From what I can tell, the Hirth 3003 engine is only 137 lbs dry. I think I might need a psru with it, because peak torque is at 6000 rpm, but if I am saving 100 lbs in dead weight, wouldn't I be able to get the performance out of an engine like this? Or even their 80 hp model?

Would I even need a psru, if I used a smaller prop?

It is only $10k new with starter and fuel injected, and obviously really really light, which would help useful load if built to 1440 gross weight.

Any thoughts? Is the torque enough to power the plane? Do I need a psru? Is two stroke bad vs corvair?

Here are the specs and power curve

If I save 100 pounds, any reduction in torque or hp (although it is a 110 hp) would seem to be offset. That is 20 percent of useful load. seems like it would beat an 0-200 at 270 lbs installed, bc it increases useful load by 100 pounds, which is 20% of plane's total useful load.


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Comment by Lawrence Van Egmond on January 16, 2013 at 12:56pm
I have 600 hours behind Hirth engines and never had a problem that wasn't my fault. I have found them far more reliable than the Rotax 2 stroke engines.
Comment by Chris Aysen on January 15, 2013 at 9:06am

Go four stroke. Weight is important but don't let that be your major deciding factor. To many other choices.

Comment by Bob McDonald on January 12, 2013 at 8:34pm
"Nothing Good" is a understatement. Personal experience in Challenger & Hornet best described as "garbage". Always an new and improved engine....because the past engines were garbage.
Comment by Randy Cross on January 12, 2013 at 5:32pm
Check some blogs...I have some NOTHING Good about the Hirth Engines....
Comment by Lawrence Van Egmond on January 12, 2013 at 4:12pm

I seriously considered putting Herth's 4 cylinder 100 HP in my 750.  It is light has a good reputation for reliablity, a good TBO and can swing a large prop because of the gear reduction. The things that kept me from using it were the lack of a firewall forward kit, the lack of acceptance of 2 stroke engines in general aviation and the higher fuel consumption. I have flown all my ultralight hours behind Hirth engines and have been very pleased with them.

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