View Single Post
Bill Verburg Bill Verburg is offline
Moderator
 
Bill Verburg's Avatar
 
Join Date: Dec 2000
Posts: 22,307
Garage
On an even fire engine a cross over gains nothing on a properly designed header collector muffler setup


B boom
S silent

911 6 is even fire
L- B S B S B
R- S B S B S

generic V8 w/ 90deg crank is odd fire
L- B B S S B B S S
R- S S B B S S B B

generic V8 w/ 180deg crank(Ferrari) is even fire
L-B S B S B S B
R-S B S B S B S

Chevrolet sb V8 is odd fire
L-B S S B S B B S
R-A B B S B SS B

the odd fires benefit from the cross over because they have 2 consecutive cylinders firing on the same bank, so the collecter either needs to be too big most of the time or to use the cross over to take up some of the excess load.

the other option is a 180 deg exhaust where 1 left cylinder is piped to the right collector and 1 right cylinder is piped to the left collector.

the 180 deg exhaust effectively makes a 90 deg V8 into a 180 deg v8

Champ cars and Ferrari use the 180 deg flat cranks, that's why the sound so different, a Chevy or Ford v8 will sound the same w/ the 180 header setup.

180 deg headers aren't common because of cost and packaging constraints. Early Ford GT 40 w/ the bundle if snakes exhaust was the last one I ever saw. Cross over is a fair substitute that uses much less space and is much easier to implement



The Flowmaster is a particularly good design becuse if the inlets are properly done the collector sees it as atmosphere, all the glass pack designs are seen as extensions of the collector and will therefore affect the acoustic tuning of the pipes sometimes for the better sometimes for the worse.

For the Flowmaster to be seen as atmosphere the pipe needs to penetrate the inlet stub

__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
| Pelican Home |Rennlist Wheels |Rennlist Brakes |

Last edited by Bill Verburg; 12-16-2005 at 12:44 PM..
Old 12-15-2005, 07:54 PM
  Pelican Parts Technical Article Directory    Reply With Quote #7 (permalink)