Lean AFR on Cobalts - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
All about MPG All about maximizing your Miles Per Gallon (MPG)

 
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old 05-23-2014, 08:09 AM Thread Starter
Prospect
 
Join Date: Nov 2013
Location: Indiana
Posts: 15
Lean AFR on Cobalts

I know the stoich is 14.7 for gas but I read that cars generally run a little richer to reduce temps by forcing incomplete combustion (some say more fuel also cools although I am not sure how much effect fuel has on cooling).

I was reading around on this forum so I apologize if I missed something but is there a way to tune the car to run a bit leaner? I looked at temps and the general idea I got was 190-200 is what most people have. Mine runs cooler at 180 (and no, it isn't the cold winter we got this year ). So I was wondering if I could increase the AFR a bit. Can this be done? I found one post about an "AFR controller" but the two links on there were dead. I found an AEM controller but that simply gives you the reading when one is tuning the car. How would I actually tune it though?

And when I do, what are safe AFR ratios? I read that 15:1 is lean but wouldn't cause problems on N/A engines. I read the science behind that and it makes sense but does anyone have experience with it?

Thanks.
maverick1989 is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old 05-23-2014, 06:59 PM
YourCobalt of the Month WinnerForum God


 
Join Date: Oct 2012
Location: Clarence, NY- Buffalo suburbs
Posts: 2,036
If you want to do that you'd need at least a wideband gauge to measure the AFR. I wouldn't want to try this on my car since at best you get a MPG better and at worst you'll blow your engine, that's just tuning and pushing it a little too far. AFR is a weird thing to understand you want somewhere in the 11-12's at full throttle and at partial throttle much leaner is fine.

2009 Cobalt LS XFE (F23) Victory Red
YYZ V.3 Springs, Koni shocks/struts, Powell XXX rear swaybar, Brembo brake swap, 5 lug conversion, Ion Redline wheels, SS/SC interior swap including power conversion, K&N intake, Trifecta tune, Ark Performance N-II catback, Ark shorty antenna, SS body kit, Powell F23 rotated mount, LNF rear mount, Powell CABs
Soon to come- EFR 6758 turbo kit and make Retro Headlights.
andrewcarr1993 is offline  
post #3 of 8 (permalink) Old 05-24-2014, 09:14 AM Thread Starter
Prospect
 
Join Date: Nov 2013
Location: Indiana
Posts: 15
Hey thanks for your response. I should have mentioned - I meant at idle. I have read several numbers at full throttle so I'm not sure which ones to believe (although 12-12.5 have come up the most). At idle though, most engines are tuned for stoichiometric ratios right? Those are 14.7.

I rarely go over 2.5k. Even on the interstates, I go around 75 and I'm at just under 2.5k. Isn't there a way to tune it so that it is a leaner mixture, but safe across the RPM ranges? Also, I'm not sure why it would blow up an engine. Overheating?
maverick1989 is offline  
 
post #4 of 8 (permalink) Old 05-24-2014, 10:37 AM
YourCobalt of the Month WinnerForum God


 
Join Date: Oct 2012
Location: Clarence, NY- Buffalo suburbs
Posts: 2,036
If the engine is too rich you get crap fuel economy and unless it's ridiculous it won't hurt the engine, too lean and the exhaust temps will be high and lead to burning parts possibly detonation. As I said it's not worth it, you're talking about $500 minimum for very little gains.

2009 Cobalt LS XFE (F23) Victory Red
YYZ V.3 Springs, Koni shocks/struts, Powell XXX rear swaybar, Brembo brake swap, 5 lug conversion, Ion Redline wheels, SS/SC interior swap including power conversion, K&N intake, Trifecta tune, Ark Performance N-II catback, Ark shorty antenna, SS body kit, Powell F23 rotated mount, LNF rear mount, Powell CABs
Soon to come- EFR 6758 turbo kit and make Retro Headlights.
andrewcarr1993 is offline  
post #5 of 8 (permalink) Old 05-24-2014, 12:27 PM
Levee
YourCobalt of the Month Winner
YourCobalt.com Premium Member
Admin


 
Leveecius's Avatar
 
Join Date: Aug 2009
Location: Battle Creek, MI
Posts: 3,210
Garage
Send a message via Yahoo to Leveecius
Here is input for you. WOT on FI cars should be low 12s:1 depending on the power you're running and fuel. High 14s to low 15s is perfect for NA. You CAN run it leaner by tuning it, and with a dd NA car you plan to never race, that's not bad. I made over 50mpg on my SS when not racing or in boost with no issues because I tuned to meet my economy needs. So yes you can lean it more.

Fuel does help cool, but not as much as people think it does. Yes running leaner will run hotter, but there is a fine line for the "perfect" ratio for optimal cooling and fuel economy.

'09 SS/TC - Stolen
Mods - Injen CAI, CIA MAF Relocate CP's, Dejon FMIC,
Custom 3" DP, 3" Exhaust, GT3076R, Pioneer AVH-4100DVD, Hurst STS, ZZP triple pod, Autometer Cobalt boost/DPIC/WB gauges, Nitto NT05 245/40/18's, H&R Springs, 80:20 Meth Spray
Future - KSport Kontrol Pro Coilovers, 10% Tint, FMIC spray
538whp/501wtq @38 psi on meth and 93 oct on stock ish motor


06 EVO IX MR/SE - Sold
Mods - *Updated 10/6/13* AEM TRUboost EBC, 4in custom TBE, SD dual 93/e85 tune, ETS 4in Race Core FMIC, Dual Aeromotive 400lph Fuel Pumps, T4 Tubular Manifold w/ dual WG's, FP Super99HTZ DBB Turbo, GSC 274 mivec cams, ARP headstuds/rod studs, FIC 2150cc Injectors, Aeromotive FPR, Aeromotive Fuel Rail, catch can, Mini Battery Kit, Slim Coolant Fan, Kiggly Racing high pressure valve Springs/Titanium Retainers, Supertech Stainless Steel Valves, Dual VTA Tial 44mm WG's, 4g64 Stroker Manley Pistons, 155mm 2.4 LR Manley Turbo Plus I Beam Rods with ARP 625 Studs, 100mm forged non-billet Manley Crankshaft, Full H/E PNP with Port Matching, Kiggly Racing Girdle, Dual Tial 50mm BOV's, Excedy Triple Disc Carbon HD Clutch, AEM EMS

'95 Ram 2500 Diesel
Mods - 5in TBE, Boost Elbow set to 28psi, Adjusted fuel pump, Open Turbo.

Future Mods- Super Street Clutch (rated @1400ftlbs tq), 67mm turbo, 160lb valve springs, added timing, tubular exhaust manifold, larger injectors, possible 6 spd swap.


Master ASE Certified Gasoline/Diesel Technician since 2004

Speed Junkies Social Group

Yourcobalt Official Facebook Page!

Syndicate of Tuners Official Page! Up and going again as of 1/11/13

Click here to PM me if you have questions or issues!
Leveecius is offline  
post #6 of 8 (permalink) Old 05-24-2014, 02:36 PM
Super Moderator


 
Plain Jane's Avatar
 
Join Date: Mar 2013
Location: Montreal, Quebec
Posts: 3,860
Garage
Why does the AFR spike when getting off the gas in gear on my NA? It'll jump to the gauge's limit of 17.0, then read --- until I apply the throttle or hit the clutch. Is that because fuel is cut off?

'07 Eclipse GT build thread - 280whp, 254wtq
Plain Jane is offline  
post #7 of 8 (permalink) Old 05-24-2014, 04:31 PM
Levee
YourCobalt of the Month Winner
YourCobalt.com Premium Member
Admin


 
Leveecius's Avatar
 
Join Date: Aug 2009
Location: Battle Creek, MI
Posts: 3,210
Garage
Send a message via Yahoo to Leveecius
Yes, it's not off, but it puts a lot less fuel in to help slow the engine down when you're not on the throttle

'09 SS/TC - Stolen
Mods - Injen CAI, CIA MAF Relocate CP's, Dejon FMIC,
Custom 3" DP, 3" Exhaust, GT3076R, Pioneer AVH-4100DVD, Hurst STS, ZZP triple pod, Autometer Cobalt boost/DPIC/WB gauges, Nitto NT05 245/40/18's, H&R Springs, 80:20 Meth Spray
Future - KSport Kontrol Pro Coilovers, 10% Tint, FMIC spray
538whp/501wtq @38 psi on meth and 93 oct on stock ish motor


06 EVO IX MR/SE - Sold
Mods - *Updated 10/6/13* AEM TRUboost EBC, 4in custom TBE, SD dual 93/e85 tune, ETS 4in Race Core FMIC, Dual Aeromotive 400lph Fuel Pumps, T4 Tubular Manifold w/ dual WG's, FP Super99HTZ DBB Turbo, GSC 274 mivec cams, ARP headstuds/rod studs, FIC 2150cc Injectors, Aeromotive FPR, Aeromotive Fuel Rail, catch can, Mini Battery Kit, Slim Coolant Fan, Kiggly Racing high pressure valve Springs/Titanium Retainers, Supertech Stainless Steel Valves, Dual VTA Tial 44mm WG's, 4g64 Stroker Manley Pistons, 155mm 2.4 LR Manley Turbo Plus I Beam Rods with ARP 625 Studs, 100mm forged non-billet Manley Crankshaft, Full H/E PNP with Port Matching, Kiggly Racing Girdle, Dual Tial 50mm BOV's, Excedy Triple Disc Carbon HD Clutch, AEM EMS

'95 Ram 2500 Diesel
Mods - 5in TBE, Boost Elbow set to 28psi, Adjusted fuel pump, Open Turbo.

Future Mods- Super Street Clutch (rated @1400ftlbs tq), 67mm turbo, 160lb valve springs, added timing, tubular exhaust manifold, larger injectors, possible 6 spd swap.


Master ASE Certified Gasoline/Diesel Technician since 2004

Speed Junkies Social Group

Yourcobalt Official Facebook Page!

Syndicate of Tuners Official Page! Up and going again as of 1/11/13

Click here to PM me if you have questions or issues!
Leveecius is offline  
post #8 of 8 (permalink) Old 05-25-2014, 12:53 PM Thread Starter
Prospect
 
Join Date: Nov 2013
Location: Indiana
Posts: 15
Quote:
Originally Posted by Leveecius View Post
Here is input for you. WOT on FI cars should be low 12s:1 depending on the power you're running and fuel. High 14s to low 15s is perfect for NA. You CAN run it leaner by tuning it, and with a dd NA car you plan to never race, that's not bad. I made over 50mpg on my SS when not racing or in boost with no issues because I tuned to meet my economy needs. So yes you can lean it more.
Thanks for your response.

Quote:
Fuel does help cool, but not as much as people think it does. Yes running leaner will run hotter, but there is a fine line for the "perfect" ratio for optimal cooling and fuel economy.
Yes this I saw on an actual test being done one an engine. The cooling effect is actually because more fuel (provided you aren't already over stoich, which you aren't at 12:1) means more gasoline molecules burn. More burn means more energy means more heat means higher temps. I saw this during an internship I had. Increasing the ratio by 0.1 jumped temps up by 8 degrees on that engine. Thought it was pretty interesting and I was playing with it until my boss came in and I had to stop
maverick1989 is offline  
Sponsored Links
Advertisement
 
Closed Thread

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome