RE: Back pressure

["Dr. Bob" <rmalinka@spec.net>]

At 03:53 PM 1/3/00 -0600, you wrote:
>REMOVE MY NAME


LORI

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>-----Original Message-----
>From: Matt Zajac [mailto:MTZajac@beloit.com]
>Sent: Monday, January 03, 2000 3:25 PM
>To: jettaglx@igtc.com
>Subject: Re: Back pressure
>
>
>Hi Bill
>Thank you for explanation. The only thing that I don't really understand is
>why backpressure is impoortant for low end torque. From what I've heard so
>far is that too low backpressure will hurt low end torque. Perhaps you can
>help me with this.
>Thank you very much.
>
>Sincerely 
>Matt Z.
>
>>>> Bill Hussey <vfrboy@home.net> 12/28 4:38 PM >>>
>    Backpressure is when your exhaust system doesn't release as much air
>as the engine is putting out.  Like dripping oil into a funnel ... the
>funnel doesn't flow as much as the larger-necked quart of oil bottle so
>the oil builds up in the reservoir.  Same thing as air .. if the exhuast
>can can't release enough, the gases build up and cause a pressure.  As
>pressure builds, it pushes back up the exhaust system ... thus the term
>"back pressure".
>
>    As pressure increases inside the exhuast system, it moves up towards
>the engine and stops air from coming in (not all of it of course, but
>some) ... this is why a restrictive exhaust system cuts power, because
>air flow, and thusly fuel flow once the EFI compensates, is cut.  Most
>engines only push enough air to cause back-pressure at higher RPM
>ranges, which is why you only get an upper-rpm power increase when
>throwing in a new exhaust system.
>
>    Diameter of the exhuast and header tubes is not the only factor
>either .. bend quality and smoothness is very very key.  If the inside
>surface of the pipes are rough or the bends are angled sharply, the air
>flow is distrupted and will slow down which will cause a "traffic jam of
>air" if you will, and again build up pressure.  Straight pipes with
>gentle bends and polished insides produce the best power, but sound
>louder than hell.  I'm going into a huge tangent now .. so I'll stop.
>Hope this helped.
>
>Bill
>'98 GLX
>
>Matt Zajac wrote:
>
>> Hi
>> Can someone please tell me what backpressure is?
>> All I know it refers to exhoust.
>> Thanks in advance
>>
>> Matt Z.
>>
>
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