OMC 3 Cyl expansion Chambers

[calvin]

Great lookin exhaust Tim..is the exhaust open all the time or is it manually operated..like slider pipes?

[Tim Kurcz]

My system is a near dimensional copy of the factory Mod-50 except it's external to the engine and has a top outlet. There are no steering bar clearance issues to deal with, but most importantly, no water vapor contamination as with a down outlet system. Simple, lightweight, and effective, it does not slide. I've got two of the three remaining as shown with electroless nickel plating at $595 each.

Tim

[johnsonracer]

Hey Tim,

How do you think that exhaust would go on the bigger 60ci (920cc) engine if I could adapt it to fit?

[johnsonracer]

sorry its 56 ci not 60. But the loss foam powerhead with the cast in exhaust

[Tim Kurcz]

sorry its 56 ci not 60. But the loss foam powerhead with the cast in exhaust

Pulse tuning is a phenomenon of design with triples firing 120 degrees apart. This type of system is employed on the SST 60 internally, and will work well with your 56.6 externally. Meg length may need adjustment to suit your desired RPM range, but this is easily accomplished because it's external.

Keep in mind the Mod-50 (49.9) system was designed to tune in the 7000-8000 RPM range, though mine turn 8500 without going on their nose. I've got a 6-pack SST 60 in construction and will pulse tune it just like the factory, but internally this time, to keep it quiet for testing, and so nobody can see my work!

Tim

[Mark75H]

Tim, can you explain how the internal lengths are arrived at on the internal 3 bank tuner?

[Tim Kurcz]

The short answer is you disassemble the well designed and proven factory Mod-50 exhaust system, carefully grid and measure it, then duplicate close as possible for external use. The longer answer starts with port-time-angle-area equations and lots of math from Jennings, Bell, and others. There are additional improvements which I've made, but those are reserved for my engines only.....

Tim

[Mark75H]

So this is all based on Ray Nydahl's work?

[Tim Kurcz]

Hey Sam,

I'm not familiar with Ray's work. If you or any others have any documentation to share I'd like to see it. Clearly there has been alot of lakeside R&D over the years. Likely there's little truly new except for materials, computer controls, and propellers. The rest is test-test-test!

[Mark75H]

I'm pretty sure Ray is the source of the "proven factory Mod-50 exhaust system"