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RichA - 11 Jun 2005 01:42 GMT

If you introduced an induction device (a scoop, if you will)
on the exhaust system, say beyond the cats? It would draw in
air at high speed, creating a vacuum and would draw the exhaust
faster than the exhaust would normally exit. Of course, the exhaust
system would have to be larger at that point, with higher flow
mufflers, but I'm wondering if there would be any benefit to this?

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ygotit@yahoo.com - 11 Jun 2005 01:59 GMT

>If you introduced an induction device (a scoop, if you will)
>on the exhaust system, say beyond the cats? It would draw in
>air at high speed, creating a vacuum and would draw the exhaust
>faster than the exhaust would normally exit. Of course, the exhaust
>system would have to be larger at that point, with higher flow
>mufflers, but I'm wondering if there would be any benefit to this?

what for
think about it

hurc ast

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Michael Johnson, PE - 11 Jun 2005 02:08 GMT

>>If you introduced an induction device (a scoop, if you will)
>>on the exhaust system, say beyond the cats? It would draw in
[quoted text clipped - 5 lines]
> what for
> think about it

Actually there is an exhaust scavenging system that can be used for
evacuating the crankcase. The tubes are typically welded into the
exhaust pipe right after the manifolds or headers. It's not the best
solution but it does work to a certain degree. Here's an example:

http://tinyurl.com/xizq

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one80out@hotmail.com - 11 Jun 2005 02:30 GMT

The psi of the exhaust would exceed the psi in the scoop's intake, such
that air would be coming OUT of the intake, not IN. In other words,
you would only have created another outlet for the exhaust gasses.

If you're interested, here is a great technical article by Dave Vizard
from the May Popular Hot Rodding:
http://www.popularhotrodding.com/enginemasters/articles/hardcore/0505em_exh/inde
x.html.
Among other things, the article explains that in an optimized (i.e.,
race) engine, there are actually five cycles, not four. The "fifth"
cycle occurs during valve overlap, when negative pressure waves (i.e.,
vacuum) travels up from the header collector to the exhaust port and
helps draw the fuel/air mixture into the intake port.

180 Out

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66 6F HCS - 11 Jun 2005 03:55 GMT

> If you're interested, here is a great technical article by Dave Vizard
> from the May Popular Hot Rodding:
> http://www.popularhotrodding.com/enginemasters/articles/hardcore/0505em_exh/inde
x.html.

Great article. Gave me some ideas for when I redo my exhaust from the
headers back.

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Scott W.
'66 HCS Mustang 289
'68 Ranchero 500 302
'69 Mustang Sportsroof 351W
ThunderSnake #57
http://home.comcast.net/~vanguard92/

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