dhdenney

iTrader: (53)

Hey guys, haven't been on here the last little while since I started my new job... I got the opportunity last Saturday to make it to Beech Bend before the season ended and didn't do too hot. Some of the problems I have since resolved (I was basically unprepared for the track but went anyway). One problem still lingers and looks like an injector size issue to me but wanted to share here. The car is programmed to shift at 6500 and as you can see by the logfile, it shifts at about 6375. It starts cutting out above 4500. Showing as much as 22 milliseconds at under 5000 RPM so my guess is it's cutting out cuz I've maxed the injectors. As a side note, should I back my spark advance down some?

infinitebird

iTrader: (11)

Look at the duty cycle (not included) and not pulse width if you want to see if it's maxing the injectors. You can easily determine it that way if the number is close to 100.

And the timing looks fine, you had no retard.

jasonp31

I'm not really good with tuning on LT1's yet, most of my experience has to do with 3.8 GM motors. (sc'ed and NA)

Correct me if I'm wrong here:

1. Timing looks awfully high, even for NA. Doesn't the best horsepower happen around 28-30 degrees of timing advance? You're hitting high 30's and low 40's.

2. Isn't your TPS reading low? Shouldn't you be seeing around 5 on the TPS voltage?

Again, just some questions, I'm far from an expert on tuning the LT1.

infinitebird

iTrader: (11)

No, LT1s run high timing. The stock file is typically mid 30s at wot and a scanner will typically show 4-5 deg higher than what is specified in the tune for whatever reason (not sure why this is). The key is that he has no knock retard, that means everything is just fine.

4.6 is fine, a little variation is normal. It correctly reads that as 100% tp.

kinglt-1

iTrader: (26)

NA LT-1, Ls-1 like 36-38 degrees of timing! 4.6 is about right on the tps voltage. you seem to be running rich according to your o2's. Im thinking you want to be 860-880mv. Not sure on this one though. 950 o2's seems rich to me.

jasonp31

Ok, well good to know that info guys for my own knowledge. I didn't notice the 950 o2 readings. That does seem awfully high to me as well. Not sure that's enough to knock down a lot of performance, but leaning it out would help some as long as KR isn't introduced.

What about the long term fuel numbers, being pegged at 128? What's that mean? Just trying to help, and to learn along the way.

dhdenney

iTrader: (53)

Well if my math is correct, my 20+ milliseconds at 4K-6K is 100% duty cycle (what I was referring to). In regard to the LT fuel trims, it has always been my understanding that 128 is the target number to achieve.

infinitebird

iTrader: (11)

Well yeah, you can calculate it from that, I just look at the DC number because that's easier.

At wot the computer essentially goes into open loop and does not change the fuel delivery based on feedback from the o2s, that is why the fuel trims don't change.

dhdenney

iTrader: (53)

Well I would have looked at the DC but my logger doesn't show it. So my math is right, I've maxed my injectors?

Puck

iTrader: (17)

Ahhh I found the problem - your oil is frozen!!

Lol, yes your injectors are maxing out. What size are they? You can probably get away with just boosting the fuel pressure.

dhdenney

iTrader: (53)

They're 30#'s. I used this setup last year with no problems but I but messed with my PE tables so that might be it. I really should be using 36#'s I know but I was trying to use what I had you know. I really need a dyno tune but with my O2's reading high, I wonder if I could back off my PE and get the DC back down? Naw... I guess I better just go bigger.

buffman

iTrader: (9)

Just remember the stock units are narrowband, and IMO are just a general guide for WOT AFR tuning. People have shown high 900s on a dyno on the stock 02s, while a wideband is showing the car is actually running lean.

Anything over 4.8 Volts will set a CEL for TPS overvolt.


The LTerm counts will not to go 128 on a stock tune. There is a program that locks the Sterm and LTerms at WOT.

DH datamaster is free for 20 logs if you need a better logger

dhdenney

iTrader: (53)

Yeah but I think I got all the info I needed though. Time for 36# injectors.

infinitebird

iTrader: (11)

Actually they will in some cases. The stock behavior is to lock them at 128 if the Lterms were < 128 when entering wot (rich condition) or lock them to the LTerm value if it was > 128 (lean condition).

That program sets them to lock in all cases (regardless of the LTerm value).

dhdenney

iTrader: (53)

Just an update for discussion. Someone on the LT1 Edit mailing list sent me a link to an Excel spreadsheet for duty cycles which was pretty handy considering long handed math was getting old and I kinda wondered if I was doing it right..... After putting in a few RPM/PW relationships, I was seeing 90%+ (over 100% in some cases) in the upper 5K to 6K range. So my injectors may be part of the problem but some have suggested my cutting out is not fuel related. So after I get some bigger injectors, I guess it's time to start testing and eliminating.

edcmat-l1

iTrader: (10)

Your cutting out isnt fuel injector related. At least not from maxing them. They will go over 100% for short runs with no problem.
128 is ZERO on your LT and ST fuel trims. Its neutral. Higher is adding fuel, lower is subtracting.

dhdenney

iTrader: (53)

From my understanding, in PE mode, the fuel trims will lock at 128 anyway. I've had LT1 Edit for quite a while now and have used scanning and logging a lot and I have never seen anything other 128 at WOT. Petering around yes, I have seen them bounce around some but in open loop and PE, always 128. So I don't see that as any indicator of the condition. As far as the condition itself, when I was driving the car my gut said this doesn't feel like a misfire. Looking at the logfile, the high DC's jumped out at me and seemed like a logical reason. I'm not saying the injectors are it but I at least wanna eliminate that as a variable. Looking at my file, all parameters seem consistent. Shouldn't I be seeing some fluctuations in O2 mV? Theoretically, if I've got a misfire or fueling issue, wouldn't that alter the unburned oxygen in the exhaust?

edcmat-l1

iTrader: (10)

You are correct. The LT should always go back to 128 in PE. This is neutral. Its not adding or subtracting fuel. I wasnt saying this is indicative of your problem, just stating the fact that 128 is zero for the fuel trims.
As for errors in ignition and fueling showing up in the O2 mv, yes you should be able to see something. BUT, the older 02s do move a bit slower than the newer ones. AND, the scanner software isnt the fastest. So, that being said, you may not see anything in the scan data, but if you were to scope the 02 sensors, you would see much more activity, and the tell tale indications of a misfire in the sharp downward spikes.

dhdenney

iTrader: (53)

Oh ok I read it wrong.

When I get some bigger injectors I'll go from there.