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Discussion Starter #1
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 :cheesy: ). 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.
 

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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.
 

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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?
 

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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.
 

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Levee
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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.
 

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Levee
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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
 

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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.

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 :cheesy:
 
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