Dar,

I wrote to you some weeks ago regarding oils loss from the front bearing and you suggested getting back to Just Engines. Well, JE reacted promptly and offered a deal on a new MVVS 91, which I accepted. The new engine has now had a gallon of 20% castor through it, most of that time in the air, and has performed faultlessly - a noticeable improvement on the last engine that was prone to cutting out.

Just out of interest, what rpm should I be expecting on a 14x6 APC. I am using 5% nitro and a throttle pipe (see piccies)? I'm still keeping the engine somewhat rich as it's new and the tacho is showing 9300.

Thanks for your advice and thanks to the guys at Just Engines for their excellent service.

Mick,


Paul and Jenny Landels of JustEngines are excellent folks.
I would expect nothing else from them but good, fair deals and service.

I have not had the pleasure of actually buying engines from them (understandable), but I have heard only good things about them.


I have seen MVVS .91 engines on the tuned silencer (#3253, not offered by JustEngines, I believe) and on the full length tuned-pipe #3250. On the tuned silencer it spun a 13x10 APC around 10,000 RPM and on the full length pipe it spun a 13x8 APC (which offers near equal load to a 14x6) at close to 11,400.

Let your engine accumulate a bit of time and then try to peak it.
MVVS engines tend to gain RPM measurably, after about 6 hours of use.

It is possible the throttle pipe you are using is marginal in volume, for an engine this large, limiting its ability to gain RPM.

I would expect somewhat better performance from any tuned exhaust.

Yeah, the throttle pipe does not let the engine peak, but I've used the "super quiet" and they have shaken apart. the last engine, on balanced props destroyed three. This throttle pipe at least seems more durable...

Those rpm figures you have quoted seem exceptionaL - that's 2000 rpm more than my set-up. As you say JE do not sell the full-on MVVS pipe #3250. Would you be able to supply that item to the UK? Do you have pictures of both pipes: the #3250 and the #3253?

Thanks for your quick response.

for additional info,
This is the rpm we measure on a very tight .61 and 14x6 MA prop, using the short MVVS 3253 tuned pipe, engine slightly rich. It peaks at 9600, and handles a 14x7 with ease on a 4-star.

Pe,

Thanks for the input: clearly the throttle pipe is not working well with the 91 and the 14x6 prop.

Mick,


Here they are from the MVVS catalog.

While we are talking about pipes on the mid size glow engines....

I have a customer who is building a twin-engined float plane. The airplane is designed to go FAST. He wants to power the plane with 2 MVVS 77s with the 3253 pipe on them. If the object is speed, Dar and Pe, what prop do you think will give the best results? Would a 13x8 be too much prop?

Thanks!