The International Cessna^® 170 Association

hilltop170 wrote:Miles-
Did #6 cylinder ever get into the fight? The EGT spreads looked pretty wide. Mine are bad also but even out almost perfect with full carb heat.

Richard,

I KNEW I should have cut that picture in half crosswise before I posted it in the Panel Lights thread)!

Yes #6 runs closer to the rest now, but still a 100 to 150 degree spread across the board. I've never paid any attention to EGT's with carb heat on; I'll give it a try next time I think about it.

What I really need to do something about is #5 and #6 CHT being 100 degrees lower than the rest. I need to install the later model baffle parts in front of those two cylinders, I've just never taken the time.

Miles

Just out of curiosity, Miles;

How is it that your tach has only 0000.5?

Iceman07 wrote:Just out of curiosity, Miles;

How is it that your tach has only 0000.5?

I took this photo on the first flight after overhauling the engine and installing a new tach.
Miles

He flys slow.

Miles-
Carb heat does make a difference with EGT's, especially in cooler temps and higher altitudes.

The baffles in front of #5 and #6 did make a difference with CHT's but if I had it to do over (and I might), I would not cut the holes adjacent to the exhaust flange on #6 or adjacent to the intake flange on #5. My #5 and #6 still run cooler than the rest, I think, because the extra air impinging in those areas behind the holes still is enough to cool them down too much. I would dimple those areas out where the holes are so air could pass by and not be trapped. Cessna put full baffles up in front of some IO-520 front cylinders and they cool just fine and match the other four rear cylinders.

Miles, did you not obtain the Airframes, Inc. baffle system? And did it not include the front baffles?

EGT is affected by carb heat application because of it's enrichening effect on mixture. (And it subsequently affects CHT, but you know all that.)

My coolest cylinders (EGT) are always 1 and 6. #5 is usually the hottest and the first to peak when I'm leaning. That implies #5 is running leaner than the others. I've carefully inspected for an intake manifold leak, but can't find anything wrong.

All cylinders run cooler when I pull on carb heat (as expected).

gahorn wrote:Miles, did you not obtain the Airframes, Inc. baffle system? And did it not include the front baffles?

George, I did buy the the complete Airframes Baffle Kit for the 170B pressure cowl, but that kit only includes the parts shown in the 170B IPC for later 170B pressure cowl-type baffling system. The 170 did not have the vertical pieces that that came later on 172's, that block the front of the barrels of cyls 5 & 6. There are photos in other threads that show where others have installed these parts (purchased or fabricated) and sucessfully evened out their CHTs.

Dale, my #5 always peaks first and runs the hottest EGT too, but #2 isn't far behind. If you look at the intake manifold, the paths from the carb to cyls # 2 and 6 are identical.

Miles