Re: Back pressure

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

gREAT bILLY I THINK WE just continue the torture!!!!



At 04:07 PM 1/3/00 -0600, you wrote:
>no!  ha ha!
>
>LORI ROSE wrote:
>
>> REMOVE MY NAME
>>
>> -----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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