Bizarre use of a chainsaw?

[BluSTi]

So, I'm a ME student and we have a Formula SAE team. We've been using Kawasaki ZX6R motors, but now we're looking for something else. An idea I'm tossing around is using four 880 pistons and cylinders, manufacturing new heads (has to be a 4-stroke) and orienting them in a boxer configuration.

Here's a link to the FSAE site to get an idea of what this frankengine would be powering:
FSAEOnline.com

If using the cylinders won't work, the option also exists to mill a full case, and use the pistons for that...

So, any thoughts? The top teams are currently using 450cc singles (yamaha, kawi, motorcross motors) and 450cc +- is what is optimal given the size of the intake restrictor (20mm dia). Am I missing something? I'd think a tiny, 450cc boxer, with a cg only a few inches off of the ground would be an interesting proposition...

I leave it to you...

 

[romeo]

You will have transfer ports and the exh and intake ports in the cylinders, windowed pistons, and no oil rings. So being that you want to convert to 4 stroke knocks those cylinder heads out of your choices.

As for the 450 F's the other guys are using, that is the best choice for a small 4 stroke with massive power to weight ratio.

Personally, I think a custom built flat four boxer would be very cool. You might look at aftermarket pit bike stuff for CRF50's. Dirt cheap and surprisingly powerful and probably much closer to what you are shooting for. But really, you are headed into uncharted waters against years of R&D the moto company's have spent in trying to get four stroke motors to perform like 2 strokes which in its self is nearly impossible.

 

[Stihlmech]

ever thought of using 4 mix engines from stihl?

 

[Penn's Woods]

1969 500cc 2 stroke or 1970-75 250-700 cc s strokes. The 400cc, 2 stroke, 3 cylinder, 3 carbs had the best power to weight ratio of the time. The 400's were popular in many winning go carts and also in airplanes.

Along the lines of what you want to do with chainsaw motors I remember this and found it on wiki..

Kawasaki triples were air-cooled, and the crankshafts were pressed together. This made it possible to cut an engine apart, press up extra sections of the crankshaft, re-weld different sections of the cases, and make multi-cylindered motorcycles. The ignition system and carburetors had to be redone. Four-cylinder 1,000 cc H2s were known to exist,[3] [4] but the most common bikes to be modified were the S series, with 5- to 7-cylinder models being built,[citation needed] and at least one "V-6" (two three cylinder banks feeding into a common transmission). There even exists a 48-cylinder bike made up of 250 cc parts.[5] These bikes were more of a machinists' skill exercise than a practical development. They were impractical because the engine was made much wider and the clutch and gearbox were put under more strain.[citation needed]

 

[tolman_paul]

Put your time and resources into building a competitive chassis. The key with the carb restriction on the SAE cars is to keep everything light, you just can't make massive power with that restrictor no matter what the engine configuration. The only way to gain power on a restricted motor is to bump up the compression ratio. The reason people are running singles is to save weight. The 4 cylinder advantage of running higher rpm is lost because you just can't run enough air through the restrictor to take advantage of that high rpm.

What you're proposing building is a one off engine will take massive amounts of your limited time and the performance gain will be minimal.

 

[Rx7man]

What tolman said!
If I were to try and make something like that, I'd go with a short stroke big bore boxer 2 cylinder, which will enable bigger/unshrouded valves.

It's a beastly heavy head, but just for fun, look at the Honda XR500 RFVC (1984) engine.., and cut the stroke in half to enable higher RPM, with a domed piston to increase the compression ratio.

Interesting idea.. good luck with it! I love thinking about this stuff