Also, how many companies have gone broke trying to better the avgas burners we are currently using. Pretty neat thing my O360.

Before companies pour money into R&D they should take a long hard look at their current product. They would discover that for little or no increase in their selling price they could more than halve the effective cost to their long suffering customers.How?

I'll use the IO520 as an example.New it currently sells for near Aust $50,000 and has a TBO of 1800 hours. Increase that to 3600hours and immediately the effective cost is halved. Is this possible? In the fifties and early sixties it was done with the most complex reciprocating engine ever built - the turbo compound R3350. This engine had 6 times the capacity of a 520 but put out 12 times the horse power. In cruise it achieved a specific fuel consumption of 0.4 or better .
They achieved the long life and low fuel consumption by running LOP.
All Continental has to do is sort out it's intake system and then bite the bullet and subcontract the injectors to GAMI.They should then do a deal with suppliers of engine management systems and mandate their installation. Finally they should educate their customers how to run the engine LOP.
I said more than half. The rest is fuel saving over the life of the engine With mine I save 5 litres per hour running LOP . At $2.2 per litre over 3,600 hours the saving would be $39,600 . Worth doing I think.

I don't think that's really true. Auto engines would be getting well over 1 hp / cubic inch - more than 2 hp in many cases. Aircraft engines get around 0.5 hp? So 80% power on an auto engine might be 200-300% of the power you get from the same capacity aircraft engine. How long could an IO-360 sustain 400hp? I don't know how much power they get out of LeMans engines. I wouldn't be surprised if it was 3x what they get from a production engine, so maybe 10x the power per cubic inch of a Lycoming?

Maybe power/capacity is not a fair comparison - but it's better than a percentage of an arbitrary number that was set in part based on the reliability required.

To be frank, auto manufacturers can't afford to make engines as fragile and finicky as aircraft engines or their reputation would be junk. I have no doubt that if you had a projected market of a few million engines, auto engine designers could easily design and build an engine that was smaller, lighter, cheaper, more powerful and more reliable than current aircraft engines.

The problem is then the aircraft manufacturers would say "What we really need is something about the same size and the same weight as the current engines. And not too much more power either..." (or you run into potential problems with VNE etc) So you need to design new aircraft too. Unfortunately, the market doesn't exist to support it.

Andy
If this is true why has every attempt to use Auto engines in aircraft ended either in abject failure or major disappointment in the sustainable power reliably produced?

It's typically not problems with the engine itself, but with changes or systems that have to be designed to install it in an aircraft:
- A custom cooling system, to provide enough cooling without excess drag
- A system to turn the propeller at an appropriate speed, without transmitting vibrations to the engine that it is not designed to handle
- Perhaps, you put a different ignition system on to give you redundancy
- Perhaps, the oil system (sump) is not designed to work in the range of attitudes encountered in an aircraft.
- You probably have to fit all this in a space designed for some other type of engine

None of these systems are likely to have the detailed engineering work done that was done on the original engine installation, and they are the typical areas where problems are encountered. It's no different to dropping a Lycoming in a car and discovering you have cooling problems, and have to strip the engine after a sudden stoppage when your foot slipped off the clutch.

I'm not arguing for auto engines in aircraft. Creating a reliable installation is a major undertaking. It's much easier to choose an engine that was designed for the task, where it is well known what is required for a reliable installation. But I don't agree that aircraft engines are superior technology to auto engines.

Some of the things encountered in aircraft engines that would not be acceptable in a car engine:
- manual mixture control. My car engine automatically runs lean cruise (lean of peak) when power settings allow.
- worries about shock cooling
- having to strip an engine or check the crank after any sudden stoppage.
- a manual primer pump, or the incantations required to start a hot fuel injected engine. Chokes on cars disappeared decades ago, if you told people a fuel injected engine could be harder to start than a carby engine they would think you are mad.
- new engines making metal with the frequency that seems to happen with aircraft engines
- worries about corrosion in engines that sit unused for a while
- changing a cylinder etc. way before the projected engine life.

Andy, An earlier post stated that aircraft engines need to be powerful, efficient and lightweight. I think reliability and (within reason) simplicity should be added to that list. Every new system introduced adds to original cost plus ongoing maintenance costs. Every additional system is another potential point of failure. If it aint on there it can't fail.

One old engineer reckoned water cooling an aircraft engine made as much sense as air cooling a submarine.
Another factor often overlooked is total installed weight. It's all very well producing 4HP per cubic inch or whatever but it's not much use if you then need huge radiators,huge oil coolers and a strong heavy gearbox specially made with appropriate torsion dampeners to make it all work.
All the above doesn't mean that there isn't room for improvement. One of the most promising is the PRISM system being developed by GAMI. If you're not familiar with it Google it up. Many of the problems with air cooled cylinders should disappear once a PRISM system is installed.

Oh yes it is. This new type auto based engine must operate at 85-100% of it's maximum rated power for it's entire life cycle at a very high RPM, which causes accelerated engine wear. Auto engines are not so designed, and hence cannot do this. An example of this is the Bathurst 12 hour race for the "showroom" class. A good many of these cars have engines fail.
All this adds weight and service complexity compared to existing aero engines.
- All these "perhaps" mean large development costs, and a high sale price to recoup investment over a very small market.

You got that right. Aero engines are Jurassic. However, like it or not...what we have is going to be around with no alternative while fossil fuels are the power source. The reasons for this are weight and cost of any new development. Don't get me wrong... I would love to be able to buy a new technology engine that costs about the same, has the same horsepower, same weight, and less fuel flow. Sadly.. ain't gonna happen

Some of Andrews points questioned
 

Some of the things encountered in aircraft engines that would not be acceptable in a car engine:
- manual mixture control. My car engine automatically runs lean cruise (lean of peak) when power settings allow.
Does it? How do you know? When did you last take your car to 10,000 feet or even go through a wide change in atmospheric pressure? You may want the mixture dumbed down, I don't.
- worries about shock cooling
I don't worry too much about this, Jabba will pipe up shortly, shock cooling is mostly an old wives tale, not an issue.
- having to strip an engine or check the crank after any sudden stoppage.
This is safety issue, not an engine issue! and how often does your car engine suddenly and instantaneously stop while developing 75% or more power? Having kicked around the industry for a while, I have seen engines suffer a prop and go straight back into service numerous times. Most engineers will tell you that a prop strike at low power settings is highly unlikely to cause damage.
- a manual primer pump, or the incantations required to start a hot fuel injected engine. Chokes on cars disappeared decades ago, if you told people a fuel injected engine could be harder to start than a carby engine they would think you are mad.
Hard to start engines can be a problem for some pilots, I have always been able to get them started without major problems. Cars aren't impervious from this problem either.
- new engines making metal with the frequency that seems to happen with aircraft engines
How many car filters have you cut open?
- worries about corrosion in engines that sit unused for a while
Made of metal? It will corrode. This problem is in all engines.
- changing a cylinder etc. way before the projected engine life.
Not all that common when the cylinders are correctly prepared before service

Andrew, old technology does not mean bad technology. Current piston aero engines are outstanding devices. If it aint broke there is no need to fix it!

As I said in post #23, rated power is an arbitrary number, based in large part on how long you need the engine to last at that power. Yes, you might have problems if you use the quoted power in an auto application as the rated power for an aircraft application - but again, that might be 4 times the power/capacity you get from a Lycoming. If you were developing an aircraft engine you would be more conservative in setting the power rating.

I see your point, however your "arbitrary" number will never be achieved at less than 2500 RPM, which is the requirement to eliminate the need for a weight adding reduction system. Auto based engines can never produce the required horsepower at such low rpm, and be of a small physical size and cubic capacity and be of caparable weight. So it's a given that some type of rpm reduction system must be incorporated, which means weight and something else that can potentially fail (Thielert gearboxes anyone?)

By your post quoted above, I think that you mean that an automotive engine capable of producing 500HP can be derated to reliably produce 300hp continuously?
For an example, I have just taken delivery of a new Mercedes Benz A45 AMG. Mercedes claim the engine in this vehicle to be the most powerful production 4 cylinder engine ever made. It produces 385hp from it's 2 litres with a large turobcharger producing 26psi of boost. It will propel the car to 100km/h in 4.6 sec and claimed fuel economy is 6.9l/100km. It is actually capable of producing 300hp at 2500rpm. So we can potentially use this engine without a gearbox.
It weighs 150kg dry compared to 218kg for your average IO550. With a cooling system and other necessary equipment, it could potentialy weigh less than the Continental. Would this Benz engine last 2000 hours? What fuel flow would you get? Would you be able to keep this engine cool at altitude? I'd rather you be the test pilot. ;)

I'm not arguing for auto conversions. My original statement was:

But, you would likely end up with a different form factor and weight, which would require airframe changes. And that size market doesn't exist, so it is unlikely to happen.

Incidentally, I suspect that if you did design such an engine, it would have liquid cooling and a gearbox. The advantages from smaller components (which are inherently stronger and lighter) and not having to have finned cylinders and head assemblies to allow a few hundred hp worth of cooling from passing air would offset the cooling and gearbox weight.

I'm sure reliable light weight PSRUs could be designed. With enough money, computer analysis, testing and engineering expertise (not to mention existing successful and less successful examples) it could be done. Would it be easier or harder than designing an automatic car gearbox? I don't know, but I suspect many of the problems would be similar.

I bet it doesn't use 6.9 l/100 km while propelling the car to 100 km/h in 4.6 sec! :suspect:

That's for sure :E

Next time you blokes see an aero engine, look very closely, for its capacity it is very small and quite light. Its fuel burn when expressed in fuel per HP is right up there with a modern auto engine and it is reliable and proven.

Just because the design is old doesn't mean it is not good. Many have tried to improve it over the years, no one has succeeded. Anyone remember Orenda? or Porsch?

BSFC and TBO

EOM

my previous neighbour had a race car that did the same speed as my aircraft's cruise speed.
I asked him how much fuel he used. 200 litres for 8 laps of wanneroo.

to do 222km I use about 21.2 litres.

</sarcasm on> aircraft are dreadful arent they </sarcasm off>

:ooh: Yep that too! Thanks Jabba, correct terminology helps ...

You had me there Jabba. I had to look it up on Google. What can I say ? WIBF?