is there major difference in hp/torque bitween open deck and closed deck DownPipe. Questioning that cause now having HKS in my car thinking of rebuilding it to something looking like H&S. Is it worth?

Neck it should be indeed :)

Massive Difference....don't wait give Ian a call at Hayward and Scott +44 1268 727256 (01268 727256) and order it now. You won't be disappointed.

You'll get 12-15 bhp increase and the turbo will spool up 500-800 rpm sooner...........Enjoy

all you have mentioned is likely with regards to STD downpipe with cat. But if we talk about HKS close neck decat DP what is difference?

The cat is part of the restriction but the waste gate is blocked off on the standard and the HKS downpipe..

This makes a big different..

Get an open neck you won't regret it.

JGM :)

Alex,

Don't bother, keep the HKS dp and spend your money elsewhere.

whats right or wrong?
Are there any Dinos check on this subject?

Did a search in Dynos - realise that all dynos differs for so many factors so may it relyed upon. Dyno below shows that SS doesnt give more HP against HKS and bit more torque. Does this dyno shows a real picture?
************
Comparison:STi IV

ScoobySport back box and RamAir n/a 271 bhp @ 6660 rpm 242 lb/ft @ 3750 rpm

plus HKS downpipe 208 303 bhp @ 6966 rpm 265 lb/ft @ 3770 rpm

ScoobySport back box and downpipe, PiperCross induction kit 212 301 bhp @ 7030 rpm 270 lb/ft @ 3750 rpm

same mods as above, different day 193 298 bhp @ 6910 rpm 273 lb/ft @ 3750 rpm

plus Magnex mid-section, Grid Flowmate 207 304 bhp @ 6900 rpm 276 lb/ft @ 3750 rpm

plus increasing turbo hose diameter and removing restrictors 209 310 bhp @ 7090 rpm 291 lb/ft @ 3650 rpm

added one restrictor back into turbo hose (ECU was cutting in) n/a 306 bhp @ 6590 rpm 285 lb/ft @ 3750 rpm

plus diameter of restrictor hole reduced in different turbo hose n/a 315 bhp @ 6750 rpm 303 lb/ft @ 3750 rpm
***************

And than i had a look there - seems that SS does difference in low and mid engine speed.

http://dyno.scoobynet.co.uk/jap/mark_aigin.htm

The spool up on the turbo is better..

I felt the car drove how it should. You floor it and it goes rather than waiting for the turbo to wake up (with the TD05 on mine anyway).

JGM :)

do open neck DP cause boost spiking often? Saw many threads on it.

From what have read here, NO, only STI7-8 have such problems but are not related with the open neck d/p.
Open neck d/p gives better boost controll in some cases.
JIM

No spike problems on my 96 car.

JGM :)

I am convinced - going for open neck :)

Just fitted open neck jap innovations DP to MY00. The abbreviation LOL is no where near desciptive enough for this forum. More like LMFTO, every time I floor it. Warp factor nine Mr Sulu...Only took 1 1/4 hours for me to fit with just trolley jack and ratchet ring spanners. Removing the intercooler makes it so much easier.

Flat Faw, did you have a decat DP before and now changed to the open neck design? If you change to the decat DP from std then it won't matter which type you put on because it will make the greatest (most easily noticeable) difference to performance IMHO. The real comparison would come from changing from closed neck to open neck and feeling a difference.

F