Well I started dyno tuning this week with some help from some friends because I haven't done it before.

Little back ground. 383, 9:1, 50# injectors, 15psi ATI D1SC, MAF on blown side

I get to about 4600-4800 rpm and the MAF locks at 504grams/sec and right then the injectors stop at 21ms or so.

I wouldn't think that the injectors would be at 100% by that point, hell the car is only making 370hp at 4600rpm and 430ft-lbs of torque. (Still have a lot of tuning to do) So I wouldn't see how the MAF would be locked and the injectors too. I am getting belt slip and the blower is only putting out 9psi of boost at this point too, but on LT1 Edit everything just kinda stops and she starts leaning out really really badly, the a/f was going from about 11.8 to 12.5 to 13.2 to 13.8 and then I just shut it down.

What are you guys doing? I know the car has a lot more in it I just don't know how or what to do. We just starting manually putting in more fuel in the power enrichment mode at that point and it still wasn't helping.

We did take off the ATI inline pump and are just going with the 255LPH high pressure in tank unit because we think it was becoming a restriction so maybe that might help but I still don't know what to do about the MAF and Injector problem.

 

The MAF table can only go to 512, that's it,
no more, and I doubt your really moving that much air, but who knows. I don't know a work around for that besides speed density.

------------------
Adam in Hurst TX
95TA M6 Borla Cat Back
!TB,!MAF,Ripper,Tuner Cat
HP160, !UD pulley,CAI,
24# SVO, 2000 console
Best 1/4 13.79 101.4

 

Well I know a few people maxing out the MAF sensor on forced induction cars. I have a friend that did a TT LS1 that did, and I'm sure that the ATI D1 can move more than what it can read I'm just not sure what to do about it, especially the injector problem.

 

There is a guy running a 383 with a 15# ATI in the Pacific Northwest forum on this site. His name is 97TA-WS6-Con. His tuning was done by OneFlyn95z28. I know they were playing with the tuning for quite sometime and finally did some dyno tune sessions. Try emailing them or posting on the Pacific Northwest forum and see if they can offer any tips. Good luck.

CanadianZ

 

Is it rich or lean when you max out the injectors?

Rich Krause

------------------
'95 Z-28 383 with Vortech, nitrous, etc.
"1FASTZ28"

 

I can hold about 11.8-12.2 a/f until 4600rpm or so then it starts going lean..by 5000 its almost to 13.5

 

I'm in the same boat as you are, except I've got 30# injectors with ~8lbs of boost. My MAF maxes at about 4000RPM+ and gets leaner going up until it cuts out on the dyno(almost like hitting a rev limiter)... I assume I need bigger injectors for my application, but was wondering if anything be compensated for within the PCM? Pulse widths for me are about 33ms...

Thanks in advance...

------------------
Paul D.

1994 Z-28 A4
Formerly Powerdyne 6# (Now ATI D-1) + NX 75 shot
G2 LT1 Ported/Polished Racing Manifold/Big Valve(2.00/1.56)Heads, CC 512/512 220/230 ls112, CC ProMagnum 1.6 RR
PCM by Ed Wright then more w/LT1-Edit, ACCEL 300+ Ignition & Coil,
G2 Wires, Borla, SLP Jet-coated Headers, G2 52mm TB, G2 MAF
3.73, G2 High Stall Converter, TG shift-kit, Built Trans
G2 Engine Brace, G2 Sub-Frame & X-Brace, G2 Control-Arms
WolfCraft 6-pt Roll-Bar
BF Goodrich 275/40/17 Front 315/35/17 Rear
ACT Aluminum/Titanium 17X9 & 17X11 Rims
11.13 @ 127.4 1.70 60ft.
480+ rwhp 470+rwt

1967 Camaro RS/SS
502ci w/Holley 177ci Blower + NX

1972 Dodge Challenger
446ci + NOS

 

The only thing we started doing was in LT1 Edit on the PowerEnrichment vs. RPM tables, we just started adding in more fuel. It seemed to help up until we ran out of fuel pressure but it didn't look like the injectors were doing anything different from 4000-5000. I would think that you would need bigger injectors, especially if you are not using a FMU

[This message has been edited by 1LEThumper (edited August 26, 2002).]

 

Yep, use LT1 Edit/Tunercat.

1) Verify your injector size is set correctly - otherwise your DC's are meaningless.

2) Make sure you have a 1:1 boost sensitive pressure regulator

3) Hook up a fuel pressure guage and verify your are maintaining pressure (it should actually increase with boost).

4) Find the RPM where your MAF maxes out - starting at this RPM you will need to begin greatly increasing the PE vs RPM table. You will probably want a wideband to do this correctly.

5) If you injectors get over 90% DC you need more injector.


Chris

 

Looks like I got ya on both boards

Thanks for all of the help Chris, its hard to find a lot of people around here that know how to tune these PCM's.

'copy from LS1Tech'
Yeah I have the stock MAF back in the car now. I do have a FP gage mounted in the car and we did notice the fuel pressure drop about 20psi around 5000rpm, This we believe was caused by the cheapo ATI inline pump being smaller than what is in the tank of the car (180 vs 255). The inline pump is now removed and if this doesn't work I'm just going to sump it and go with a big external.

I have a AeroMotive LT1 regulator that seems to be increasing at a 1:1 ratio right now. I am currently NOT using the ATI FMU that came with the kit.

The one thing I was wondering about rescaling the MAF tables is what will this do at low rpms? Will this throw the car into fits especially with as big of an injector that is in the car?

 

Jeff Stevens is the man to hunt down if you have not talked to him already, he worked some trickery to get beyond the MAF limitation, and I believe is also running 15PSI recently (I believe he upgraded from 10 not long ago?).

If your not on LT1 Edit list or don't have his email I can pass it on.

 

Yeah that would be great, I just got LT1 Edit about 2 weeks ago, so like I said its all kinda new to me. I was really hoping Ed would have been a lot closer on his programing than what he was.

 

Just program the injector flow rate and offsets correctly (or as close as you can on the latter) and it will be fine. You shouldn't need to do massive scaling changes - 104 to 106 (4-6 percent increase) should be enough to get you solidly negative (-2 to -7) at part throttle on the l-trims. This will keep you from adding extra fuel at WOT.

Once you have that down then you can start playing with WOT fueling and leave the MAF alone. It's really not very tricky or complicated - you will just need to start adding extra fuel after your maf maxes out and increase the value in the PE vs RPM table as rpm's increase.

Chris

 

You need larger injectors (or more FP).

Rich Krause

------------------
'95 Z-28 383 with Vortech, nitrous, etc.
"1FASTZ28"

 

Rich: note in one of his posts he indicates that he was not maintaining fuel pressure - so he still may be able to get away with the injectors he has after he solves that problem

Chris