Hi, i have a completely stock 2008 tc and a HAHN cool ram intake is on its way in the mail.
The car is stored all winter, so I decided next spring to get the GMS1 and the HAHN catless downpipe and catback, followed by more but lets just start there.

There are people here that seem to know a LOT about these cars. So I have a few questions.

Due to extremely low kms on the car I WILL be flashing it with GMS1 to retain my powertrain warranty. I get a good deal on it as a GM tech also. I will not flash with any other aftermarket tune.... yea I know. Keep in mind I live in a fairly isolated area with no speed shops or tuners around.

So basically my question is really about the exhaust, will the catless downpipe with slanted o2 bung going to work well with the GMS1 and Intake? Any known or suspected drivability issues with that setup? Any estimates on the HP & TQ with this combination?

Comments and suggestions please!

 

would be best to get a custom tune with the tintake and dp, since gms1 does not tune for that. However you will gain a little power with gms1 but not a huge ammount.

 

I'm currently running a GMS1 with Hahn Catted DP, Hahn Catback, and K&N SRI. No problems, but the difference in your setup is the Hahn intake. From what I've heard the Hahn intake will skew fuel trims something like 18% which is pretty high so you might throw a code there (We would have to ask anyone else on the board to see if they have GMS1 and Hahn intake). Although you went with the catless downpipe from hahn it still has the o2 bong so from what I've read people have not been throwing codes with that particular downpipe. The catback shouldn't have an issue what so ever.

In terms of performance gains, they will be minimal until you get tuned for the upgrades. From what I have researched the car will only gain something minimal from 10 HP - 20 HP for a fully bolter on car with GMS1 over the GMS1 stock. This is because the car was tuned for all stock components and even though it learns the new upgrades, the power added will be minimal. I will say that I think my car has a little more power over GMS1 originally; however, I don't know if thats just myself telling me that its going faster because it sounds different ;-).

I would just recommend what I'm going to be doing with a tuning setup. I'm going to get tuned in a couple weeks, and I'm just going to keep the tune files on the computer, and if I go in for service work I'll reflash to GMS1. As long as the car functions fine without throwing any codes with the GMS1 tune you shouldn't have an issue. Trifecta would probably be the easiest solution for your situation. The only thing you might have to change out when doing this is your stock airbox as I do not know if the Hahn intake throws codes.

 

Yes, it will be okay. However I (personally) would have went with the K&N intake, like the member above this post. Hahn uses mild steel on their intakes, over time with water/moisture in the air, it rusts.

Also save your $ and get the Turbo XS Downpipe and exhaust system. Best in value, awesome quality.

 

Good info, thats exactly what I was asking.

Ive read about tuning on top of the GMS1 kit with an aftermarket tuner, which will give even more power? How does that work, I couldnt find anything explaining this.

And talking about having someone "tune" for the intake and exhaust system does that mean it has to be custom tuned by.... somebody... that knows what they are doing, or does it mean I need to simply buy a tuner and flash the ECM based on the bolt ons I have?
If someone could clear this up that would be great lol

 

like everyone say a custum tune would be good especially to take advangtage of the dp,, turn off the cat code and to compensate for intake to avoid codes thrown by the fuel trim. Also even tho you are isolate you can still obtain tunes...since im assuming you dont have hptuner I think trifecta maybe the best way for you to go. You can get a real mild tune that accounts for your mods and its all done through email.

 

Does Trifecta tune work WITH the GMS1 kit, or completely override it?
Just trying to figure out if the GMS1 is a complete waste if i decided to do a trifecta tune after.


edit: nevermind I found the answer. Overrides it completely.

 

Alright, does ANYBODY have a HAHN intake, catless DP and catback WITH the GMS1 kit?

I would like to know for sure if it works well from someone who has real experience with this combo.

 

Just to follow up on this, you read about HAHN intakes causing 18% fuel trim readings, is that a positive 18% - ECM adding fuel due to high intake & exhaust airflow?

On this engine, the "normal" fuel trim reading is 0-20%, above 20% for a set amount of time it will set the code. So if I am at 18% there shouldnt be any negative side effects as long as it doesnt exceed the threshold. Am i right? Any idea if the fuel trims are high during idle, cruise, WOT....etc? The more info the better! Im assuming these are Long Term fuel trim values...