aero engines

As I understand it, that round the world jaunt was an exception. I don’t know how true it is but I’ve heard that in some cases you were lucky if they took you to the other end of the country (exaggeration but you get the idea). There again though that could have been due to the Porsche having different operating procedures to most aero engines and people were using standard aero engine practice which caused the problems, I really don’t know. It is definitely not unusual for people to blame the machinery rather than admit it was their finger trouble that caused the problem.
I never knew they were fitted in so many aircraft, also never knew they did the 4 cyl one. The only one I knew about was the PFM

Times must have changed from 1986 when Porsche flew around the world!

http://emeraldinsight.com/Insight/viewContentItem.do?contentType=Article&hdAction=lnkpdf&contentId=1683554&history=true&StyleSheetView=all

A list of some of the aircraft that used Porsche engines, not forgetting of course, the Tawny Owl G-APWU, it is still lyng around isn’t it?

http://home.comcast.net/~aeroengine/Porsche.html

I agree with you about the difference in production scales between aero and automotive engines.
I seem to remember that compensation scheme also, but I also seem to remember that the withdrawal was as much due to reliability problems experienced by the owners of a few of the Porsche engined Mooneys. Was the Porsche engine ever fitted to anything else? I only ask because I don’t remember seeing news of any other installations.

The choice of Subaru, Chevrolet Corvair, air cooled VW and BMW boxer engines is often as much governed by their flat-cylinder configuration, which makes fitting into exisitng airframes much easier.

‘Upright’ four cylinder engines pose some ‘interesting’ design challenges in terms of propeller size, visibility and centre of gravity if you mount them the same way up as in a car.

Inverting the engine gets the thrust line in the right place, but adds to complexity with the need for ‘dry sump’ lubrication in order for the oil system to work properly. If you compare a vintage DH60 Moth with an upright engine to a DH82 Tiger Moth, you’ll get an idea of the challenge.

In Germany, a number of homebuilts fly with adaptations of SmartCar three cylinder engines. I also seem to recollect that this engine forms the basis of a diesel power unit too?

The Honda and Nissan engines in some Australian homebuilts seem all to be fitted in pusher designs, where they achieve a higher thrust line by using belt drive to reduce propeller speed. The bulky installation seems less of an issue in the depths of the fuselage.

There are two challenges for a car maker aiming to get into the aircraft market. The first is the relatively small sales volume offered by light aircraft.

If say, 1200 aircraft engines were to be made available, they’d flood the market for a year. Most car engine plants regard that figure as the minimum viable, per day!

Secondly, there is the question of product liability, which thanks to all those pesky lawyers (thanks TT!:diablo:) is a minefield. It was for that reason, rather than any technical issue that Porsche withdrew their excellent engine a few years ago. I seem to recollect they even paid owners compensation to retro-fit the old cast-iron ship-anchor Lycomings!

Possibly the fact that, even with the weight of the gearing, a modern alloy car engine is lighter than the old iron Lycomings and Continentals. I know that the 100hp Rotax including radiator and other necessary bits is about 25kg lighter than the O-200 Lycoming or Continental ( I can’t remember who made it.)

Thanks. The twin ignition system was expected,the rest makes sense too but then why would someone choose to modify and install an automotive unit to an aircraft. I can understand larger capacity engines being put into replica fighters but I have heard of nissan engines in vari-ez and bede bd-5’s.

I think one of the major changes that is made in the conversion of car engines for aviation use is to incorporate a second ignition circuit as most aero engines are dual ignition. Given the number of units sold in the average auto application there is not really any need to find diverse applications for the engine in order to cover the R&D costs. This is even more true when the same engine is fitted to more than one make of vehicle. A good example being the number of cars fitted with a Mazda or Isuzu diesel, I won’t mention the number of vans with Perkins diesels as the Perkins 108 found its way into all sorts of machines like dump trucks fork lifts and water pumps as well. The other thing is the cruise speed of the engine. The traditional piston aero engines (Lycoming, Continental etc.) are mormally limited to about 3000-3500rpm and cruise at anything between 55 to 75% of that. The average car engine cruises at 3-4000rpm at about 70mph and about 50% power. This means that for driving a propeller at its optimum speed there is sometimes no need to gear the engine down. The modern aero engine as per Rotax has a red line of about 5000rpm which means it needs gearing down to provide a sensible propeller speed. Of course the gearing adds weight which is neccessarily kept to a minimum in aero engines but is not such a critical matter in automotive use.