3" Over 2.5" Inch System ?

[~ ~ Cal ~~]

Fellas,

Debating whether to switch to a full 3" system ? I doubt I'll ever run over 350bhp so do I really need a 3" system ? I was out a run tonight and even pushing out somewhere between 310-320bhp it's pretty scary given it's

propensity to rev forever on 5 speed.

Having bought Arch's ported headers as I missed the burble so intend to fit them soon along with a new exhaust system ( i'll likely loose at the top end but spool up a little quicker) . Current exhaust system is a C&C snakehead decat downpipe with an odd combination of pipework meaning that I cannot switch backbox easily without *******ising the flanges. Incidentally, the snakehead is an impressive bit of kit. I just want to be able to run some conventional length aftermarket pipework incase I need to swop out come MOT time.

Pretty sure I'll stay decatted for now though.

There's tons of mixed advice on SN so turn to you guys for some wisdom ? What's the thoughts on 2.5 v 3 ? IF I were to ver run an 18G would I need 3" even then ?

Cheers

Cal

p.s spec. below for info

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Engine:

STI 7 engine adapted for phase one car. STI v2 RA heads and cams port matched to all manifolds and ported and polished. Standard size valves. Phase one inlet manifold powder coated blue with manifold insulation spacers, and port matched to fit onto the STI v7 block with STI v2 RA heads and SS gaskets. Engine built & supplied by Dave at API. It is a JDM block crank pistons and rods & semi forged very strong.

Sards 550cc injectors on phase one rails which have been powdercoated STI pink. Throttle body onto manifold is ported and knifedged.

Equal Length tubular headers

Mapped to 1.4 bar by Andy Forrest. Tweaked recently by Wallace Performance.

Apexi Power-FC ECU and Commander

Apexi AVCR boost controller

Apexi Induction Kit

Forge BOV

Autobahn88 FMIC

Fully decatted exhaust system with snakehead down pipe made by C + C Exhausts

[colin_ross]

2.5 is not going to hurt you at your current power levels. IIRC Andy competed in the first TOTB with a 2.5 system.

However, as they are the same price I opted for a 3 inch system when I was buying mine. You'll barely notice any differnce in the spoll and will give you more headroom if you want more power later on. Makes it a bit louder too but I don't know if you'd consider that a pro or a con.

P.s. how the family Cal, you got the hang of your new life yet?

[~ ~ Cal ~~]

That's pretty much what I thought - I'd love to go for more power but when I watch people take their cars above 350bhp it a ) costs a fortune and b ) things go wrong and you end up doing a "Fai17"

Not only that - my 5 speed box would not cope with > 350 torques likely ( even though I have an uprated clutch)

>>

Family life is good - got another baby on the way ( think I forgot to tell you lot actually !) Sprog 2 shall be here in mid- October

Finlay is now 18 month and getting well acquainted with modding and anything with wheels ! A few recent pics :-

Hows your team Col ?

Back on topic !

edit :- gash spelling

Edited May 22, 2009 by ~ ~ Cal ~~

[fai17]

Cal

doing a "Fai17"!! i like your wording:P

Life would be boring if we all do the same thing...but at least i'm not the one that has spent the most on these forums..you know who you are

Back to topic...no need to change back to a 2.5inch system if you have a 3inch already and i know what you mean about not having interchangable exhaust because of the flanges but at least you won't have gasket issues.

BTW...modding is for men and not just for christmas!

Edited May 24, 2009 by fai 17

[~ ~ Cal ~~]

By doing a "Fai17" I meant that you apply the " don't fix it upgrade it" mentality and your chariot end up being off the road for lengthy periods . It then get's hard to be satisified with current power levels. You know what I mean - I could have said doing " a Higgy " and it would have painted the same picture.

Loving where your turbo is mounted Pete >> pretty trick as the yanks say

[Maxxed_Ross]

I've just put a 3" system onto the RB and the main issue I had was space. The bend to the back box was either touching the wish bones, wishbone mounts or the diff casing because the gap it has to fit through is so tight

After a bit of modification to the last pipe hanger all is good again

[colin_ross]

Hows your team Col ?

Congrats on the good news mate, it's nice work if you can get it.

Team Playsatan are well and as troublesome as ever. You pics reminided me of a couple of my own

[ciaranrb5]

Cal im running a full 3" currently.

Can't realy tell if it was the 3" exhaust that made the difference as i fitted a de-cat down pipe at the same time.

I personally had no issue with space fitted straight on the RB5 all hangers lined up perfect and no banging or knocks at all

just like standard bar the extra power and 50dB increase in noise

[johnnyr6]

If you don't need to change stick with what you got but if you're changing anyway go 3", you won't notice any difference with spool but it's easier to get power from a 3" system. The downpipe your using will make the biggest difference anyway.

I run a full 3" system from turbo back with a td05 16g and it spools fine (ask Playsatan or Coulty). Made 290bhp at 0.9bar.

Johnny

[~ ~ Cal ~~]

I was checking out my pipework yesterday. Without getting underneath the car ( on a ramp ideally) I cannot really tell but it looks like it might be 3" from the bottom of the dp to the backbox. Weirdly it looks the diameter increases at the backbox

Cheers for the info Johnny

Col - nice pics but I am mostly diggin' your daughters choice of slippers

[RA Dunk]

Weirdly it looks the diameter increases at the backbox

its not unheard of Cal, my 3" Fujitsubo tapered down to 2 1/2 in the back box, till i chopped it off and welded a 3" power flow back box in its place , a bit bloody stupid making a 3" exhaust then tapering it down to 2 1/2, kind of missing the point is it not lol

[~ ~ Cal ~~]

i hear your brother - I have the opposite problem though - it looks like mine goes up in diameter at the backbox

[RA Dunk]

i hear your brother - I have the opposite problem though - it looks like mine goes up in diameter at the backbox

ooops, must remember to read read properly before i type lol

[TrackScotland]

mine does the same....

std down pipe and front/centre THEN tapers up to 3" for the HKS ( i think rear bit)