Big bore pipes do not produce a lot of power, but they produce some. It is an easy mod to simply increase the pipe bore and get some power down low. Vincent rarely did engine development due to the lack of money. Their only resort was to try and out-design competitors and even that is a option that it limited by money.
For road racing, the high pipe is the best way to go. Too many clearance issues with low pipes...both with the track and with oil catch pans, which have to live down low. Additionally, if you have to run a silencer, where are you going to put that? Tim's high pipe is a nice design.
The standard Vincent lore is that megaphones don't work on a Vincent (at least, the singles), but they work quite well and produce the same gains that benefit the Manx or Gold Star. If you look at pipe bore, the target is somewhere between 250 and 280 cubic feet per minute. Above that you get increased friction with the port walls, below that you don't get enough momentum to pull the intake charge into the combustion chamber efficiently. The big bore pipes run as low as 120 cu.ft./min at just below redline. The good news is that with low redlines the power isn't too bad. I think Phil Irving simply made a decision to keep low redlines and rely on the torque rather than do a lot of development. No sense making the Mk2 work over 6000 rpm because only the single could go there and Vincent was not sponsoring a road racing team, they were dabling and doing quite well just picking off a decent number of finishes with talented riders. As for the twins, they did spectacularly well with the straight pipes in record breaking.
The Vincent production 2" pipes were a good compromise and a nod to performance. The Ginger Wood style high pipe was probably a better race design. If you look at the single, the most advanced exhaust design is the McIntosh pipe used by Lindsay Kyle. This design has had thousands of hours of design on Manx engines. McIntosh and Lindsay applied that knowledge to the Comet. It starts as a 1-5/8" pipe, steps up to 1-3/4" and becomes a megaphone with a silencer. BHP is high 40's.
Now, if you are judging sound....
David
For road racing, the high pipe is the best way to go. Too many clearance issues with low pipes...both with the track and with oil catch pans, which have to live down low. Additionally, if you have to run a silencer, where are you going to put that? Tim's high pipe is a nice design.
The standard Vincent lore is that megaphones don't work on a Vincent (at least, the singles), but they work quite well and produce the same gains that benefit the Manx or Gold Star. If you look at pipe bore, the target is somewhere between 250 and 280 cubic feet per minute. Above that you get increased friction with the port walls, below that you don't get enough momentum to pull the intake charge into the combustion chamber efficiently. The big bore pipes run as low as 120 cu.ft./min at just below redline. The good news is that with low redlines the power isn't too bad. I think Phil Irving simply made a decision to keep low redlines and rely on the torque rather than do a lot of development. No sense making the Mk2 work over 6000 rpm because only the single could go there and Vincent was not sponsoring a road racing team, they were dabling and doing quite well just picking off a decent number of finishes with talented riders. As for the twins, they did spectacularly well with the straight pipes in record breaking.
The Vincent production 2" pipes were a good compromise and a nod to performance. The Ginger Wood style high pipe was probably a better race design. If you look at the single, the most advanced exhaust design is the McIntosh pipe used by Lindsay Kyle. This design has had thousands of hours of design on Manx engines. McIntosh and Lindsay applied that knowledge to the Comet. It starts as a 1-5/8" pipe, steps up to 1-3/4" and becomes a megaphone with a silencer. BHP is high 40's.
Now, if you are judging sound....
David