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Re: SVO: Re: Some Ideas on Preformance Exhaust For The Turbo Coupe



Continued thread...
Scott said

> they do??  not saying that none do, but I have never seen one. Only times
> I see it go down is in a y pipe on a V engine...

They do.  Look at mom and pop type cars, and read.  I'm not making this up.

> And I hav enever seen a pipe size change as drastic as 3" to 2.25". Thats
> rejected.  how coem the outlet piping is not smaller on intercoolers? the
> change in temp is high there too.

When AIR cools is becomes more dense, you don't want to waste that by
making the piping on anintercooler smaller.  And exhaust gas is not air.

>  Ergo,
> 
> what does ergo mean?

Look it up, I don't think I can explain it properly.  Sorta, if this is
true, and that is true, then this other thing must be true.

>  make big tubing
> > (downpipe) at front.  Yes, the rear will help too, but I believe that
the
> > improved compopnets contribution to poewr is almost equal.
> > 
> 
> your saying that just having a bigger downpipe for about 40" of the
system
> is equal to having a bigger cat back, AND bigger mufflers? I would be
> willing to bet that if you put a 3" downpipe(especially a crushbent one),
> on a stock exhaust, you would be hardpressed to gain much of anything.

Maybe, maybe not.  But I ante'd up the money and bought one, and I'm glad I
did.  I think it works.

> But lets talk disturbances of flow.....
> lets say you put on a 3" downpipe.  Right at the joint where the pipe
goes
> from the outlet of the turbos 2.25 inch to 3", there is a resistance to
> airflow, that is not there with a stock pipe.  

A step up in size does not create a disturbance, quite the opposite in
terms of impeding flow.

>then the exhaust happily
> flows thru the larger pipe, until we get to the point where it meets up
> with your stock cat, or stock cat back.  thre is another decrease in flow
> there, where the pipe has to drop down to 2.25" again.....

And the exhaust gas has now cooled, and needs less space, or volume.

> And your running
> the beutiful stock duals rite? well, that y connection there adds more of
> a restriction. 
No, I'm not, and you're right.  The stock Y pipe sucks.  KENNY, get a
custom one made. It's worth the bucks.

> its a whole lotta reduction on flow.  made up for by the cooling of the
> pipe? I doubt it.  

Maybe not completely compensated for by the cooling exhasut gas.


> if the cooling affect helps so much, why do the nascar guys step UP their
> header size as they go away from the head??  

Gee this works for them, but you just said that the step up in the headpipe
causes a "resistance to
airflow, that is not there with a stock pipe".

It works the same way.


> Like i said, I dont know the quantification of the cooling of the exhaust
> and its affect on pipe size requirements, but it helps more than the
> addition of a higher flowing, bigger muffler, especially with all the
> resrtictions that system has...
> 

Huh? That sentence lost me..


I am not saying that this is an all out race system, but I think a lot of
guys don;t want to pony up big bucks for a complete system.  This *is* the
cheap way out, but it's a big improvement.

So, to sum up, $130 downpipe is a GOOD thing.  Big cat is a good thing, but
2.5" is ok too, but I would still do a 3".  Shop around.  Ditto for
mufflers.  Dynomax has a 3".  Neck it down into a SINGLE 2.5" tailpipe from
Dynomax or one of the other companies.  Result? a good exhaust, cheap.

J.C. Whitney had a sale this summer and 3" cats were $101 and 3" dynomax
mufflers were $39.  And the early SVO owners don;t have to do al the fuel
mods to fit a second muffler.

Dave
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