GTPprix

OK I'm at my wits end with these things, so hopefully one of you can help I've got a 100% stock GTO with a ProCharger P1SC on it pushing 9PSI. The injectors that come with the procharger kit are 38lbs (L67 3800) and I'm currently at 23ms or about 115% duty cycle on them at 6000 RPM, not good.

Anyhow I have a set of flowmatched 60lbs Mototrons that I tried to tune in today and I'll be damned if I didnt rip my hair out. With the 38's in the LT's between banks are within 1% typically or dead even (pretty nice eh?) with the motortrons in at idle, the PCM is ADDING fuel no matter how I scale the IFR, and the bank to bank LT's can be as much as 6% off. Even stranger I had one bank (B1) hang itself at 880mv at idle, but as soon as the fan turns on or some other load is applied to the engine, the O2 swings again. Any input? I'm at my wits end here I thought for sure this would be an easy swap, to that end is there a competant tuner in SE Michigan that could help me out with this? Any input is GREATLY appreciated!

EDIT: My Fuel pressure is 62PSI at idle but drops to about 58 under load. I've also got a walbro 340 intank (Racetronix Prototype Sender).

pkincy

iTrader: (1)

Chris,

Forgive me if I ask the obvious, but first) are these high impedance injectors?

If they are the next obvious question is how the injector constant (opening/closing speed) is different from the stock injectors. And I presume you have made that adjustment.

The next question is more of a comment. Why don't you run the low impedance injectors with a converter box. They are fast enough that you shouldn't have much problem tuning them for idle.

Perry

GTPprix

Yup, high impedance and I scaled the IFR for them (I tried two or three different scales all "should" be in the correct area) nothing really helped. I'll try tuning these suckers one more time, then I'll probably go to a Low impedance setup. Thanks for the input!

GrannySShifting

iTrader: (10)

are the GTO vac referend or same as Fbody style? shoot me your file if you dont mind

pkincy

iTrader: (1)

Try increasing the injector constant (not the IFR) by 10% at a time.

I would guess those big inj are slower than stock and your idle pulse width could be getting lost in the injector constant.

Perry

Tomcat

Chris , your injectors are too big for what your engine requires at low rpm , basically you are commanding too small a injector opening and the injector cant accurately respond.
I use these injectors no problems on 383 but on a 346 I only ever use the 43lb injectors.

The other option may be to crank your pressure up with a rising rate and stick with the 38lb injectors , if you are using a 2 bar program like I am you can compensate in the IFR table for the fuel pressure rise and have a accurately mapped tune.

If you are determined to stay with the 62lb injectors you will need to drop you fuel pressure down and use a vacuum referenced regualtor to lower it further at low load.

dragginwagon

I think they are disc type, therefore they need to be tuned like a stock injector- adjust flow but leave time stockish. I ran into this last week- give it a whirl. I don't know hard facts on this, but it seemed to work as I tried to multiply by 1.5 or 1.8 and it wouldn't work. The injectors seem to be pretty fast.

Racetronix

iTrader: (2)

The Mototron / Siemens 60's are stable down to apx. 0.7-0.9ms. They are a very fast injector and very linear. Buick GN customers have these things running like a factory injector in a small 231 V6. Andy @ A&A and a few other dealers have these working well in LS1 motors. It all comes down to the tune. The GTO fuel system can not be converted to a boost referenced FPR type easily due to its factory configuration.

MIGHTYMOUSE

iTrader: (59)

shouldnt be a big deal.. i posted the right ifr table for this maybe 6 months ago with stock displacement and stock fuel pressure and stock injector offset.

Tomcat

We convert all our Blown or stroker monaro's to vacuum referenced fuel pressure , BUT we also use a surge tank and motorsport pump in the setup.
basicall the std pump only supplies fuel to the swirlpot , the std reg gets removed and we run a extra fuel line to the other end of the fuel rail - using the original as a return with a vacuum referenced pressure reg - it solves a lot of hot fuel and flow issues.

Looking at chris fuel pressure drop his pump is suffering anyway so it makes sense to fix that issue at the same time.

like I said we normally use the ractronix 43lb injector for a stock cube combo and their 62 lb for the bigger capacity , its not the injectors problem that it cant go to low enough duty cycle , if the injector opening gets too low the PCM thinks it cant control it at that low a opening so it goes into Single fire mode.
Single fire fuel delivery doubles the output fuel pulse and delivers
it each two revolutions. This is used to deliver pulsewidths too
small for the injectors to deliver reliably.

If (base pulsewidth<NPWL) then narrow pulsewidth mode is set.
If (base pulsewidth>NPWH) then narrow pulsewidth mode is cleared.

If (narrow pulsewidth mode set) then single fire is enabled.

Blackbird

60# motrons here.
zero issues.
just as easy to tune as my 30's, and 42's were.
I have lowered my base FP though, so I am sure that helps a bit.

MIGHTYMOUSE

iTrader: (59)

how did my ifr work i sent you?

SSkeet

He is right. I had these when my car was stock cam, stock heads turbo car. I also had stock FPR. I could not get them to idle at any leaner than 12:1

I blame it on stock motor and stock FPR. I think maybe if you were able to drop the FP with an aftermarket FPR, it may work for you. But with a stock setup, it will only allow you to go so lean and then the inj pulsewidth cannot come down any more.

I ended up ditching them and going with 42# which worked right off the bat...

slow

iTrader: (7)

making it vac referenced will lower the delta p of the injectors, that will help with idle.

I use these 60's all the time and they idle like stock, but its all ford vehicles with 39# delta P systems.

Ryan