Exhaust question

[bales]

Just a quick question I have been thinking about recently, what is the theory on V-configuration engines with linking the two seperate banks together.

I am thinking more about performance engines here so assume every aspect is designed with this in mind.

Some cars have the exhaust systems completely seperate and both pipes would exit seperately. Some have link pipes between the two banks but still run seperatley, and some run seperately and then merge together into one pipe later on in the system.

I am pretty well up on exhaust theory etc...and like to think I have a decent general understanding of engines but it has always interested me what the are the different pro's and con's of linking or not linking the pipes as I cant see what the advantages are in theory to be honest.

What really got me thinking as I am thinking as a next project of turboing an E30 325 BMW probably with two smallish T25's but was thinking about the exhaust system, would you just run the two pipes seperately or would you merge them? I guess with it being turbo'd you've used most of the exhaust energy anyway so it probably doesn't matter a huge amount compared to a n/a engine.

Also with two exhausts do you just divide the BHP by two and size each bore in relation to that, say for example you had 400bhp, then a suitable bore for FI making 200bhp, so say around the 2.5" area?

Thanks

Alex

(Oh and without wanting to sound geeky I would prefer some in depth theory rather than just 'it balances the flow' or something, so stuff from Marquis Rex or Puma racing would be good.)

Cheers

Alex

[lenientism]

bales said:

Just a quick question I have been thinking about recently, what is the theory on V-configuration engines with linking the two seperate banks together.

I am thinking more about performance engines here so assume every aspect is designed with this in mind.

Some cars have the exhaust systems completely seperate and both pipes would exit seperately. Some have link pipes between the two banks but still run seperatley, and some run seperately and then merge together into one pipe later on in the system.

I am pretty well up on exhaust theory etc...and like to think I have a decent general understanding of engines but it has always interested me what the are the different pro's and con's of linking or not linking the pipes as I cant see what the advantages are in theory to be honest.

What really got me thinking as I am thinking as a next project of turboing an E30 325 BMW probably with two smallish T25's but was thinking about the exhaust system, would you just run the two pipes seperately or would you merge them? I guess with it being turbo'd you've used most of the exhaust energy anyway so it probably doesn't matter a huge amount compared to a n/a engine.

Also with two exhausts do you just divide the BHP by two and size each bore in relation to that, say for example you had 400bhp, then a suitable bore for FI making 200bhp, so say around the 2.5" area?

Thanks

Alex

(Oh and without wanting to sound geeky I would prefer some in depth theory rather than just 'it balances the flow' or something, so stuff from Marquis Rex or Puma racing would be good.)

Cheers

Alex

Perhaps they can have the system completely separated, but it wouldn't be practicable and spend to much spaces. Exhaust system from each manifold would normally merge into one bigger pipe. This main pipe may be heading for single exhaust end or breaching out to two ends, depends on engine size and diameter of the pipe. The bigger engine would normally use standard two exhausts, or one bigger exhaust.

The rough concept is to make less barrier in the exhaust system.
Just IMO, I want to do examination and clean up the beneath of car, but my garage wasn't designed to do so...