Eggenfellner - Page 3

Steve A · #21 10-13-2006, 09:03 AM

I have to comment on the 4 cylinder underpowered post. Dan Checkoway rated various RV's and power components. Apparently he tied the planes to a device that measured force on the ground developed by the various engines. The plane that came out on top was Robert Paisley's RV-7 with a four cylinder supercharged Eggenfellner Subaru engine. Checkoway's plane was second (I believe he has the 200 hp 360 Aerosport). In addition, Paisley and Checkoway flew side by side and Dan said the Subaru flew away from him and had a passenger to boot. I believe Checkoway's effort as a fair post as opposed to a "I have a friend that can't go over 160...

prkaye · #22 10-13-2006, 09:12 AM

Naive question here - I've read a lot that the actualy HP that you get at the propeller may be considerably less than the rated HP of the engine (in the case of the Eggenfellner), and this is why planes with these engines are often under-powered and need a CS prop. My question is, where is the extra horsepower going? If the engine is rated at 165HP, why are people only getting the equivalent performance of a 120 aircraft engine? Is it simply because the auto engine isn't able to develop it's full horsepower in thinner air at altitude?

Would a 200hp Mazda Rotary exhibit a similarly reduced actual HP at the propeller?

cjensen · #23 10-13-2006, 09:20 AM

HP is lost at altitude with ALL normally aspirated engines. I don't recall reading anything about conversions losing HP at the prop, but I could be wrong. There may some loss due to the power having to go through the reduction drive to get to turning the prop. Same theory applies to cars and the horsepower that actually gets to the driving wheels. The torque that engines produce is a real factor (not the ONLY, obviously) in determining performance, and the geared engines work well with torque because through the reduction, torque is multiplied. The rotary's work in the same fashion as a Subie.

gmcjetpilot · #24 10-13-2006, 09:34 AM

Quote:

Originally Posted by Steve A

I have to comment on the 4 cylinder underpowered post. Dan Checkoway rated various RV's and power components. Apparently he tied the planes to a device that measured force on the ground developed by the various engines. The plane that came out on top was Robert Paisley's RV-7 with a four cylinder supercharged Eggenfellner Subaru engine. Checkoway's plane was second (I believe he has the 200 hp 360 Aerosport). In addition, Paisley and Checkoway flew side by side and Dan said the Subaru flew away from him and had a passenger to boot. I believe Checkoway's effort as a fair post as opposed to a "I have a friend that can't go over 160...

Yea you tell em Steve, that's right, that is why Subaru's are winning all the races: Reno, Sun-n-Fun 100, Airventure cup and cafefoundation challenge.

Oh,

My bad, that is Lycoming winning all the races.

I guess per Dan's test if you want to pull something across the ramp may be the Subaru is better?

cjensen · #25 10-13-2006, 09:42 AM

Quote:

Originally Posted by gmcjetpilot

Yea you tell em Steve, that's right, that is why Subaru's are winning all the races: Reno, Sun-n-Fun 100, Airventure cup and cafefoundation challenge.

Oh,

My bad, that is Lycoming winning all the races.

I guess per Dan's test if you want to pull something across the ramp may be the Subaru is better?

Here we go again...What point can this possibly have?

Do ANY Subaru drivers care about winning a Reno race? SNF 100? Cup? I don't think anyone has claimed to win a race with a Subie. We do know that Robert did pull away from Dan though...

(Sorry Dan!)

prkaye · #26 10-13-2006, 09:44 AM

>> What point can this possibly have?

The point, as far as I am concerned, is not to win any races, or even to install a Subaru engine. Right now I am just trying to educate myself. No, I don't "live under a rock" as someone suggested in an earlier post. I am just new to all this, and am trying to draw on other people's expertise to gain a better understanding of all the issues involved with these things.

cjensen · #27 10-13-2006, 09:46 AM

Phil, I hope you didn't take that as directed towards you...it was for George's race comment.

prkaye · #28 10-13-2006, 09:51 AM

ah, now I understand... sorry... just don't want people to think I'm "stirring the pot", or trying to provoke an ongoing debate. I am curious about this loss of HP though... I read a lot of people saying they get really poor performance without a CS prop on the Eggy. When I saw the engine is rated at 165hp, this confused me. People running a 160 hp O-320 on their -9 get great performance!
I guess the power being eaten up by the reduction drive makes sense. Maybe part of it has something to do with torque? Maybe this would explain why a CS prop is needed? Again, I'm pretty ignorant when it comes to these things... but I'm learning (mostly thanks to people's replies on this forum).

DGlaeser · #29 10-13-2006, 09:53 AM

Quote:

Originally Posted by prkaye

Naive question here - I've read a lot that the actualy HP that you get at the propeller may be considerably less than the rated HP of the engine (in the case of the Eggenfellner), and this is why planes with these engines are often under-powered and need a CS prop. My question is, where is the extra horsepower going? If the engine is rated at 165HP, why are people only getting the equivalent performance of a 120 aircraft engine? Is it simply because the auto engine isn't able to develop it's full horsepower in thinner air at altitude?

Would a 200hp Mazda Rotary exhibit a similarly reduced actual HP at the propeller?

The HP developed is a function of the engine RPM. The HP doesn't "go" anywhere, it just isn't created. The max RPM and therefore HP is determined by the gear ratio in the PSRU and the max prop RPM (typically 2700). The original Eggenfeller PSRU is a 1.86 ratio which does not allow the engine to get to it's max HP rpm - and that was by design to be conservative. The latest PSRU is a higher ratio, 2.01, which will up the max HP.
There are folks who have Jan's engines with a FP prop. A CS prop with any engine just gives you better efficiency, particularly in cruise where you can operate at higher MP and lower RPMs.

cjensen · #30 10-13-2006, 09:56 AM

Ah! Okay, yes you are very correct that these engines DO need a CS prop. The problem with fixed pitch props on a coversion is that the engine cannot reach it's horsepower rated RPM. That's the issue there. As you know, the FP prop is pitched for one realm of flight, climb or cruise. Even with a cruise prop, the RPM is restricted enough that the engine cannot develop the power needed to get the speeds desired or tested.

An FP prop on a 320 works fine because it is direct drive, and engine can reach the needed RPM.