Sport_Pilot

If he wants a 4-2-4 break the differance is significant. TheMagnum is set up for higher revs and no regare with a 4-2-4 break. These engines will four cycle at lower RPM's then if they break into a 2 cycle run on the upline, they will either stay in atwo stroke run at way too fasta speed, or they will take way too long to break back to the 4 cycle mode.

There are people who reportsleeves to make normal sport engines run in 4-2-4 mode and the result is aless powerfullengine but more torque, especially when runningin 4 stroke mode.

aspeed

I was always on the quest for more speed, so never bothered with the 424 thing. I have a Twister and an FP to try out maybe this week though. Some guys used pipes on stunt planes, do they do the 424 thing? I can't imagine that. I think a sleeve would have to be dropped in the case a bit to get the lower timing required (without a pipe anyway)

ghost123uk

Thanks for the info - Actually I think I will keep the Magnum GP as it is and use it in summat else as I have now found a NOS FP piston & liner There may not be much change in power but that high timed port has got to affect the soft 4-2-4 I need (and like !)

The pipe on a c\l stunter does the opposite of that on a fast plane, it artificially holds the revs down, but when the engine loads up in a climb the pipe holds the same revs as in level flight, so the engine does not slow up.


Correct, hence my decision not to use the Magnum internals in the FP

Sport_Pilot

Most of the time that is what they did, but I think they have used the 4-2-4 break with a pipe. The old V series 60 was popular with a pipe. When used with the pipe the pipe will make the break stronger as it will get on the pipe when it speeds up. But I think this was difficult to tune and the engine took a bit longer to get to the higher revs and would be too fast in the downline. So I think most dropped the break in favor or tuning the pipe for slightly lower revs in level flight, preventing the revs from dropping but a very small amount.

stuntflyr

The V60 was never popular as a piped engine in C/L Stunt. It was used as a muffler engine in the 80's. I used it as such and most of the upper National competition group did so in the same way. A few east coast flyers tried the V60 on a pipe. It was not a success because it is loop scavenged and timed too low.

The OS 40 VF and OS 46 VF were the standard in 90's piped Stunters. Randy Smith must have sold tens of thousands. I had four for two models. Hunt and Pappas used OPS 40's and other Pattern style stuff, they were also not very popular.

The 4-2-4 break is sometimes used by some pilots using pipes in Stunt. The typical set-up is a near-constant rpm runs with little change.

Chris...