Mods - 47 lb/hr injectors (brand new), Stock GMPP kit, stock pulley, full exhaust, 62mm TB. 300 cc/min progressive water/meth (20/80). IAT is in the s/c manifold reading air actually going into the engine.

Issue - The car can be perfectly dialed in, and relatively small changes will murder my AFRs. IMO, it's swinging too much. ~30*F change in ambient can move me almost a full AFR point.

Discussion - We have an injector constant, that works ok for injector upgrades on the smaller side. Once you go bigger than say 36 lb/hr or so, it starts becoming ineffective. It seems like having some sort of offset or low pulsewidth modifier would help the low end, but we just have a scalar. Here's an example. Using the correct injector constant for what i'm running (0.178 * 24/47 = 0.0909), my WOT low and high RPM VE was reasonable, but i had to run 125%+ VE in idle and coastdown tables just to keep fuel trims below +25%. Knowing this makes no sense at all, i dialed up the injector constant a bit to allow use of more reasonable idle and coastdown VE tables. Got it dialed in and thought all was good.

So now that we are in mid spring and temps can vary from 55*F-95*F from day to day, i'm seeing this isn't going to work. If i tune 11.9:1 afr on the 55*F day, i'll get <10:1 on the 95*F day. It shouldn't swing that much.

So my theory now is that using the higher injector constant for "faking" smaller injectors (leading to high PW across the board) is screwing with whatever IAT correction we do not have access to. Is it better to run the correct injector constant no matter what and deal with the lower pulsewidth issues via VE and/or injector pulsewidth vs vac tables? Or am I likely to have the exact same issue no matter how it's done due to the lack of an IAT fuel modifier/correction?

The other theory is since the air is almost always artificially warmer than ambient because of the blower, that an IAT correction just doesn't work If that is the case, i'll deal because having the added safety barrier of the IAT ignition timing modifier in case the water/meth goes out is valuable to me.

Honestly these are the biggest injectors I've ever tuned on a 1-bar jbody. I've love tuning and never had a real issue but this is trying my patience as it's a daily driver. I'm worried that winter will bring 15:1+ afrs when it's dialed in now for 11.9:1 if left unchecked.

So you are using a 1 bar map sensor? Not a 2 bar, or 2.5 bar?

Also what about a ECU swap and run the LD9 reflash?



FU Tuning

Yep, stock 1-bar MAP. I'd love to do the ECU/Harness swap and run the LD9 reflash. But on the other hand, 1-bar should work. Do you have reason to think the reflash would help the issue?

oldskool wrote:Yep, stock 1-bar MAP. I'd love to do the ECU/Harness swap and run the LD9 reflash. But on the other hand, 1-bar should work. Do you have reason to think the reflash would help the issue?

Because its already "faked", its a little easier to control larger injectors, also would give you true speed density....





P&P Tuning
420.5whp / 359.8wtq

Alone the line of what Ryan said.

With Roberts car and 650cc injectors. We had a time getting it tuned right, and was getting it close. We had to raise the VE offset up alot to get enough fuel. What is your offset?

Once we switched to the LD9 reflash it became easiy to tune it and get the results I wanted.

I have tuned a Eco on the 1 bar and a GM charger before no issues, but was either the 42 or 36 lb injectors, don't remember. I'm about to give it another try on another car. GM charger and 60lb injectors. This might be the last time I go this route depending on my results.



FU Tuning

Im running 80lbs stock pulley, one step colder plugs, full exhaust, 32psi on fuel regulator, i know i dont have the 2 bar sensor, its hpt im still having issues with the idle at 500 rpms they jump up to 700 sometimes plus my afr swings from low 14 to mid 15, at 10 psi of boost the afrs reads 10.1 either summer or winter im running just a regular intake but thinking about installing a cold air. I was thinking to as john to see if he can try to tune it better

Oh also if i turn the car off and try to turn it on again it wont i will have to press the gas a little i guess the tps reads it like that.

In your case i'd say the injectors are way oversized for what you are running power-wise. 80lb/hour on stock M62 pulley? That's over two times what you really need. So unless you have BIG plans in the future, 42lb/hr is more than enough. Also, over the years, i've become a believer that 10:1 afrs is not safe, it can be as dangerous as well. Even if y ou keep the 80lb/hr injectors in there, i'd get it tuned to low 11s at the richest.

I agree 10:1 is way too rich for a Ecotec.



FU Tuning

i do agree with you two i might buy some 42lbs and sell the 80lbs im not looking for nothing over 20 psi in the future just cams, rods, pistons, 8.9:1 compression

jair wrote:i do agree with you two i might buy some 42lbs and sell the 80lbs im not looking for nothing over 20 psi in the future just cams, rods, pistons, 8.9:1 compression

I would be interested in your 80lb injectors. I'm actually running 42's now, but have the need for bigger.



FU Tuning

jair wrote:i do agree with you two i might buy some 42lbs and sell the 80lbs im not looking for nothing over 20 psi in the future just cams, rods, pistons, 8.9:1 compression

there is no reason you need low comp pistons unless you're shooting for mega high numbers. I made that mistake on my first motor/first car



LE61T PTE6262 Powered

Quick update: Completely retuned starting with the correct injector constant. Took a shot at what the VE tables should look like s/c'ed, mostly leaving the low TPS or MAP rows stock-ish. Adjusted the IPW vs VAC table using a histo to log AFR error against that table. First impression is it worked great. I barely had to touch the low TPS VE, idle and/or coastdown. Basically dialed in WOT and low TPS in three flashes from scratch lol. Intersting note, my IPW table has ~1.3 in the leftmost column and tapers to 1.0 at zero vac. That is how far off the slope is on the bigger injectors (I guess!).

The true test will be if it holds up any better to drastic weather changes.

Funny i was coming to find this post.

I put a rough tune on this M62 setup. VE tables are all stock (except idle, taking some fuel away). Car has 60lb injectors. Put the correct constant in idles pretty well.

I used the IPW multi to add fuel in boost, and going to use the VE tables to fine tune.

OldSkool you said your at a 1.3 in the far left hand column? the 95kpa? That is idle. 0 is boost. 0 should be the far right, and 95 far left.



FU Tuning

Screaming for Mercy!! wrote:Funny i was coming to find this post.

I put a rough tune on this M62 setup. VE tables are all stock (except idle, taking some fuel away). Car has 60lb injectors. Put the correct constant in idles pretty well.

I used the IPW multi to add fuel in boost, and going to use the VE tables to fine tune.

OldSkool you said your at a 1.3 in the far left hand column? the 95kpa? That is idle. 0 is boost. 0 should be the far right, and 95 far left.

You are correct. That was the problem i was having - with the correct injector constant, i had to raise the idle and low TPS low RPM VE columns abnormally high. Now the idle and coastdown look normal. I cannot explain why i'm needing so much more fuel in the low vacuum areas with the bigger injectors, but the method i described was easier to address it. Like i said, nail in the coffin comes when the weather changes again. 70*F tonight here and dialed in, lets see what 95*F and 50*F bring...




Edited 2 time(s). Last edited Thursday, June 16, 2011 7:40 PM

I was running 36lb injectors, just simply ran a summer and a winter tune optimized for each season, worked easier for me that way rather than chasing it back and forth



1989 Turbo Trans Am #82, 2007 Cobalt SS G85

Seems like that's inevitable Matt. If that's the case, so be it lol

I've since tuned another s/c L61 in the meantime. 60lb/hr injectors and 3.1" pulley, 1-bar MAP. It required the same sloping of the IPW vs vac table to keep reasonable idle and low load VE mapping. Nearly 25% gain at full vac tapered down to about 5% gain in zero vac.

Weird. Are you on beta or 2.2? I noticed that my pcm did different things when I started flashing with beta rather than 2.2. Some things I liked and some I didnt. Having the IPWM vs VAC histogram actually work is the big reason I stick with beta.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
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I'm on 2.22. I couldn't stand the beta scanner the one time i used it. My IPW vs VAC histo works fine....

Yeah, for some reason I had a lot of issues with 2.2, like dfco either never being able to be turned off or never able to be turned on.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

I just wanted to update that I have tuned the M62 setup on 60lb injectors and for the most part very pleased with it. VE offset is stock. Car made good power at 236whp. Might make some small tweaks.

I have noticed that the idle will sometimes be right at 14.7, and other times it will be in the target AFR for WOT. Makes me think there is some other files we do not have access to.

Still car is very driveable and fun. Owner is very happy.



FU Tuning

Wow 263. What pulley size? And how did you keep the ve offset stock?

Mine occasionally drops to PE rich at idle. I think its my completely bonkers fuel pressure though, which will be fixed tomorrow the aem afpr next to me.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

no 236, not 263. using the inj pulse width vs. vac field. used ve for fine tuning.



FU Tuning

Also curious to what size pulley was on the blower. Nice numbers regardless!







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