High HP engine mods? Lycoming thread.

[Toobuilder]

Buying a faster airplane often comes at a steep penalty at the other end of the speed range. I often speed hours on end in a straight line at 200+ k ktas in the Rocket because it's a convenient way to get from point A to point B. I could go a bit faster with a glass bird like a Legacy, but I really don't want to fly an airliner pattern and burn up a mile of runway getting it stopped. I like the fact that the Rocket can easily get in and out of a 2500 strip regardless of loading or DA.

But the point is somewhat valid - going really fast in an RV is not going to happen by throwing a bunch of HP at it. The best bang for the buck is to build light, drag reduction (with specific emphasis on cooling), and optimized engine management (ignition, induction, exhaust). Get it right and you have an RV that will outrun your formation buddies, burn less fuel, and still retain the docile low speed handling RV's are known for.

[Turbo69bird]

Originally Posted by rzbill

Great. For zero dollars I can make a stock bug do 0-60 in 2.73 seconds by pitching it off a cliff.

Automotive experience does not automatically translate to aviation. Specifically, the systems used for the highly variable speed automotive engines are simply dead weight for essentially constant speed aviation engines.

Addition of those items probably won't kill you, but your craft will be heavier and more unnecessarily complex than mine at the same engine output.

Here's an idea. How about listening to the advice being given rather than constantly arguing with it. Ask why rather than state yeah but I....

Yeah cause cessna and piper never put a turbo charger on an airplane before.
How about contributing something useful

This was supposed to be a fun thread to get information out about options and experimentation not get snarky comments from people.

[rocketman1988]

While I love the experimental part of this hobby and have completed numerous mods, I think that you need to shift your focus a bit, as has been previously posted, to aircraft and away from automobiles.

What works in a car may or may not work in an airplane. Yes, an engine is an engine but there are many other factors to consider in an aircraft. Consider that you car engines are predominantly liquid cooled. Any increase in HP WILL come with an increase in the amount of heat that needs to be rejected...and in an aircraft with an air cooled engine, this can become problematic.

In the RV series of aircraft, you are also limited to Vne on the airframe...unless you want to be a test pilot and push the flutter margins. Again, this has no relative bearing on cars...go as fast as you can.

...and, of course, when things turn bad in an airplane, you can't get out and walk...

I like the discussions, though. Have you read the thread about the guy building up a turbo Honda in an RV? Pretty interesting read...

[Toobuilder]

Keep in mind that power or torque do not move airplanes or cars. In airplanes it's applied thrust through the prop; in cars it's tractive force through the tires. A 1000Hp Pontiac Firebird is not going to perform well on a frozen lake with street tires, and neither will a high HP airplane with a mismatched prop. In cars, tractive force is easy to modify for the conditions. You can ditch the Redline tires for sticky drag radials or full on slicks, prep the track with VHT and be assured that you can get all the power to the ground. With RVs the thrust device (the prop) is limited by diameter - strike one. It's also limited by reynolds number (RE) - strike two. Then we have tip speed and Mach which is a combination of prop RPM and aircraft forward speed - strike three. The bottom line is that our a ability to convert additional power to thrust is limited and is subject to diminishing returns.

As a traditional Pontiac street racer since my teen years, I can appreciate the corollary to the Lycoming design - both designs are stout and well adapted to their intended use. I have stomped many a Chevy that had the entire Summit catalog thrown at it with my stock appearing Firebird or GTO.

Like the traditional Pontiac V-8, Lycomings respond well to optimization without a reliability penalty. This is also handled within the limits of available propellers. Once that's done, the airplane is limited by thrust to weight (takeoff and climb) and thrust to drag (speed). There is money to be made to improve these two areas by reducing weight and reducing drag.

The bottom line is that you can have a significantly better performing RV than most of your buddies without even touching the inside of the engine.

[Mike S]

Originally Posted by Toobuilder

Keep in mind that power or torque do not move airplanes or cars. In airplanes it's applied thrust through the prop; in cars it's tractive force through the tires. A 1000Hp Pontiac Firebird is not going to perform well on a frozen lake with street tires, and neither will a high HP airplane with a mismatched prop. In cars, tractive force is easy to modify for the conditions. You can ditch the Redline tires for sticky drag radials or full on slicks, prep the track with VHT and be assured that you can get all the power to the ground. With RVs the thrust device (the prop) is limited by diameter - strike one. It's also limited by reynolds number (RE) - strike two. Then we have tip speed and Mach which is a combination of prop RPM and aircraft forward speed - strike three. The bottom line is that our a ability to convert additional power to thrust is limited and is subject to diminishing returns.

Here it is in a nutshell.

Good job Mike.

[Turbo69bird]

Originally Posted by Toobuilder

Keep in mind that power or torque do not move airplanes or cars. In airplanes it's applied thrust through the prop; in cars it's tractive force through the tires. A 1000Hp Pontiac Firebird is not going to perform well on a frozen lake with street tires, and neither will a high HP airplane with a mismatched prop. In cars, tractive force is easy to modify for the conditions. You can ditch the Redline tires for sticky drag radials or full on slicks, prep the track with VHT and be assured that you can get all the power to the ground. With RVs the thrust device (the prop) is limited by diameter - strike one. It's also limited by reynolds number (RE) - strike two. Then we have tip speed and Mach which is a combination of prop RPM and aircraft forward speed - strike three. The bottom line is that our a ability to convert additional power to thrust is limited and is subject to diminishing returns.

As a traditional Pontiac street racer since my teen years, I can appreciate the corollary to the Lycoming design - both designs are stout and well adapted to their intended use. I have stomped many a Chevy that had the entire Summit catalog thrown at it with my stock appearing Firebird or GTO.

Like the traditional Pontiac V-8, Lycomings respond well to optimization without a reliability penalty. This is also handled within the limits of available propellers. Once that's done, the airplane is limited by thrust to weight (takeoff and climb) and thrust to drag (speed). There is money to be made to improve these two areas by reducing weight and reducing drag.

The bottom line is that you can have a significantly better performing RV than most of your buddies without even touching the inside of the engine.

You had me at stomped many a Chevy 😃👍

[skylor]

Originally Posted by Turbo69bird

Question:
If the prop was maximized for that 2000 rpm wouldn?t it do the same. Like gearing in a car.
One thing I?ve learned w Pontiacs is they like to be maximized for torque and at a lower RPM can?t build them like a Chevy they won?t live. So if he made the same
Torque at a lower RpM and proped it accordingly like a 308 gear as opposed to a 4.11 gear wouldn?t that make the same amount of work? and therefore propel
The plane the same speed at a lower rpm?

If the engine is still providing 603 ft-lbs of torque at 2000 RPM's you are still going to be down 80 horsepower over an engine producing 603 ft-lbs of torque at 2700 RPM. You most likely can't make up for that large a difference in power with a more efficient prop.

Skylor

[Ralph Inkster]

Maybe we are looking on this the wrong way & Turbo69bird is on to something here. A High Output light weight engine, maybe driving a split drive train to twin props mounted on a high tilting wing for the new RV-15 VTOL model.
We can dream!
Oops! Wrong thread.

[rocketman1988]

A single engine driving TWO props through a drive train?

My God, man...where is your redundancy? It's a single point failure waiting to happen!

[NewbRVator]

Thanks for the discussion. Back to the airframe. So cooling drag is worth the focus? General rigging?
Great to learn from you guys.