Joe,
I also have to disagree with the info you got from Flowmaster. The stock
2.5" exhaust may be "adequate", but it still presents more ristriction
on the exhaust than an aftermarket single 3" or dual 2.5". Exhaust
restriction is a cumulative effect due to the fluid resistance between
exhaust gases and the sides of the pipes and any obstructions. The
resistance values for all exhaust components are added together to
calculate a flow rate for the system. In other words, even with a 2.5"
openning through the cat, you will have a higher flow rate with a 3" cat
back than a 2.5" cat back.
There is a point of diminishing returns, however. I agree that the duals
don't do much for you from a performance increase standpoint vs. a 3"
single, unless you have other mods to take advantage of them.
My biggest objection to leaving the stock exit pipe (muffler back) is
2.5" with crimped bends. The crimped bends produce increased exhaust gas
turbulence and flow resistance. The aftermarket pipes (even custom bent
jobs from the local muffler shop) are mandrel bent, which provide a nice
smooth curve and less restriction.
jeff
98 RC 4x2 V8 5spd 3.55SG flares
Klaus Wilkens wrote:
>
> Joe,
>
> Flowmaster is trying to sell Flowmaster. What youwere told doesn't compute. If the Y
> pipe and Cat are the major restriction opening up the exhaust system after the cat
> would have negligible effect.
>
> I have a 94 Sport with the 5.2, 5spd, and 3.90 gears. I've had the truck since new
> and have had it to the track a few times. The most marked single improvement was the
> Gibson cat back exhaust with a set of JBA shorty headers which use the factory Y
> pipe. I picked up 2 mph at the strip and 2 mpg on the road with this modification.
>
> A few years ago CC did a 2.2 turbo package called the Super 60. The development was
> done on a dyno and with mufflers and the Dynomax Ultra made 20HP more than the
> Flowmaster.
>
> KW
>
> Joe Borg wrote:
>
> > Jeff, I recently called flowmaster. They stated with minor mods, the
> > stock exhaust system is more than adequate when a flowmaster 2 chamber
> > muffler is installed. They stated 3" pipe does not have enough
> > backpressure and although sounding "meaner" woulsd actually slow you
> > down. The concept of single in dual out mufflers is pure show and no
> > go. An exhaust system can only be as efficient as its weakest point -
> > the 2 into 1 y pipe and cat. Unless you install 2 cats with a true
> > dual setup you are gaining nothing but sound and appearance. Joe Borg
> >
jeff
98 RC 4x2 V8 5spd 3.55SG flares
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