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Engine basics => Engine set up tips => Topic started by: Michael Palm on November 20, 2014, 02:31:44 PM
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I have this old MVVS 6.5cc (40) that i bought a long time ago. I have never got it to run well. Always runaways, what ever i did. I have the 8 cc (49) Acrobat that runs lovely with or without pipe. I have compared the porting (just visualy) between the 6.5 and the 8. The transfers are much lower compared to exhaust on the 6.5. So my question is: Can i get a good run with a pipe on the 6.5.
Michael
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I aquired one of these recently. A beautiful piece but on the test stand it came at me like a hungry gator. I had Jim Lee make a new much smaller Venturi and relocated the spray bar. I'm going to try to tame it for my Supermaster without a pipe but I'd say it's a great candidate for a pipe. I sense this has .60 power but needs a leash.
Dave
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Depends what timing it has. Those engines had exhaust timing from 179 degrees for racing and pipe, little less for R/C guys at high rpm down to 140 degrees for C/L stunt. Later they did larger bore in the same case which was 7.2ccm and later also new shaft with 7.9ccm both for c/l stunt called Acro.
I think 6.5 is too heavy for good c/l use, but if it is stunt timing, it will work nice with pipe and also without pipe. I had several, all worked nice, especialy those with rear inlet, rear exhauset mounted sidewise. However I think you have r/c version with high timing, I affraid it will not work very well with or without pipe, it needs some 14 - 16 000 for good power and does not have good 4-2-4.
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I don't know which I have but here it is with Jim Lee Venturi now at about .156 and new spinner adapter. Haven't tried it yet with this set up.
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It's 11.8 oz. as shown.
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Mine has a venturi since it was new, lets hope its a c/l version then :D And its a ringed version.
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Thanks got your pix Michael. That's not the Venturi that was in mine. It was quite long and the spray bar through the center further up. It was new but I think it might have been an R/C version conversion attempt.
Dave
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I think mine looks a little bit different on the outside were the transfer port is. I will try it with a pipe on my engine testing plane. But it will be next weekend if the weather allows it, cant do it on the weekdays beacuse of work and wery short time of daylight now. I will post here what happens.
Michael
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There definitely is a way to stop that engine from running away - but you are not going to like it.
Whack a diesel head on it, these engine are built like brick outhouses and take to the conversion well.
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That would have been an option. But the drug addicts have made it so hard to get the fuel here.
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That would have been an option. But the drug addicts have made it so hard to get the fuel here.
I am surprised that you are even talking to me after the diesel suggestion, but I too have an older Modela MVVS 40 with an AJC diesel head on it!
That said I have always wondered how the standard tuned muffler would work with something like a double length header pipe at lower rpm. The standard pipe cuts in at 13000 rpm and suits the 40,45 and 49 range so I am guessing the smallest engine with the biggest resonator just may work at a longer length.
I have heard of the reverse being true, a smaller resonator upped the pipes start point to a higher rpm, the real problem here is that MVVS resonators have about a 3000 rpm operating band and produce broad power.
So you will have to find if there is any limit point definite enough and low enough to be of any use to you.
Power boat guys reckon on a double length header as a good place to start experimenting with.
Good luck.
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I know this posting is over two years old. Checking to see if you used the engine and how it worked for you. I acquired one in United Kingdom in the early 90's while based there (USAF). Finally getting around to using it and just trying to get some info on the engine. Thanks for the help.
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I had the R/C version. Served me well in Q-500 racing. Hot motor
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No I have not tried it with a pipe yet. I was fiddling around with a piped Irvine 46 Mk II mounted on the engine test plane when a link broke and it crached. And I have not had time to fix it yet, my sons planes take all the time. Maybe this summer the time comes to fix it. I will giva a report as soon as I get it in the air.
Best. Michael
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I have this old MVVS 6.5cc (40) that i bought a long time ago. I have never got it to run well. Always runaways, what ever i did. I have the 8 cc (49) Acrobat that runs lovely with or without pipe. I have compared the porting (just visualy) between the 6.5 and the 8. The transfers are much lower compared to exhaust on the 6.5. So my question is: Can i get a good run with a pipe on the 6.5.
Michael
I sold quite a few of the 40s that have low time, they work OK for piped stunt, the high times versions do not, and A PA 40 ,
OPS, or OS VF are better engines for F2B
regards
Randy
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Thanks for the feedback. I'm getting back into U-Control and assessing my possibilities with the engines I have. The MVVS is a heavy engine, that's why I wanted more info in it. I have two OS FP 40's and a FP 35 I can use for recreational stunt, which will probably be the avenue I will take. Thanks for the info..............