RV-9 with 180hp

[rvbuilder2002]

Originally Posted by Bryan Wood

We're going to have to agree to disagree. I don't want to argue with you either, but you should know just how condesending your response to the picture was. It certainly had the potential to encite rage.

While my plane meets the published specs or better , it lacks the ability to get to the yellow unless in a 200 fpm decent of so in cruise. As for going all in down low, well that is what a throttle is for.

Brian,
I want to apologize if that is the effect my post had. I am not always good with words. That is not the intent I had, I am sorry. I also hadn't noticed previously that you represent your airplane as having 170 HP, not 180. You have always seemed to be a big proponent for using 180 HP in an RV-9 so I made an incorrect assumption.

The point I was trying to make was that showing an IAS at 8500 feet that is in the green arc is not relevant to the reason the RV-9 is recommended for engines only up to 160 HP. A 180 HP RV-9 at 75% power at 8500 ft probably would be about 7-8 mph IAS short of the yellow arc, but at 75% power at 2500 ft it would have an IAS that was well into the yellow arc. Please note that at 2500 feet, "all in" is not 75% power, it is well over that.

That is the reason the RV-9 is only approved for up to a 160 HP engine.

[rvbuilder2002]

Originally Posted by n5lp

Scott, I'm on your side in this stuff, but for the engines we are talking about, normally aspirated O-320s and O-360s I can't find anything from Lycoming that limits the engines to 75% continuous power. I believe they are rated at 100% continuous power. Please advise me if I am wrong. I certainly can't find anything about a 75% power limitation.

Your right Larry. I did a quick look in some of the documentation I have at home and even the type certificate data sheets list max HP and RPM as continuous.
I didn't remember that, thanks for pointing it out.
That would make the RV-9 160 HP recommended limit even more relevant.

[Bryan Wood]

Originally Posted by rvbuilder2002

Brian,
I want to apologize if that is the effect my post had. I am not always good with words. That is not the intent I had, I am sorry. I also hadn't noticed previously that you represent your airplane as having 170 HP, not 180. You have always seemed to be a big proponent for using 180 HP in an RV-9 so I made an incorrect assumption.

The point I was trying to make was that showing an IAS at 8500 feet that is in the green arc is not relevant to the reason the RV-9 is recommended for engines only up to 160 HP. A 180 HP RV-9 at 75% power at 8500 ft probably would be about 7-8 mph IAS short of the yellow arc, but at 75% power at 2500 ft it would have an IAS that was well into the yellow arc. Please note that at 2500 feet, "all in" is not 75% power, it is well over that.

That is the reason the RV-9 is only approved for up to a 160 HP engine.

No worries, accepted and back at you. If the truth be told I've flip flopped on the engine debate over the years. I guess it is the grass is always greener thing playing out.

[rvbuilder2002]

Not to drag this out any further, but for anyone lurking in the thread that has an interest in an explanation of this issue far better than I can make...
Check this link http://www.vansaircraft.com/pdf/hp_limts.pdf
Scroll down to the third article in the document

[Finley Atherton]

Originally Posted by n5lp

Scott, I'm on your side in this stuff, but for the engines we are talking about, normally aspirated O-320s and O-360s I can't find anything from Lycoming that limits the engines to 75% continuous power. I believe they are rated at 100% continuous power. Please advise me if I am wrong. I certainly can't find anything about a 75% power limitation.

I think you are correct that they are rated at 100% continuous, however this is from Lycoming for normally aspirated engines:

For maximum service life, maintain the following recommended limits for continuous cruise operation:
a. Engine power setting ? 65% of rated or less.
b. Cylinder head temperatures ? 400˚ F. or below.
c. Oil temperature ? 165˚ F. ? 220˚ F.

Fin
9A

[smithhb]

Originally Posted by rvbuilder2002

In the case of an RV-9 with 180 HP flying at 2000MSL at 75% power, the IAS would be well into the yellow.

Not to beat a dead horse here but this is not true for my beast. I guess I had better get those wheel fairings finished....

[rvbuilder2002]

Originally Posted by smithhb

Not to beat a dead horse here but this is not true for my beast. I guess I had better get those wheel fairings finished....

I'm not sure what you have installed for fairings right now, but a full set is good for about 15 MPH at cruise power settings.