What is the difference between the 260 HP/manual trans engine and the 235 HP/auto trans?

And please don't say it's 25 HP

 

But that's the answer. Everything I've heard is that they were trying to keep the transmission alive and so detuned the motor. Besides the tune, everything else is the same. If you purchased the GM power adder option they both ended up with the same horsepower.

 

The GM Power Adder option? Is that something I can get now or did it have to be done when new?

 

GM Stage One tune. Or most other tunes that change the MAP sensor. If it was installed correctly there is sticker in the engine compartment and one at the gas fill stating 97 Octane REQUIRED (not recommended). It was a GM authorized tune sold and installed by GM.
Don't know if or how to get it now.

 

The “stage one” (I think they call it something else) from GM claimed 290 for BOTH the automatic and manual, although I’ve read a few reports that it might actually produce a bit more, even more than 290 to the wheels. Depends on the condition of the car and the weather of course.

My local dealer quoted that tune a couple years ago. I imagine if they can get the MAP sensors they can do it, but I imagine some may not want to.

Much of the Ecotec community seems to thing there are better and cheaper alternatives. Some are done along with other mods, including a larger charge pipes, larger turbo, larger injectors, even ethanol-compatible injector seals for tunes for E85 or “E47” which you blend yourself. Also, you don’t necessarily need the MAP sensors, depending on your maximum boost.

It’s my understanding that the 2010 injectors are both larger and have ethanol-compatible seals.

As always, it’s complicated.

As I only drive my SS on the street for now, I’m not in a big hurry to do these mods, as it already has just about all the power appropriate for use on public roads.

 

The Stage 1 stickers don’t list an octane number. The stickers do say “Premium Fuel Required”

 

The "required" is the important part, right?

 

Here are the GMTU(Stage 1) stickers for the HHR SS. Thought I would post some pics since I couldn’t find any recent ones on the site.

 

I never noticed the date on the filler door. If that is what it is.

 

To the original question...

The 235 is sort of an average of available torque in all 4 gears. GM was pretty conservative for the stock automatic SS. They varied the available torque between gears with the torque limiting function of the ECU.

If you do some searching on HPTuners website, you'll find some better information. If I hop on my computer, I'll take some screenshots of the table in HPTuners so you can see the different torque limits per gear.

Regarding the GM Turbo Upgrade Kit availability, my local dealer ordered a kit and installed it in my manual SS about 2 years ago. I also bought another kit from Jegs. They're still available. It's a a good place to start tuning. As I understand it, it makes some changes in the ECU for higher boost reliability that aftermarket tuning software can't make.
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Robert