RaceCity

Hello Pe'...

Dar dropped off a pair of these little sweethearts at my house as he was passing through. Oh so cool!!!

Not being able to resist, I brewed up a batch of 5% Nitro, 23% straight castor fuel and lit one off on the test stand. Very good. Despite being diabolically tight at TDC (by far the tightest ABC I've ever seen), I've put about a quart through the motor this afternoon and have been pleased!!!

Astoundingly fast & linear throttle response. Needles don't seem to be excessively fussy. MVVS did a good job!

What should I be expecting to see from this motor performance wise? I started out the day with an 8-6 APC, then moved up to a "flying prop" toward the end of the bench session. Conservatively...it's turning the 9-5 APC in the mid 15's with needle valve to spare. The motor seems plenty stable enough to take to the field tomorrow, and I'll be comfortable leaning it out further once it has some air time on it.

For now though...I'm very impressed.

pe reivers

And then to think that MVVS almost did not build it, because they had the .26! I had to persue them a bit, after I built some ten engines of parts myself.
The .21 spools up slightly better, but this jewel has more low end torque, and takes the allowed 9x5 right up to the 16000 rpm limit.
Very good results with 10x4 as well. As a bonus it's the fastest starter of the bunch in the le-mans routine. A quick tap with the starter is all that is needed, when the engine is set up in readiness at half throttle.
BTW, I fly 1% nitro, and in this engine 20% oil will do fine after the first run. Less oil allows me to use a smaller tank, so I went as low as 10% oil without wear in the engine. Now I am back at 20%, because overall behaviour is better.

RaceCity

Well Pe', I applaud your efforts. It's a very nice motor.

I am curious however, HOW You/Svadja/MVVS managed to get such a good fuel draw through the cavernous carburetor???

7mm would be a large carb on a .46. How in the world it works so well on a .25 has me puzzled. Amazing!!

Thanks in advance...

pe reivers

That puzzles me as well. MVVS's inner design is not along the well trodden path's concerning port shapes and timing.
Want to see that .25 realy go? Shim up the cylinder 0.8mm, and turn .8mm off the cylinder flange top. Then ask the judges to leave their tach at home

RaceCity

Pe',

Thanks for the tip, but I'm afraid my machine shop skills might not be up to such a task. <GGG>

When my break in fuel is used up, I'll go back to my normal MVVS/Fox brew of 20% oil.

I did have the opportunity to put 6 flights on the engine today and had great results. It's starting up in one flip, and I try as I might to get the engine to cough, sputter or otherwise act up with hard +G and -G maneuvers....there was nary a burble. Granted, this engine is for a pure "sport" application, and will never see any combat. It's still nice to see it run so solidly at any throttle setting in a variety of precarious attitudes. The motor is still tighter than a banjo string at TDC when cold, but....that's what you're paying for.

Very nicely behaved motor...well worth the price.

pe reivers

The tightness in top dead center is not a quality error. It is the mark of all good ABC engines. If you treat the engine well, it will stay that way for quite a long time.

RaceCity

Well understood...thanks.

AERORICH73

Well now, so you are the fellow Dar mentioned in his e-mail about dropping off a couple of engines. I have been dealing with Dar lately for shims to lower the compression on 4 MVVS
engines a widow has in her late husbands RC stuff that needs new homes. What models are
these engines going into? Since this is my first experience with these engines, I am interested
in how they perform in various airframes. Give me a holler sometime.

Rich S.