I don't actually read the list, but saw this note while cleaning up some
stuff. Sort of neat how the various Triumph related lists worked just fine
while I was cavorting about in Maine, but the MG, Healey and Mini lists all
had troubles with their respective digests. Well, there may be more troubles
that I have yet to discover hidden in the over four thousand error messages
awaiting my attention.
Anyway, I have a Supertrapp on the Killer Spit. It is an autocross car
built to meet the SCCA DSP rules, which means stock compression ratio,
stock cam, basically no internal engine mods other than balancing. And quite
a few hours put into assembly, I might add. You know, for Portland next year
I really am thinking about building a VTR legal motor for that car. Some day
maybe Killer with a limit of the rules VTR motor will go against John Lye's
TR4 with all that SCCA mandated ballast thrown out....
Anyway, for the exhaust I have a 4 to 1 header, and run a 2" pipe from there
to the first muffler. This is a Walker Turbo-Tube, I think it is called, which
is your basic straight through glass pack unit. By itself, way too loud, even
with the fairly mild engine I run. And I have an 18" Supertrapp, which also
was too loud by itself. The combination of the two, though, works just fine,
reading about 82-86 dB at our local autocross events, well under the 92 dB
limit. Well, there was that one time the folks on the meter had it set wrong.
When running this combo on Junior, the predecessor to Killer, I used 4 disks
on the Supertrapp for street driving. The claim is that the disks make the
Supertrapp quite adjustable in terms of noise and backpressure. I found that
with 3 disks, the car ran like, uh, crap. Four disks was passable. Five or
more gave no more power, just more noise. Basically there is about a three
disk window where one sees a difference. For the last few years with this
motor and exhaust system in Killer, I've been running the Supertrapp with no
disks, which yields the dB figures noted above. What I really ought to do is
come up with a business plan to arrange sufficient financing so the Fat Chance
Garage can move into a nice new home, complete with dyno facilities to put some
real numbers on all this handwaving and hearsay.
In truth, my future plans call for installing a 4-2-1 header and a single
muffler, some sort of basic rectangular unit under the trunk floor. The way
I have it now, the Walker Turbo-Tube runs right under the rear frame cross
piece, which gives Killer much too little ground clearence. Fine for racing,
but I have plans for making it street legal. With the limited mods to the
1500 motor, there should be several off the shelf mufflers that can be pressed
into service, offering the needed flow and noise reduction. But to tell the
truth, the way Killer is set up now sounds pretty sweet!
mjb.
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