2.5" or 3" straight through?

[Aaron1.8t]

Hi guys..
I have a toyo 3" dp n decat fitted to my agu 1.8t k03s fitted.. Need to fit a powerflow back box i have for it.. What pipe shall i mate from decat to back box? 3" or 2.5"? Alot of ppl here have 2.5" so wondering whats best for flow as i dnt wanna loose back pressure.
Thanks

 

[16Klappe]

Less back pressure will help the turbo spool quicker. So you want the best flow.

What you want to do is 2.75".

The downpipe is 3".

The first stage of the decat is 3" then it steps to 2.75".

Then it steps to 2.5".

Like so...

Cut off the 2.5 section just before it becomes 2.5.

Et Voilà.

 

[Prawn]

The above from Jardo is sadly untrue, but we'll let him off because he's currently very ill. So even less with it than usual

Decat as pictured above is 3"-2.5"-2.25" to mate up to the stock 2.25" system.

You ideally need to decide how far you'll want to take the car in the long run. If your long term goals remain below 300bhp, then a 2.5'' system will be absolutely perfect for you.

long term, if you plan to exceed 300bhp by any considerable margin, then you want to be looking at a 3'' system.

In reality 2.5'' systems are very common, and 3'' systems are very rare and expensive, apart from one single ebay option that many of us use.

 

[antwan64og]

In reality 2.5'' systems are very common, and 3'' systems are very rare and expensive, apart from one single ebay option that many of us use.

Jetex sel a 2.5" and 2.75" mid pipe for £90 delivered if thats the route you wanted to go.

The exhaust can be as simple (and loud) as you want it to be, lol

http://www.eurosportacc.com/products/euro-sport-race-exhaust-system-vw-mk4-tdi-1-8t-with-hidden-tip

 

[Aaron1.8t]

Ahh cool yh no more than stage 2 so 2.5" brill guys thanks.. And that center pipe jetex... Is it to fit from the decat to the back box? Will that fit my a3? If so ill order that n wack it on myself if poosible?

 

[8pot]

I have a 3" full system on mine with 3" down pipe from pipewerx. Been on for about 3 years now and really pleased with it

 

[Mikemc]

8pot, how loud do you find this? Thinking of upgrading my polos to a 3" system

 

[Robi_redman]

Iv just had a custom made exhaust done last week end. Had a 3" turbo back exhaust systerm. And have a miltek back box, noise wise is pretty quite with a little note to it. And when opened up the roar kicks in lol. Chuffed to bits with it and done for half the cost a full miltek normally cost.

 

[Lavis89]

thats exactly what im looking for when i get my system made up, quite subtle on tick over with a bit of grunt when you put the power down.

 

[8pot]

Mine is not that loud.