Rear Engine wants to Die!

[Dave Underwood]

Can we all try and stay on topic please.

Walter, in an e-mail you suggested a 20 degree C drop in temperature with your blast tube and cover. That is great and would make a real difference at altitude.

Is your test bed similar in configuration to our aircraft with the pump at the front (propeller end) of the engine, below the baffling?

When the RVP is only 7.3 in summer mix and it is a warm day at 18 K your margins for fuel vapourisation are very narrow.

I had thought the summer RVP was over 8, but perhaps you could comment on that and the effects for us please.

As a side note, apparently adding additional cooling to the dry vac. pumps increases their life significantly as well. That has been the comment of a certain Cessna 210 owner who writes in Flying at any rate.

Walter could you please give us the benifit of your experience with fuels and temperatures and the results of your measurements on the the fuel pump.

Regards - Dave

[Walter Atkinson]

Mark:

Intercoolers and their effects are often misunderstood. They are VERY good things to have on a turbocharged engine because they widen the detonation margin. That is their major effect and it is a biggie. Based on the test data I have seen, *I* would not want to operate any turbocharged engine without an intercooler.

Intercoolers do not increase HP output as some suggest. There is no reason to reduce MP on intercooled installations as some claim. Why? Well, the increased exhaust backpressure that results from the use of an intercooler almost exactly offsets the increased HP from the cooler intake air. This effect is from a loss in volumetric efficiency. They forgot to calculate that factor in the equation! That statement usually starts a firestorm of protests from owners but we've proven this on the engine test stand as well. The numbers don't lie.

Ernie:

Two points:

1) the need for all cylinder monitoring is not related to whether or not one runs ROP or LOP. It is a very valubale tool in monitoring the health of the engine and it's value in leaning is actually quite minimal. If the engine will run smoothly LOP, it means that it has balanced F:A ratios and can be leaned using a single probe EGT guage with accuracy. If it will not run smooth LOP, then that means that it has poor F:A ratios ROP as well. I have seen so many engine saves by the use of a good engine monitor that I consider it a NoGo item for an IMC flight. The list of engine *saves* grows monthly.

2) the "Experts are Everywhere" document from Lycoming is interesting. It has one big problem in that it does not even agree with Lycoming's own engineering data. We pointed that out to Rick Moffet, the head of that divivsion of Lycoming who was responsible for its wriitng and he published it anyway. If you read it with care, here's what it really says. "LOP works. LOP operation does not hurt the engine. Pilots are too stupid to do it right."

No kidding, that's what it says. So Lycoming knows it works and says you are stupid.

Personally, I think you're not stupid. I teach engine management to a class of 35-50 pilots on a regular basis and find them to be a very savvy lot. Way above average and capable of very advanced techniques with a little training and education.

I read the post you directed me to (thank you) and found it to be of a vague nature where your worries are concerned. I find that to be a common situation. We can allay those generalized concerns if one asks a pointed question to which we can address a specific answer. A series of specific answers and the understanding that goes with them generally works to allay a generalized lack of understanding of the big picture. It's all in the education. I have found that *I* am a little leary and cautious of things I don't know a whole lot about.

So, what SPECIFIC question might anyone have?

Respectfully,

Walter