Aircraft certified motor vehicle engines. Is there a niche for them

[Wirraway]

One factor touched on a few times, but never (I do not believe) answered, is the fact that auto engines, (including motorbike engines) are not designed to run at high revs continuously.

Now I'm the first to admit, I'm no engineer or mechanic, and I am firmly in the camp of, "turn the key, make a noise, let's go".

 

I had a Yamaha XJ900 Diversion. 900 cc air/oil cooled 4 cylinder inline. Sold it with about 230,000kms done.......I say about because the odometer didn't work for the last 2 years I owned it.

Not a bad run. From memory it was redlined at 9000rom. But I never got there. The closest, was attempting to travel from Coolgardie to Southern Cross in one hour....about 185kms.

After 20 minutes 60 kms., after 40 minutes 135 kms travelled, but soon after came up behind a police car and obviously had to slow down.....

 

My point is, that engine showed fantastic reliabilioty, but was not really run anywhere close to redline.

One of my current bikes is a Moto Guzzi Griso 1100.

Yes I've done 200+ km/h several times, getting close to redline, but again, not for long periods. It has more than 100,000kms on the clock.

 

Auto/bike engines can be very reliable, but when they are run close to redline for long periods?????

 

A few years back, I read an article about the differences between the Ducati and Honda V2 engines run in World SuperBikes. Apparently the Ducati's needed a rebuild after 700kms, the Hondas could manage 2000 kms. Given that testing and race kms meant that 700kms was about 3 races........yes the bikes were run at max power, no thought to longevity.

But that's my point.

 

Auto engines....are they really designed to be run at max or close to max revs for long periods?????

 

As I said, I am no mechanic nor engineer, but I am not sure how long my engines would last in a race type useage, day in, day out!!

[Paul davenport]

Not disagreeing with anything you said W but how do we explain some of the small micro cars Daewoo matiz 800 cc, Suzuki Mighty Boy also 800 cc and a plethora of other small car engines from 1300 cc and down doing huge mileages . At 110 mph on the freeway for hours at a time, they are pretty much sitting on at least 75% or better of their output and reving their proverbial what nots off. These are amazing little engines and we rarely see them give any problems. I am not suggesting for one moment we fit them to aircraft but they certainly don’t fit your explanation of lack of durability at high power settings, I wonder why ?

[M61A1]

Not disagreeing with anything you said W but how do we explain some of the small micro cars Daewoo matiz 800 cc, Suzuki Mighty Boy also 800 cc and a plethora of other small car engines from 1300 cc and down doing huge mileages . At 110 mph on the freeway for hours at a time, they are pretty much sitting on at least 75% or better of their output and reving their proverbial what nots off. These are amazing little engines and we rarely see them give any problems. I am not suggesting for one moment we fit them to aircraft but they certainly don’t fit your explanation of lack of durability at high power settings, I wonder why ?

Yep....The Suzuki G engines are the same as used on their outboards which have similar loads to aircraft engines. They will happily run at high power settings all day and for a long time.

[Paul davenport]

Oops 110 kph don’t think they would have a snowballs chance to make it to 110 mph

[mnewbery]

We had a serial offender here who waxed lyrical about a certain murder cycle engine for years. A bit of digging proved the engine in question was capable of over 80hp continuous around 7800 rpm.

 

The operators in Europe were guessing their cruise performance was more like 34hp based on fuel consumption figures. Their comment was that this power setting contributed very strongly to the time between overhauls.

 

I will leave it to others to comment on the validity of these statements and the validity of the statements made by the original forum poster

[facthunter]

Depending on frontal area mainly a motorcycle needs about 40 HP or less to do 100 MPH (160 k's). British bikes like an Inter Norton or a Post war Velo 500 and some Rudges, did the ton on less than 35HP.. The 38 Harley model EL 61 inch OHV Knucklehead (bog standard, about 36 HP) did the ton with an English tester being given great acclaim at the time for the ease it reached it's top speed.. ALL these are done without fairings . A british BSA ZA 7 500cc twin clocked 123 MPH on Bonneville salt lake in the US about 1948. As you GO faster you need an increasingly large amount of horsepower. like an aircraft does. DOUBLE the speed, FOUR times the power. Nev

Edited July 12, 2020 by facthunter

[Old Koreelah]

Yep....The Suzuki G engines are the same as used on their outboards which have similar loads to aircraft engines. They will happily run at high power settings all day and for a long time.

Lots of G-10 engines have been used in little aircraft; I was pretty enthusiastic about converting one until I checked out their weights. Geared PSR units make them heavier than a Jab, but I suspect a reliable belt-driven reduction could be made. One of the attractions (besides the engines' legendary reliability) is the flexibility an external radiator gives to installation.

[Flightrite]

If all these car engines where so good why isn't the market flooded with them.Jab, Rotax, Lyc/Conty should all in theory be going out of business???

[facthunter]

It's been ever the case. The Italian Bugatti efforts were the best examples of a near total failure and the Porsche attempts ( even though I would suggest they made the BEST high performance aircooled motors ever used in cars) didn't get anywhere. with their light aircraft engine project. Napier produced good engines of considerable complexity, based on sheer good quality engineering. I reckon the engine must be purpose built from scratch for the job. A well designed aero engine has little room to be developed further also as if it does, it's overdesigned for the job in the first Instance. which might be OK in a truck but too heavy in a plane where weight is a prime factor in it's suitability. A think aero engines predispose to higher capacity than equivalent horsepower road vehicles which DOESN'T always mean less fuel efficiency (BHP/Litre). Example.. superlongstroke ship's engines 76 RPM's turbocharged running on Bunker fuel. Nev

[Paul davenport]

I am sorry did any one give an explanation for the small car engine reliability?. The only thing I can think of is even at almost flat out speeds they are not over stressed. Never had a tachometer on the Matiz I drove probably a good thing as the revs would have scared me at highway speeds. At 110 kph there wasn’t much left and the fuel economy was not as good as you would think

[facthunter]

Some motors do rev high but most engines today sit on a bit over 2.000 rpm. Some are actually going too slow for optimum clutch life and some bearing at high boost are too high with load. You learn a lot about these things with experience and time in service..( The industry does.) I keep hearing of various things, Major parts and even engines, being changed without much comment. Not hearsay People I know personally. They can even trace their records back to find a different spec head gasket was fitted erroneously and replaced the gasket and a NEW head with it even though it was running OK. Today some basic engines come with vastly different outputs depending on the vehicle they end up in and the right bits must be accurately programmed into it. as it's built. ALL pretty complex and impressive. Nev

[Geoff_H]

It's been ever the case. The Italian Bugatti efforts were the best examples of a near total failure and the Porsche attempts ( even though I would suggest they made the BEST high performance aircooled motors ever used in cars) didn't get anywhere. with their light aircraft engine project. Napier produced good engines of considerable complexity, based on sheer good quality engineering. I reckon the engine must be purpose built from scratch for the job. A well designed aero engine has little room to be developed further also as if it does, it's overdesigned for the job in the first Instance. which might be OK in a truck but too heavy in a plane where weight is a prime factor in it's suitability. A think aero engines predispose to higher capacity than equivalent horsepower road vehicles which DOESN'T always mean less fuel efficiency (BHP/Litre). Example.. superlongstroke ship's engines 76 RPM's turbocharged unning on Bunker fuel. Nev

The Porsche engine failed because it too heavy compared to its competitors Lycoming and continental. I believe that one of the modern engines that use a dual cycle engine would be so much lighter. Run 1 litre at 3000rpm without gearbox, dual electrical and liquid cooled can put out 160hp. Efficiency of 40% is easily achieved! As good as any diesel cycle! Mercedes, BMW and Audi make dual cycle engines.

[facthunter]

Well who's running a prop at 3,000 for a start? WE will see about all these promised amazing figures. It's been going on for ages Sarich etc. It was easy to see his design was not going to do what some thought/hoped it would. Lot of money lost there by investors.. Better get moving or the opportunity for ICE engines will be gone. Reciprocating engines are grenades. Nev

[Geoff_H]

I read from a Mercedes engine that would normally run st 6500RPM. 215HP from 1 litre. Any combination of speeds are possible. Not a lot of extra HP from 6500RPM so why use a gearbox? Extra weight for little gain. However from the little interest shown here for a dual cycle engine with a massive HP per litre and 30% promote fuel efficiency over an Otto cycle I thought that people on this site had little interest in such an engine. I certainly drive two cars, both with the dual cycle engines and am amazed at hp and fuel efficiency. I think that a reduction in size of an aircraft engine from 5litre to one litre would reduce the weight so much that the weight of liquid cooling and dual electrical would be great. More range from increased efficiency.

[facthunter]

But who runs props at 3000? Some of these engines are breaking parts that never broke before. There HAS to be a practical safe limit for power extracted from a small engine. The pressures and loads are just too high. Nev

[onetrack]

The Australian Revetec engine showed great promise - a Controlled Combustion Engine that dispensed with the normal crankshaft and plain bearings, and which utilised a tri-lobe crankshaft, with connected pistons running in guides.

However, this engine was trumpeted with great fanfare about 2003, got a heap of money from investors, produced a few trike engines, produced a few prototype engines - then moved manufacturing and engineering to Turkey about 2011-12.

They have stumbled and bumbled along ever since, gone off at a tangent on a regular basis - and now, they are effectively broke, and no longer in operation.

This is typical of so many "exotic" new engine designs, that promise a lot in a short time, end up making that a long time, with no major results - then they run out of money, and willing investors.

 

https://www.revetec.com/latestnews.htm

 

I think the simple problem with so many of these engine ideas and their promoters and backers, is that they lack a clear objective target market and users, lack understanding as to the complexity of engine design and combustion principles - and they lack the constant supply of multiple millions required to get new projects into commercial production - over an extended period of time.

 

I have read the books detailing the history of Clessie Cummins and Frank Perkins, who both eventually found success with their automotive and industrial diesel engine designs.

In Clessies case, he had a friendly and willing merchant banker who backed him in engine development for 25 years, before he saw any return on his investment.

 

In Frank Perkins case, once again, he had a number of wealthy willing financial backers, and one primary financial backer, who always came good with more money, when things went sour.

In both cases, the development of their engine designs took more than two decades before they finally gained commercial success. And both these companies had their sights on a very large market, which eventually provided good returns.

 

But the aircraft engine market is one of limited numbers and limited sales, and therefore is not attractive to investors who like to see good returns from large markets.

Edited July 12, 2020 by onetrack

[Thruster88]

I read from a Mercedes engine that would normally run st 6500RPM. 215HP from 1 litre. Any combination of speeds are possible. Not a lot of extra HP from 6500RPM so why use a gearbox? Extra weight for little gain. However from the little interest shown here for a dual cycle engine with a massive HP per litre and 30% promote fuel efficiency over an Otto cycle I thought that people on this site had little interest in such an engine. I certainly drive two cars, both with the dual cycle engines and am amazed at hp and fuel efficiency. I think that a reduction in size of an aircraft engine from 5litre to one litre would reduce the weight so much that the weight of liquid cooling and dual electrical would be great. More range from increased efficiency.

 

Geoff, as an engineer you would know that 160hp @ 3000rpm is 380nm of torque. A good naturally aspirated engine will produce about 100nm per litre, so about 3.8 bar (60psi) of boost pressure required, alot of heat on those little pistons. Spoolling? Up the turbo on such a little engine with a big propeller could be an issue as well as the gyroscopic? Forces acting on the tiny crank. I can't see it happening my friend??

[spacesailor]

But who runs props at 3000?

McMulloch

Two-stroke, 4-cylinder opposed, 72 HP @ 4,100 rpm, turning a 75 inch prop. 79lb / 35.5 Klgms weight.

One in a HummelBird goes well but thirsty.

spacesailor

[facthunter]

Tips would be supersonic. No? I know the motor. Enfield mcCulloch. Was used in small autogyros. Nev

[Geoff_H]

Geoff, as an engineer you would know that 160hp @ 3000rpm is 380nm of torque. A good naturally aspirated engine will produce about 100nm per litre, so about 3.8 bar (60psi) of boost pressure required, alot of heat on those little pistons. Spoolling? Up the turbo on such a little engine with a big propeller could be an issue as well as the gyroscopic? Forces acting on the tiny crank. I can't see it happening my friend??

I would expect the manifold pressure would be somewhere in the 2.5to 3bar, Mercedes did not publish a lot of data on their current technology limited engine. The efficiency is higher than a diesel of the same compression ratio, so this would reduce temperatures somewhat. Specifically designed pistons and crankshaft would be needed. I do think that your comment about gyroscopic effects could be a very real project killer, in a car not significant, in an aircraft very significant.

The dual cycle starts every cycle as an Otto cycle, then becomes a diesel cycle on gasoline. Given that given the same compression ratio an Otto cycle engine is more efficient than a diesel the dual engine uses the constant volume of the Otto to increase the pressure in the cylinder then starts injecting very high pressure gasoline in a diesel cycle constant pressure. Best of both cycles. Many manufacturers are now using it. Some are saying that they may drop diesel engines from their range as these engines offer better efficiency.

[M61A1]

If all these car engines where so good why isn't the market flooded with them.Jab, Rotax, Lyc/Conty should all in theory be going out of business???

The Suzuki G engines are quite popular, especially in poorer countries. (In the Ukraine I have read they flog them day in day out even cropdusting with them)They aren't as light some might like either but still quite reliable. There are two factors in countries like Australia and the US, one, is that we are highly regulated and limited in wight so the few extra kilos are important to carry larger people under the legal weight limit and two, in both countries we have a lot of crusty old shellbacks that simply cannot deal with the idea that you could use anything but a certified aero engine in an aircraft. Even Rotax has taken a long time to be accepted in the US.

[Wirraway]

Not disagreeing with anything you said W but how do we explain some of the small micro cars Daewoo matiz 800 cc, Suzuki Mighty Boy also 800 cc and a plethora of other small car engines from 1300 cc and down doing huge mileages . At 110 mph on the freeway for hours at a time, they are pretty much sitting on at least 75% or better of their output and reving their proverbial what nots off. These are amazing little engines and we rarely see them give any problems. I am not suggesting for one moment we fit them to aircraft but they certainly don’t fit your explanation of lack of durability at high power settings, I wonder why ?

 

Paul, I have no knowledge of the cars you mention, their RPM at 110km/h nor their longevity, so I will not comment, but it is an interesting point.

Is gearing the answer????

 

My Suzuki V-Strom 1100 has 6 gears (5 + OD), and I don't bother with 6th(OD) unless I'm doing at least 85 km/h. It certainly drops the revs.

[Geoff_H]

I have been researching dual cycle engine after I noticed that mine has a relatively low inlet manifold pressure at full power. I believe that the manifold pressure for 260hp/lire@3000rpm may only need to be about 2bar. Consider the first part of the cycle, Otto cycle with a charge of full air some fuel ignited by the spark plug. Pressure extremely quickly rises. Normally in the Otto cycle this pressure would decay as the piston moves down. But now convert to diesel and inject fuel in a constant pressure diesel cycle. In reality it does drop but not as much as an Otto. The pressure vs volume graph shows this rise then not decaying as much. I have not read that this is the case, but seems plausible.

[M61A1]

I saw this and was rather surprised that certified aero engines were this bad. Perhaps someone here who operates or maintains some of these engines can enlighten us as to whether or not these figures where engines require "top overhaul" long before TBO are accurate.

Note: I do understand that frequent operation is one of the best things for an engine.

 

[turboplanner]

I have been researching dual cycle engine after I noticed that mine has a relatively low inlet manifold pressure at full power. I believe that the manifold pressure for 260hp/lire@3000rpm may only need to be about 2bar. Consider the first part of the cycle, Otto cycle with a charge of full air some fuel ignited by the spark plug. Pressure extremely quickly rises. Normally in the Otto cycle this pressure would decay as the piston moves down. But now convert to diesel and inject fuel in a constant pressure diesel cycle. In reality it does drop but not as much as an Otto. The pressure vs volume graph shows this rise then not decaying as much. I have not read that this is the case, but seems plausible.

Diesel engines changed dramatically as designs were changed to meet emission standards. For example, a couple of decades ago fuel pimp pressures increased to over 2000 psi and we were told to warn operators not to crack injector unions to bleed engine because the jet of fuel could kill them. We went to common rail systems where the injectors were controlled electronically and today there are multiple injections before and after TDC - I've seen specifications for as many as 8. Valve opening and closing would have also changed radically along with intercoolers being pretty much standard, and in many cases duel in-line turbo chargers, the overall principle being to allow air as cold as possible into the cylinder as quickly as possible, heat it to make it expand for more power, ignite it and keep burning it (thus keeping pressure up) and then restricting it through the diesel particulate filter at the back end. All of that development has led to the latest sparkless petrol engines. Somewhere in all those changes is a mean pressure curve, and someone may have taken the time to work it all out, but to do what you want to do, you'd have to make sure you were researching the older material pre those changes.