CRE MZ202 Engine

[Soleair]

I'm posting this because a question arose from my post on Bubbleboy's 'Freighting an engine from the USA' thread, & I didn't want to hijack his thread. So some of it is repeated from that posting.

 

I needed an engine for my MiniMax Eros under construction. The plans call for the dear old Rotax 503, no longer in production & getting scarcer to source. And costing $4k+ to rebuild.

 

So I researched the few engines in the 45 - 65 hp range. I discounted 4 strokes because their weight would be excessive, & reliability on hot VW base engines is arguably less than that for modern 2 strokes properly set up (pause to don flak jacket).

 

3 engines & their variants selected themselves: Rotax 582; Hirth 3202/3 & CRE MZ201/2. I did not shortlist the Hirth F23 50hp boxer because I understand it needs quite sophisticated mounts to achieve acceptable vibration; it relies on prop wash for cooling, so I'd need to get the cowl exactly right; it uses belt drive instead of a gearbox; it is very expensive per horsepower.

 

I initially only wanted 50hp. But Rotax don't offer this. Both Hirth & CRE offer the same engine in 2 different states of tune: the 3202 & the 201. Both these base engines are very similar: 625cc reed valve inline twins, fan cooled, installed weight 98/97lbs.

 

Given that the higher powered options, the 3203 & the 202, are very similar weights, it seemed foolish not to go the extra mile & give myself the option of reserve power should I need it, for short field ops or for the boost in climbout that might just save my ar$e one day. And operating at reduced percentage power should result in better TBO.

 

I contacted all 3 purveyors of said powerplants. Hirth fell at the first post because they ignored my email.

 

After email enquiries & responses, I phoned Bert Flood's emporium re the Rotax & Leon Massa in Canada re the MZ. Both were helpful, Leon in particular.

 

In the end I went for the MZ202, because the Rotax 582 needs a radiator, and this would add a fair bit of cooling drag to my plane. The 582 is also a fair bit heavier. I have an old Rotax 503, and I weighed this next to the 202. The new engine is almost exactly 10kg lighter than the Rotax, and also has electric start; produces 30% more power from its extra 120cc capacity, and at lower revs.

 

When it came to costings, the MZ202 was the cheaper option by quite a margin, especially since I was able to haggle a bit with Leon at CRE. Leon is an expat Aussie who owns the company, & a very easy guy to talk to. Also knows his engine inside out, since he has been building them for quite a few years.

 

I am in contact with a Swiss guy building an Eros in Thailand. He bought the Hirth 3202. With the same shipping costs that I paid, his engine was 50% more than I paid for mine (though this did include some spares). And his is 55hp, while mine is a detuned 60hp. His makes 53 foot pounds of torque @ 5000rpm, mine 61 foot pounds @5200rpm.

 

The final price of my engine, on the bench in my shed with all freight, duty, airport & agent fees was approx 10% cheaper than the Rotax 582.

 

Of course it remains to be seen how the engine will perform on my plane. But it is beautifully made, and all those Mosquito helicopter pilots have put in a lot of high continuous rev operation hours. Time will tell.

 

Bruce

 

 

[fly_tornado]

what do you think of the gearbox quality?

 

 

[Soleair]

Very hard to tell just from looking externally - and I do not plan to strip it down to inspect the internals!

 

Casting quality appears very high. I'm surprised at the lack of more pronounced 'buttressing' to feed prop loads back to the main block. Large dia PTO shaft (30mm?) & bearings. Very small backlash evident in gears (& no oil at the moment).

 

I asked Leon about any gearbox failures. None known.

 

The general appearance of the gearbox is very similar to Rotax & Hirth.

 

 

[Deskpilot]

Bruce, thanks for a nicely detailed expose' on your approach to a 'problem' many home builders are likely to experience. The only thing you omitted were the photos that make our juices flow.

 

 

[Soleair]

Thanks Doug. I'll post some pix when my installation is a bit further along. I'm busy making my prop at the moment, so will be a while yet.

 

Bruce

 

 

[facthunter]

Put a magnetic drain plug in and check for metal. You don't have to drain the oil if you are quick. Just lose a small amount. The original MZ were leaders in two stroke development. Power to weight hard to beat but I keep suggesting the small Wankels, as an alternative. Probably liquid cooled though. Nev

 

 

[jetboy]

and there was the Simonini for a while - one in a Zenair 701 at Rangiora which i'd like to find more about. I think it got swapped out for a Rotax 912.

 

likewise the small Wankels, all of which are unobtanium around these parts. Diamond AE50R / AE75R is the last heard of.

 

A gear drive 75hp would do for my application. I used to run 503 in Bantams and liked them (except for the grenade episode)

 

 

[facthunter]

Well of course, only the 582 is made or supported now and with radiator(s) and a bulky exhaust are not that clean. Some of the better ride on mower engines may be a possibility for cheap power. ( They won't be as light as a two stroke and it might be advisable to upgrade some internals) Nev

 

 

[microman]

Actually the Simonini (92 hp) was in a couple of Skyrangers, also one in a Pulsar, one in a Baby Lakes, and another in a Rans S10 currently under construction. I owned one of the Skyrangers, and although there was tons of power, there was also a lot of vibration which I could never cure, and the fuel consumption was nothing like what was claimed (9 litres p/hr - actually more like 18) When I was in the UK in 2004, the Skyranger agent laughed when I told him about the Simonini - their experiences with the engine had apparently not been good. Pity really because the idea was ok - copy the Rotax 582, add well-tuned pipes to give it more power, and sell it for a lot less. My understanding is that the factory out-sourced a lot of the work involved in putting the engine together and there was very poor quality control. Just two examples of that were the rubber donut in the gearbox bolted in off-centre and rubbing on the case, and the cylinder head bolts not torqued properly.

 

 

[facthunter]

Sometime vertical twin two strokes vibrate quite badly. Something going up and down isn't balanced by things going round and round. I designed an opposed piston two cylinder motor some years ago that had good balance, that might have had some potential but it was a little bit wide. It's not going to happen. but a radial two stroke with forced scavenging could be a goer. (4 or 6 cylinder with 2 throw crank) .Nev

 

 

[Ada Elle]

and there was the Simonini for a while - one in a Zenair 701 at Rangiora which i'd like to find more about. I think it got swapped out for a Rotax 912.likewise the small Wankels, all of which are unobtanium around these parts. Diamond AE50R / AE75R is the last heard of.

A gear drive 75hp would do for my application. I used to run 503 in Bantams and liked them (except for the grenade episode)

There are some Israeli made 50-80hp Wankels used in their UAVs. I wonder if they'd sell the engines to civvies.

 

 

[facthunter]

Norton made one (Aircooled) but it is gone now. They were a big success in Outboard Racing in the USA. which is high load like flying. You use sun and planetary gearing from auto transmissions for the reduction gearing. Nev

 

 

[Soleair]

The only thing you omitted were the photos that make our juices flow

I finally reached the stage of being able to test run the engine. I wheeled the fuselage out of my shed, tied it to a handy gum tree, and chocked & lashed it to a couple of giant batteries.

 

I rigged up a temporary fuel system (can with tube in it), checked everything again, & hit the go button. And it went! Ran really well - very smooth, even at tickover. I only took it up to 5000 rpm, but all went very well indeed. My prop seemed to be generating a pretty impressive amount of thrust too.

 

This was really only to prove the systems & installation. I will do the run in & more extensive running when I get to the airfield - still a while to go yet, sadly.

 

But the engine is most impressive thus far. Shaky video of an early run here:

 

 

I would attach some installation pics but I can't find how to resize pics on this MacPro. . .

 

Bruce