Joe,
I don't know where your getting your information but it is contrary to my
experiences with Otto cycle engines. Generally an engine which performs better with
back pressure has an underlying problem causing this condition.
KW
Joe Borg wrote:
> Yes, the 2.5 offers more resistance than a cat back 3". Engines NEED a
> certain amount of backpressure to operate efficiently.
> My point: if you are NOT installing headers, new y pipe AND hi flow
> cat in a TRUE dual exhaust setup you dont gain much and may even lose
> due to turbulance and resonance.
> You are absolutely correct in stating that aftermarket or custom
> mandrel bent pipes are better than stock. Joe
> An indication of "over exhaust conditions" is a very noticable "bap,
> bap bap bap" sound during decelleration. Ever have a muffler fall off
> a Vega??
>
> ______________________________ Reply Separator _________________________________
> Subject: Re: DML: Gibson exhaust installation
> Author: <dakota-truck@buffnet.net> at internet
> Date: 2/20/98 9:16 AM
>
> 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
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:08:14 EDT