jas03WRX

I have a scoobysport (janspeed) backbox on MY03 and looking to add possibably the centre section (2 pieces). What sort of gains will I be looking at (if any)??

SL_WRX

I also have an MY03. Have you thought of replacing the front cat pipe, leave middle as standard, and keep your janspeed backbox ?

I was thinking of doing this - any comments if this is a good idea, and performance gains.

jas03WRX

No, haven’t thought of that. is it an easier part to replace? given there is 3 cats on the damn is there any pros and cons from derestricting from the front back? or is it better to derestrict from the back to the front??

SL_WRX

I think you would get more performance by improving the front - gases can get out quicker, turbo spools up better etc. Was going to keep middle box to stop dronning and keep the emission levels okay.

Will run it past Bob R if I see him this weekend.

KJD Mk1

iTrader: (3)

i am the same changed the rear box (magnex) should i change the middle section? i want to leave the cats in place and dont want to upset the ecu.can you get single mid sections?

Steve vRS

It should be a bit louder and add a couple of bhp but nothing that is noticable. The big gains are to be made by changing the downpipe.

Steve

GaryCat

I agree with Steve - I changed the mid cat pipe on my 03 WRX and there was very little difference. The most gains are from changing the downpipe.

subarujimmy

iTrader: (3)

I've got an 03 wrx, and I changed the backbox, which seemed to free the revs slightly (or it could have been my imagination lol). Then took the centre cat off, and a stainless centre section, this gave the car a much better noise, but wouldn't say it did anything for performance. I could have done the downpipe (which i believe is the best part to do for more performance), but decided not too because of insurance and emmission regs.
Hope this helps

JIM THEO

In my WRX03 with full Scoobysport exhaust when took off the back box (I didn't like the extra noise) I lost according to DeltaDash road dyno from 7-10ps ATW and added 150-170rpms in spoolup point (bear in mind my new back box is an STI that is slightly better than the factory WRX)!
So yes a good muffler does a lot to the final performance!
JIM

jas03WRX

Thanks for all your help guys....

I think you helped make my mind up that destroying my warranty is best!

marklemac

Go on Jase, just do it.

Spend the money, get the downpipe, then go for a trip and see Bob

jas03WRX

The wifes gunna kneeCap you...... and you know it!