Hirth Vs. Rotax [Archive] - Rotary Wing Forum

Screw

11-09-2003, 11:00 AM

Hi All, Just doing a little reseach on the Rotax and Hirth line of engines.  Looking for a better than 100hp application for later down the line. As far as up front cost:  Hirth F-30ES @ 105hp $5,800. prior to gearbox and accessories with a 1000 hour TBO. Rotax 912S @ 100hp $12,995.  600 hour TBO. Any idea on overhaul cost on each? What does a Subaru 110-115hp set up run?

GyroRon

11-09-2003, 11:39 AM

The Hirth costs at or over 10 grand ready to fly. The Rotax 912 has a TBO at or over 1200 hours. The Soobs are the way to go for cheap power. Check out Sub4 or Stratus or the many other conversions. Or do like Dave thump daddy did and build your own converson for lot's less.

Screw

11-09-2003, 11:54 AM

I am not one with the force like Thumppy One Kanobee.  I have to buy retail. The specs I saw on the Rotax gave it a 600 hour TBO. Oh well, I'll keep on researching.

GyroRon

11-09-2003, 01:43 PM

They just recently upped the point of TBO to 1200 or it may have been higher. It was in all the kitplane type magazines. Still is a lot of smack for a engine.

PW_Plack

11-09-2003, 02:54 PM

John, Ron is right. I read in a couple of the mags that the TBO for the 912s and 914s was upped to 1000 hrs or more. Subarus are much cheaper, but much heavier. A 912 with accessories and fluids is about 150 pounds, a Subaru EA-81 well over 200. Like your VW, however, the Sub will be MUCH cheaper at rebuild time. If it's going on a two-place, consider the EJ22. They'll get you into the 130-170 HP range, depending on the conversion, around 300 pounds, and generally a better engine than the old 1.8 L engines.

Aussie_Paul

11-09-2003, 10:36 PM

Hi guys, I flew a 912 uls 100 pony power in S/Korea in a Raf. Very marginal. The next day we put the ej-22 back on and I nearly got whiplash in my neck. The 912uls is a nice engine but compared to the Subaru ej-22 they are only pony power. Aussie Paul.

Screw

11-09-2003, 10:47 PM

Thanks guys, This info is very helpful.

Brent_Brown

11-09-2003, 11:11 PM

Look at the MZ 301 P 90 hp 7000 bucks, it is just like my 202 but with one more jug.

PW_Plack

11-10-2003, 09:45 AM

Steven, The new NSI/Subaru 2.2 has no internal modifications by NSI, only a better intake manifold with larger throttle body. The engine itself comes in a crate direct from Subaru. The problem so far with the new NSI 2.2 is the aftermarket ECU, which is designed to operate without an O2 sensor, but has some serious bugs.

Brent_Brown

11-10-2003, 11:06 PM

I can never grt a reply from NSI I wanted to use the gear box on a corvair maybe or a SUB4 box. Anyone have a real point of contact for NSI?

Udi

11-11-2003, 03:43 AM

One fact that nobody has mentioned yet is that TBO doesn't mean didly doo unless the engine has a proven record for making and exceeding this TBO. Rotax took the conservative approach and started with a low published TBO for their 912/914 lines of products, and raised it as they gained experience. Hirth, on the other hand, is doing the just opposite by giving their 2 stroke engines a 1000 hr. TBO BECAUSE they are built with these super hard materials. *I don't know of ANY Hirth engine that made it safely to the TBO mark. *I've heard many stories though of Hirth engines busting their crank shafts at less than 300 hrs. I wouldn’t hang my hat on a published TBO unless is has a proven record. One more difference between Rotax and Hirth is that some Rotax models (912/914) has already received certification in many countries, including FAA, however, the ULS ultralight models are sold without certification to keep the costs down.  I don't know whether the Hirth engines are being certified anywhere, but I doubt it. Udi