Re: Mufflers-another scam item

[Tom Jennings <tomj@xxxxxxx>]

On Tue, 17 May 2005 ameskg@xxxxxxxxx wrote:

> When one tests mufflers, can you be sure that the flow with hot, pulsing exhaust
> gas will be the same as a cool, steady flow of air? Or at least comparable from
> one muffler to another?

While I don't know squat about hydrodynamics, my sense is that
you're right, the dynamic stuff matters a lot. But a static test
might give at least SOME relative data. That's all I was thinking.

It could be misleading though; a muffler that looks bad (lots of
restriction) with a steady stream of 400CFM air might be well
designed for a series of pulses.

But at least, bad data would be refuted by the manufacturer :-)



> ;)
>
> Ken
>
> Quoting Tom Jennings <tomj@xxxxxxx>:
>
> > On Tue, 17 May 2005, Bruce Hevner wrote:
> >
> > > Ahhh, mufflers.
> > > Ever wonder which "flows" best?? Which "is louder/quieter than the others?
> > > So have I!!
> >
> > NO SH*T!!! I didn't even bother to ask casually on the list about
> > that stuff I guess because mufflers (and street-type exhausts in
> > general) are one of those areas with a knowledge and info vacuum.
> > It's been like that for so long I gave up trying. I suppose if I
> > was in your shoes I'd be more upset by it like you are :-)
> >
> > Summit lists CFM for a few higher-end racing mufflers, but that's
> > it. The $29 muffler looks no different in the catalog than the $200
> > job. Besides hype, there's got to be some difference, but what that is
> > is a mystery.
> >
> > Using hocus-pocus and the brains in my ass I decided (not
> > determined) that the better brands around $50 in Summit are
> > probably the best choice for me. That's the basis for me asking.
> >
> > What a way to choose.
> >
> > I'll go with dynomax (or closest spelling thereof :-)
> >
> >
> > I know that the physics of flow in pipe is well known, and there's
> > good rules of thumb for determining losses (diameter, bends,
> > length, etc) and a lot of it is obvious, but mufflers need to be
> > tested.
> >
> > It would make a good article for one of the 'rod mags. Just bench
> > flow 'em cold, at least hit the barn door with data.
> >
> > And noise, that can't be that hard to test either. Standard pipe
> > setup on probably a chevy 350 at two, three RPMs would also hit
> > the barn door.
> >
> > Bandsaw 'em open, hit the parts with a rubber mallet, guess whose
> > will fall apart first.
> >
> >
> >
> >
> > > Read an article in one of the car rags a while back comparing a few of the
> > > leading brands. They made an interesting statement. Their comparison
> > showed
> > > that matching a mufflers "flow" to your engines size and HP output is
> > > important. And that although a mufflers internal design affects sound,
> > > matching a mufflers "FLOW" is the important part. So WHY aren't mufflers
> > > rated in FLOW so we know which one to choose?? Turns out the exhaust
> > system
> > > industry as a whole IS fighting publishing flow ratings for mufflers.
> > There
> > > IS a formula for choosing the approximate flow rating for your muffler. If
> > I
> > > can find out what I did with it I'll post it.
> > > And WHY isn't there some kind of standard "Noise" rating for mufflers? As
> > > it is now unless you have actual experience with a muffler you have NO
> > idea
> > > how quiet they will be. I DO realize that the installation affects the way
> > > they sound.
> > > I have tried finding a source that has compared mufflers that does not
> > > actually SELL them. The only place I've found so far wants $65 for their
> > > book.
> > >
> > > In my opinion mufflers should AT LEAST be rated in FLOW! That way we could
> > > at least get some kind of idea of which one to use for the performance we
> > > are looking for.
> > >
> > > But HEY,,, that's just me.
> > > Bruce Hevner
> >
> > >

>