I'm just curious as far as what you guys are running as far as a/f ratio at wide open throttle, idle and just basic cruising.

FYI: I'm looking for actual numbering range from widebands...thanks.

 

Air fuel ratio on a stock Cobalt SS/SC is too rich and range from 11:1 to 10.6:1 (at least the 2005 Cobalts SS/SC). 2006 tends to be slighlty leaner for the last RPM's.

 

Is this basically compression ratio? And what is running rich or lean?

 

We are talking about air fuel ratio which is read through the exhaust with an Wideband O2 Sensor. Compression ratio has to do with the volume of your combustion chamber when the pistons are at the bottom of it's stroke.

Running rich is when there is too much fuel being sprayed into the motor. Running lean means there isn't enough fuel being sprayed into the motor. Both in extremes can hurt your performance or damage your motor...of course there are degrees of both...you can run slightly rich and be fine and run slightly lean and be ok but on boosted applications, it's best to run rich than lean. Leaning out leads to detonation.

 

And this is with what size injectors? 36#?

Do you happen to know what the base fuel pressure stock?

 

Would getting your car tuned fix this? Any suggestions...

 

Stock injectors are 34 lbs/hr (rated at 43,5 PSI) but the fuel rail pressure is set at roughly 60 PSI.

 

Thank you very much.

 

Yes. Not exactly sure how you would with the SS/SC though...

 

I saw in these forums that you can tune the SS coupe but nothing about the s/c Cobalt. Why cant they do it with the s/c Cobalt?

 

I think you're referring to the "reflash" that some of them are getting.

I think the reason that GM has their motors running so rich is to prevent detonation...I mean, stock they are doing about 10-11 PSI max.

You could always get some type of standalone unit to take full control but that's the only thing I can think of.

 

whats an ideal air/fuel ratio?

 

In what situation?

 

I did mine yesturday idles at 14.4 crusing at 14.0 pretty solid at crusing. Then after 3800rpm the A/F ratio starts to drop from 14.0 to 13.1 it stays that way till 5200rpm then it drops to 12.4 then it drops again at 5800rpm from 12.4 to 12.0 then again at 6200rpm down to 11.1 I'll draw it out.

14.4----2300-3600 rpm
13.9----3600-3900 rpm
13.9 decends to 13.1----3900-4500rpm
13.1----4500-5200rpm
12.4----5200-5800rpm
12.0----5800-6200rpm
12.0 decends to 11.1----6200-6400
11.1----6400-6500rpm

That as accurat as I could write it without showing you the sheet sorry. BTW This is all with a CAI installed on the car stock the A/F ratios were 0.1-0.2 lower. Not much of a difference

 

Thank you very much

Looks like the computer knows exactly what it's doing to keep you guys from detonating

 

What a/f ratio would you guys reccomend. At my peak RPMs, I want to run very slightly rich. Check my sig to see what mods I want too. Also, can you tell me of a 2.7 in. pulley will be safe or should I stick to the 2.9?

 

mmine is 14.7:1 at idle, is that bad? I have a 3 inch pully and an intake, how can i fix it?

 

First, I would buy a wideband to know what a/f ratio you're running at NOW.

 

14.7:1 is fine for idle. Frankly, as long as you're not in one extreme of an a/f ratio (example: you're idling at 10s or idling at 18s), you should be fine.

 

I am running at almost exactly 14.7 at cruise and I am at about 12.5-12.8 at WOT at the redline.

These readings from a WB 02 pre cat and a CAI/Exhaust and 3 inch pulley.

 

All of those A/F ratios I gave you are at WOT. By Cruise I meant slight acceleration 15% throttle but if you are on flat ground maintaing speed you will be at 14.7 so don't try to "FIX" it besides (it's good for the environment) you could use less fuel going to 15.0 at cruise. But for more power you can make the A/F ratio begin to drop at 3200-3300rpm instead of 3900rpms you will see an increase in TQ sooner rather than waiting for 4200rpms to get most of your TQ.

 

Agreed.

 

Those of you who are saying you are at 14.7 and asking if it's bad take a look at this.
BTW try to keep the stock A/F ratios when modifying things and change MAP tables if you are using HPT

9.0:1 BLACK SMOKE (NO POWER)

11.5:1 RICH BEST TORQUE @ WOT

12.2:1 SAFE BEST POWER @ WOT

13.3:1 LEAN BEST TORQUE @ WOT

14.6:1 STOCHIMETRIC AFR ( CHEMICALLY CORRECT )

15.5:1 LEAN CRUISE

16.5:1 BEST FUEL ECONOMY (EXCEPT FOR HONDA MOTOR COMPANY)

18.0:1 CARBURETED LEAN LIMIT (EXCEPT FOR HONDA MOTOR COMPANY)

22.0:1 EFI LEAN LIMIT

 

If you hit 9.0, your car must be completely off balanced and you are gonna flood your motor in no time lol

Bye Bye O2 Sensor lol

 

Why are you guys with 3 inch pulleys, cai's, and exhausts getting 12.5-12.8's when I'm getting 13.5-13.7 WOT!?!?!? I have the same mods.