On Wed, 23 Jul 1997, David M Brock wrote:
> Congratulations on getting her going. What a feeling, eh? (CDN licence)
It's a rush. :)
> I have a similar problem with non-stock (cheapie flow-thru) exhaust,
> backfiring on decelleration and engine braking (downhills, etc) and would
> appreciate anything you learn about how to prevent it.
My 'Vette does this as it sits right now, but there's NO muffler (kinda
fun but people keep mistaking me for an airplane). The stock Chevette
muffler is something like $90 plus tax. Hence, the cheap muffler.
There's two kinds, however: the "cigar" (or Thrush) design, and the
"turbo" design. Turbo design is shaped like a conventional muffler, but
I think the holes that connect the chambers are larger, and they're
probably not packed with any absorption stuff.
The 'cigar' kind doesn't have any chambers, it's just a pipe with louvres
in it, with fiberglass wrapped around the louvres(sp?). My choice for
the Chevette of Doom will probably be a turbo-style, small-port muffler.
For the TR4 I have a lead on a muffler from a Ford Courier (2.0L engine)
for $15. Good enough for now :)
I figure that the cigar kind will promote backfiring more than the turbo
kind, but if I'm wrong I shan't be surprised (no testing done, just
speculation)
> I posted a similar message many months ago that used the phrase
> "too-little-backpressure" and was accused of listening too closely to my
> dear-departed grandmother's engine tuning opinions, thought! ;-)
For a true rumble, little backpressure is fine. For good, clean, sound
(and flash suppression), you need something there. The 'Vette tended to
rumble quite a bit when the tailpipe was broken (and the muffler wasn't...)
It has about 3-4 feet of tailpipe. Perhaps sticking more pipe on will
stop your banging, or putting in a reduction fitting/smaller pipe?
Again, I'm not too sure on this.
-Malcolm
Too many rocks and not enough sand.
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