AFR tuning theory
Jan 31, 2010, 08:55 PM
#16
ok...
so in a nutshell:
richer or leaner than 11.8:1 results in slower flame front, this means you may need more timing to make the same power
richer than stoich = cooler
richer (11:1) = dirty burn, carbon deposits etc
leaner (12:1) = cleaner burn, hotter burn
I would have thought that in an effort to keep temps down, running richer is better???
I do notice a difference in how the engine "sounds" when running 10.5 vs 11.5 - less "grindy" if that makes sense...
so in a nutshell:
richer or leaner than 11.8:1 results in slower flame front, this means you may need more timing to make the same power
richer than stoich = cooler
richer (11:1) = dirty burn, carbon deposits etc
leaner (12:1) = cleaner burn, hotter burn
I would have thought that in an effort to keep temps down, running richer is better???
I do notice a difference in how the engine "sounds" when running 10.5 vs 11.5 - less "grindy" if that makes sense...
Last edited by tephra; Jan 31, 2010 at 09:00 PM.
Jan 31, 2010, 09:02 PM
#17
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I'm not 100% on the theory as to why the burn is better when leaner ( I have my ideas but not enough proof to make a confident claim yet), but yeah over rich mixtures tend to burn poorly and also increase the chance for missfire..
Give it a shot and let me know how it works out.. Next evo I do I'll post up some graphs at different AFRs to show the difference in power.. Hopefully they won't delete my post. We posted up a graph a couple days ago and they deleted the post since were not a sponser.
And if you go leaner, you will probably make the same power with less timing due to the effeciency of the burn being better, but MBT will be reached with slightly more advance then if it was richer. All of this of course is assuming you can even reach MBT on this motor without knock on pump gas which I don't think is very likely.
Give it a shot and let me know how it works out.. Next evo I do I'll post up some graphs at different AFRs to show the difference in power.. Hopefully they won't delete my post. We posted up a graph a couple days ago and they deleted the post since were not a sponser.
And if you go leaner, you will probably make the same power with less timing due to the effeciency of the burn being better, but MBT will be reached with slightly more advance then if it was richer. All of this of course is assuming you can even reach MBT on this motor without knock on pump gas which I don't think is very likely.
Last edited by Bugermass; Jan 31, 2010 at 09:04 PM.
Jan 31, 2010, 09:18 PM
#19
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I've been wanting to try your rom out.. I've got a customer thats gonna let us use his EVO8 for testing some parts and what not, and he was down to let me test your rom on his car.. Anything special I need to know? Or just flash and tune like normal??
Feb 1, 2010, 06:49 AM
#24
Good read, I actually noticed this with my car. If I tune for a bit leaner usually the knock goes away. It may be the case that these engines prefer a slightly leaner AFR. Not super lean, just leaner than the norm.
I will we could have direct injection the Sky/Solstice turbo cars run like 12.8/13's AFR at WOT.
I will we could have direct injection the Sky/Solstice turbo cars run like 12.8/13's AFR at WOT.
Feb 1, 2010, 12:03 PM
#25
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LOL.. Yeah I doubt it's possible just from the handfull off evos I've done so far.. maybe with a really good manifold and a good sized turbine housing and wheel and some good cams. But I havn't had the chance to do one like that yet.
Feb 1, 2010, 01:15 PM
#27
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I see these threads pop up every half year or so.
Hopefully we don't start seeing melted pistons after people think they can run 12.5-12.8 AFR's on pump gas
- Bryan
Hopefully we don't start seeing melted pistons after people think they can run 12.5-12.8 AFR's on pump gas
- Bryan
Last edited by GST Motorsports; Feb 1, 2010 at 01:17 PM.
Feb 1, 2010, 01:51 PM
#30
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My thoughts as well..12 AFR can be just fine for NA K series engines..but for evos/turbo cars it could be dangerous...EGT's will be high...but nonetheless OP has quite interesting points there..subscribed..