bit of confusion on exhausts

[ralexander03@snet.net (Rick Alexander)]

I missed the start of this thread due to being bumped so often already th=
is
week. Here is my understanding of backpressure. It's only an opinion base=
d
upon 25-30 years of reading and my recall isn't perfect.

Back pressure is no myth. Backpressure is required and even calculated by
the engine designers to prevent the raw fuel charge from flowing right
through the engine without going through the compression cycle. What can
happen is that during valve overlap (more important with a hi output cams=
)
the fuel charge enters the intake valve and flows directly out the exhaus=
t
valve that happens to be open at the same time. Not only will you not bur=
n
that fuel for go but your fuel economy will turn to crap and you will fai=
l
emissions.

Keep close to the backpressure that the engine was designed for.

Rick Alexander
'87 MKII Rolling Roc
'86 Cabbie
'81 "S" MKI G60 in progress
'80 MKI (Parts)
'73 Baja Challenge car
'65 Brubaker Box
'62 Tuff Tubb dune buggy

----- Original Message -----
From: "Shawn c Meze" <skerocdriver@juno.com>
To: <sad_rocc@veedub.com>
Cc: <scirocco-l@scirocco.org>
Sent: Wednesday, November 27, 2002 12:35 AM
Subject: Re: bit of confusion on exhausts


>
>
> On Tue, 26 Nov 2002 11:40:22 -0800 (PST) Dan Smith <sad_rocc@veedub.com=
>
> writes:
> >
> > And do others agree that backpressure is a myth?
>
>
> I do not subscribe to this therory. if you need no backpressure then wh=
y
> doesnt everyone run a 5" systems on their cars?
>
> Why do 2" systems work best on mild 1.8L 8v motors?
> Why do 2.125" work best on 2.0L 8v motors?
>
> Gee, must be the scavenging effect of the back pressure. Hmm?
>
> Well, to each his own, think what you think its all really ok to me. Ba=
ck
> pressure scavenges ports, simple as that. Im not daying you need ALOT i=
f
> backpressure, just enough to help do its best is all.
>
> I also like the Dynomax mufflers as well as the Ultra flow mufflers.
> Thats me tho. I dont like the center resonator either.
>
> go fourth...
>
>
> Shawn M=E9ze
> 86' Jetta GLi 8V   88' Corvette -SS- #30  2001 SDR Solo2 Champion
> Scirocco" 84' Scirocco 8V 82' Scirocco RIP 80' Scirocco S 79' "Project
> FSP
> The Fastest, Quickest, Cleanest and best looking Scirocco(s) in all of
> San Diego!
> http://www.Geocities.com/MotorCity/Speedway/1308/index.htm
>
>
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