Automotive V8 Engine Conversions for Aircraft
 

It's been long postulated that car engines are unsuitable for aviation use because of the high continuous power demands compared to motoring. Is this still true in the days of 1000 Hp Helephant crate engines (7 ltre supercharged), V8 Supercar engines that have the majority of components last indefinitely and now 600 Hp 4 litre power units are common.
The Heliphant engine is a good example. 1000 Hp put of the box, why couldn't it be run at 500 Hp in an aviation context. What am I missing. I'm not even touching the 500 CID billet engines that have set 4000 Hp on dynos. This unit costs approximately the same as a brand new TIO-550 ($130,000 USD). So has the game changed?


Some interesting videos I have discovered.

I've seen Spitfire replicas running LS v8s and Isuzu V6s so it already been done for a while.
I'm not that familiar with them but the first I saw was about 10 years ago and I assume the kits are still being built.
Google says they are good for 250-430 HP, if you need more power you probably need a second engine or a turbine rather than a relatively obscure piston car engine with four digit HP figures.

The obvious questions are:
- How are you going to cool it? I would imagine that we're looking at a large radiator, a lot of water, etc.
- How much does it weigh? Especially once you add the water cooling.
- How will you connect it to a propeller? Most propellers are happy around the 2500 - 2700RPM mark, which is also where most aviation piston engines operate. You can add gearing, but that adds weight, adds a point of failure, and potentially requires a flywheel to smooth our torque on the gears.
- Can you get it certified and persuade an aircraft manufacturer that it's a valid option?

With regards to lifespan - suppose you put this in a car, hooked up a massive trailer that will require 500hp continuously, and went for a drive on the highway at 100km/h. How far do you think you'd get before the engine needed an overhaul? 1000km? 10,000? 100,000? I'd be guessing somewhere substantially less than 100,000km. But that's only a thousand hours of use, and most aviation engines are very conservatively rated to at least 2000 hours before overhaul.

That may have been the case 40 to 50 years ago but does not appear to be the case today. The two Mercruiser V8's in my boat are 5.7 liter Chev small blocks. According to Mercury they are designed to operate continuously in the power range 3500 RPM to 4000 RPM and are governed at 4500 RPM max by the prop size. My engines have approximately 1,100 hours since new and run perfectly. Not too thirsty, around 40 liters per hour (for two) at 3400 RPM.

Didn't the replica Southern Cross have V8 engines? VW and Subaru engines have been converted for aviation use. I suspect some of today's light weight aluminum engines and particularly the light weight turbo diesels could be re purposed for aviation use. I wonder what happened to the Porsche PFM 3200 aircraft engine and the Chev Turbo-Air 6 engine?

Weight, complexity, support & resale value, all these factors are why auto engines haven't flourished at the GA level. Cessna & Mooney I think dabbled in it, soon fell by the wayside. I like my simple air cooled 180HP, Lyc 4 banger, it's easy to maintain, parts are available at any milkbar around the corner & every LAME knows about them far & wide. With Electronic Ignition, a good engine monitor display & a known history I see little reason to make the powerplant complex like that of an Auto engine. A Vans RV8 powered by an Auto donk recently sold in flying condition for around half of what it would have fetched if it where properly set up with a 200HP Lyc, there's another reason!
Each to their own as choice is there but not taken up in large numbers.

I'm not into these light things but I would have thought building one with a serviceable auto engine would also be less than half the price of building one with an Lycoming or Continental aircraft engine?

Orenda Canada built a modified V8 replacement for PT-6 in King Air 90 many years ago.

Fact check: The Lang Kidby/Peter MacMillan Vickers Vimy replica was Chevvy V8 powered not the Southern Cross replica which has Jacobs radials in all three positions...

Think of the rev range required for a propeller to be efficient.

Think of the rev range required for a car engine to be efficient.

You might well say, "That can easily be solved by a gearbox". (More weight)

So you try it anyway, and find the engine destroys the gearbox. Why? No flywheel to damp out the "pulses" of power as each cylinder fires.

So you add a flywheel between the engine and gearbox, just like on a car (More weight) to get it reliable, but find you need a bigger aircraft to lift it all.

Which of course requires a bigger engine...

Some more stuff I have seen over the years. It's interesting to witness the development of the mechanical side of things. A friend of mine has a Golf R with a Stage 3 mod package. He has done 50,000 km in it and tracks in at least every 3rd weekend as well as being a daily driver. It produces 630 hp from 2 litres......on stock internals. No rods, pistons, crankshaft or bearings have been touched.

I used to fly one of these - air cooled flat 4 VW engine. It worked very well!

It was for the England Australia flight but was then fitted with BMW V-12s.

I seem to remember that the 'autotug' was touted by GFA to be really something, but suddenly all development ceased and the project stopped with just the one example.

kaz3g; You got any info on just what transpired with that project? And why it has not proceeded?

The most disappointing thing about this thread is that they never built a production radial car engine.

Most car engines have puny little cylinders that need to work very hard to squirt out their power, whereas most aero engines prefer big bangs and operate that screw nice and slow.

Two of the bigger aerial ag companies on this side of the ditch spent copious amounts of money developing V8 replacements for the IO720's fitted to their Fletchers. One went down the Ford route using a 10 litre engine the other the Chev 6.5 litre engine. Both engines were slated to produce 550 BHP with a gearbox used between the engine and the propeller.

I think in one case the gear box was one of the major hurdles.

Long story short the Ford version actually flew but was cancelled before testing was finished, the Chev version was cancelled before it flew. I understand development costs and getting suitable reliability were the major factors for the projects being cancelled.

[QUOTE][ screw nice and slow /QUOTE]

mmmmmmmmmmmmmmmmm

That machine on shutdown sounded like a 44 gal drum full of spanners bouncing down a very steep hill.

Cimco owns a company that is producing diesel outboard marine engines, they have the 200Hp unit on the market already. They are developing a marine version of the BMW I6 Quad turbo 3 ltr to be rated at 300 Hp on a light duty cycle. Interesting bit is that all these engines have a patented Belt drive systems as seen in the video. Could this work as a PSRU?

This is the bomb for your scale Spitty or Pony.....V12 LS Engines - Race Cast Engineering

But they did build a production radial engine tank - many of the M4 Sherman tanks (49,000 built) had a Continental R975 Whirlwind radial engine. Interesting the M4A6 Sherman had a diesel Caterpillar D200A radial engine. "The Wright RD-1820 was converted to a diesel by Caterpillar Inc as the D-200 and produced 450 hp (340 kW at 2,000 rpm in the M4A6 Sherman". Who would have thought the engine family commonly fitted to the DC3 was also converted to a diesel? :eek:

But radials were fitted to a few road vehicles......... Looks like a corn cob in this monstrosity:
https://i.pinimg.com/originals/f8/7c...a0f4cd3604.jpg

Folks,
Because, over many years, CAA/CASA stalled the "auto tug" program. Why?? Because they could, despite US experience.
There are thousands of aircraft flying behind "auto" engines, ranging from certified engines (many based on a Mercedes alloy block) through many V-8 powered smaller ag. aircraft in US, and the largest number in Experimental" aircraft.
There are some "interesting" engineering issues, particularly engines based on the Chev. "small block", these are well known and understood.
For those of you pontificating on proposition of potential propeller problems --- what, in heaven's name do you think reduction gears/drives are for??
Tootle pip!!

PS: Alvis radials were extensively used in military vehicles, plenty of boats with Merlin (Meteor) and Allison V-12s.

"For those of you pontificating on proposition of potential propeller problems --- what, in heaven's name do you think reduction gears/drives are for??"

Of course there are reduction drives on many aircraft engines Leadsled, that goes without saying.

Point is, many look to auto conversions due to the affordability factor, without considering the need for reduction.

A planetary reduction like on a PT6 or double helical reduction like on a Merlin adds cost.

Company I worked for tried it, sunk a lot into it and ultimately failed to achieve a reliable cost effective auto conversion that suited their operation.

Which was a shame, as they put quite some effort into it.

A question for those who may know; Which of the above is the better?
Or is it a case of 6 of one and half a dozen of the other?:confused:

Currawong; Any idea what was used in various other engines such as the big radials?

And BTW, what was used in the GTSIOs used in the C404/421 series?

Currawong,
The only Merlin/Griffon reduction gearboxes I have seen/played with have been straight cut spur gears. A major source of noise.
Tootle pip!!

PS: The pom's ability to cut helical gears, let alone hypoid bevels or double helical gears has always been rather marginal, and in the mid-1930's --- effectively non-existent.

Not a proven option yet, but Raptor Aircraft (a brand new kit aircraft designed and being built by an Aussie in the USA) has a 3.0 litre turbo Diesel which is estimated to put out 350 HP.

Raptor Aircraft Home

These VW/ Audi diesels can be truly disruptive - they can run on Jet A1 and their SFC is half that of your air cooled flat sixes.

Fingers crossed they can deliver even half of their promise.

No they're not. If you're lucky they'll be at or around 220g/kWh. A IO-550 is easily good for 250g/kWh and probably less when things are leaned properly - maybe closer to 235...

Andy RR,
I did say marginal.
Could you, perhaps, guess why RR Cars used diffs. imported from USA (GM) from about 1952 ---- sorry for the minor thread drift.
I loved the example illustrated ---- a truly terrible gearbox, base don my experience rebuilding same many moons ago.
Tootle pip!!

a 44G drum an hour & quarter $mill @ to buy? Yep I'll take 4!......…...

I googled "IO-550 SFC" and this came up on the first line: https://summitaviationmfg.com/wp-con...-TI_Engine.pdf

It quotes a 0.385 lb/hp.h which is 234g/kW.h although it may have got the best economy and best power figures switched on page 3. These numbers are, however, typical of what I've seen quoted around the traps for many years. As far as BMW diesels doing 198g/kW.h that's a very best-point number and there would be some celebration in the engineering office about it. Some of the old VW PD diesels are sub-200 but it's quite difficult to do and even more difficult to spread out across a useable area. The fuel consumption you see in the day-to-day use of a car is waaaay worse than these numbers, especially on a gasoline engine. If you could cruise at a steady 100km/h at 200g/kWh in a modern car you'd be seeing 3.5-3.8L/100km That's not typical of anything I know of.