This question has been asked of me and I’m interested in folks opinions:
(both my scoobs have decat systems so it is not of direct concern for me)

The prodrive pack on both the wrx and the sti for hawks makes no change to the downpipe or mid-pipe only changes to a stainless silencer (back box) so it would appear to be mainly cosmetic (for noise) but partially with a bigger bore tail you will get a greater out rate. Note the up-pipe on a hawk does not contain a cat, like the pre-catted up-pipe on a blob.

2006 prodrive stats:
Wrx
http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=2&cad =rja&ved=0CDUQFjAB&url=http%3A%2F%2Fwww.prodrive.c om%2Fup%2F06MY%2520WRX%2520PPP.pdf&ei=y9UGU-e7JMmw0QWbw4GwBw&usg=AFQjCNERC5SayJn8brVFGKvVDpioM efIwQ&sig2=Hs9MD5yOO2jR2zsZocIo8A&bvm=bv.61725948, d.Yms

sti stats
http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&cad =rja&ved=0CC0QFjAA&url=http%3A%2F%2Fwww.prodrive.c om%2Fup%2F06MY%2520STi%2520PPP.pdf&ei=y9UGU-e7JMmw0QWbw4GwBw&usg=AFQjCNEZJv8SmASYvGPk4Z0rsHqju wIF2A&sig2=6czIYFA5Ghp1f4a1Cln5lw&bvm=bv.61725948, d.Yms


The only difference between the standard sti exhaust and the wrx is that the end section at rear axle is ¼ inch wider on the sti. Though the fitment at the turbo will be different.

So the question is this:
is there really a need to change the sti exhaust if you are only going for a stage 1 (ppp equivalent). A sport cat is recommended by Andy Forrest, but if the standard ppp doesn’t have one why is it necessary.

Have a look at Andy Forrest’s site about tuning options
http://www.andyforrestperformance.co.uk/27671.html

I am fully aware that the catted downpipe is the major restriction to power levels cos of backpressure against the turbo and any restriction is not a good thing. It is said that a change to the exhaust and a map is the most important thing, but is a change to the downpipe absolutely necessary?

Note: my latest hawk sti was prodrived and the cat in the downpipe was totally goosed when I got it. So maybe a standard pipe will deteriorate with only a stage 1, but the car did have a custom aftermarket non catted middle and back section fitted which may have caused some problem. Of course the humped, catted downpipe could have just been swapped back in before I bought it.

cheers
Ken

 

mate if your wrx is so good just leave it how it is ;-)

 

its not for me mate - its for someone else, but Im interested in the answer too.
My hawks are both decatted

 

it's just the same bollox wrx vs sti

the sti is a better car out of the box , end of story

same as the m3 is better than the 330ci

etc etc etc


show your mate this and tell him to save his money modding a wrx and just but a sti

just my thought

 

ok let me rephrase the question...

is a change to the downpipe necessary on a hawk STI for a stage 1 increase in power as per the prodrive pack, as only the rear silencer box is changed on ppp

I agree there is no point in comparing wrx and sti - but I do find my modded hawk wrx more fun than my modded hawk sti, just not as satisfying - the other post is just a bit of fun !
Ken

 

but I do find my modded hawk wrx more fun than my modded hawk sti

 

get a life

 

No.