Just a few quickies,

Ive already got a scoobysport backbox on my classic (Uk turbo). Am i right to believe that i should have about a 10bhp increase at most from it?

If i were to add the rest of the exhaust system (maybe straight through depending on how hard it is to replace the CAT at MOT time, is it that hard?) what sort of power/torque am i going to be looking at?

Thanks in advance guys

Ollie

 

Hi Ollie. replacing the full exhaust including the cat should give about 25/30 bhp it can differ from car to car. best to get it on rollers for b4 and after results. as far as mot is concerned save oem centre section and put it back on mot time warm up car b4 mot and it should pass.
ken

 

Ok cool, ive not even looked at the centre section so i dont know how hard it is to put back in. Is it just a matter of a few bolts and slotting the old one back in?

Ollie

 

I reckon the figure is nearer 20BHP from a full decat - most gains are to be had from the downpipe where the big CAT is.
A mates MY99 with a scoobysport downpipe, the STi centre section [ no cat ] and scoobysport back box + an uprated panel filter made 240BHP on the rollers at Powerstation. According to the guys running the session that was a very good figure for just exhaust and panel filter mods.

 

*real inexperience showing here*

Would a remap help, im wondering if its really going to be worth it because the mods are so small


Ok ok sorry lots of questions!

With regards to replacing the downpipe/uppipe/centre section, what would i need to look for? Diameter (do they come in different sizes)?
Something made me think there were 2 CATs in an exhaust system, 1 in the centre section and 1 somewhere else??
For the downpipe what size is recommended, do i have to match the rest of the system in some way?

 

You should be O.K without a remap if you are just doing the exhaust but a knocklink would be a good idea.

Although the BHP increase may not be huge, the most noticable improvement from the de-cat is the way the turbo spools. It comes in quite a bit earlier and the car feels much more willing and torquey in the low to mid range. It hugely reduced the flat feeling before the boost arrived on my car, instead of going "nothing, nothing, nothing....LOTS", it swells up in much nicer way, and earlier in the rev range.

At this level there isn't too much point in doing the up-pipe, most people just go with down-pipe, centre and back. Diameter wise you'll do best with a 2.5" system, full 3" tends to be too big for cars running under 350bhp and reduce the mid-range torque in exchange for top end, which is pointless on a TD04. I'd go for either Hayward and Scott or Scoobysport (Janspeed) and get the standard de-cat system which is an open neck 3"-2.5" downpipe, then a 2.5" centre, and standard (also 2.5") backbox. This is a straight bolt on and will work very nicely on your car as it is.

Your car currently has 2 cats, a big one in the downpipe and a smaller on in the centre section. It should pass it's MOT with just the centre one in, which is a 2 bolt flange at each end and 1 hanger - easy DIY swap.

 

as avalanche said the scoobysport and most systems are 3" at turbo tapering to 2 1/2" from midpipe back your existing b box will be 2 1/2".
bhp figures as I said vary from car to car and also from day to day (warm or cold) You may only get 25 bhp there again you may get 30 bhp with full decat my MY99 got 240 bhp with just scoobysport decatted midpipe and b box at powerstation if you want pops and bangs go for scoobysport down pipe and midsection but make sure you lag them.
ken

 

they can vary in a very big way sometimes,ive got a MY98 uk turbo with a ss back box and centre,and an itg panel filter,and i got 250bhp and 237 lb/ft torque.
ive now just fitted the ss downpipe,and i have a pipercross induction kit waiting to go on,time for another visit to power engineering me thinks,and Ken,what do you mean about lagging them?

BM

 

I found lagging the down pipe quietens that part of the exhaust and because it keeps the heat in it adds to the pops and bangs. there's plenty of threads on here regarding lagging I used cooltek exhaust wrap 30m x 50mm wide from www.proven-products.co.uk There was enough to do down pipe and centre section.
ken

 

Ok cool, thanks for the info guys a great help.

Just need to find the second hand parts now!

oh and check that tesco are ok with me doing it

 

cheers ken

BM