Randall Young wrote:
>
> I believe Helmholtz's ideas have been extended to create a resonator
> that has a fairly wide peak, giving at least some improvement over about
> a 3:2 range (like 4000 rpm to 6000 rpm). (At least one design has two
> peaks offset from each other, giving a response curve with a dip in the
> middle, like a bass reflex speaker.)
I would say, yes, entirely possible, but I just went to the Flowmaster
site (something I should have done in the first place) and had a look at
the construction of each series, and with the exception of only one, the
rest do not use a free-standing tuned chamber, strictly speaking.
What is interesting, however, is that, for the most part, only one
feature of the the original Helmholtz resonator seems to be retained.
The resonators created by Helmholtz are distinctively shaped--they
resemble a short cylinder with a cone on top, and soundhole in the side.
In cross-section, the top is v-shaped. And this is a prominent feature
of the baffles in the Flowmasters--v-shaped free-standing baffles, of
differing numbers and sizes, depending upon the sound quality desired.
> In any case, I've seen the Helmholtz name used elsewhere in reference to
> motorcycle exhaust systems that apparently really do produce more
> power. That doesn't mean Flowmaster is on the level, but they might be
> <g>
Their site seems to very big on testimonials, which are very often
subjective. But, I will give them this--the internal construction is
quite free-flowing, from appearances. That gives them a plus over other
designs which depend upon pierced baffles feeding dead chambers, or
glass packing, to cut down on noise. So, the baffles used have to be
free resonators to do the noise cancelling. Otherwise, they would all be
quite loud.
As for using pressure waves to improve exhaust performance through the
entire pipe, I have no way of determining that such is the case from the
general construction. They may be onto something, or not. At any rate,
I'll eat a little crow and not try to dissuade anyone from trying them.
And, looking at the means of construction, I can see why they would want
to use mild steel--with a free-standing resonator (attached on one side,
rather than rigidly attached to upper and lower walls like a fixed
baffle) the vibration would work very hard on the welded connection.
They would have to use slower and more expensive welding techniques like
TIG to insure that stainless parts would stay together.
However, I would recommend that anyone considering them go to their site
and look at the descriptions for each series (there are seven, I think)
because each series has different sound characteristics, and some create
quite a bit of interior resonance. If one wants to be able to hear the
stereo, some series might not be recommended.
Cheers.
--
Michael D. Porter
Roswell, NM
[mailto: mporter@zianet.com]
`70 GT6+ (being refurbished, slowly)
`71 GT6 Mk. III (organ donor)
`72 GT6 Mk. III (daily driver)
`64 TR4 (awaiting intensive care)
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