Engine weight vs performance

[Chewie65]

I am not building. But an honest question. I am for giggle looking at E-LSAs as a way to break into flying until the money is availible for an RV of some type.

Flipping through the Kitplanes Engine Buyer's Guide, I have noticed some engines are similar HP but very fifferent weight wise. Such as:

Hirth F-30 100hp, aircooled and 105 lbs. 4 cylinder
Jabiru 2200 85hp, air cooled and 140 lbs. 4 cylinder
Jabiru 3300 120hp aircooled and 180 lbs. 6 cylinder
Rotax 912S 100hp, water/ aircooled 133lbs. 4 cylinder

I understand that a liquid cooled will add weight, but why the large difference for the above engines?

Could it be dry weight of complete with accesories?

[Geico266]

Hirth is a 2 cycle engine not worthly of an aircraft IMHO.

Jabiru has no gear box, they are direct drive and are alittle better than Hirth. The Jab 3300 is a fair engine, but the extra weight is a killer.

Rotax 912(S) is the gold standard of LSA aircraft engines. There are more Rotax engines flying world wide than any other aircraft engine.

[mcjon77]

Keep in mind that the REAL weight difference between a Jabiru 3300 and a Rotax 912S, once all accessories are added for both aircraft, is ~15lb. Certainly not 45lbs, as implied by the published weights.

[N941WR]

You will also want to know what the RPM the prop was running at for those HP numbers. Engine RPM means nothing, since some of them have built in PRU's, you want to know the speed of the prop. If it is turning really fast, say over 3000 RPM, move on.

[Mel]

Check deeper into what's included in these weights.
The Jabiru for example is all up installed weight including exhaust system, etc. The Rotax is plus radiators, coolant, etc.
And as stated before, the Hirth is 2-stroke.

[breister]

If you aren't buying immediately, don't forget the Gemini engine. I hear varying rumors that they are in production or very close.

This design flew scheduled commercial service in the 1940s, so although the company is new the design is not.