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-   -   AF vs timing ? (https://www.miataturbo.net/general-miata-chat-9/af-vs-timing-11312/)

mtncrvr 07-18-2007 06:35 PM

AF vs timing ?
 
I've searched the forum and surprisingly didn't find a thread on this.. so

What's the general concensus on tuning ? 12.5 A/F under boost and less timing or 11ish and more timing ? What's the best A/F / timing compramise for power ? I've seen various opinions generally more towards tune for 12.5's then add timing where you can.

hustler 07-18-2007 06:49 PM

tune fatter if you want it to last longer. I hear 11.5:1 is what the high end professional tuners use at 10psi+ for a car you want to last.

He also suggested not even messing with time until you can get it on a dyno.

I had a long conversation with many notes from a guy at boostlogic

I was thinking about advancing the timing as much as I can without knock, then taking it to a dyno and backing it off where possible without a power penalty

.

y8s 07-18-2007 08:15 PM

there's a timing value for all load and rpm points that will maximize power.

same for AFR.

12.5 is pretty lean for boost above about 5 psi. I run a fairly lean 11.8-12:1 at 9 psi.

The thing you wanna do is set your fuel to be fairly conservative and find the MBT point. that's ummm Maximum advance for Best Torque I think. Add timing so that your torque increases. when it stops increasing, go back to the last value that was an increase and you're at MBT. If it knocks during this process, add fuel. Going too rich will sacrifice power though.

etc etc.

Marc D 07-20-2007 06:10 PM

great, this should help me in tuning my car. thanks for the posts.

mtncrvr 07-23-2007 06:13 PM

Good feedback thx guys :-) and I forgot to mention I'm running 12psi.

Mach929 07-23-2007 07:36 PM

at the dyno it seemed most cars were making best power around 11:1


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