I'm after quicker spool on my blob Sti...

The Cat in the centre section has been removed, am I right in thinking there are two now left, one in the downpipe, and one in the up-pipe?

I was going to change the the downpipe for a sports cat pipe (Japspeed are doing a promo, are these worth a punt?). Do I need to change the up-pipe for a de-cat too?

Thanks

 

You have STi or WRX?

If you have STi you have just one CAT at Downpipe,if you have WRX you have two cats(downpipe and up pipe)

If you have STi i would say for better spool i would go with decatted downpipe,your STi up pipe will do better job than oversized up pipe from Japspeed and on STi its decatted up pipe,if you are looking for better item,i would contact Harvey for his Up pipe,which is proven.

If you have WRX i would go with decatted dp and STi up pipe or Harvey Up pipe,oversized up pipe with flexi joint will slow spool your turbo

In both cases you will need Remap as well

Jura

 

Car is STi

Will go de-cat then

 

You will need just decatted downpipe and good remap and you will see difference after this in term of spool and power/torque..

But if you are looking for more power with good spool,i would go with Harvey ported headers and his Up pipe.





Jura

 

Quite happy with power. It's spool I want to smooth out

 

But you will need remap for these modification(decatted downpipe or if you want better up pipe as i suggest Harvey up pipe),because you can suffer with overboosting and other problems,which can end in damaged engine...

For best advice i would contact Harvey about the Up pipe and he will explain all about this

Jura

 

does harvey have a website or contact number? am also interested in this as looking to improve spool up on an sti

 

Am I right in thinking the biggest gain is in the downpipe - can you recommend one?

 

On STi yes i would say is biggest gain is in Downpipe,all DP are OK just beware before the downpipe with flexi joint

Japspeed is OK,Cobra too or Hayward and scott,really depends on your budget.

On WRX i would say replacing DP and Up pipe,its biggest gain and afterwards remap

Jura

 

Managed to get a 'used' one from scoobyspares yesterday - £100 delivered

 

On a WRX, if you still wanted to pass emissions test at MOT, you could not remove both u/p and d/p? If this is this case is it better to replace d/p only?