2005 2.0L WRX STI Remap and Exhaust mod advice

[HappyTorque]

Hi Guys,

Will be joining the STI fold as of this Friday having just got rid of my E46M3. I fancied something a bit more involving, torquey and planted to drive and anyway I never really liked the M3 - nowhere near as good as everyone reckons!

So, I will be taking delivery of my lovely new (to me) 2005 2.0 WRX STI this week and plan to get it remapped ASAP to give it the midrange and top end grunt that it deserves.

I am looking to get the car up to around 340 / 350 bhp with similar torque figures. I understand this fairly easily done with a good remap and maybe some exhaust work, given that the PPP kit gives the car all the other bits needed for this sort of power (fuel pump, injectors etc).

My question is: what is / are the best exhaust mods to make the most of the remap that I have booked? I want the car to be MOT legal so a full de-cat is not an option.

I have been asking around and so far have been getting slightly conflicting advice so I figured I would listen to all you guys before I make any expensive decisions.

So far the advice has been:

1). Keep the Prodrive sports cat downpipe and just replace the centre section with a 3" pipe. Reasoning here was that the Prodrive down pipe system is very good already so why waste extra cash on replacing it with something that will ultimately be the same.

2). Replace the Prodrive downpipe with a Meercat snake head sports cat (or similar) system. Argument here was that the Prodrive downpipe does limit exhaust flow a bit so as to err on the side of caution unlike the Meercat design which should maximise the exhaust flow thus improving torque etc

3). Replace the whole lot (sounds unnecessarily expensive to me!)

4). Don't touch it and just go for the remap. (Will I still get the torque and power I am looking for?)

So, what’s the verdict guys?

I don't want to spend shed loads of cash if I don't need to but what I REALLY don't want is to end up with a car that feels a bit down on performance (especially mid to top end torque) even after the remap.

Cheers in advance for your thoughts.

[Vixpy1]

Prodrive sports cats are really good and quite happy at the power you want, As for the rest of the system 3 inch is good. uprated panel filter is the only other thing you need. Be aware that it is very rare for these to make 350 on the standard turbo. I've only ever seen one do it. 330 to 340bhp is more likely.

[HappyTorque]

Vixpy1 said:

Prodrive sports cats are really good and quite happy at the power you want, As for the rest of the system 3 inch is good. uprated panel filter is the only other thing you need. Be aware that it is very rare for these to make 350 on the standard turbo. I've only ever seen one do it. 330 to 340bhp is more likely.

Thanks for this Vixpy1: I hear what you say about the turbo. No real desire to play aroud with this just yet. Good to hear that the Prodrive downpipe is up to the job.

One question - is it worth changing the back box as well as the centre pipe or is this just for sound rather than performance?

I'd be happy with 330 / 340 bhp as long as the torque is up there too. My only experince of turbos before this was my mucjed loved remapped Audi S4 2.7 bi-turbo. That was putting out 330 bhp with 370 lbs/ft torque - and the shove was just great! Given that the STI is much lighter I guess 330 lbs/ft would be a good target.

[Vixpy1]

320 to 330 ftlbs is a good target, i'd do the centre and back box, but make sure you don't buy an earbleeder as they just become embarrasing after a while

[Panthro]

Hi mate, having owned one myself, my personal choice would be as follows:

Full Miltek turbo back exhaust system with a Milek sports cat - I prefer the subtle non boomy sound the Miltek makes, but its a huge improvement over standard.

Walbro 255 fuel pump - I think the PPP kit included an upgraded fuel pump but not 100% sure. A must have before remapping.

NGK PRF7 cold step spark plugs - another must have before remapping.

STI panel filter - big improvement over the standard fit.

ECUTek remap - lots of good mappers about to live map the car exactly to how you want the car to drive. Or invest in a Simtek ECU which leaves a lot of scope for future mods.

With the above mods you will definitely see at least 330bhp. The PPP didnt upgrade the injectors, but they are 550cc so you wont need to be touching them unless you go for more power, and by then you will have to be changing the turbo etc. HTH

Edited by Panthro on Saturday 24th October 03:12

[HappyTorque]

Panthro said:

Hi mate, having owned one myself, my personal choice would be as follows:

Full Miltek turbo back exhaust system with a Milek sports cat - I prefer the subtle non boomy sound the Miltek makes, but its a huge improvement over standard.

Walbro 255 fuel pump - I think the PPP kit included an upgraded fuel pump but not 100% sure. A must have before remapping.

NGK PRF7 cold step spark plugs - another must have before remapping.

STI panel filter - big improvement over the standard fit.

ECUTek remap - lots of good mappers about to live map the car exactly to how you want the car to drive. Or invest in a Simtek ECU which leaves a lot of scope for future mods.

With the above mods you will definitely see at least 330bhp. The PPP didnt upgrade the injectors, but they are 550cc so you wont need to be touching them unless you go for more power, and by then you will have to be changing the turbo etc. HTH

Edited by Panthro on Saturday 24th October 03:12

Thanks Panthro,

Sounds like there is a consensus forming from your and others advice.

My plan is to go with:-

Straight through 3" centre pipe, keep the down pipe and back box (as the power gains seem minimal for the extra cost), new panel filter, replace fuel pump, high quality remap. I suspect this will leave me somewhat shy of the 350 bhp mark but if I can get around 340 with an excellent torque profile I can live with that.

There is some debate about the fuel pump. Some say it is uprated as part of the PPP kit and therefore does not need to be replaced, other say definitely replace it to be on the safe side. Decided to replace just to be sure as there is no point shelling out for the remap and then being limited by the fuel supply.

Still to check up on the plugs.

Also think the car could do with some uprated brakes and something to tighten it up in the corners (lower springs and / or strut brace of some sort).

Went for a long drive today and it really is a very capable car for the money - much more fun than the M3 which, although very fast, was nowhere near as much fun! That said I am hoping that the remap + other mods provides a slightly more progressive torque curve as the car does seem a trifle asthmatic at higher revs after that initial boost.

[JollyGrnMonster]

agree with v1x and pan

one of the better models for minor mods and map to make good power

Simon

[tbtstt]

I have an '05 STi Type UK with PPP (so pretty much what you're getting/have got) and I've yet to ascertain whether the fuel pump has been changed.

My car currently has the Prodrive sports cat, a 3" centre section and a 3" backbox (to 5" exhaust). I'm looking at changing the backbox as the 5" exit looks a bit OTT (in my opinion). In that configuration though my car ran 307 BHP on the dyno a couple of weeks ago - on the standard PPP map.

I intend to swap the panel filter (for either an STi or Cosworth panel filter), then change the exhaust, most likely for a 3" full decat. I would like to replace the ECU with a Simtek or Solaris so I can run ALS later, but thats dependent on money - and I'd rather spend it on suspension (booked for next month!) and brakes first.

As has been said I think you'll be lucky to hit 350BHP without changing some major components.

[HappyTorque]

Thanks guys.

Well the car is booked in for Wednesday for a new panel filter, 3" centre section, fuel pump and remap. Going to keep the Prodrive downpipe as the cost of replacing it is not really justified for the small power and torque gains I'll get.

Might just have a look at a new back box too. Sounds really good at the moment but could maybe do with a tad more growl!

I will let you know how it feels post fettle. My gut tells me that the car will go from good to great - hope I am right. Will be interested to see what effect the map had on fuel economy too.

[tbtstt]

How did this go? I've been reading some more information this week that indicates the 2005 PPP STi's actually received an uprated fuel pump as part of the PPP kit. I'm going to try and give Prodrive Parts a call when I get a moment and get the word from them.

[scoobyPPP]

Hi guys I have a sti ppp on a 05 plate and can confirm as part of the ppp the fuel pump was upgraded to a walbro pump hope this helps

[RASTIVL]

HI THERE, YOU WONT LIKE WHAT I HAVE TO SAY BECAUSE ITS EXPENSIVE , THE CHOICE IN MAKES IS MANY BUT JUST GO FOR 3" ALL THE WAY , YOU NEED TO REPLACE HEADERS BACK IF YOU REALLY WANT TO SEE A DIFFERENCE ALL THE OTHER MID SECTIONS AND BACK BOXES ARE MEANINGLESS WITHOUT THE MANIFOLD AND UP PIPE REPLACED , YOU WILL ALSO NEED TO GO FOR A HIGH FLOW CAT AND HAVE IT IN YOUR MID SECTION UNDER CAR NOT THE HOT CAT IN THE DOWN PIPE , THIS SET UP WILL LAST FOREVER AND YOU CAN BE SHURE OF A NM INCREASE WHICH IS THE IMPORTANT NUMBER , YOU CAN GO THE WAY THE LADS HAVE SAID , THERE IS NOTHING WRONG WITH IT , BUT IT IS CUTTING CORRNERS JUST TO SAVE MONEY ,THE MORE YOU TRY TO SAVE MONEY ON THESE THINGS THE MORE IT WILL COST YOU , EXAAUST IS VERY IMPORTANT SO DONT SCRIMP , AND AS FOR THE REMAPPING GET A MANIFOLD PRESSURE READ ECU SUCH AS MOTEC GEMS , THEY ARE EXPENSIVBE BUT YOU WILL NEVER NEED ANY THING ELSE , MY ADVISE, SAVE YOUR MONEY AND ENJOY THE CAR TILL YOU CAN AFFORD TO GET THE LOT DONE AND THEN YOU WILL HAVE WHAT THE CAR DESERVES TO HAVE . I DID IT THE WAY YOUR GUNNA AND THEN A YEAR LATTER RIPPED IT ALL OFF AND DID THE BUISSNESS ON IT WHICH I SHOULD OF DONE IN THE FIRST PLACE , GO WITH WHAT YOU WANT NOT WHAT IS CHEAP . CHEERS

[tbtstt]

Thanks ScoobyPPP, I tried to call Prodrive Parts and, after being passed around, I spoke to a very helpful bloke who told me that the Prodrive Engineers "wouldn't reveal the exact configuration of the PPP setup".

I assume its a Walbro 255? Pretty handy if it is, as that was on my shopping list of things to buy...

Good advice RASTIVL, but damn man, turn your caps lock off!