6.9 exhaust

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This was based on a minimum ID of 40.5mm (1.59”) for the 560. Minimum ID of 41.5mm (1.63”) for the 6.9.
 

Oversize

Master
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I was speaking to a mate who races a 450SE & his mods have been recommended by a well known racing team in V8SC. They specified an OD of 1 7/8” (47.63mm) and a minimum primary length of no less than 28” (711.2mm)!! Of course that’s in an ideal world with no space limitations.... So based on a wall thickness of 2mm that leaves an ID of 43.63mm. Not far off my calculations which were minimum sizes not taking into consideration size availability....
 

Oversize

Master
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I just measured the collectors of a Euro 6.9 , Aussie 560, 450 & 420. I can confirm they are all around 43mm!!

So basically the 420 has the same size outlets as the worlds fastest sedan (in 1975)!! And the 420 inlet (throttle plate) is actually BIGGER than the 6.9! The fact the 6.9 performed as well as it did seem to be purely down to CCs!
 

Oversize

Master
Messages
5,244
Points
191
Location
Melbourne
I just measured the collectors of a Euro 6.9 , Aussie 560, 450 & 420. I can confirm they are all around 43mm!!

So basically the 420 has the same size outlets as the worlds fastest sedan (in 1975)!! And the 420 inlet (throttle plate) is actually BIGGER than the 6.9! The fact the 6.9 performed as well as it did seem to be purely down to CCs!
Note that figure is four into one (the collector) on each bank/side. Not to be confused with individual exhaust ports.... At not even 2” per side it can be seen that even changing an exhaust system from the manifolds back will not increase power or torque significantly unless the existing system is faulty or very poorly designed. The main result will be a change in note/tone/noise levels.
 

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