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Rear exhaust 91 glow options - 8/16/2010 5:28 AM   
bunsen



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From: stoughton, MA, USA
Status: offline 		Hi

I have a Zlin 526AS scale aerobatic plane that has a fairly narrow cowl.  Presently running  a Saito 90 4 stroke and I was able to just fit the silencer inside the cowl.  I am looking for a bit more power and am considering fitting a 91 2 stroke with rear exhaust if I can find one.

Other than engines for Helicopters almost everything out there seems to be side exhaust except for the MVVS engines that allow rotation of the cylinder head for side or rear exhaust.  One option would be the MVVS 15 GFS/R ABC which is a 91 (15cc).

Would appreciate any feedback on this engine or other options to consider that may offer rear exhaust for a sport aerobatic plane, not a racer.  Would very much like to fit the silencer within the cowl.

Cheers

Ray


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RE: Rear exhaust 91 glow options - 8/16/2010 5:35 AM   
w8ye



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Status: online 		Better go with the MVVS. ( from Pe Reivers?)  http://www.mvvs.nl/


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RE: Rear exhaust 91 glow options - 8/16/2010 5:58 AM   
turbo.gst


 

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Status: offline 		You might consider a K&B 1.00. It is rear exhaust, has a built in in cowl muffler that also is a motor mount. It is very light weight and goes for about $170.

turbo

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RE: Rear exhaust 91 glow options - 8/16/2010 6:57 AM   
earlwb


 

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Status: online 		I would concur and check out the K&B 100 engine, it is rear exhaust. But the MVVS would be good too.
I don't know how hard it is to get one, but webra has a Racing 80F rear exhaust engine too.
http://www.webra-austria.at/motor.php?search=1039CP&folder=AERO&lang=EN


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RE: Rear exhaust 91 glow options - 8/16/2010 7:12 AM   
w8ye



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Status: online 		Pe Reivers is very easy to deal with in spite of being in Europe

DARZEELON also sells MVVS



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RE: Rear exhaust 91 glow options - 8/16/2010 8:19 AM   
rcdude7


 

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Status: offline 		http://www.mvvs.nl/

I bought my .91 from Dar in Israel

You could also try a YS 1.10 in your plane, lots of power.

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RE: Rear exhaust 91 glow options - 8/16/2010 8:38 AM   
w8ye



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Status: online 		I do not see how the MVVS could be rear exhaust though?


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RE: Rear exhaust 91 glow options - 8/16/2010 10:01 AM   
fiery


 

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Status: offline 		The MVVS cylinder can be rotated 90 degrees to a rear exhaust configuration.

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RE: Rear exhaust 91 glow options - 8/16/2010 4:25 PM   
proptop



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Status: offline 		The upper / finned portion of the case is seperate from the lower portion.
When you remove the 4 short head bolts and then the head, you see the heads of 4 more, longer bolts that go down through the finned section and into the lower case. You just remove those 4 long bolts...turn the upper finned section and sleeve, then bolt it all back together.

It's best to do this before the engine has been run...or broken-in.

I did this to an MVVS .49 (very nice engine )

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RE: Rear exhaust 91 glow options - 8/16/2010 7:00 PM   
bunsen



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From: stoughton, MA, USA
Status: offline 		Thanks for the excellent feedback.

I will look at the size of the MVVS 91 and see if it fits.  It is likely the best shot.  On the Zlin the engine sits fairly far forward and there is space behind it for a muffler I believe.  Side to side it is very tight.

The MVVS also apparently runs FAI fuel which would be nice as that is what I use in my MOKI 210.

Thanks.  :-)

Ray




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RE: Rear exhaust 91 glow options - 8/16/2010 10:47 PM   
MJD



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Status: offline 		A high-end solution:

Jett F.I.R.E. 120L with TurboJett in cowl muffler





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RE: Rear exhaust 91 glow options - 10/11/2010 5:20 AM   
bunsen



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Status: offline 		Hi

It has been awhile but I recently installed an MVVS 91 in a  ZLIN 526AS.  Got it running this weekend without much trouble and runs well on FAI fuel.  Starting up is much like my MOKI 210 in that it seems to like to be wet to start. If it is primed well one or two flips and off we go.

Was not able to locate an off the shelf muffler that would fit so did some experimenting and made my own.  Tried to copy some of the OS 91 type mufflers I have seen with regard to size and exhaust port.  The aluminum solder seem to hold up OK after a few long runs at speed.  We will see.  For soldering the aluminum used Dura-Fix from Weeks Distributers.

At this point have about three tanks thru it and it behaves well.  Experimented with a 14 x 8 and a 15 x 6 APC  prop and will stick with the 15 x 6 and see how it flys.  So far see around 8,800 rpm with the 15 x 6 APC prop.  Not sure if this is being limited by backpressure perhaps.  I might experiment with a more open internal baffle.  The pressure tap to the fuel tank is on the rear of the fuffler. 

In any case appreciate the feedback from folks on a rear exhaust 90 glow engine. 

Offer a few pictures below with regard to the installation on the ZLIN.

Ray





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RE: Rear exhaust 91 glow options - 10/11/2010 6:20 AM   
earlwb


 

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Status: online 		That is a great muffler you made. I like it. Great job. way to go.



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RE: Rear exhaust 91 glow options - 10/11/2010 6:29 AM   
Konrad


 

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quote:

ORIGINAL: bunsen

Hi

It has been awhile but I recently installed an MVVS 91 in a  ZLIN 526AS.  Got it running this weekend without much trouble and runs well on FAI fuel.  Starting up is much like my MOKI 210 in that it seems to like to be wet to start. If it is primed well one or two flips and off we go.

Was not able to locate an off the shelf muffler that would fit so did some experimenting and made my own.  Tried to copy some of the OS 91 type mufflers I have seen with regard to size and exhaust port.  The aluminum solder seem to hold up OK after a few long runs at speed.  We will see.  For soldering the aluminum used Dura-Fix from Weeks Distributers.

At this point have about three tanks thru it and it behaves well.  Experimented with a 14 x 8 and a 15 x 6 APC  prop and will stick with the 15 x 6 and see how it flys.  So far see around 8,800 rpm with the 15 x 6 APC prop.  Not sure if this is being limited by backpressure perhaps.  I might experiment with a more open internal baffle.  The pressure tap to the fuel tank is on the rear of the fuffler. 

In any case appreciate the feedback from folks on a rear exhaust 90 glow engine. 

Offer a few pictures below with regard to the installation on the ZLIN.

Ray

Was this just a SWAG? No attempt to make an optimized muffler for sound suppression or a tuned unit to boost power. Please do a follow up post about your success (or failure) with the construction method.

Looks like the effort was well worth it, you have a real nice clean front end!

All the best,

Konrad

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RE: Rear exhaust 91 glow options - 10/11/2010 6:34 AM   
bunsen



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Status: offline 		Hi

The header I purchased from Pe Reivers as part of a tuned pipe that he sells for the MVVS 91 .  The rest of it was T6061 1/16 inch Aluminum sheet with some brass tubes.

The Durafix Al solder seems to work OK as long as you make sure the metal is heated up real well so it flows along the surface after going over it with a Stainless steel brush.  I used a MAP gas torch. 

I am somewhat concerned that there is too much backpressure.  First time making a muffler so we will see.

Cheers

ray


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RE: Rear exhaust 91 glow options - 10/11/2010 1:36 PM   
Harry Lagman


 

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Status: offline 		Great choice of engine! Ther MVVS engines are powerful, great throttling, great running engines that are very tolerant of a wide range of props. A flying buddy has a .77 with a pipe - it's a very strong performer - 10,300 rpm with an APC 13 x 10 and perfect carburetion throughout.

What's she do on the APC 14 x 8? With a relatively low restriction muffler, a good .91 two stroke should do about 9500 - 9800 rpm with the 14 x 8. For comparison, we tached a brand new FX .91 we broke in on the stand, fitted with its stock muffler. It peaked just after break-in at 9700 rpm on 10% nitro. If you're getting these sorts of numbers or better, you are right in the ballpark with that muffler.

Great job with the muffler and nose installation BTW - excellent work!

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RE: Rear exhaust 91 glow options - 10/11/2010 5:26 PM   
DarZeelon



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From: Rosh-HaAyin, ISRAEL
Status: offline 		The MVVS 15.0/.91 GFS/R is a powerful engine, but it does not like RPM very much.

It has a 15 mm diameter crankshaft, like most .40-.56 engines; which might be the main reason for this trait.

It will, however, spin large props with great authority; considerably faster than can most other engines of the same displacement.

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