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[quote author=CosmicBlueMS3 link=topic=71369.msg1255278#msg1255278 date=1173317522]
dang af of 15:1 it seems
you think thats due to the intercooler?
id be a tad nervous that you are running so lean in warm weather. I really wonder if thats somehow a function of the larger diameter cai or the maf sensor getting some bugged readings.
hopefully someone dyno's the mazdaspeed cai to get some comparisons becuase I dont see how the intercooler could make it so lean, but i dont know volumes about intercooler physics to rule it out either.
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I'm not sure why everyone seems to think he's running "so lean". Must be a Mazda thing where we get comfortable at 10 and 11:1.

He's *crossing* 15:1 for a nanosecond at a given rpm on the way to 13:1. By 4000rpms, he's solidly at 12:1. From the programmable ECU tuning I've done, this seems nearly optimal. Granted, not much room for error, but his #s support that things are working very well. And considering the tempermental nature of the Mazda ECU, I've got think it'll prevent itself from hurting the hardware. Just dicing it up for conversation and exploration but it looks pretty good to me. At least we don't have rotor seals to worry over....
 

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[quote author=desperado callado link=topic=71369.msg1255383#msg1255383 date=1173320298]
[quote author=dread link=topic=71369.msg1255358#msg1255358 date=1173319339]
I have no idea what optimal is, it would be interesting to ask some of the tuners on this forum what they think.
[/quote]

GT1 posted a link to a turbo manufacturer awhile back where they state that 12:1 is borderline lean in a turbo application vs. 14:1 for N/A. But I don't know if they mean across all rpms or just at higher rpms.
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That was from the Garrett sight IIRC. I'm in no position to argue with a company as big and successful and full of engineers as Garrett, but.....in the world of aftermarket programmable ecu's like SDS, Motec, Haltec, MegaSquirt, etc, most turbo guys are tuning for 12:1 AFRs to be safe, not on the ragged edge. 12:5:1 AFRs for max effort and hope an injector doesn't hiccup. And it works well very well. Normally aspirated engines are usually tuned to 13.6 or 13.7:1 AFR for max output and 14.7 and leaner for cleanliness. I offer this only as a point of reference. I think Garrett is being very conservative in that statement.

Now the lean burn angle of direct injection is interesting. Now that it's mentioned, I recall that as well. Stratified charges and all that, although it's being used alot more in Europe than over here from what I recall.....
 
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