ATLsilverSS

heard and agreed

bignose94015

All I want to know is if I should see the same boost level through all four gears at the drag strip? It shocks me that I see about 6 less psi in third in fourth on a 0-100 run on a closed course.

bignose94015

So just to clarify. From a stop mash teh throttle. 22-23 psi through first second and then once in third I only get about 15 psi. So what you are saying is that this is torque management? If that is the case GM has been advertising false information because there is no way @ 15psi that the car is making the 290hp as claimed. I highly doubt you are only to get the full HP out of 1st and 2nd gear.

So if I ran this thing on the dyno right now they would dyno it in fourth gear. That would be at 15 psi. I would not get the claimed HP.

Who else has an Auto HHR with GMS1. What are you seeing for boost in 3rd and fourth?

Thanks,

ERic

Victory Red SS

I have an 08 Auto which is HPTuned right now. It's very fast but still working on the tune esp the shift points. Because of the lack of other Auto owners it is hard to get tuning help but I am making progress. As for with the GMS1 I seem to remember 20-26 in all gears but I could be misremembering (is that a word?). I re-loaded the GMS1 (GMTU, same thing correct name) recently to check on some tuning issues and got between 17 and 22 in all gears. It's winter here so heat soak is not a problem right now but my earlier stated numbers are from the summer.
I don't believe with the GMTU you should ever be below 17 psi even with most things weather related considered.

bignose94015

Fianlly some relevant info.

Thank you very much!

Eric

russruth

When the GM tune is stable, my auto HHR SS pulls a constant 20 to 22 psi (from the pillar gauge) virtually at sea level and with 91 octane petrol through the first three gears up to 105 mph, then going to 4th gear it drops.

When it's not stable it goes from 15 to 27 psi but most of all surges and moves around, doing this it doesn't throw a code, but it will go into limp mode. I takes a restart to get it back to boost.

FYI, this week I ordered a complete wiring harness and the crate engine depot connectors to get rid of the in stability which I think comes from the splicing of the connections, even though they've been soldered and sealed twice.

FYI 2, I also have data logged the car and am having a third party review the results.

Don't be mislead from people that say if you expect the car to pull strong and stable your expecting too much, or that no manufacturer was ready for 300 hp 4 cylinders. Mitsubishi , Subaru, Volvo, and a lot more have made 275 to 300 hp turbo 4's and 5's for a long time that pull strong and reliably.

After talking to a lot of people that know these cars, the issue seems to come from an overly sensitive computer program that protects the drivetrain, shift changes and of course the 100,000 mile warranty.

If your car was stable in stock form (mine was) and then you go to the GM tune, you'll find that any changes can upset the balance, even changing an air filter.

Though nobody is running a score card and no manufacturer is going to give you details on how many specific problems they have, I do know that out of the 6 dealers I've contacted about this, three absolutely will not work on the stage 1 tune going back to when I first bought the car.

Obviously they knew something I didn't.

FYI 3. It seems the most problems with the GM upgrade is the splicing of the wires. Cobalts or HHR's it makes no difference, many have problems and the rule of thumb seems to be if your connectors are spliced and don't have a problem today, you will tomorrow.

FYI 4. My car at stock pulled steady at 15 psi, so if 17 psi is the standard of the upgrade (it's not), then who would pay nearly $1,000 for a 2 psi upgrade?

IMO

KissMy08SS

I've thought about doing this as well. Where did you order the harness from? part number?? You think it'll be that big of a deal to change out the harness??

firemangeorge

Well folks, I had the GMTU installed this past week with the new plug and play wire harness' (no splicing). Was 14lbs boost stock. Now it's 17lbs. Tech said everything was fine. Was expecting more boost,but guess I was wrong.

SS fan

Fireman 17 sounds low, mine does 20 or more on the stg1. But the fun is over 25, ask Vince he will give you more boost.

XtremeSS

Same here. I rarely see 20lbs and when I do its usually at about 50 mph in 3rd after I drop the clutch.