OK guys I keep seeing members telling members that a 2.8" pulley and 42l. injectors are OK. Just like this.

Q. Ok nother easy question

will 42s work with a 2.8 pulley?

thanks

A. Yes i ran a 2.8 and 42lbers with a maf-t for about 4 months.

IT IS NOT OK!

Your Fuel injector duty cycle will be over 100% around 6,300 rpms.

Anything over 90% can easily become static.

Static means your fuel injectors have no control over themselves.
So having your injectors go static can lead to them getting stuck open or closed.

Yes, your car will "run" with a 2.8 and 42's. Not for long when you keep going static.

There have been countless screen shots to prove this.

If you want to run a 2.8" pulley buy at least 50lb. injectors and get tuned. That's it!
You can get 50lb. injectors here. http://www.cobaltperformanceparts.co...ion-p-215.html

For those who need to see the proof again.

 

An interesting post... good graph too... so, what about a 2.9 and 42lb injectors?

 

Now that is perfectly OK even with the GM stage 2 tune.

Your fuel injector duty cycle will be about 82-84% at 7,000rpms. That's perfect.

You just don't want to touch that magic 90% IDC.

 

exactly, i had to retune my car because i went with an injen intake due to fitment issues with my jbp, as soon as the intake was installed we did a test pull, its amazing how much an intake can change eveything, i was running mad rich and idcs were at 94!
after fine tuning meister got it down in the low to mid 80s, and we also proved that my 3 inch intake dosnt make more power than the injen, the numbers were almost identical(every day is different at the dyno) so if anyone wants to keep the 42's in the car for a long time go 2.85 smallest(tuning may be required) if you actually care about your car

 

Haha, I've been trying to get this point across for a while, but you get a lot of people who say "I did this, its ok, you just lose power at higher RPMs" and bullshit of that sort.

They go on to tell you how its ok because your injectors are spraying all the fuel they can, therefore the car isn't running lean. However, they neglect to tell you that a injector duty cycle of 122% is bad, and that having your injectors go static can lead to them getting stuck closed or shut.

 

Thank you for chiming in distillion. I just want people to know the truth.

Bad advice seems to be the new plague of .net

You are exactly right distillion. A 2.85" pulley with a custom tune (Not GM's Tune) is the smallest you want to go.

Exactly cds00bsmg. I hope people wake up and realize what the real deal is.

 

no worries CT, anyone else,check my sig id say thats pretty good for alot of bolt ons, 2.85 pulley and 42's with tunning

 

Yea, I was running 42lb/hr injectors with a 2.8" pulley and to what the image above shows is exactly what I read on my Aeroforce... Needless to say im running a 3" pulley, I may buy a 2.85" soon..

 

so with a 2.85 with the 42.5 inj. would you still run into 100% duty whenever you get near the 7,000 mark

 

ok so 2.9 and 42s it is now

thanks for the good info

 

um if im not mistaken IDC can be through the roof if you tell the car to put out a certain amount of fuel at a certain rpm. If you tell the car to dump fuel it will the whole time and the IDC's will look crazy. I'm not saying your wrong but if you had a wide band read out that reads some outa wack a/f with that nice HPT print screen it would make more sense to me. I'm just saying it seems like its possible to have 42 pounders and a stock pulley but if you have the car dumping fuel and your IDC's are in the 80's or 90's but your a/f's are in the 10's It doesn't mean your outa injector. Hey i could be wrong though would like some feed back on that.

 

Here we go again ...............

 

Que?.............

 

All I know is that I have been running a 2.8" with 42's for a couple months now on a custom tune. Everything was running great, no KR at all, then the weather got cooler. It's still getting into the 80's around here, but when I recently went to Atlanta, it was dropping below freezing at night. 4-5 KR above 4k rpm's, sometimes even 2-3 KR with light accelleration at only 2500 rpm's. Then there was the P0103 (lean) that I had to keep clearing. Sure, it doesn't help that when my car was tuned it was 98 F in the shop, but I'm not taking any chances as this is also my daily driver. I've got 60's going in with a new custom tune this Tuesday, hopefully drivability won't suffer too much.

As some mention going with 50# or 55# injectors, are there any good recomendations, would they make a better difference than the 60's I already have considering that I don't plan on going any smaller than a 2.8" pulley? (don't want to machine the snout for a 2.6" and 2.7" isn't going to be enough of an increase for me to drop money into a another hub and pulley plus installation)

 

hrmm new question

how bout

44 injector with the 2.8 would this work what do u guys think

 

I have tuned and retuned a 2.85 car, with the GMPP 42lb Injectors. When the car was pig rich, the HIGHEST the duty cycle ever got was 93%. After leaning out the AFR to my commanded of 12.0 the duty cycle dropped to below 90%

There is no leaning out of the air fuel or any other signs of fuel system components being maxed out

 

If your car was tuned properly, air temperature or air density should not affect your tune. Unfortunatly, most GM tuners are still working backwards and yes, air density will drastically change your tune

The code you are getting is because of a lean mixture at idle and part throttle, and has nothing to do with what is happening at WOT. Your 02 sensors are not even being used for WOT fueling. Your 02 sensors are having to over compensate beyond their normal thresholds to try and achieve commanded STOICH.

 

hey miester i asked u something on ur fender forum lmk

 

Ok so let me get this right i have the stage 2 with the pulleyboys 2.8 and your telling me that its ******* up my car with the stage 2 injectors....so then tell me what i should do..who sells 50lb injectors

 

So what is the smallest pulley you can go with a GM Stage 2 injectors and programming? 2.9? 2.85?

 

The GM calibrations, even from the factory are crap. First thing I would do is get a custom tune from someone with a good reputation. I would like to do a 2.8 with the 42's and see how close it gets to 100% IDC

2.85 is the smallest I would go with 42lb injectors until further testing

 

2.85

like meister said

 

Yeah I agree with you. I would like to see the PCM commanded AFR, it could be commanding 10.8:1 AFR and hence a 100% IDC....

You can't make a statement like this without a WB O2 to back it up. I am running 42# injectors and a 2.85 and I get it down to ~11 to 1 AFR which is plenty fuel. Piston protection and COT will drop your commanded AFR by several points and in turn to add to the IDC to keep the engine running rich and safe.

 

I do a lot of things different in my tunes and we are no where near 100% IDC with the 42's and a 2.85

I have a WB02 on every car I tune, so I know there are no signs of running out of fuel. If you are getting anything other than your commanded air fuel your tune needs to be redone

 

Just FYI, you can do a 2.8 and 42's and you car will run fine. There are plethora of RL's that have run this setup and run it fine from the second they got there car 2 years ago. Just letting some guys know that want another opinion. And from personal experience, I have run a 2.7" and 42's for more than 7 months and kicked alot of cars asses doing it. Car ran beautifully and took it up to 7100 all the time. Wideband looked great cept for the last couple rpm the car would richen itself up. So just FYI:

2.7" pulley and 42lb. injectors is REWARDING! VERY, VERY, REWARDING!!!