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Old 07-03-2010, 01:19 PM   #77 (permalink)
jdgFirefly
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Join Date: Jun 2010
Location: canada
Posts: 48

the dented fly - '96 pontiac firefly
90 day: 52.21 mpg (US)
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Quote:
Originally Posted by ShadeTreeMech View Post
a thought just occured to me concerning removing heat from the exhaust.

I don't claim to understand all of it, but while reading up on backpressure in exhaust systems, I read a somewhat technical article concerning the need to keep the exhaust as hot as possible to facilitate it moving down the pipe as efficiently as possible. To that end, some car makers will insulate the exhaust piping to keep it warm. I'm all for getting "free energy", but I am concerned about the cost of cooling the exhaust.
You are right about that. However about a third of the heat produced in your engine goes out the exhaust so the potential for gaining back that preformance loss is huge. Plus the preformance loss of cool exhaust vs hot exhaust is marginal in my opinion, I don't have anything to back that clam though. Also how much the exhaust is cooled will depend on how much we take for power and how eff the system is, So its not like the exhaust will be ambient temperature. The exhaust temp can be no less than the temp of the boiler otherwise there will be no heat transfer.

I suppose if it becomes a problem you could put the boiler at the end of the exhaust pipe to mitigated the losses due to cooler exhaust.
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