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Location:
Adelaide
Registered:
May 2002
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Another Idea (exhaust pump)
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Sun, 23 June 2002 12:19
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Alright,
You've probably all heard or seen of that little 'TurboZet' doohickey which has been around for some time. What if one was to place a similar device within the exhaust line (able to withstand the heat of course). The purpose being to suck the gasses from the pipe and create a permanent vacuum within the system. Maybe cam ovetlap may need altering or fuel delivery retarding slightly so as not to pull any fuel through during valve overlap.
Bye, Bye back pressure. Hello possible smaller exhaust.
Of course as with most hair-brain schemes maybe it needs a tad more thought.
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Location:
Brisbane, QLD, Australia
Registered:
May 2002
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Re: Another Idea (exhaust pump)
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Sun, 23 June 2002 12:22
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I was thinking of something like a reverse turbo before. But I never put any serious thought into it.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Another Idea (exhaust pump)
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Sun, 23 June 2002 12:39
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I'd wondered about such an idea before too. Although, when thinking about it, it's got a number of problems:
1. A well designed exhaust/intake can already achieve greater than 100% volumetric efficiency, so you wouldn't gain a whole lot there...
2. Sucking intake air through the exhaust is a good idea to a certain extent, but the injection would have to be carefully timed sequential/direct injection to avoid fuel being sucked out as well
3. I'd imagine it'd be a lot more beneficial to pressurise the intake side of the engine and make use of the cam overlap to the clear the exhaust (once again, requiring direct or carefully timed sequential injection to avoid fuel loss)
No harm giving it a try, but I'd imagine that you wouldn't gain anything over a carefully designed exhaust anyway. Once the cylinder is empty, its empty...
Don't let that stop you though - After all they said the world was flat till it was proved otherwise.
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Location:
Brisbane
Registered:
May 2002
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Re: Another Idea (exhaust pump)
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Sun, 23 June 2002 12:50
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I think you'd reach a certain point where a vacuum in the exhaust would do more harm than good, ie suck unburnt fuel/air out of the combustion chamber if your cams have a bit of overlap.
As has been mentioned, a well designed exhaust system can use pressure waves to create a vacuum in the exhaust ports (this is the idea behind "extractors"), so there isn't much more to be gained by pulling the exhaust out of the engine.
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Location:
Canberra
Registered:
May 2002
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Re: Another Idea (exhaust pump)
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Tue, 25 June 2002 07:50
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If you have a look at some racing sedans (old DTM cars in particular), you'll notice that they all have the exhaust swept up into the low pressure area behind the car.
I'm not sure if that was in an attempt to either:
- reduce exhuast backpressure,
- get the exhuaust gas out of the underbosy airstream or
- reduce drag by letting the exhuast gas fill the void behind the car
Either way, there would be some suction on the end, and it mustn't have hurt anything, or they wouldn't have done it..
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