does anyone know the diameter of the exhaust ?

i think the bottom of the sports cat is 2.5" to the centre pipe.

i'm after the diameter of the pro drive back box joint as i want to upgrade to a 3" turbo system and keep the prodrive back box


thanks for the help

 

i am pretty sure its 2.5" as when i was speaking to my mapper about my 53ppp sti he said the prodrive backbox can be quite restrictive, i sold the car before getting it mapped, so cant tell you power it was good for.

 

2.5inch. Restrictive above 360bhp, had 353bhp on a blob sti ppp full exhaust yesterday

 

thanks simon

wanted to keep the quiet back box

 

Simon, was that 2lt or 2.5lt and was there enything else done to the car to reach 353bhp?

 

Standard ppp 2litre sti with a panel filter (not sure what make)
Was on a dyno dynamics rr.

 

Was very impressed with that car when it was being mapped

 

was awesome car, test drive was funny as no loud exhaust but went like stink

Simon

 

What torque didnthat produce Simon ? Asuming it was on a vf35 as well.

 

345lb iirc

Simon

 

Simon, are you saying that the Prodrive bb is restrictive beyond 360bhp.... or any 2.5" system, in general, is?

 

ppp complete system, 2.5 after market consider restrictive about 400 on

Simon

 

Simon

I currently have a bit of a Frankenstein's monster setup:-

* Syms equal length headers
* Syms sportscat (don't know if it's 100 or 200cell)
* 2.5" straight-thru - no resonators/no cats - centre (of unknown brand)
* 2.5" Prodrive bb

(I'll also add a slip-jointed 40mm uppipe when I fit those 20g/550/FMIC/3-port BCS/FPR, etc. ).

What would you estimate its max power potential is likely to be? <400? i.e. is it likely to limit the 20g's potential max output?

 

The STi PPP system (on the MY03 at least) kept the original resonator section which was actually smaller than the 2.5" of the rest of the PPP pipework.

JohnD

 

Hi Simon, i am planning on having my 02 bug sti mapped with you very shortly. I was planning on keeping the prodrive backbox and centre pipe and using a after market decat downpipe. I am also planning on fitting a 3 port, magnex headers and up pipe. Do you think the centre pipe would be too restrictive?? Also is there any other mods you would advice on for a better mapping session?


cheers

 

Hi Simon, i am planning on having my 02 bug sti mapped with you very shortly. I was planning on keeping the prodrive backbox and centre pipe and using a after market decat downpipe. I am also planning on fitting a 3 port, magnex headers and up pipe. Do you think the centre pipe would be too restrictive?? Also is there any other mods you would advice on for a better mapping session?


cheers

 

the problem is you need to look at it as how much will it reduce it by as a percentage rather than a how much will it restrict it too..

if you put a large turbo on it then it will still make reasonable power but the back pressure will cause issues elsewhere along with the power.

I would assume 380+ would cause you issues.. you could well get 400 but you need to then consider the back pressure and the effects on the engine, I had 416bhp on my 2.5inch exhaust, changing to 3inch allowed me to remap it to 451bhp.

A car running 500bhp on a 3inch system on the dyno we put the 2inch holed bung in the tail pipe.. it lost over 100bhp.. and the engine sounded so restricted and only sounded fine at actuator pressure.

If you want quiet then get one of the quieter 3inch systems

Simon

 

header change is not really neccessary at this point and the standard centre shouldn't be restrictive at this level no..

Panel filter change would be worth while

Simon

 

When we took my wr1 running sc46 with sportscat it was fine up to 360bhp. But at 400 it really started suffocating. As soon as we decated her (3" decat downpipe and remaining 3" Cobra straighthrough) it changed her into an absolute animal!

 

Thanks

If I therefore change to a Cobra 3" straight thru system (from d/p back), will it free up everything? (not worried about noise lol ).

Or will my existing sportscat still limit it significantly in any way?

 

what power can you run the standard headers up to presuming you have a full 3" de-cat exhaust ?

my thoughts are i have a choice of 2 turbo's but rather than chase a big bhp number i want something thats enjoyable as a road car

 

what power are you aiming for?

on the standard turbo no it won't alter it much at all having the sports cat in there

if 400 then yes it will restrict it

Simon

 

stsandard headers okay to early 400s.. without issue

Simon

 

While we are talking PPP - do the 03-05 PPP cars have cats int the up-pipe? Anyone know what changes on the PPP exhaust front to back? New downpipe? Freer flowing cat ?

 

thanks simon thats just what i wanted to hear

 

i'm sure someone will put this right if i have got it wrong

depends what model you have, the sti has no cat in the up pipe but the wrx does.

my car currently (sti) has a prodrive sports cat at the front, straight centre section (getting rid of one cat) and the pro-drive back box. the previous owner did this to get a bit more power, nicer burble and still pass mot's with no problems.

 

Yeah, c.400 would be the 'goal'.


So what you're saying is:

A) At the moment, if I get mapped on the std VF28 I should make around 320, and therefore the exisitng sportscat and 2.5" system are fine?

B) But when going for 400, even if I did get a full 3" system, then it'd be 'wasted' somewhat, UNLESS I also changed to a full decat d/p at the same time, prior to the remap?

 

Yes

you could get the sportscat downpipe altered to 3inch at the bottom but still the sports cat will be restrictive a little

Simon

 

Just one more question:-

If I get a full 3" decat and system... BUT... it has a OEM sized 2.5" join between d/p and centre, does this restrict things loads then - compared to if it was a "true" 3", flanges and all?

 

Yes it will.
Get it altered when taken off for turbo fitment