need tuning help for LT1

[yellowlt1ta]

I have a 93 Trans Am with a turbo LT1 and a MS3.57 using TunerStudios. I have put all new sensors, wiring and connectors. I have revised all of my work and its correct. I did put bigger injectos as well, the thing is that it's idiling iradicly all the way up to 3k rpm's. I'v tried to messing with the tune and it works but when i turn off the car and turn it back on it gose right back to the way it was can you guys help me out here, im all stressed out.

Thanks, Dave

[jsmcortina]

Please post a datalog of a start and slowly increasing the revs on the engine. Also attach your MSQ (File SaveAs.)

James

[atomic6]

I'm interested to see also, I am pretty familiar with LT1 engines. What is the lobe seperation on the cam(just curious), and how are you running the ignition? are you using the falling edge of the low resolution signal on the opti. Or did you put a dizzy in the back of the intake?

[yellowlt1ta]

Alright I will do it today and post it up as soon as I can. the motor is fully stock and im using the stock ecu for Ignition, ac and all that stuff except fuel.

[yellowlt1ta]

2010-06-20_17.09.54.msl revs.msl

on this one the car was turned on and warmed up then i started the log. I reved it up a few times and the rpms were steady at a high point.

(85.24 KiB) Downloaded 12 times

[yellowlt1ta]

2010-06-20_18.23.50.msq tune.msq

this is the current tune

(46.05 KiB) Downloaded 10 times

[atomic6]

Which computer is controlling your iac valve?

are you running high or low imp. injectors? you msq has bank 1 and 2 set differently. fix this first then, run a log as you star the car, and a longer log.

I have a feeling the factory computer is controlling the iac and it may be confused, but I think we will need more information. to have clearer picture.

[yellowlt1ta]

IAC is directly connected to the MS. and i have 96lbs low imp injectors. ill fix the injector banks and make another log.

[atomic6]

also you know you have no kpa bins that go above 100 kpa. you're going to need those for a boosted application.

[yellowlt1ta]

alright then how do i do that? oh and today i turned it on and reved it up three times and it didn't want to rev to 6K take a look here.

2010-06-21_18.51.48.msl second time with rev.msl

(254.91 KiB) Downloaded 9 times

[atomic6]

I can't look at the log right now, I on a computer without MLV.

But are you just sitting there and reving the engine to 6k? In neutral. To experience this??

If it is not going lean or rich, it is likely mechanical. like valve float. VERY common with the factory valve springs, I would hope you no longer have those in there. Then there is the whole Optispark mess, You said the engine is stock, is it really bone stock??? If it is you have some work to do, to make the turbo work properly. The really bad thing is the "93 still has the non-flash ecm, so you will have a hell of a time changing the tune in the factory computer. (IE timing for boost) Maybe, you have a Boost-timing-master pulling timing, that would be better than nothing.

I am just guessing on most of this, more detail on the install and pics would help, narrow down the problems you will have and fix the ones you running into.

On changing the bins, it is very easy, just click on the bin and renumber it. but export the table first, or write down the numbers. because changing this will require retuning the the VE table.

did you do the tuning on this or did you have someone (maybe the turbo installer) tune the car?

A read of the Mega manual would help greatly on fixing alot of this. I will look at the log later when I can download it.

[yellowlt1ta]

yea im just sitting there. the motor is bone stock but I do have an MSD, 6al, coil, plugs, and distributor so it can be manualy adjusted. AFR gose up and down (LC-1) kindda crazy. I made the turbo system myself and Im tuning it too, I ran the car for about a year the way it is now exept I used the stock ecu and an FMU reved to 6200 with out a problem.

[yellowlt1ta]

dose anyone have a base tune for LT1's that i can use?

[atomic6]

Tunes for an LT1 factory ecm, or the Megasquirt, or Both??


I have alot of tunes for the LT1, but it is going to be more complicated than that. because none of them are for a 93,And the tunes I have are either controlling the timing(with a rear mount dist.), and controlling the idle with the factory Stepper IAC valve thru the squirt . Or they are in conjuction with an OBD1 computer that controls those things, but those things have been retuned with Tunercat(lt1 factory computer tuning program)

Is your factory ecm still controlling the IAC valve? I'm thinking it has to be. do you still have a tps input to the factory computer, or did you remove it for the squirt to use. If the factory computer is still controlling the idle, and there are acouple sensors being shared, or not hooked at all, that the ecm is normally using to keep the idle target, there may be a problem with the idle.

It is going to be a long process if we don't know more detail of the install, I learn more with each post you make but a complete run down of what is controlling what and how, would help me understand more of what you have going on without being able to see it.

Like you said adustable dist. Is it an adjustable MSD Opti-spark, or did you cut a hole in the back of the intake for a conventional dist. back there, and that is adjustable.

Hope to help you before you push that headgasket out, or worse.

[yellowlt1ta]

Id say tunes for the megasquirt, let me post up something i made when i did all the wiring for the MS.

93 LT1 ECM To MSII.doc

I made this to make sure I get all the wires right but I later changed the factory wires and connectors for a new harness I made

(54 KiB) Downloaded 8 times

the distributor is an MSD billet adjustible opti, all of my ignition components are MSD.

I aslo have a diagram for the stock ecu that show's all the pin out's. and i did not share any sensors between computers.

If its alright with you id like to pm you my cell number to see if you can help me out.

thank's Dave

[atomic6]

IAC is directly connected to the MS. and i have 96lbs low imp injectors. ill fix the injector banks and make another log.

Sorry I skipped right over that earlier, Is this a log with the injector constants fixed, or before?

pointer over idle area

graph2.png (39.14 KiB) Viewed 303 times

same log tuning console removed

graph.png (33.57 KiB) Viewed 303 times

This log has alot going on, it seems your idle is way high, but it looks like the IAC valve is doing something because later the idle is getting lower, but still high at 1300 rpm. and it surging probably because it is way too lean. Of coarse I have no idea what o2, or wideband you are running, so can not say the Default I used is even giving the right number.

What if anything is the factory computer running? Is it decoding the opti wheel for the megasquirt. If you are controlling the ignition from the MS2 explain how you went about this.

Narrow band o2, or wideband and which brand?

I can help all I can in this forum, but I wouldn't be able work any better over the phone.

[yellowlt1ta]

The log that you posted up right now is with the injector constants fixed.

The MegaSquirt is used for fuel only. If you take a look at the word document that i posted you will see the things i have connected to the megasquirt.

I am using an Innovate LC-1 wideband. its 0V=7.35AFR 5V=22.39AFR (Default).

[atomic6]

I downloaded the doc,and read it, but It's like I would have expected. except for the fuel pump being neg. trigger, I thought most of the GMs I wire to are pos. trigger pump relays, and the pin 30 to the "egr" are you using the fidle for the egr,or is that your boost control?

But,Since those injector constants are fixed and you remapped the kpa bins in the VE1 table up to your max boost level.(If not yet, do that before you go too much further)

You can work on tuning this idle, you need to get the car to idle(below 900 rpm) in gear and in Park/Neutral. Without stalling when put in gear.

Then post up another MSQ and log, no need to rev the car. Just idle and a little throttle, in gear and out of gear(both less than 2000 rpm). Then you will see where the car idles on the ve table and where it goes to in gear. That is where to start tuning.

If you run into any problems getting the idle rpm right the MegaManual(http://www.msextra.com/doc/index.html) has all the info on getting it set correctly.

Then you can move on to the rest, Maybe I am writing things you already know but, looking at the ve1 table I don't see any idle "plateau"s and other signs. Something just doesn't seem right with your ve table, are you running a vac/boost ref. fuel pressure regulator? Just seems like a huge swing in numbers on the table.

Ve 1 table

yellowTA VE1 table.bmp (729.01 KiB) Viewed 287 times

It should look more like this. This table is for a MS1extra install, that is why the table in not as big, but you can see this car like to idle around 38 kpa. This one is far from perfect but It is the best I could find on this computer, right now.

boosted ve table

closer boosted ve1 table.bmp (729.01 KiB) Viewed 287 times

This thread should probably be moved to the General,New Users section.

[yellowlt1ta]

I had the egr hooked up but untill i got rid of it. oh and the fuel pump relay is connected to the stock ecu.

I am using a vac/boost refrence fuel pressure regulator.

ill post another log like you said, and i dont know how to move the thread.

[yellowlt1ta]

sorry nothing yet it broke something but i dont know what, im going to check it out when i get back from vacation,