RV-7 Egg H-6

[rv6ejguy]

Originally Posted by flyeyes

I really like the idea of auto-engine conversions. I like the water cooling, smoothness, and potential economies of scale, but I haven't seen one that performs as well yet wasn't either very labor intensive (Tracy Crook) or expensive (Mistral)

The Thunder Mustang is the fastest naturally aspirated engined aircraft in the world and holds the fastest race lap in the Sport Class at Reno. Not bad for an auto/boat engine.http://www.bluethunderairracing.com/about/results.htm

Several auto powered canards easily outperform their Lyco powered sisters.

My Sube RV does 0-60 knots in 8 seconds without holding it up on the brakes and without ramming the throttle ahead.

We trade installation and development time for lower up front costs.

You are correct in stating that no turn key auto conversion is currently available which can match overall Lycoming performance in an RV but properly executed auto conversions can certainly match climb and cruise numbers.

Chad, some people are just very negative about this subject and will attack most anything you post on it. It's not their fault. Being subjected to years of Lycoming vibration levels is bound to result in some sort of brain damage- they seem to turn nasty.


My initial reaction to the video was negative as well until you enlightened me about the conditions with the shortened grass takeoff area due to an accident and the high density altitude. Naturally the zoomed lens gives an illusion as well. We are quick to jump to conclusions when all the facts are not at hand. It would have been in context only if you had followed the takeoff of other RVs or aircraft to judge relative performance. Thanks for posting.

[TSwezey]

Ross ,
How is the -10 going?

[rv6ejguy]

Once I get the pinholes and depressions in the cabin top filled (arrgghh) and my magic coating on the inside of it, I'll get that sucker bolted on. Then it's on to the doors which I understand are the most fun part on a -10.

Most of the other metal work is done so mainly final wiring, lots of fiberglass "fixing", windows, rebuild the Sube (the fun part for me) and a bit of fab work on the turbine oulet pipes. I'm leaving paint to the shop who did my 6A. I hope to fly it sometime in '08.

I'll be looking for some Lyco -10s to do a flyoff against eventually. A friend has one nearby who just started test flying last week. Maybe we can get together sometime and do a Chevy vs. Subie comparo too.

You gonna be flying soon?

[TSwezey]

Hopefully we will get this bird in the air next month. Both of us have been swamped with work and life. It is coming together though. All the parts are built. We have to fit the cowl, finish the panel, EFIS/One wiring and some paint and we should be ready to go. Hopefully I can start the engine with the prop on in the next week. It's been a great learning experience but now it needs to be a great flying experience!

[captainron]

Originally Posted by rv6ejguy

My Sube RV does 0-60 knots in 8 seconds without holding it up on the brakes and without ramming the throttle ahead.

Where does all that horsepower go? I'm sure that same engine, if you had left it in the car, would do 0-60 in much less time than 8 seconds. And the car probably weighs 3250 pounds and doesn't get any "lighter" on its feet the faster it goes! What does your RV-8 weigh when it's getting this performance?
In the car, horsepower is sapped by the transmission, 4WD running gear, air conditioning, exhaust system, etc..
On your plane, the only thing you're driving is the re-drive and a propeller.
Where's the performance?

[TSwezey]

Sorry to do a little thread stealing but it is about car engines in planes!

[cjensen]

Alright ladies and gents...here's the new thread with a link to ALL of my Subaru video's currently in my library...

VAF link to my Sube videos

[Kevin Horton]

Originally Posted by captainron

Where does all that horsepower go? I'm sure that same engine, if you had left it in the car, would do 0-60 in much less time than 8 seconds. And the car probably weighs 3250 pounds and doesn't get any "lighter" on its feet the faster it goes! What does your RV-8 weigh when it's getting this performance?
In the car, horsepower is sapped by the transmission, 4WD running gear, air conditioning, exhaust system, etc..
On your plane, the only thing you're driving is the re-drive and a propeller.
Where's the performance?

In a car, the engine's power is transmitted via transmission, CV joints etc. The transmission is very efficient, so the vast majority of the power produced by the engine is available as thrust horsepower. On an aircraft, the engine's power is sent to the propeller, and the prop creates thrust. But, the prop is optimized for high speeds, which is where the aircraft spends most of its time. The prop efficiency is almost certainly less than 60% during the takeoff, and it is probably less than 50% during the early part of the takeoff roll. So, if the prop efficiency is less than 50%, that means that less than 88 hp of the 175 hp is actually used to produce thrust. This is one big reason why an aircraft will have worse low speed acceleration than a car of similar power to weight ratio.

[Yukon]

Apples to apples Kevin. Doesn't this apply to Lycoming aircraft also? How does Van's claim 350 feet for takeoff for an RV-7 on 88 hp???????

[szicree]

Originally Posted by captainron

Where does all that horsepower go? I'm sure that same engine, if you had left it in the car, would do 0-60 in much less time than 8 seconds. And the car probably weighs 3250 pounds and doesn't get any "lighter" on its feet the faster it goes! What does your RV-8 weigh when it's getting this performance?
In the car, horsepower is sapped by the transmission, 4WD running gear, air conditioning, exhaust system, etc..
On your plane, the only thing you're driving is the re-drive and a propeller.
Where's the performance?

I'm not following this. First off, will a Subaru car really do that much better that 8 seconds? Secondly, why would it matter if a car was "lighter on its feet"? The car's (or plane's) inertia is a function of its mass which is constant regardless of lift, and is the main thing preventing acceleration. Finally, the fact that the prop is operating in air makes it a completely unfair comparison unless you want to put the tires on some slippery surface.

In any case, I can't for the life of me understand how there can be hundreds of these conversions flying and not one single set of dyno data.