RML:
A minor detail; I noticed that the stock
dual exhaust manifold has a hole in it between
the two exit ports, presumably to provide the
function of a cross over pipe. That is an old
trick to share the pressure pulses between
the two pipes, permitting higher flow since
the peak pressures are reduced in each pipe.
I thought this was rather clever, although
I don't know how effective it is compared to a
more conventional solution. I am used to the
hot rodders method of installing a true dual
exhaust, but then adding a crossover underneath
the car. For a V8, putting a crossover in the
manifold itself is not an option, but for a
straight 6 motor, it is.
Gotta admire those Brits. They are a clever
lot.
Vance
-----Original Message-----
From: Robert M. Lang [mailto:lang@isis.mit.edu]
Sent: Thursday, April 22, 2004 7:31 AM
To: Navarrette, Vance
Cc: 6pack@autox.team.net
Subject: Re: Single vs dual exhaust
Hi,
One aspect of the single pipe setup that has not been discussed is the
pulse phasing and how this helps scavaging. All the high HP TR6's that
I've seen have "tricks" in this regard. For example, the Gp 44 TR6 as it
currently exists has a box located about 30 inches down the tubes. The
header enters as two seperate pipes and exits as two seperate pipes. But
the key is where the box is and (clearly) the volume of the box.
This box would work very much like an H-pipe on a V8 or perhaps like the
now popular "x-pipes" on same.
But the key for this type of system is that you need to tune it on a
dyno
to get it right in the RPM range you want.
For "regular guys" and street cars, you want the least restriction you
can
get with the least amount of noise. This is a delicate balance. Note
that
the wrong size pipe (either way, too small or too large) will rob power.
Regards,
rml
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