3" vs 2.5" downpipe on a stage 2 k03s

[James.Judd.1]

What are the advantages in having a 3" downpipe into a 2.5" catback over just a 2.5" all the way?

Sound?
Performance?

Surely it cant flow anymore because it will be restricted by the 2.5".. just a bit further along the exhaust.

Cheers

 

[tarzan]

mine is 3 all the way to the2,5 back box

 

[James.Judd.1]

You notice any gains?

 

[tarzan]

had standard downpipe with 2.5 catback before and the difference were fater/better spool and great noice when i floored it

 

[James.Judd.1]

most of the gains probably came from ditching the standard dp, i already have a 2.5" milltek on it. Im trying to find out if its worth going any bigger as my exhaust is blowing like a bitch and I might just get a new system.

 

[Damoegan]

most of the gains probably came from ditching the standard dp, i already have a 2.5" milltek on it. Im trying to find out if its worth going any bigger as my exhaust is blowing like a bitch and I might just get a new system.

Waste of time on a little k03/s... Remember that you need some back pressure to help aid the turbo..

 

[James.Judd.1]

Yeah i was thinking that, it doesnt really flow enough to warrant 3" getting it up on a ramp friday so I will find out then where exactly its leaking

 

[Prebs]

mine is 3 all the way to the2,5 back box

This the one going off for MOT?

 

[D--R--E--W]

I was advised to fit a 200 cell cat to my turbo back 2.5" system to add back pressure, would lose a tiny bit bhp but gain torque

 

[James.Judd.1]

I was advised to fit a 200 cell cat to my turbo back 2.5" system to add back pressure, would lose a tiny bit bhp but gain torque

This does make sense, Thats what i already have, i think its just a case of if it ent broke dont fix it!

 

[Mark300zx]

With a 3 inch dp you would get better spool up and better bhp but may a smidgeon less torque, I think I would prefer to get rid of back pressure and the higher egts that go with it!

 

[fourtwofive]

Decat all the way mines jbs decat to jetex back box love the sound

 

[NVM]

its all dependant on wastegate setting.. boost settings to adapt to a 3" dp..

the general rule for a turbo that size is 2.5".. Stepping a 3" to a 2.5" box is a good idea so long as total calculated EGT is cool enough by the time it gets to the backbox, for it not to be a restriction!

 

[James.Judd.1]

Decat all the way mines jbs decat to jetex back box love the sound

Does it sound alot different to mine?

 

[fourtwofive]

Sorry late reply i have been flat out with my engine rebuild. Yes it does sound a lot different lots of pops and bangs one time it flamed and scared the hell out of me I love it and would recommend it to anyone over a cat. my lambda has been mapped out too.

 

[James.Judd.1]

Thats alright mate hows it going anyway.. found the problem?.. Dont you have to have CC software to be able to map it out though? What would happen if i didnt get it mapped out? Throw up a warning light?

 

[tashacupra]

Revo stage 2 maps it out, is that not what you are already running?

 

[fourtwofive]

Yer the builds going well got je forged pistons uprated rods. New gearbox. Ported and flowed head. Bored out to 1.9. New turbo. It's all go. The car will be ready for bt if I decide to go the route next year.
And yer it would throw up a code if it's not mapped out.

 

[James.Judd.1]

It is all go! you doing the work yourself? did you change all the gaskets when you fitted the k03s on mine? cos the turbo to manifold gasket has blown.. sounds like a tractor also how long you reckon that would take to change?

 

[James.Judd.1]

Revo stage 2 maps it out, is that not what you are already running?

Is it written out in the standard stage 2 map? or is it something ill have too take it to revo to do?