Fitted a H&S decat downpipe yesterday to my sti 4. What a difference! Had the car nearly 2 years now, mods now include:

Full H&S decat exhaust (3 inch from downpipe back)
Ebc discs and red stuff pads
Rota alloys with toyo t1-s tyres
Hks turbo timer
Hks boost guage
PE geometry setup
NGK PFR7B spark plugs
Knock link
Green panel filter on its way!

I had fitted a magnex decat pipe around a year ago (twin dump) but it caused overboost which was a bit worrying, especially without a re-map. So re-fitted original downpipe until I had both the time and the money to buy and fit an 'open neck' downpipe.
Only took 1 hour 45 minutes! Does help when the engine is cold though!

The car has so much more 'punch' through the gears. Only really need to go to 5500rpm in each gear now, there is just so much torque!

Only £800 to go and I can get the Jolly Green Monster to fit an Apexi FC!!

 

I've done the magnex s/s exhaust conversion from 1st cat back on my 2000 classic turbo and not got it on toyo proxie T1RS tyres matched set of 4 and the difference is amazing. Thinking of getting the front end of exhaust system decated soon but wondering where you stand with regard to getting your car mot'd and what effect it has on the rest of the car setup.

 

what dp u all yis bother with these knocklinks?? loada bolox

 

WTF??

 

Again, WTF???

 

Interesting reading. I too have an sti 4 (wagon) and am looking at a decat as well. You giving it full berries (throttle) without a remap (you remapping to 100 or 98RON)?

With the decat where does the turbo kick in? At the mo I would say 3k to feel it spin up, 3.5k you've got assistance, then at 4k you're outa-here!!!

How did the PE geometry setup go? The STi has "better" suspension (from my understanding) so what difference was made?

Any thoughts would be welcome.

 

1)Going to remap to optimax, when I can afford it!

2)Turbo kicks in around the 2800rpm mark with full boost by 3300/3400rpm, with a much stronger hit. Throttle responce is sharper at all speeds. Recommend though that you go for an open-neck downpipe as opposed to the 'twindump' design. I fitted one of these (twindump) a year ago. The car felt stronger but suffered with overboosting. The open neck design allows a clean exit for the waste gate gases.

3)Before the geometry setup, the car always wanted to understeer (normal for impreza's I know) more than I was comfortable with. After the setup, turn in was improved and understeer reduced, but the big improvment in handling came when I fitted larger alloys (each 8kg's lighter than the oe alloys) along with toyo T1-S tyres. The car immediatly felt more planted and inspired more confidence in the bends. To be honest, it felt like the car had lost 100KG's!