 7th injector. Then after letting off the gas, the 7th injector stops firing and the existing injectors run lean until the computer can adjust after the 7th injector stops firing. So here are my questions:

1. Is this a significant problem that I should address ASAP?
2. Any ideas where to start on correcting this issue?

Thanks guys! Any input is greatly appreciated.

 

where is your boost at during those times?

 

Boost is near full, 6-7psi. After I let off, it goes back into vacuum.

 

the urd system kind of sucks in my opinion. It really only works for wide open throttle. Closed loop enrichment will always be fought by the ECU. In wide open throttle you want to be at high 11's for AFR's

 

You are more or less right. like was said above in closed loop the ECU will try to maintain 14.7:1 AFR. Without messing with the O2 Sensor signal it is almost impossible to really change that. If you give it more gas then it will go into open loop and then the AFR's should be stable at the tuned AFR.

When you let off the gas the spike in AFR's is perfectly normal, it is simply the ECU going into fuel cut mode to allow for engine braking. No worries there. I wish I could tune my vacuum areas to run at ~16-17:1 all the time frankly, improve MPG. Only in boost do you need richer AFR's.

This is why I prefer meth injection over the 7th injector, the tuning resolution is about the same on both but with the meth I don't have to worry about the closed loop AFR's as the extra octane more then makes up for the lean mixture. But the price for that is you need access to bulk pure methanol.

 

Meth. It's what's for dinner.™

 

Awesome, I pretty much figured this was the conclusion I would come to. Just figured I would cover all my bases and get some input from others. Thanks.