which stock exhaust manifold is better for spool and low end power? has anybody compared the the two back to back, not just the manifold swap but also with the s4 twin scroll still installed and working?

i will be used with a turbine housing modified for a p-trim wheel, and full 3" exhaust, if that makes any difference

 

S4 is more for top end, S5 gives better spool

 

all i can say is the the twin scroll is amazing you get instant turbo responce at any rpm and off the line full boost at 3000 rpm or less without a precat and full exsaust. i love my s4 turbo. buddy has the s5 and i would not swap it. at high rpm the s5 turbo has trouble keeping the boost pressure up due to a smaller exsaust wheel. and like i said at low rpm full boost at less then 3 grand seems pritty damn good unless the s5 is ALOT lower i would not worrie about it leave the s4

edit: if anyone knows what rpm the s5 turbo will produce at what rpm according to an aftermarket boost controller let me know

 

s5 has same exhaust wheel. it is the turbine housing that is different (besides the manifold).

If you use the s4 you really need to have the twin scroll actuator and solenoid working properly.

 

Both s5 and s4 are identical... only difference is duh.. manifold and hot side. Both lose pressure at 6,000rpm. Stock turbo speaking of.

 

Stock for stock, if the twin scroll was working 100%, I would say the spool is relatively similair. However, if you open up the intake and the exhaust, I would say the S5's design is much better and would result in a faster spool. Not to mention you could remove all the emissions stuff on the S5 and not have to worry about relying on a 20+ year old auxilary system to keep the turbo spooling quickly.