One messed up 3800 Tune

[VodeAn]

I typically work with LS engines but have been branching out to other platforms. Recently someone with a 1999 Grand Prix with a GTP Swap came to me for a retune. Now, I do not know the person who did this calibration or if they intended it to be permanent or just something to get the vehicle running but damn...

Attached is the original tune, a few logs with the owner driving and me in the passenger seat logging, and the config file for the logs
Vehicle has a ported blower, a smaller pulley, higher compression bottom end from a Series III 3800, long tube headers, catback, intake.

I wasn't looking at the screen during one of the runs, but as soon as the run was over I noticed that the vehicle was running at 120% duty cycle on the injectors! Turns out the vehicle still has stock Grand Prix injectors.

The vehicle experiences severe KR during acceleration but only intermittently.
(I haven't logged again with all spark and knock parameters but will)

Also because this is a non GTP ECU the MAP sensor is only reading vacuum (1 bar). This I am actually a little confused on because there are no enhancements for these PCM's. So if I want to set the vehicle up in SD I have to obtain a GTP PCM or licence a GTP PCM Calibration to flash onto this PCM in addition to purchasing a 2 bar MAP sensor, correct?

Also the owner complains that his plugs are fouled black every 1000 miles or so.

Just thought I should share The owner is currently installing a Wideband sensor so we can get everything sorted out. If anyone else notices other stuff please sound off, I'm sure there's more I didn't include here.

[VodeAn]

Oh ya, and COT protection is enabled, although the vehicle has no cats.

[Shane Hewitt]

Looks like the tune is commanding air/fuel ratios < 10:1 if you a on it for any length of time.....that would explain the 120% duty cycle. Once you alter that to something a little more reasonable & then tune the MAF to make actual = what is commanded, duty cycle should come way down. GTP injectors are good to almost 300 whp, doubtful this car is making that kind of power with the mods you listed.

[5FDP]

Okay, so someone set the PE table to 10.5 AFR, but then still kept the "Add vs RPM" table active, so its dumping fuel like a mother fucker there.

Likely making it go all the way down to 9 AFR causing the injectors to go static. You need to fix that asap. Either zero out that table and set the PE table to 11.4 or find a stock gtp tune and copy over the numbers for those tables.

Someone also removed all torque managment which isnt the best idea either, its good to have some to help save the transmission unless otherwise built for the abuse.

You could use a 2 bar map, but it seems that it would make another issue because of the GT pcm.

Swap in the L67 Good Fuel Spark timing table, PE settings, the injector constants, and you should be good to go. Make sure you dont try to use the 2bar map sensor.... You may see alot of extra KR, which is due to a bit different sensitivty, but I have been able to tune around it a bit with the PE vs Coolant temp table. Be careful with coolant temp PE, as if you go too low it will add alot of timing vs the AFR Spark table, which I suggest you zero out before you start if you have access to it (tiny tuner does).

From a source.

[5FDP]

They also set the fans to come on at 150º, which is stupid.

Change that back to around 200 and 210.

[VodeAn]

Tomorrow this thing is coming to get fixed, I'll post files when it's done.

[VodeAn]

Here's the fix I came up with, AFR holds steady at 11.7 at WOT on the wideband. (wb afr and target aren't in this log, but when targeting 11.2, 11.7 is actual the will check this and dial the maf in. The vehicle has a 160 degree t-stat so I set the fans accordingly now.

Vehicle runs much better, night and day difference. The vehicle isn't running the ludicrous timing at part throttle anymore either, and doesn't pull as much if any at all. (kr<2.0)

The bad news is above 100mph the vehicle sometime shuts off. This was a previous issue too, according to the owner. I did not get a log of this, as the vehicle did not die at anytime when I was in it. Any ideas on this?

Attachment 40795
Attachment 40796

[5FDP]

Havent looked at the file, but if you havent,

Make sure to set the knock sensors to turn on sooner if you they want to run a 160.

The factory settings will not turn them on till 160.

Its a better idea to run a 180 as 160 is far too cold and the motor will like it better when its warmer. A 160 is fine for hot lapping, not a daily driven car.


Not sure on the vehicle shutting of part.

[VodeAn]

Knock sensors turn on at 100 degrees F, I recommended a 180 to the owner.

[5FDP]

I quick looked at the scan and saw only 11-12 degrees of timing at WOT, are you going to deal with that next?

Figure most guys try to run 15-16 to be safe.

[VodeAn]

Thanks, I was going to run more but wasn't sure exactly how much is typical on these vehicles. I plan on working on making more power once a few issues are sorted out.

[JerryPH]

For 1999 GTP's, 15-16 degrees of timing is stock. Also the stock timing tables are very conservative and easy to bump up 4+ degrees in the tune. There are places in my tune on my 99 GTP that I was getting +10 degrees. Before I stopped with the tuning thing, I had it topping out at around 45 degrees during cruise and 19 degrees at WOT with 0 KR. This is with headers, XP cam, N* throttle body, etc...

Oh... I also was running only 87 octane fuel at the time too, something that I would like to continue doing, in the face of near $1.50/liter for regular fuel prices.

[MMGT1]

Jerry has the same results Id expect. I would have that car at 18* WOT, 11.6AFR and 42*-44* cruising. I also agree with a 180* stat. I've seen guys get them to 20-22* tuning. But have always wondered if timing that high was ok on the dyno but not so good on street. So, I go as far as 18 and stop there.

And that trans needs a lot of tuning. Would transmission tuning part of what you are doing to the car? The trans, to me, makes those cars an entirely different ride when set up properly

[VodeAn]

Haven't kept this thread up to date, sorry to anyone following. Found out from the owner the previous work was done by a so-called professional, who is "famous" in the 3800 community locally. I cringed because it means this probably isn't the only vehicle which they worked on, but I digress.
I was scheduled to finish the vehicle a few times now but every time something comes up and thew owner can't make it. He's a acquaintance of mine, so far every time he can't make it his reasons check out. It's annoying to say the least.

I have not touched the transmission cal in this vehicle yet. I am slightly hesitant to do so as the vehicle does not always grab 1st gear on mid to high rpm downshifts. I may return to transmission cal to factory the next time I work on the vehicle and then see if the problem still exists, if it does we can troubleshoot mechanical/electrical issues. If it does not, I'll just re-cal the trans starting with stock settings. I've done several 4L60E's with great results. This is all if I ever end up seeing the vehicle again.

MMGT1, if you've worked with these vehicles a lot and have any tables or data you'd like to send me on the trans it would be appreciated.

To re-cap the current laundry list for this vehicle is as follows,
Brakes (squeak while driving)
Replace O2 sensor
180 degree thermostat
Add timing (re-visit entire high octane table)
Return trans to stock cal, diagnose trans problem
Find out why the vehicle dies on the freeway.
Get target WOT AFR closer to actual. (MAF table)

[Kyne]

I'm pretty sure most of the 3800 tooners are hacks. I'm constantly getting in arguments with them on the GP sites. Which one was it? It blows my mind what they think is the correct way to tune things, like adjusting IFR since the maf is already calibrated. Then when they don't have an answer to my argument it's "well you don't understand these PCMs" sorry end rant. Also I will second what has been said about timing. I seem to get MBT in cruise about 40-42*. Really bumps up gas mileage.

[5FDP]

I'm pretty sure most of the 3800 tooners are hacks. I'm constantly getting in arguments with them on the GP sites. Which one was it? It blows my mind what they think is the correct way to tune things, like adjusting IFR since the maf is already calibrated. Then when they don't have an answer to my argument it's "well you don't understand these PCMs" sorry end rant. Also I will second what has been said about timing. I seem to get MBT in cruise about 40-42*. Really bumps up gas mileage.

I could agree alot of the time. The 3800 pcm is pretty stupid aswell, and it can handle alot before you really even need to adjust anything major.

From what I've read and what other friends have tuned an L67 motor, the 97 GTP was the only year with the correct IFR table, though the change in numbers from 98-03 is so minimal it really doesnt matter that much. A bigger problem was that after 10ish seconds of full throttle the fuel pressure could drop off from lack of voltage to the pump, hence why the fuel pump rewire is needed. GM decided to cheap out on the gauge wiring used, I'm sure it saved them tons of money.

[MMGT1]

If its dying at highway speeds its either a bad MAF or crank sensor or both. Bugger of it is they wont throw a dam code for it for some reason. You have to have been down this path, pulling out your short and curlies for two years and finally find a GM mechanic that actually knows his shit to set you right! Start there with your issue and check all wiring and harnesses to both, I bet its the crank, but could be MAF too....
I'll PM you some stuff to try as far as your trans tune goes once you get it mechanically sound and your stalling issue is fixed. Shoot me a PM as to your progress and I can help bud...

[MMGT1]

And I hate to say it too man, but a friend of mine took his Grand Prix to a 3800 tuner and within a year, two trannies and an engine later he finally let me have a go at it. What a mess it was, I was dumbfounded and quite honestly there are guys a hell of a lot better than me with the 3800's but holy hell it was bad, real bad. The tune blew up his car, no doubt about it

[Mac7504]

Doh!!!!

Sooo, I'm about to take the plunge and attempt to either top swap/engine swap/ or turbo my 3800 (L36) and this is exactly what I'm worried about. I've heard about too many horror stories about these tunes, and incorrect bin writes which is why I've held off.

If I were to do this work, and were emailed the "recommend" file, would anyone here be able to review it before I loaded it up?

I just simply can't let the car go due to sentimental reasons so I'd like toy a bit but I don't have any real reliable tuner in my 3800 community anymore and I don't want to end up with a 3750lbs donor...

http://www.superchevy.com/features/0...onte_carlo_ss/

Anyway, here is the car before a functional ram air hood and a few other mods.

Would any of you be able to assist?

Thanks,

Johnny

[VodeAn]

Threadjacked I jest.

incorrect bin writes

It's usually not necessary to preform a full rewrite, just do a compare and change what needs to be changed.
Full rewrites, other than for upgrading to a HP tuner modified operating system, are more trouble then their worth.

I'll assume you don't have unlimited licences and break it down like this:

Cost of 3800 PCM ~$100
Cost to licence PCM, 2 credits, $100

To do a full rewrite you have to license that file and your PCM, so if everything goes correctly you have just spent $200.
If something goes wrong, (laptop drops the connection, you flashed the wrong file/a bad file...) you are out the PCM (bricked), it's licence, and the license for the other file, $300!

If you start with your PCM and just compare values and make changes, you are much better off. Even if you screw up your only flashing a calibration and don't risk the PCM itself. Furthermore, you never had to license the other file you copied the values over from, and save that money! You have only licensed your PCM and have only spent $100!

If you post your file and setup (in a new thread) we can share our opinions with you.