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Forced induction transition afr

EFI Tuning Fundamentals

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Discussion and questions related to the course EFI Tuning Fundamentals

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So I was just watching the section on afr selection. On the graph the area where wot na/ fi transitions are I am curious what I should try to target. On my subaru I keep my cruise and higher load cruise up to about 80kpa around 1 lambda but as I'm climbing hills but not quite crossing into boost I usually targeted it around .92 lambda I see that n/a cars respond the best around .87-.9 lambda but for my turbo setup where I'm cruising up hills in that 90-110kpa range I felt as if I was wasting gas/torque. I leaned it out to .95 lambda and haven't noticed any I'll effects and slightly better climbing power. But is holding that lean of an afr alright in that transition zone? Subaru so of course were knock sensitive and I'm running 28° total advance at 100kpa

There is no set number unfortunately and each engine and setup might require something very different.

Things to take into consideration when choosing an AFR Power/torque, it sounds like you're making best power/torque at your chosen AFR

Knock, is the engine suffering from detonation which could damage the pistons etc

Temp, combustion temperature, is there adequate fueling to keep combustion temps down under prolonged conditions, protect piston, valves, sparkplug tips, high exhaust temps etc. This is usually the harder one to check unless running EGT, usually high combustion temps will show up when you start to pick up knock, however, this isn't always the case.

I tune plenty of the Subaru EJ motors and to be honest I don't see what you're doing being a problem. I have come to the same conclusion when tuning these. Typically around .95 at 100kpa which tappers down to .90 by 120kpa

The above things are just somethings to keep in mind when choosing your AFR, plus other factors.

At least now that you have this course you can refer back to it at any time!

Thank you for the reply! I appreciate the help

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