So I rewired my fuel pump a while back and it's been running pig rich at idle ever since, like 11.5:1 and it stinks like gasoline.

How do I go about trimming fuel so it's a more reasonable AFR? What cells should I be correcting and what's a realistic correction factor to get it back to normal? What is a proper AFR for idle anyways?

I have also heard mention of a variable resisitor function, what's that about?

Thanks for any help here!

 

The Variable resistor is an item found on S4's which helps adjust the amount of fuel during idle. It can be adjusted to either more rich or more lean. The FSM details how to adjust it.

 

you kind of did this backwards. the scientific approach would be to put the old fuel pump back in, see what afrs its running, and at what rpm. then put the new pump in and just correct those spots on the map until its the same as the old one.

its pretty simple, just see what the AFRS are at idle, 1000, 1500rpm, 2000rpm, in neutral, and then maybe cruising, and then put new pump in.

 

I was referring to the Variable Resistor function in the rtek ECU, I looked it up and seems like the idle setup should allow me to lean out the fuel rather than trying to do it in the fuel table.

And it's the same walbro pump, just rewired for full 12v which results in rich conditions down low.

Thanks though.

 

Since you have a turbo then you have a fuel relay found on turbos which allows the fuel pump to receive 9 volts unless you place the engine under load which then sends a full 12 volts to the pump. It appears having the pump receive 12 volts all the time is too much for the engine to handle.

 

I thought rewiring fuel pumps was common place around here, at least it was a few years ago. I don't think it should have any negative effect on the engine itself, just running a bit rich right now. It seems like I am the only one asking how to correct the difference in AFR at idle after a fuel pump rewire...... is everybody else just running super rich or am I missing something here?

I will try to go through the idle setup tonight after I mix up some fresh pre mix and will update later on.

 

it is, i don't recall there being any functions in the ECU to lean out the idle without making cell correction. get out your stylus and do some finger pushups before getting started..

any modified car should consider rewiring the fuel pump, especially if you need that little kick of extra fuel pressure for more volume. but this also requires a way of removing fuel from low load maps.

 

I rewired my FD fuel pump after installing my Rtek but I kept the low voltage functionality and just ran a new fused wire direct to the battery and used the existing wiring to activate a relay.

I did notice it running a little richer, but not 11.5 after rich. Try redoing the entire idle setting procedure and adjusitng the VR as lean as the engine will allow. Also, consider rotating your afm slightly if that isn't enough.

Unfortunately the Rtek does not have idle/cruise control since they are closed loop so your options are somewhat limited. What size injectors and what fuel pressure are you running?

 

I'm going to be rewiring mine soon I just have an rtek 1.7 , I hope I don't get any issues.

Rotary > Pistons

 

Thanks for the input fellas.

I am running 720cc all around and should be "stock" fuel pressure, or I should say I haven't done anything to alter the fuel pressure other than the pump rewire.

I am going to give it a shot and see what I can do, I'll follow up here when I have something to report.

 

should get some input from the RTEK section too.

If you find the values too high after checking everything try 5 or 10% different values across the board..
My engine would run 12 Afr's on the RTEK 2.1.I had 750/1000.
I thought that was ok.

 

Yeah I tried the Rtek section but it's very slow in there. Figured there had to be a few members who have done the same thing. Gonna head out now to give it another try.

 

Ya,No offense to the guys that have an Rtek,but that was a reason that I went to another ECU.
I couldn't get answers.
I got a Haltech and now the Tech is a member and a vendor and answers the questions nice and quickly...lol!

 

Good news, was able to go through the Idle Setup and adjusted the TPS, RPM via BAC and finally set the Variable Resisitor value to around 3.4. End result is a nice smooth idle around 750rpm that runs about 12.5:1 AFR.

 

Sounds like an improvement!

Not sure how much adjustment you have left, but mine idles between 13.4 - 14 afr, after its warmed up. And that's running 4x750.

 

I have some left but that's about where it's the smoothest right now, it will stumble a little bit if I raise it into the 13:1 afrs. I will keep finetuning it as we get settled back in, just took it out today for a nice long cruise and it was very good.