I have heard, and then found, some interesting information which may apply to the HHR 2.4 engine.

First, I need to ask a question......

Do the Solstice 2.4 and the HHR 2.4 share the same ECU, in regard to specific engine management?? If they do....

Contrary to information that has been shared on this forum, the HHR 2.4 air fuel mixture LEANS OUT at HIGHER RPM's. Apparently GM intentionally programmed the 2.4 to lean the a/f mixture at, or around, 4200 RPM. The belief is this helps GM attain the fuel mileage claimed.

A friend, who has a Solstice, mentioned this. I did some research on the Solstice forum and apparently it is true. EVERY dyno test done, that also performs the a/f mixture diagnostic, displays data to confirm this.

I believe this would be contrary to the historic a/f mixture belief, and I'm trying to check with people who can absolutely confirm the ECU use and a/f mixture data.

For more information go to the Solstice forum and look under Dyno Tests.

Oh, I want to say...my intent is not to start a "flame war". I believe this is information that the "mod" people need to know.

 

I am thinking of getting an S-AFC to help change that's and gain hp just my 2cent's


thanks phillip

 

Thats not the only auto manufacture that does that..
Nissan does it too.. my G35 used to.... only open up to 80% of full throttle.
Nissan did that to prevent us of reaching fast speeds.. This is done more easier by the fly by wire system.. The ECM software controls the throttle.... my G35 & HHR ECM throttle control has been fixed.. and I have 100% full throttle.. thats another benefit an ECM upgrade does for you...

 

Check with the cobalt performance forums and the ecotec forums first. The AFC's do NOT work well with out engines. Save your money and get a good tune from a reputable company.

Snoopy, good info to know. Now I'll have to check my TPS for WOT %. Thanks!!

 

Ok just did some research on this with some local Cobalt guys. They have HPTuners and it shows all the parameters for these cars. They show the exact same thing... TPS Voltage only reads at 80-86%. However there is another parameter that lists as EPS% which is the actual MOTOR for the throttle and it shows at 100%. I'm guessing the low % on TPS is to prevent the throttle from "over opening". TPS at 100% might take the throttle past wide open and start to reverse it shut again...?? (always a possibility) So for those that need pics I'll try... 0% is like this: | 50% is like this: / 80% like this -- and 100% like this \ Soo... hopefully this helps illustrate a little of what I am referring too!

 

You have more power when running on the edge of lean, thats probably why.

But what do you call lean? I need an actual a/f ratio number.

 

Hmm, well lets see. If 14.7:1 is ideal...im gonna say 14.7000001 is lean, lawl. But in all seriousness i'd say doesn't get any worse than 15:1...

 

Lean really depends on the condition of you making power. If you're naturally aspirated, 14.7 is a fine air/fuel ratio. If you're running forced inducation, people consider 14.7 lean (I would as well) cause of the extreme temperatures and highly likelyness of detonation.

FYI: 14.7 is technically stoich (stoichiometric)