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please all MZ2 Mosquito owners... Reply
Hope you make it to the Pacific Northwest and fly with us. Google-maps: or Purple Computing. Jets? I have jets.
there have been some great podcasts on  about 2 stroke jetting. too hot and the aluminum will melt. do a search for it. this is a fun site. 
that site has now been replaced with this new one  . there are some podcasts associated with it too. 
i did a quick search and came up with mike stratmans stuff. it is all about engines.
here is the link on site to get the podcasts info. it is under psfradio.  find the one you want , then click on read more, then listen now. away you go. these podcasts are amazing. 
one more thing. they have a forum link for the MZ engine. may be a good source for you mosquito owners. they had over 3,000 hits on the MZ202. 
I have treated Stratman's stuff like it's the bible on 2-strokes, since I discovered it 10 years ago!!!

It does not give any guidance at all though, about NEEDLE-JET sizes FOR A HELICOPTER during the FULL-RPM+LOW-THROTTLE "unloaded" times.

This is like the engine is running and revving high without a prop installed!
(As you can see, there is a HUGE difference. There is no significant difference at FULL THROTTLE so the main jets called out in the published charts, are for the most part correct.

THERE is a BIG PROBLEM with using the NEEDLE JETS called out in the charts because, in a helicopter, the engine runs at FULL RPM even when the throttle is decreased to the midrange.

THIS STARVES THE ENGINE FOR OIL IN THIS RANGE because it is spinning at full RPM with a lower amount of fuel available since the throttle barrels are partially closed.

Do you feel this is what is applicable to the Mos?)

Yes, and no (I should have been a politician) Wink
The short period of time the throttles are partially opened should not starve the engine for oil. If you have ever looked inside a 2 stroke engine you will notice the internals well coated in oil. I would be more concerned with burning a hole in a piston top.

Having said that, I think we're getting a little over concerned. The MZ engines have shown to be tolerant of the way we use them. and I don't remember any issues with heat. And to answer the original question, I'm using 175's on the mains, with stock idle and needle jets. I'm at 4000 ft, and DA can go quite high in the summer.

...the short period of time the throttles are partially opened.

Skeeter, I THINK you are referring to the time during spooling up and down? How about the sustained period of "partially open" during descent to land when the NEEDLE-JETS are what's controlling the amount of oil getting in, and the engine is still wound up to 6,200 RPM? This could last for 10 seconds all the way up to 1.5 minutes.

As I stated...EGT is like the EKG of the engine. If your EGT gauges are pretty accurate, and the EGT's behave correctly when power changes are made, and they fall within and never exceed the limits specified by the engine manufacturer...YOU ARE IN GOOD SHAPE.
A couple of points in the previous threads – you can’t make absolute direct comparisons between the Rotex Bing 54 and the MZ Bing 54 because they have different throat sizes. Also, the oil to gas ratio is a fixed percentage ratio so your carb are not starving the engine of oil no matter the throttle setting. If the temps are running up at flight idle and during an auto you have a (mid range) needle jet issue. The EGT temps should run between 1150-1200. If you are on the ground, full throttle, no collective pitch and your temps are getting hot. The needle jets are to lean. To check it pull the collective up to transition from the needle jet to the main jets and if the temps drop the needle jets are the wrong size. The stock needle jet is 2.76 go to a 2.78 – it will probably cure the running hot at flight idle as well as during autos.
Hi Marcher,

This concept could get some folks hurt so it is sooooo important to understand it.

YOU ARE RIGHT that the fuel/oil ratio is a constant on the Mosquito, because you mix the gas, right? It is always 50:1 or 60:1 or whatever everyone is mixing it to.

BUT... (please stick with me and don't tune me out)
* if you do a full throttle climb, for 1 minute, THE PISTON GOES UP AND DOWN 6,200x, 10 oz of fuel are consumed, that means at 50:1, the engine has been lubricated with 0.2 oz of 2-stroke oil.
* if you do a half throttle descent for 1 minute, THE PISTON GOES UP AND DOWN 6,200x, 3 oz of fuel are consumed, that means at 50:1, the engine has been lubricated with 0.06 oz of 2-stroke oil.

This has nothing to do with comparing Bing 54's. The point is...jetting tables that were written for airplanes, cannot be used to determine needle jets for a helicopter because in a helicopter, there are many periods of extended flight when throttle is low, oil supply is low, and rpm's are high. Not the case with fixed wing aircraft.

Now I agree with you 100% that while sitting on the ground at full rpm and collective down, the NEEDLE JETS are metering fuel and if it's getting hot, the Needle Jets are too lean. I also agree with you 100% that if you pull up on the collective to 75% throttle or more and the EGT's decrease, that tells you your Needle Jets are too lean. (If your MAIN JETS are correct)

I TOTALLY DISAGREE WITH YOU when you say during an auto, you are in the midrange, YOU ARE NOT! The Needle Jets ARE NOT metering fuel during an auto with the throttle closed! The IDLE-JETS are. If the EGT's rise during a flightIDLE auto, you will have to install richer IDLE-JETS. If the engine begins to LOAD-UP during a flightIDLE auto, then leaner IDLE-JETS need to be installed.

Please FLAME ME if I am wrong, guys! I may be the one who needs to understand, but right now, I am 100% certain I am correct. My only intent here is to focus on an area where many Mini-500 pilots had engine seizures, and help Mosquito Pilots avoid the same by stating the lessons that were learned!

Bryan Cobb


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