PT: Exhaust Egli Headers/down pipes

[tom wilson]

Why are the Vincent Egli Headers/down pipes swaged out to a larger diameter? Just asking as to what is wrong with the standard pipe sizes? The exhaust hole size in the head is still standard Vincent size, this is then adapted to a larger 2"? pipe, as the gas leaving the cylinder head is still restricted at source it hardly seems worth the bother ...... or am I wrong?

 

[davidd]

The cones still do not present a theory that sounds correct to me. I do not see any data supporting the use.

Back pressure always presents a problem with overheating the head and raising intake manifold pressure.

At Bonneville, a stock Vincent will burn a hole through the piston as you are crossing the timing mark. Racers like Alp are running a large amount of unburned fuel through the engines to keep them cool for three or four miles. Running rich with nitromethane is important.

I don't think there is too much danger in running cones, even without any data. I think there is much more data on step headers being beneficial, mostly from McIntosh, who has tested step headers on Vincents. I don't see Horners or Godet doing either of these mods.

David

 

[tom wilson]

our pipes on the Goodwood racer are bigger but for a very good reason, who wants too fiddle with that fine thread exhaust nut with the tannoy announcing the next race? fitting those stubs was a great idea
The next road Comet I do will have a copy system
Incidentally a bigger pipe will alter where your power curve will go the Vincent is best against opposition in the mid range
View attachment 59705

our pipes on the Goodwood racer are bigger but for a very good reason, who wants too fiddle with that fine thread exhaust nut with the tannoy announcing the next race? fitting those stubs was a great idea
The next road Comet I do will have a copy system
Incidentally a bigger pipe will alter where your power curve will go the Vincent is best against opposition in the mid range
View attachment 59705

Hi Vib I have to agree those fine threads are a nightmare so I have stubs fitted on my Rapide which ave been on there since the late 80s. As you say to start them threads in a pressured race environment would only lead to trouble. May be for racing fatter pipes are worth while but cannot see much benefit on road going bikes.