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Lean AFRs for cruise
Posted: Fri May 26, 2006 4:20 am
by coyoteboy
I know to get economy you should have leaner AFRs on cruise but how lean can you go without causing problems like burning valves? (toyota 3sgte engine BTW) I could fit an EGT but I would have to dismantle half the engine bay to do it - are there any guidelines? Im getting better than ever fuel economy just with my base map corrected by narrow-band so i dont want to push it too lean by being greedy!
J
Posted: Sat May 27, 2006 8:42 am
by Bernard Fife
CB,
Lean cruise mixtures won't generally burn valves, instead you get a lean misfire. This cause the engine to 'surge' (you can feel this if you watch carefully for it while driving) and the fuel from the misfires is completely wasted, so fuel consumption gets worse instead of better.
On my car, I cannot run leaner than 16.5:1 at cruise, but yours will probably be different, depending on things like the compression, cam, ignition, etc.
Lance.