On 25 Nov 1998, Mike Thompson wrote:
> 2. how they work - They make a smooth transition between the air and carb.
Ooops, I think we need to supplement that: The thing with proper ram pipes
is that they, in a somewhat analogous manner to a flute or trumpet,
should be tuned to the frequency of the air pulsating through them. To work
at their best, they need:
- One distinct pipe for each cylinder, right down to the intake
valve. You can some effect with manifolds, but not very much.
- A tube that is as "clean" as possible. Injection is much better
than carbs, whose venturis disturb the flow. A sliding throttle is
better then butterflies.
- To be matched to the RPM range of interest. They really only work
over a narrow RPM band.
The only Triumph that has ram pipes is the 2.5 PI. They are not ideal,
though, because they contain a butterfly each (instead of having a common
butterfly before the plenum chamber, as is common nowadays), but mostly
because they far too short for a long stroke engine like the 2.5 that
gets the shivers at anything above 6000.
(The next time you see a 50s gull-wing SL, take a look under the bonnet.
Those ram-pipes would probably be much more appropriate for the 2.5)
Egil
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