Reply To: Evindure 56 CD smokes

[Don]

I know it seems counter intuitive, but using high octane fuel in this engine may be a mistake. I’m not referring to “no ethanol”, just high octane. These engines have very low compression and oftentimes were run poorly on high octane fuel. Higher octane fuels have a more controlled burn and burn slower. These low compression engines kind of need more “volatile” lower octane fuel in order to develop a stronger burn in the combustion chamber. Again, I know this seems counter intuitive, but I proved it to myself several years ago with one of my old Fleetwins. I thought I was being smart buying no lead (no ethanol) 91 octane aviation fuel. Mixed up a fresh batch for our first outing…The engine started, but didn’t really idle all that well, and did not develop full power…Was very confused indeed, what could have happened to this engine since the last time I used it? Finally tried Will’s regular fuel mix, the engine idled and picked up a few hundred RPM at WOT. I had a hard time believing this, so brought both tanks for a test ride. Took off on Will’s tank at WOT, then switched to my high octane tank while running, the engine actually lost a few hundred RPM at WOT. Made this swap several more times, not really believing what I was seeing, same results repeated every time I swapped tanks…
Hard to believe, but something to consider….