Leaning out on Dyno/Heat Issues

[Narsh]

Hi All,

I recently put a Vararam and a 160 deg. TSTAT in my 08 LS3 A6.
I've been working with my tuner on getting it tuned up.

The issue we are having is that the car heats up to about 250 deg (Coolant Temp) and the car starts to lean out at WOT to where the car is untunable after a few pulls. When its cold, its fine. It put down 377/372 with a base tune. We've tried reverting to stock and its the same thing.

The dealer says the car is fine, no issues. We started noticing that there is a smell of sulphur so we are going with the cats being bad and trying to get the dealer to replace them.

Anyone have any similar issues in the past?

[c4c5specialist]

HI there,

#1, remove the vararam and install the stock thermostat. If you have 250 on the coolant temp, the low temp thermostat is doing nothing and you may have debris in the radiator/condensor which is inhibiting your air flow and raising the coolant temperature.

#2, sulfur smell at WOT is completely normal at WOT, due to fuel formulations and power enrichment calculations.

#3, based on your numbers, the tune is doing nothing and the fact that you have tuned the engine, it can be seen and someone at the dealership could actually void your entire powertrain warranty, including cats.

Put it back to stock, and you will do just fine.

I have replaced a number of engines that were "tuned" and never recommend it.

Allthebest, c4c5

[Narsh]

That's the thing the car drives around at 180-215 depending on the SFL weather all day. These conditions only became apparent on the dyno.

How is the tune doing nothing? The car put down 362/360 with just the vararam on a mustang dyno after minor calibration it went 377.

Your advice is to leave the car totally stock or is this just to iron out the issue?

Also, how would I check for debris in the radiator condensor?

We ran the car in stock trim, stock tune, aside from the TSTAT - nothing changed. It still leans out on the top end.

Thanks!

[c4c5specialist]

HI there,

It didnt change your running condition, did it???

Thats why your TUNE is doing nothing.

You can build all the power you want, but if you check your torque numbers, they will be more peaky with your tune. Your losing part throttle drivability and torque.

Also, how do you know you are lean????

Factory calibration is 12 to 1 at WOT, which is rich to enable cooling of the pistons and keeping spark detonation at a minimum.

If you are overheating, that is due to someone not having a cooling fan in front of the car while running on the dyno, a basic NO NO.

How many runs did you do back to back???

The fans turn on at 200 and Maximum fan duty cycle is 90% at 235, so SOMETHING is wrong with the cooling efficiency.

POWER means nothing without reliability.

Allthebest, c4c5

[Narsh]

Believe me I agree.. I don't want a fast car that can only be driven two blocks!

I wish I would have the graph beacuse it was much more linear than the stock graph.

The basic calibration of the transmission did make a world of difference. I will say that. The HP numbers are negligable but with a unit like the Vararam you wouldn't see much differnece til the car was moving and taking in air.

I am relying on the tuner's info and the Chevy tech that was at the shop. I know very little about tuning I am only repeating was I was told.

The funny thing is that I am not overheating at all. The car runs fine, we just can't throw a tune on the car because the computer is compensating.

At first we did about 9 runs with 10-30 minute gaps. We thought it was just too much altogether and we let the car sit overnight and tried a run the next morning and the condition was gone.

By the second run, the condition was back.

The dealer checked the car and its fine, no codes, no overheating - zero zilch...

Now that you mentioned the fan on the front of the vehicle I went back and checked a few pictures I took and there is no fan in front of the car. There is a small fan of to the side though.

[c4c5specialist]

HI there,

There should be a large fan, about 4 ft tall in front of the vehicle prior to strapping it down.

Tuning a 6L80 automatic is asking for trouble.

I have rebuilt 3 transmissions JUST for tuning issues. Maximum line pressures create alot of issues, but its just because of shift feel that people do that. They dont realize that when your in S, and use the paddle shifts, your gonna help the shift feel, and if you keep it in S, it looks for a shift time of .35 of a second between shift points and clutch engagement.

Personally, based on what you have told me here, I would have your GM technician reprogram your engine and transmission control modules with the latest correct GM calibrations and leave it alone.

And with no wideband oxygen sensor readings, no documentation for the work that was done, your coolant temperatures when not changing while cruising and the vararam only good when you are driving over 100 mph, the mods arent good for anything but racetrack.

Allthebest, c4c5

[Narsh]

The GM Tech did recalibrate and the car went back on the dyno. I believe you may have hit the nail on the head with the fans though.

Thank you so much for the advice.

[c4c5specialist]

Its our pleasure.

Allthebest, c4c5