So you guys know about my E85 setup but I have recently added the GMS3 PCM and installed a DynoTune Nitrous kit.



I noticed that it takes a while for my ARF to get to normal once I start spraying. My GMS3 PCM is configured to start spraying at 3750rpms. You can see in the this log that my AFR gets down to where it should be in PE before the nitrous sprays. Once the nitrous sprays, my AFR jumps up to almost 14 and takes about 600 rpms to get below 12 where they should be.

Here is a screen shot of my log.


Is that normal for the AFR to take that long to get back down?

I know I already pushing this fuel system pretty hard with my 2.6" and E85 setup. My feeling is that the fuel pump can not keep up with initial increase of demand in fuel and that is why it goes lean. Then it takes my pump 600rpms to "catch up" with the new fuel demand.

My thought is this is common on Wet Nitrous setups but I am concerned with how long it takes for the fuel to catch up. If it was 100-200rpms I would not care. But 600rpms seems a bit long.

Thoughts?

 

Fuel pumps don't "catch up". They just flow constant. So no.

 

yea a lean spike is common on a nitrous setup, try commanding really reach right before the nitrous hits and taper it out to the ideal a/f over the 600 or so rpms

 

So how would you explain how the afr gets back to normal?

Is it normal for the spike to last 600rpms?

I could do that but then I will run rich when I am not spraying. But it is normal to start a little rich down low and lean it out up top. So that is a good suggestion.

My thought is that the pump can not keep up with the initial demand of fuel once the nitrous kit is fired. So it is not only effecting the amount of fuel being delivered from the nitrous fuel nozzle but it also effects the amount of fuel being delivered by the fuel injectors.

I think I am going to install a FP gauge at the end of the fuel rail and see what is going on.

 

bump.

 

Im not running e-85 but ive had the same thing happen to me when i spray. Your running a wet kit right? im curious what is your jetting size and how big a shot are you running?

 

needs a shorter fuel line. nitrous hits at 1000+psi. fuel at 58psi. i was having bad lean spike problems. i bought a shorter fuel line after the solenoid and all was well

 

Wet. Yes.

I am running 50 shot nitrous nozzle (.034) with the equivalent of a 75 shot nozzle of premium fuel (.024).

I can't run any shorter lines in relationship to where the solenoids are mounted. My only option would be to mount the fuel solenoid on the injection nozzle. Even then, I am only saving 2' from the pluming.

Does 2' make that big of a difference?

 

my fuel line was 5 inches shorter with the new one

 

And 5" makes that big of a difference?

 

it did in my system. removed the lean spike of ~14.0AFR down to 12.5 and then richened up quickly to my commanded 11.8

 

If you can't shorten your fuel line, lengthen your nitrous line.

 

yes, and if you have a returnless fuel system you will NEVER get rid of the lean spike, 600rpm is an eternity... just make sure you have extra timing pulled there and you'll be fine. its not the lean spike that kills the motor, its timing that does. if you want to be safe about it you need to run a stand alone fuel system. NitroDaves sells them for camaros and what not for about 700 bucks... 1 gallon fuel cell with a pump and regulator.

also, why so rich? i'd be shooting fo 12.2:1 on nitrous.

 

shorter fuel line.

 

Fuel cell for nitrous in engine bay, IMO.

 

Very Interesting.

I CAN but I don't want to. I have such a CLEAN install!

That's the plan. I think I am going to make a bracket I can mount to the holes for the stock HE filler neck and mount my fuel solenoid under the inlet neck on the SC.

Yeah I don't think so...



Thanks for all the help guys.