dyno tests?

[13brv3]

Greetings,

Someone on an alternate engine list made the following comment:

You will be surprised to find out that real airplane engines have nothing close to their advertised HP.

I would in fact be VERY surprised if he was right. My impression is that the majority of Lyclones are probably making a few more horses than advertised, particularly with the addition of electronic ignition.

Can someone point me to some dyno data for stock engines?

[Jamie]

Maybe he meant at altitude? For normally aspirated engines the statement is true...but this applies to aircraft AND automotive engines so his statement is pointless.

[mahlon_r]

Rusty,
What an engine makes for HP in a test cell and what it makes on the aircraft are likely different. Exhaust configuration, air box and filter configuration, accessories being driven, air temps, exhaust back pressure, prop configuration all have an effect on the power an engine will make. So the statement is generally true, that the engine rarely produces the same power on the aircraft it did in the test cell.
The power an engine produces in different test cells will also vary with the individual test cells in some cases, because of many variables that can be different between the cells. The same engine in two vastly different test cells would likely produce different raw and corrected horsepower output as well.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are
hopefully helpful to you. Please use the information provided
responsibly and at you own risk."

[mgomez]

Yeah, they mean the power as INSTALLED in the airplane, not the power on the dyno. Lycoming can be trusted to publish good numbers, but once it hits the Cessna/Piper/RV installation, who know what you get?

[13brv3]

I appreciate the comments about dyno methods. I also realized that a seasoned, and properly motivated dyno operator has some control over the numbers you see.

I guess the real question is whether the average new Lycoming will make it's advertised HP at the stated RPM if a fair dyno test were performed. I have to believe it will.

Thanks,

[13brv3]

Originally Posted by mgomez

Yeah, they mean the power as INSTALLED in the airplane, not the power on the dyno. Lycoming can be trusted to publish good numbers, but once it hits the Cessna/Piper/RV installation, who know what you get?

There is a big difference in how the dyno numbers are created, which would appear to make the Aircraft engine appear weaker. As has been noted, the Lycoming numbers are best case, before losses that occur with the installation in a plane. Auto engines are just the opposite. Their rating is worst case, as installed, with the losses that go along with it.

All that being said, the guy on the other list understands all this, and I think his comments are more along the "evil empire", "big lie" theory that plagues companies like Lycoming, Microsoft, etc.

[rv6ejguy]

The Aviation Consumer had some dyno testing done on some Lycos in relation to exhaust systems a few years back. I can't find my issue but I think they said that in some factory installations, they were short as much as 17 hp from the bare Lyco rating. Some were better than others depending on the air filter arrangement and muffler/ exhaust. Someone can correct me if my memory is in error.