As the title says I have air fuel ratio inconsistency's. I have my car back on the road finally. I installed my friends wide band o2 sensor, and when we went on the high way and to see the ratios everything was looking good. We started doing some pulls in different gears which would result in having to back off due to lean conditions developing. There was spikes over 14 and up to 15 and it was still going. Lower rpm acceleration is good with the ratio hovering around 11 or a little lower, the lean conditions seem to develop around 3500 and on.
Now this isn't always so, as sometimes I can do a pull through the rpm range and it reads 10 to 11 right to red line. This is baffling my mind.
Could I be looking at a fuel regulator that is dying but still works sometimes, or some sort of poor connection to my secondaries, maybe the ecu is damaged?

The car:
Stock engine
Opened intake
Inter cooler
Non-sequential twins
Fully opened exhaust with silencer on the end.
Pettit unlimited ecu
Aeromotive 340 fuel pump.

 

Get yourself a aftermarket ECU and have it tuned, 14-15's under boost is a massive failer waiting to happen sooner then later....

 

Still running your air pump?

-Geoff

 

The stock ECU (or a pettit reflash) was never programmed to run non-sequential twins. With a parallel setup, your making more torque sooner then you would on twins so it needs more fuel even though it spools a lot later.

Also, did you follow the instructions and run 10 gauge wire from the battery to the pump (inside the tank).

It doesn't sound like he has and airpump but even if he did the pump is turned off under WOT conditions and anything over 3k RPM.

thewird

 

I do not have a air pump on my car, I used a pulley to replace it. As for the fuel pump I did rewire it up to the clip harness that was supplied with my pump which is not 10 gauge wire. I did a manual rewire from the battery, I'll go out and confirm that its 10gauge a little later today. I am going to assume that this little wire supplied with the clip is not going to be good enough for the power that's being drawn? I'm going to look into a power fc for my next purchase. In regards to the pettit reflash I've read in a few places that it was good enough for non-sequential setups(now I question this too) but, and as I said before not all the runs leaned out.

 

Finally got around to a bit more work, and testing. The fuel pump wiring is now 10 gauge as recommended right to the pump itself. Upon retesting we saw the same thing, some runs in 2nd 3rd and 4th were nice and rich between 10 and 11. And other runs would start to lean out around 3500 to 4250 rpm which I'd then back off, we would see mid to high 13 sometimes getting up into 14 before letting off.

I agree I need a new ecu but it still bothers me why some runs are rich to red line and other lean out early. Half way through testing we switched to another factory (supposedly reflashed) ecu just see what the air fuel raitos would be like and we saw the same thing. Some runs are rich and some are lean. Is there any theories on this difference? Is this something to do with the more torque earlier on as thewird mentioned. I want to get as much insight as possible regarding this information that I'm getting from my car so I can over all the possible issues even before getting a new ecu in the car. Thank you.

 

If you had a PowerFC, you could look at the sensors to see if they're were any issues or even datalog to see whats up. Your trying to make a pizza without the right ingredients. Your just going to be guessing until you have the right equipment.

It's not a Honda, you don't just swap ECU's and step on it after you've made modifications to the car. That is how people end up with blown engines.

thewird

 

Yes I'm waiting for a power fc, it just bugs me that some runs are rich and others are lean. I'm gonna stop before I wreck something. Thank you for the input so far.

 

Here's an update, I've had my power fc for a bit now. My friend was able to tune it for me, while I drove. My afr at idle and cruise is generally around 15ish, tip in richens up right away. WOT up to 7000rpm ranges from 11afr to11.6afr at aprox 9 psi for now. 7000rpm to 8100 rpm richens to 10 afr (could be richer as this is the lowest read out on my gauge). None of the ignition stuff was changed. 83% fuel injector duty was the max. Were going to raise boost next. Any suggestions or feed back? I'm very happy so far with how the power fc has worked. My friend has done lots of tuning in the past, but this is his first go at rotary, and his first go with power fc. I think he's done a great job. I made sure he knew that rotary should be in the 11.1 range.