Jamie:
Conceivably, quite a lot. In actuality, who knows?
The issue is that you need to know what kind of back pressure
the stock muffler creates. I don't know of anyone who has any numbers on
what it flows.
I believe (not sure on this point) that '72 is when Triumph
switched to the dual pipe exhaust system. You can take some comfort
knowing that this was the exhaust system that was used for the 150HP PI
model in the UK, and therefore it offers at least some performance
potential. This doesn't mean that is optimum, only that it is better
than the single pipe system. The system was installed in the US cars to
restore some of the power that was being choked out of the engine by
lowering the compression ratio to meet US NOx requirements. The factory
also switched to the UK style of cylinder head, altered the intake
manifold and increased the cam timing for the same reason; from 240
degrees to 256 degrees (which is the GT6/125 HP PI cam). The 150HP PI
engine ran 280 degrees of cam timing, and so was on the beastly side.
FYI, the major restriction in any system is the muffler, not the
pipes. The factory dual system offers no more cross sectional area than
the single pipe system; but presumably it offers almost twice as much
flow cross section once it enters the muffler by virtue of it's dual
pipes.
If you are installing a header, you are serious about extracting
power from your exhaust system and it is almost certain that there will
be some power locked up in the muffler. But without flow numbers, there
is really no way to know how much. As I mentioned earlier, a Cyclone or
Dyno-max muffler would almost certainly free up a few ponies, perhaps
many ponies. But any gains would be in the upper RPMs, as this is when
the exhaust pressure really builds. If you never drive up past
3,500-4,000 RPM, it may well be a waste of time. It just depends on your
engine combo and driving style.
Cheers,
Vance
------------------------------
Cogito Ergo Zoom
(I think, therefore I go fast)
TR6 Web page: http://home.comcast.net/~v.navarrette/
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Jamie Palmer
Sent: Tuesday, October 26, 2004 10:05 AM
To: 6pack@autox.team.net
Subject: Another Exhaust (ing) Question for you folks
I know the merits of the various exhaust systems have been discussed
multiple times here...but I haven't seen an answer to this question:
I plan to modify my car somewhat for higher performance (cam, induction,
slightly shaved head, etc) but plan on driving it daily. I've had a TR6
with the Monza system before, and I'm not willing to put up with that
much noise. The "sport" SS systems are a little noisy for me, too (lots
of long-distance driving). Consequently, I'd like to go with the "group
44" header in SS BUT a "stock" SS system from there on back...how much
performance will I really be losing??
Thanks in advance,
Jamie Palmer
72 TR6 CC84513U
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