need performance data for MVVS .77 with APC 14" props
05-27-2014, 02:12 PM
#1
need performance data for MVVS .77 with APC 14" props
I am getting a maximum of 8000 rpm with the MVVS .77 and a 14x8 APC prop. The engine was bought used but looks like it has had minimal running. The compression is very strong with a distinct pinch at TDC. I am running it a bit on the rich side with 5% Cool Power. The engine is also running with the stock MVVS muffler (not the tuned muffler). I plan on using this engine with an APC 14x4W on the Aeroworks Extra 300 .60-.90 . The top rpm sounds a bit anaemic . Any experience/data with the above mentioned props/muffler/fuel combination would be most appreciated. Thanks.
05-29-2014, 01:02 PM
#3
Airraptor, thanks for your thoughts on the prop selection. I was told that it is a long stroke engine and works well with bigger props at lower rpm.
I managed to dig up an old RCM review of the engine by Clarence Lee, in which he quotes a 9500 rpm on a Zinger 14x7 prop, using the tuned muffler and 15% fuel. Assuming an rpm increase of about 400-500 by using the tuned muffler over the conventional one, my engine is still a 1000rpm short. I will try and run it this weekend, weather permitting, on 15% fuel and lean it out a bit. I am a little hesitant though about the 15% nitro as I hear they don't like anything above 5%.
I managed to dig up an old RCM review of the engine by Clarence Lee, in which he quotes a 9500 rpm on a Zinger 14x7 prop, using the tuned muffler and 15% fuel. Assuming an rpm increase of about 400-500 by using the tuned muffler over the conventional one, my engine is still a 1000rpm short. I will try and run it this weekend, weather permitting, on 15% fuel and lean it out a bit. I am a little hesitant though about the 15% nitro as I hear they don't like anything above 5%.
05-29-2014, 05:51 PM
#4
Long stroke engines breathe better usually and if timed even modestly, should turn up a bit. My suggestion would be to lighten the load some. If it has low runtime, definitely run it on a smaller prop for awhile. It's ABC right?
The first post says a 14x8 APC was used and 8,000rpm was the top, and the review said 9,500rpm on a 14x7 zinger. The APC is a higher loading prop and could be part of the lower power. Higher loading prop and non tuned muffler both can really hit performance. If the engine isn't propped for the tuning range of the pipe, performance gains won't be as high also.
The first post says a 14x8 APC was used and 8,000rpm was the top, and the review said 9,500rpm on a 14x7 zinger. The APC is a higher loading prop and could be part of the lower power. Higher loading prop and non tuned muffler both can really hit performance. If the engine isn't propped for the tuning range of the pipe, performance gains won't be as high also.
06-02-2014, 12:46 PM
#5
Thanks for your input, 1QwkSport2.5r. I haven't had a chance to run the engine with the smaller props. In the meantime, I heard back from Mr. Josef Svajda of MVVS and this is what he had to say, "
for standard muffler the 14x8 prop is probably too much. Each prop mark has another air-resistance, the RpM for the same marking prop from various are up to 1000-1500 different There should be 10000RpM on the groud at least Use 13x7, or 13x9 prop(APC) Or use the tuned pipe 3250 (3255N is NOT tuned muffler)"
Thanks again for the input and in the meantime I'll try to play around with different props, pitches and nitro content.
for standard muffler the 14x8 prop is probably too much. Each prop mark has another air-resistance, the RpM for the same marking prop from various are up to 1000-1500 different There should be 10000RpM on the groud at least Use 13x7, or 13x9 prop(APC) Or use the tuned pipe 3250 (3255N is NOT tuned muffler)"
Thanks again for the input and in the meantime I'll try to play around with different props, pitches and nitro content.
