ORIGINAL: david92692
DarZeelon,
I was going to ask in the first post, but didn't want to sound too gullible. On Morris's site, they list the MVVS at 15500+ rpm with a 12.25x3.75 prop (APC I assume). This sounded very high, probably too high. What kind of rpm's should one expect from one of these 49's with this prop?
I run Powermaster 15% almost exclusively, can the MVVS engines handle this, or will I need to get lower nitro fuel for them?
Are you saying that the Webra outperforms the MVVS with the smaller props? I assumed they were pretty much similar in performance.
David,
Spinning a 12.25x3.75W prop, at 15,500 RPM, requires the engine to output no less than 2.04 HP!
I don't know if this is a hoax, a misread measurement, a misprint, or an utter lie, but this engine cannot make this kind of horsepower.
In another thread in RCU, the Jett .76L, with the Turbo-Jett muffler, is quoted to spin this same prop at only 14,500 RPM (1.67 HP), on 15% fuel.
Do you think it is possible the MVVS .49 makes 22% more horsepower than the Jett .76L?
I don't and I didn't think that you do either...
The MVVS is built to run 0-5% nitro. The factory recommends 80/20 fuel, without nitro.
It is possible, however, this engine comes with a different head in the USA, with a larger combustion chamber and the same squish clearance (shimming the head is the last thing I would do), so it could use 15% nitro.
If in doubt, write to the factory in Brno, Czech Republic:
[email protected] .
If you buy this engine from Morris and it doesn't stand up to this claim, I don't think they will be very happy to take it back....
The MVVS tuned silencer is capable of boosting power in the 11,000-15,000 RPM range.
If the engine is propped to spin much higher than that, with a 10x6, or smaller prop, the Webra may have a slight edge, since the MVVS tuned silencer is beyond its effective RPM range (and is just a silencer...).
On larger props that offer real thrust and pulling power, the MVVS will eat the Webra and most other high RPM engines for that matter, for breakfast...
The Webra is a very good engine, but like Rossi, it should be allowed to rev, to be at its best.