what size exhaust bore???

[Jono FD3]

guys, my exhaust broke going to combe yesterday, so I am going to be making a full sustem from the down pipe back!
The spec of the engine at the moment is:

Apexi power FC
Custom stainless intake with K&N filter
Massive blitz V-mount
Stock twins on custom high flow pipework
greddy intake elbow
double throttle removed
HKS downpipe (80mm)
255 fuel pump

New engine is going to have street porting done once everything is sorted!

The common stainless pipe size is 75mm OD so we are probably looking 72-73 internal would this be OK or should I try to go slightly bigger than the down pipe?

Cheers
Jono

[vest_racing]

guys, my exhaust broke going to combe yesterday, so I am going to be making a full sustem from the down pipe back!
The spec of the engine at the moment is:

Apexi power FC
Custom stainless intake with K&N filter
Massive blitz V-mount
Stock twins on custom high flow pipework
greddy intake elbow
double throttle removed
HKS downpipe (80mm)
255 fuel pump

New engine is going to have street porting done once everything is sorted!

The common stainless pipe size is 75mm OD so we are probably looking 72-73 internal would this be OK or should I try to go slightly bigger than the down pipe?

Cheers
Jono

U don`t have to go bigger than the downpipe..
So 72-73 would be just fine..


I`m going to build my exhaust with a bigger size downpipe than the rest.
That is because I want the exhaust away from the trubo as fast as possible..:yes

[kev-yorks]

Really depends on future plans Jono what noise level is acceptable and if any future quest for more power is on the agenda as its much more cost effective to get it right first time. I\'ve a Gallon water container in the truck now so next time I\'ll be of more assistance good to see you got back okay though.
 

I`m going to build my exhaust with a bigger size down pipe than the rest.
That is because I want the exhaust away from the turbo as fast as possible..:yes
 

Be very careful with the down pipe sizing especially the transition area from the turbo exit as too large a jump in size causes a high turbulence area that can impede rather than assist flow from memory but don\'t quote me on it i think the idea angle for increasing pipe size is 20 degrees or there abouts.

[shaunwil]

Another decision would be to look at what V-clamps are easily available and what radius bends you can get off the shelf easily (and cheaply). Not sure what wall thikness would be on seamless tube at 75mm. If you are using mig make sure the wall thickness allows you enough to weld to too !

Would be a cool project and please take plenty of photos :Giggle

Shaun

[Timmy]

Thats the wrong way around isn\'t it the pipe if anything should get a larger id as you go alond the exhaust. That should cause the ventrui effect. The disadvantage to a too larger bore is flow can almost stop and this actual causes a large bore to come restrictive.

[Jono FD3]

just to clear guys... she is on stock twins & I am going to be going from the end of the HKS downpipe (80mm) to the rear of the car!

Cheers Kev... Hopefully next time I wont be needing any water
My ears were still ringing this morning Saw a few of the lads with you looking as she started & drove off

Jono