Inverted LS2

[fmarino1976]

I was looking at the GM performance catalog, and some tuned LS2 engines produce about 230 HP at 3000 RPM. This could be enough for a direct drive but the crankshaft location would be a problem. If one could install it upside down on a -10, what would be required to make a compatible lubrication system? Any other considerations?

[rv6ejguy]

You'd need a multi stage dry sump system to scavenge the oil from the valve covers and other areas. Most compatible props are not rated at 3000 unfortunately. Cool idea, maybe 4 psi of boost would give you 270 hp at 2700 rpm?

Probably should have a good bearing setup to take prop loads and supply oil for the prop unless you go electric.

[TSwezey]

Just go with an LS6 or LS7 for your extra HP.

[kristoffon]

The engine will wear down quickly because the crankshaft isn't designed to bear the thrust loads from the propeller and then you still have all the headache associated with inverting the engine which isn't a trivial matter...

Using a PSRU with offset and a slightly smaller engine might be a better idea.

[elippse]

Many WWII aircraft used inverted V engines. You could get a smaller diameter three or four-blade prop which would easily convert the power to thrust very efficiently, even mounted normally. A 68" diameter prop would have a tip speed of M0.85 at 3000rpm and 200 mph TAS. A 56" three-blade could still produce the same static thrust as a 68" two blade, or the same with a 48" four blade, but these would have much lower tip speed and noise.

[rv6ejguy]

LPE was developing some inverted V8s based on the SBC 10 or 15 years ago, not sure if they are still around.

Most auto engines are dogs direct drive for their weight unless you go on a massive weight reduction program. Turbos or gearboxes help make things right with some added weight. The only direct drive V8 which has really impressed me is Gary Spencer's Ford small block Long Eze. He regularly trounces a number of traditional guys in races with the same size engines.

The stock LS2 only develops about 200 hp at 3000 rpm and about 175 at 2700. You need more cubes, some boost or more rpms to make it viable for an RV10. Not a fan of radical changes within an engine for aircraft use unless they have been very well proven in some other applications like off shore racing.

Some of the modern large V6s from Chev, Ford, Hyundai and Honda are around 300hp stock and would be considerably lighter than a LSX but you'd need a gearbox of course.

[Skybolt Al]

But what you really need is torque and with direct drive, I don't think that you will get enough to swing the prop.

[rv6ejguy]

Originally Posted by Skybolt Al

But what you really need is torque and with direct drive, I don't think that you will get enough to swing the prop.

A 6L V8 producing 200 hp at 2700 rpm results in exactly the same torque as a 200hp Lycoming delivers at 2700 rpm. HP X 5252/ rpm= torque. (389 lb./ft. in this case) Please, let's not belabor this one any more!

[TSwezey]

Originally Posted by kristoffon

The engine will wear down quickly because the crankshaft isn't designed to bear the thrust loads from the propeller and then you still have all the headache associated with inverting the engine which isn't a trivial matter...

Using a PSRU with offset and a slightly smaller engine might be a better idea.

I would hope somebody would not just bolt to the crank without some form of thrust bearings and flex plate.

[rv6ejguy]

Actually most cranks can easily handle the thrust as many clutch release mechanisms apply considerable force. Of more concern are the bending loads imposed by the prop as the aircraft changes direction. The prop is like a giant gyroscope and likes to remain as is while the forces concentrate at the end of the crank (more accurately behind the last crank throw).

These facts have been driven home in the last few years on Corvair DD installations after multiple crank failures. The fix is the famous "5th bearing" setup bolted to the end of the case. There are many DD engines flying with a lot of hours on them and no changes to the thrust bearings inside the engine and even a few flying with lightweight propellers and no radial support bearings but it is a scary thought as no testing has been done to validate the concept.

Fingers crossed is not the best method to approach these sorts of things in aviation so an engineered piece to take prop loads would certainly be a good idea.

Other mods to invert the engine would be to the crankcase breathing system and cooling system.