MZ201 questions

I remember that someone was familiar with the MZ201 and I have a few questions (I was thinking that Mark had one).

The web site does not give the fuel consumption at the various power levels. Does anyone have a good estimate?

The front page states it is a 30 hp motor, but the graph shows only 27 bhp max. Which is more correct?

Is there any problem getting one of these shipped from Canada?

Can the MZ201 be run at max power (or 6000 rpm) for very long?

Phil

i think mz 201 is two cylinder 45 hp engine ou must look at mz 34 ,that one is 30 hp

Yes, and thanks

The MZ34/35 is what I was meaning. With that in mind, does anyone have info on the MZ34?

I actually found the thread from Mark that described the info I need (I think). It helps when I search for the right thing (duh).

Let us know if you get an MZ34, and what you think of it, Phil. Compact Radial Engines makes good engines. (I'm glad they finally updated their web site.) I'm afraid to try one, fearing its vibration will be too extreme.

My first engine was a Hirth F-33, which has almost exactly the same weight and displacement. It vibrated violently... hard enough to tear up a perfectly good airframe.

I'm getting frustrated with 2-stroke engines. The singles vibrate too much and have reliability problems. And twins are heavy, and tend to burn more fuel.

I decided I don't trust my little CorsAir engine. It's an amazing, little engine, that gets good power from small displacement by using an expansion chamber exhaust and high RPMs. But that high level of tuning makes it touchy and less reliable. If you don't trust your engine, what good is it? I just hope it lasts until this winter when I can build a new fuselage for a heavier engine.

I'll probably try a fan cooled Kawasaki 440 with multi-V belt drive for my next engine, like the one in this picture, from J-bird or Vortech. The price, power, and weight are all good. And its vibration should be only moderate.

Hi Mark,
Have you considered the 35hp Briggs? Or is it too heavy for your application? Reports from the discussion groups are indicating that once the extraneous bits have been removed (engine covers, oversized mufflers etc) the engine weighs in at about 90lbs. I am now seriously considering fitting one of these in the Razorback. And best of all - they're CHEAP (brand new = $1995).

Duncan

Thanks Duncan,

I keep looking at the different industrial engine conversions. The only ones that have decent power to weight ratios are hopped up and stripped down. I'm not comfortable with hopping up an engine for aviation. Normally, aviation engines are de-rated for improved reliability. An industrial engine should be reliable if you don't hop it up or rev it past its normal red line.

The inherent problem with industrial engines is they weren't designed with light weight as a priority. They are convenient to buy and convert. But they're generally too heavy for my bird. 35 Hp at 90 pounds would work, if that includes the prop and whatever it needs to run (like a battery).

Do you have a web address for that Briggs, lightened, with reduction drive and all?

Hi Mark,
I'll have to check - but I suspect I don't. I can't even find a post to this site which I saw a few days back and now can't find again.

Cheers,
Duncan

Originally Posted by mstull

...I decided I don't trust my little CorsAir engine. It's an amazing, little engine, that gets good power from small displacement by using an expansion chamber exhaust and high RPMs. But that high level of tuning makes it touchy and less reliable. If you don't trust your engine, what good is it? I just hope it lasts until this winter when I can build a new fuselage for a heavier engine....

Interesting, Mark. You were pretty 'up' on this engine, earlier in the year. What happened to change your mind? Have you been having difficulties with it?

This is my 3rd CorsAir engine, Topaz. So I knew what I was getting into. Yes, I had to de-carbonize it already at 47 hours, as it gradually lost power and increased fuel consumption. I found the top compression ring was no longer free. It and its piston groove were all carboned up and gummy. And it was already time to scrape the carbon out of the head and exhaust port. The compression release also gradually failed.

Like most 2-stroke engines, the CorsAir has some serious shortcomings. First the good things about it: It has an excellent power to weight ratio. It gets excellent fuel economy; Parts are dirt cheap; The distributor is very helpful; It vibrates less than some other engines of this horsepower; Clever crankcase mounted reduction drive; Exhaust system comes with a mounting system that is relatively reliable.

The shortcomings: It vibrates too much at idle; No spark advancing ignition; Cheap Walbro carb; No air filter; Needs top end rebuild every 50 to 75 hours; Recoil starter is very light duty; Insufficient flywheel mass; Unreliable compression release; Very marginal engine cooling; You're only supposed to use full power for a minute or two; With that, and my higher density altitude, power is marginal.

We're not sure why my engine carboned up so quick... probably too much of the wrong oil. Alex suggests decarbonizing every 75 hours as normal. And use fully synthetic oil at 50 to 1, with no extra oil. I would replace the whole engine every 300 hours to be safe. Fortunately it's inexpensive. I'll probably replace the piston, rings, and upper connecting rod bearing every 100 hours or so.

The failures of my previous CorsAir engines were mostly my fault. Learning from my previous mistakes, I decided to leave my present CorsAir almost completely stock. The only thing I've changed is I put a real air filter on it.

Does anybody know of a good product for dissolving carbon deposits out of piston ring grooves. I'm not real comfortable with scraping them out.

Originally Posted by mstull

This is my 3rd CorsAir engine, Topaz. ... The shortcomings: ....

Interesting and interesting. Thanks. I've had a back-of-the-head notion of a tiny, single-seat motorglider and using this motor for the powerplant. While the fact that it'd be off for most of the flight would help, the cooling sensitivity would be a problem: I'd need to have it buried in the airframe (or retractable somehow), and would very likely need to run it at full power (for climb) quite a bit longer than "one or two minutes".

My first impulse on your carbon fouling is simply to say that it was running rich, but most of my experience is with four-stroke engines. Not sure how applicable that might be to your situation. Any chance the air filter is causing a richened mixture?

Thanks for the information!

Thanks Topaz,

No, it's definitely not running rich. My spark plug burns CLEAN. I wondered if the problem could partially be from running on the hot side. The oil scorches in the ring grooves, instead of staying liquid? I did use extra oil during break in, and even after that for a couple months, burning Amsoil 100 to 1, but mixing it at 80 to 1. I'm using Castrol PowerRS TTS at 50 to 1 now. It's supposed to leave less deposits.

All in all, I think this is the price you/I pay for using a race tuned engine. It puts out an awful lot of power for its tiny displacement. So there's a lot of fire happening in there all the time. It's a completely different ball game from conservatively tuned engines that run "Rotax rich."

I would suggest some kind of closable duct (cowl flap) for engine cooling on your motor-glider. The CorsAir is made for free-air cooled PPG pushers, where there's very little cooling breeze. I stuck a large duct on my U/L, that directs air to the head and cylinder.

Originally Posted by Topaz

Interesting and interesting. Thanks. I've had a back-of-the-head notion of a tiny, single-seat motorglider and using this motor for the powerplant. While the fact that it'd be off for most of the flight would help, the cooling sensitivity would be a problem: I'd need to have it buried in the airframe (or retractable somehow), and would very likely need to run it at full power (for climb) quite a bit longer than "one or two minutes".

Would it be feasible to put the prop AND motor on the extending boom so that cooling and belts would not be an issue?

Bruce

Originally Posted by bmcj

Would it be feasible to put the prop AND motor on the extending boom so that cooling and belts would not be an issue?

Bruce

CG shift might be a problem there. I'm talking really tiny. At any rate, this is a down-the-road project. I've got a little tailless sailplane to finish designing and actually build, first.

You could avoid the CG shift with an elbow mechanism or a sliding track that pulls the base up under the engine as it rises vertically.