I have a 2006 STI (2.5L) which has been remapped to 344bhp and 382lb ft.

I have the standard downpipe in place and a decatted mid section, like the PPP set up. Car is otherwise standard apart from a panel silter and RCM fuel pump.

I'm wondering if it might be better to replace the downpipe and the decat pipe with 200 cell sports cats.

So my question is this:

What's better for performance, a single OE cat in the downpipe or 2 x 200 cell sports cats (one in the downpipe and one for the mid cat)??

Strange question perhaps but emissions regs over here in Switzerland force creative thinking...

 

im running the same setup as you and my downpipe has just failed. got a h&s sportscat downpipe going on friday.

do you need to have 2 cats ? if so a sports cat downipe and the std centre cat would prob be the easiest option.

 

Let us know if the sports cat downpipe makes any difference.

Guess you'd need to get it remaped?

 

Yeah will let you know.

Hoping to remap it at the weekend.

 

cool.

do you know what you are currently running?

 

Don't know what it's running.

Mapping has been done on the road so can not tell. Might be able to get it onto a RR soon and see what it's making.

 

I have a 2006 wrx 2.5L with vf48 turbo, panel filter, Walbro fuel pump, STI intercooler etc with a 200 cel sports cat downpipe and resonated mid section. Only 1 sports cat and the car made 334bhp & 381lb/ft.

I’d say stick with your current setup if you made that power. Little to be gained!

 

thanks for the feedback, very interesting - sounds like there's basically no massive difference between the standard dp and the sports cat.

Sure we're running different maps but it doesn't sound like there's much difference either way.

I'm on a vf43, not sure if that produces more or less power than the 48?

Do you find you are still able to hit EU4 emissions with the sports cat?

My figures are from a road dyno (Bob Rawle), not sure if that makes a difference?

 

VF43 and VF48 are basically the same turbo. VF48 is the updated version but so similar. Expect them to make same power / torque.

My car has just flown through its MOT with the sports cat exhaust on so no problems there.

My figures were from rolling road but I think Bobs road dyno software is also pretty accurate.

My car is running a 2.5” system still but 3” 200 cel sports cat downpipe tapering to 2.5” at the mid pipe flange. The turbo was mapped with a 3 port boost solenoid to 1.35bar max as it had slight crack in wastgate housing. Yours may be mapped to more boost and making more power. Every car is different but sounds like yours is making good power on the current setup to be honest. Only way you would increase that by much would be to decat completely.

 

cool, thanks for the info.

Would you be able to send me the emissions specs of your car from the MOT? I'm trying to work out if I'm going to be able to get my car through the testing over here and it sounds like we're running a pretty similar set up so if your sports catted car got through I should have no trouble... (in theory!)

 

No problems.

Haven’t got them on me today but will try see if I have them in my latest MOT paperwork.

 

Mine was a Cobra exhaust system with 200 cel sports cat, could always ask them if a sports cat of this type is likely to pass American standards and what sort of emissions testing results they have? (Just in case I can’t find my results fast enough). lol

http://www.cobrasport.com/

 

Just be aware that the sport cat downpipe HAS to be hot or it will fail UK emissions nevermind Swiss ones!

 

That’s certainly the case for the less restrictive 100 cel sports cat, but my 200 cel more restrictive one was no problems.

 

ok, thanks for the advice.

When the MOT is carried out in the UK, what specifications are the emissions values measured against? Is it just a measurement of the emissions at idle?

I'm trying to figure out if the car is really still EU4 compliant even after a remap and removal of the 2nd cat...

 

Hang on, if the STI can meet EU4 emissions standards with only the cat in the downpipe, why did Subaru fit the second cat in the mid pipe as well?

The JDM STI's only have the cat in the downpipe so they could've used the same decat mid section from that.

The RB320 only has a cat in the downpipe and that seems to still comply to EU4. Any ideas???

 

Pic of my standard emissions test results with standard exhaust, are turbo etc before remap.

 

Pic of emissions results with cobra 200 cel sports cat, turbo changed etc and remapped.

 

super!

so essentially in the UK the MOT only tests CO and HC and both limits are massively high so you'll quite easily get through.

and you failed after the mods??

 

Took 2 attempts by the look of it with sports cat. Big difference in emissions too.

 

Still passed. Lol

 

yeah massive difference in emissions. Hmm, bit worried now!

Thanks for posting these up, very interesting to see.

It seems the RB320 is still EU4 and that doesn't run a mid cat so perhaps I'll be ok.

 

I thought the PPP kit as fitted to the RB320 is essentially a post registration mod. so it is classified differently to EU4 as hinted on the Prodrive docs

www.prodrive.com/up/06MY%20STi%20PPP.pdf

 

That's the case with the ppp kit fitted to the std sti but the rb 320 is listed from new as an eu4 car

 

Bobs just mapped my 07 sti to 360 / 440. Its standard apart from 100cel sport cat, japspeed pipe, K&N panel filter and 3 port solenoid.
Its an RB320 so has a prodrive pump

 

Crikey mate! that's 16bhp and 58lb more than me and the only difference is that downpipe!

So in summary yes, sports cats are worth it...

 

I have an H&S sportscat downpipe and pass the mot everytime and the rest of the exhaust is straight through without a mid cat.