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Old 05-23-2020, 07:28 AM   #26 (permalink)
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Gaptooth (retired) - '00 Honda Insight
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Originally Posted by California98Civic View Post
How important are such timing changes under light load? You are at like 20% load at 60 mph, right? Seems slight risk of problems under such conditions, no?
You're right in that at light load I'm not going to hurt anything, it's more about efficiency.

If the timing is too retarded, cylinder pressure won't peak until the piston is already well down the cylinder, and a lot of potential work will go out the exhaust. Advance it too much and a larger portion of the work will happen while the piston is still rising on the compression stroke, and will be essentially trying to turn the engine backwards. Either way, fuel economy and power both suffer. Even been a couple of degrees off and the differences will outweigh and gains.

I want to say the Insight's stock engine advances ignition timing 20+ degrees when it goes into lean burn, and being off 3-4 is significant, so simply leaning out without adjusting timing isn't likely to do any good.

I *think* it can be done with an EGT sensor, but may require dyno time.
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