A stock Irvine with KY Mouse can or UltraThrust muffler is as powerful as any engine on the market. The motors I run have had the crank timing opened up as well as the exhaust duration. These mods net around 700 rpm. My Irvines, modified, consistently turn a 9x4 MAS propeller between 19.0K and 19.2K on the average combat day on 15% nitro. A stock Ivine with after market pipe will consistenly turn a 9x4 MAS 18.5K on 15%.
Like any engine, the Irvine has its weaknesses. The thing I have been most impressed with though is their longevitity. I have 2 engines I purchased in 2001 that have many gallons of fuel run through them and have been stuck in the dirt many, many times. These engines still turn with a couple hundred RPMs of my strongest engine. That's a lot of bang for your buck in my opinion.
There a couple things with the Irvine that needed attended to.
1) The carb barrel screw needs to be glued in place or it will back out. I generally red loctite this screw in and then put a dab of IC2000 CA over the head. IC2000 is the black CA used for gluing fiberglass. Regular CA works fine as well.
2) The phillips screws that hold the carb in need to be replaced. The factory screws are soft and will back out. Replace the 2.5 mm screws with a good hexhead machine screw and red loctite them in place.
3) Once bent, the needle valve will break off from the cylinder. This usually occurs after a hard dirt nap or nasty mid-air. This bit me in the final round of the NATS this year and I think I may try a remote needle valve to eliminate this problem.
IMHO, Magnums are more trouble then they're worth. I own 2 of them and the carbs are notorious for falling apart and the quality control was not very impressive.
As others have said here, the OS FX is probably the best all around combat engine. Good power, super dependable, and parts are readily available. I chose the Irvine because at the time I could get them from direct from England for about $70. If I had it do all over again it would be a VERY tough choice between Irvines and FXs.
Tom,
Just like anything, you'll likely get a dozen different answers to your question. I think the best piece of advice is to stick with one engine and learn all its weaknesses. Ohh, and use those Norvels for paper weights and save yourself a whole lot of frustration...
Looking forward to seeing you on the flightline this season...
A.J. Seaholm
TEAMseaholm.com
[email protected]