Quote:
Originally Posted by captainron
Seems to me that if you were using 300 hp in your car, you would be writing this from jail, and your car would be in an impound lot somewhere. It probably takes only 45 or so horsepower to run your car at 75 mph, which is why modern car engines can usually run trouble-free for a couple hundred thousand miles. To be pulling 300 hp for take-offs and climbs, then cruising at 225 hp, the odds of long life don't seem so good.
On the other hand, Lycomings with directly driven propellers were built for this kind of stuff.
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We've discussed this before. We're not talking about flogging the engine at 6500 rpm and full boost but rather derating it to about 4500 and about 45 inches. The WRC Subaru engines on which the STI is loosely based were pumping out nearly 420hp at 8500 rpm with good reliability. Stresses at the 250hp level and 4500rpm are a fraction of these levels. As previously stated, Fuji engineers have the right stuff in these engines for sustained high power levels. Yes, they are designed to do this if called upon to do it. Piston speeds and bearing surface speeds at 4500 rpm are only slightly higher than a typical Lycoming at 2700 rpm. All well within what is considered low stress for the parts used in a continuous application- about 3000 fpm.
It may surprise many lay people that auto engines today are designed and routinely tested to higher standards than certified aircraft engine requirements. The FAA only requires 100 hours of full throttle, full rpm for certified engines and another 50 hours at 75-100% power, 50 hours of which are required to be at redline oil and cylinder head temperatures. Most auto engine manufacturers today do a minimum validation of 200 hours of WOT at rated hp rpm and some as much as 1200 hours. In addition to this test, they perform cold weather testing to the tune of 1000+ cycles of cold soaking the engine to 0F and immediately taking the engine to WOT and high rpm until coolant reaches 240F. While the engine is still hot, 0F coolant is pumped into the engine until the block achieves 0F and the test is repeated- over 1000 times. Additional tests often include idle testing to 2000 hours with oil temperatures of 260F+ and transmission validation where the engine is cycled from low rpm to shift point rpm at WOT while the transmission is shifted up and down for up to 1600 hours. Not just one engine is put through these tests- dozens are. Wear rates are noted and obviously failures are not acceptable before release of the design.
The EJ series Subaru has proven itself capable in the real world of sustained high rpm/ WOT operation with the 1989 world speed record of 100,000 km by three Legacy RS turbos over 447 hours of 138.78 mph and an estimated 250,000 flight hours by over 1000 Subaru EJ powered aircraft including gyroplanes from RAF and Groen, fixed wing conversions such as those from Eggenfellner Aircraft and hundreds of other private conversion worldwide. One high time gyro operator in Australia reported 3800 hours on an EJ engine without overhaul!
You have to understand that liquid cooled engines are not affected from a materials/thermal standpoint like an air cooled engine. Head materials (aluminum) retain their T6 heat treatment in use unlike air cooled aircraft engines which basically operate in an annealed (weakened) condition.
Wear rates have a lot to do with how well oil films are maintained on touching parts. With closer dimensional and temperature control possible with liquid cooled engines and full synthetic oils such as Mobil 1, wear rates are very low. This is why 200,000 miles (average 8000 hours) in most modern car engines is no big deal today.
To answer the other question on the EG33, this engine was only used in the SVX sports car produced in the early to mid '90s.
I agree with Randy, the STI is probably the best basis for a Lycoming substitute- tough, light and relatively inexpensive.
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