AFR too lean? Couple of quick logs from MP215 tune with an E17 blend

#1
Looks like I am peaking at 22.7ish psi in 3rd gear and leveling out at 11.61 Lambda AFR. Unfortunately the MP215 doesnt log knock parameters which is retarded. 2nd gear peaking at 19psi ish. Is this too lean or am I just about right? Was hoping the E17 blend wasnt running it too lean.

3rd Gear Log 1.jpg 2nd and 3rd Gear Run Log.jpg

Car seems to have more backfires lately after a WOT run in 3rd or 4th I noticed too.
 

Hardline

Senior Member
#2
The AFR values are corrected to an E0 value. So think of it more like a Lambda reading. The wideband sensor has no way of knowing what fuel you are running, nor does it care.
 
#3
11.6 is plenty safe imo

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Xaendeau

Senior Member
#4
Looks like I am peaking at 22.7ish psi in 3rd gear and leveling out at 11.61 Lambda AFR. Unfortunately the MP215 doesnt log knock parameters which is retarded. 2nd gear peaking at 19psi ish. Is this too lean or am I just about right? Was hoping the E17 blend wasnt running it too lean.

View attachment 15868 View attachment 15869

Car seems to have more backfires lately after a WOT run in 3rd or 4th I noticed too.
The ideal AFR for maximal engine cooling without losing a significant amount of power is about 11.5 AFR for all the literature I've read for gasoline. Going in the 10:1 to 11:1 AFR range is too rich, you lose a bit of power and fuel economy...emissions go up too. So anything in the 11:1 to 12:1 range is ideal for a forced induction car on gasoline.

Running at 12:1 to 12.5:1 or above on a turbocharged motor for more than a second is a bit...hot. Things will start to have issues. For NA engines, running around 13:1 AFR provides most power without it getting too hot. Nothing really wrong with going too lean except for the heat generated. If it gets too hot in the cylinders (you can tell from an EGR, which we don't have), you start having pre-ignition...and that can wreck things quick. Think of pre-ignition as superknock.

Knock happens around top dead center (TDC). Pre-ignition happens on the intake stroke or the beginning of compression. The reason this is so devastating is because the motor tries to compress an exploding ball of air and fuel...pistons and rods don't like that. Keep it around 11.0:1-12.0:1 and you're fine.

This is perfectly safe.
 

jmrtsus

Senior Member
#6
I was under the impression my MP-215 was optimised for 93 octane. My runs much better with non-ethanol 93 BTW. Why E17?
 

TDavis

Senior Member
#7
My AFR gets to around 10.8 WOT on my tune [wave]
 

hendrixsrv

Senior Member
#8
Mine too. I slightly die when I see 10.8 haha.
 

TDavis

Senior Member
#9


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