exhaust restrictor?

[Sean in CT]

My question is: wouldnt it make more sense to restrict exhausts rather than intakes?
Seems like the intake restrictor makes fuel injection/carb tuning unnecessarily complex.
Restricting the exhaust (ie 1-1/4 header tubes or some such thing) would be just as effective
and make it easier for less experienced/limited resource teams to compete.

i am not an engineer or part of FSAE, but i read the forums for time to time.

[Pat Clarke]

I doubt it Sean, After all the engines range from 250cc singles up to 600cc fours, some turbocharged or supercharged (after the restrictor), some not.

And the intent of the restrictor is not just to reduce performance. Remember, FSAE is an engineering design competition with a motorsport theme, so tuning the restricted engines is part of the challenge.

Pat

[Mbirt]

An exhaust restriction may not be without small engine engineering merit--check out the small pea-shooter tailpipe orifices used around the world to silence street-legal single-cylinder engines.

But I would not say that an exhaust restriction would make the engine design process less complex. It is far easier for teams to predict the effects of reduced intake manifold pressure and design accordingly than to find in-cylinder exhaust residual content and prototype large exhaust plenums that are prone to failure and present safety issues due to high temperatures.

[Charles Kaneb]

If anything, an exhaust throttle would make these things harder to tune. A tiny little pipe would trap hot gas near the valves, so you'd have worse and worse combustion as you went down the straight - as seen on an indoor kart on a hot day. You'd also end up building an exhaust that looked like someone had misread the drawing for a two-stroke pipe.

Next time I get my hands on a dyno, I'm putting an exhaust throttle on a tuned two-stroke engine. It'd make the carb work better at least.