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Home > General Chat > Is 2.5" too big??

1293 sprite

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Melton Mowbray

Hi,
I've got an abbott racing 2.5" decat downpipe to suit the 9-3 / 9-5 GT17 turbo. Just wondering if its too big for a 1293 engine at hopefully around 15-18psi and 160ish hp at a guess. It's got an o2 boss in the elbow and looks like it wouldnt need too much cutting and shutting so would be nice to use if poss!

Thanks,
James.

On 25th Sep, 2009 mini13 said:
cool, i'll pop over with my tool and some lube, lol

1293 88.8hp 82.2ftlb

17.3 1/4 @ 78 mph

Naturally Aspirated (for now)


BENROSS

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9812 Posts
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Resident Cylinder Head Modifier

Mitsi Evo 7, 911, Cossie. & all the chavs ...... won no problem

no its not, 2" system genrally up to 250 bhp, 2.5" 300 odd bhp

hope this helps






Sprocket

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Preston On The Brook

Might struggle to squeeze it down past eh subframe and pot joint though

On 26th Oct, 2004 TurboDave16v said:
Is it A-Series only? I think it should be...
So when some joey comes on here about how his 16v turbo vauxhall is great compared to ours, he can be given the 'bird'...


On 26th Oct, 2004 Tom Fenton said:
Yep I agree with TD........


1293 sprite

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536 Posts
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Melton Mowbray

Didn't think about that, it is quite chunky!

Yes that does help thanks, looks a bit big for my setup! Shame.

On 25th Sep, 2009 mini13 said:
cool, i'll pop over with my tool and some lube, lol

1293 88.8hp 82.2ftlb

17.3 1/4 @ 78 mph

Naturally Aspirated (for now)


matty

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Turbo Love Palace Fool

Aylesbury

It will go past the subframe with a bit of trimming.

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi


Sprocket

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Preston On The Brook




On 25th Feb, 2012 matty said:
It will go past the subframe with a bit of trimming.


Or hammering

On 26th Oct, 2004 TurboDave16v said:
Is it A-Series only? I think it should be...
So when some joey comes on here about how his 16v turbo vauxhall is great compared to ours, he can be given the 'bird'...


On 26th Oct, 2004 Tom Fenton said:
Yep I agree with TD........


tadge44

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Buckinghamshire

Perlease, we dont do hammering on here - its called "adjustment"


1293 sprite

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Melton Mowbray

Would it free up a few extra horses on a fast road spec engine or only really benefit a 200+ hp engine? Trying to work out if its worth making up a new exhaust or sticking with the 2".

On 25th Sep, 2009 mini13 said:
cool, i'll pop over with my tool and some lube, lol

1293 88.8hp 82.2ftlb

17.3 1/4 @ 78 mph

Naturally Aspirated (for now)


Sprocket

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Preston On The Brook

I've gone for 2.25" and aiming for 200hp tops. if that helps any

On 26th Oct, 2004 TurboDave16v said:
Is it A-Series only? I think it should be...
So when some joey comes on here about how his 16v turbo vauxhall is great compared to ours, he can be given the 'bird'...


On 26th Oct, 2004 Tom Fenton said:
Yep I agree with TD........


bennyy

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Doncaster, yorkshire

While I am making a new system I am going to go for 2.25", hoping for the 200hp figure

Audi s4 b5 - 470bhp & 486ft lbs

On 15th Mar, 2012 wil_h said:

Yes, Carl says he gets requests for rimming all the time

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble *wink*


wil_h

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Betwix Harrogate and York

The GT17 is 2.25" on the turbine exit, so makes sense to stick with that as a maximum. But 2" is easier to source and fit. It's tight on the subframe and past the selector.

Power wise, on a turbo I doubt it would be power sapping to use the larger size.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph



On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


Brett

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Doncaster, South Yorkshire

my mid pipe is 2" currently no issues with 20+psi boost
although i am building a 2.5 inch system for it

Yes i moved to the darkside *happy*

Instagram @jdm_brett


apbellamy

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King Gaycharger, butt plug dealer, Sheldon Cooper and a BAC but generally a niceish fella if you dont mind a northerner

Rotherham, South Yorkshire

We used one of those pipes on the upside down skip, it was snug, but went down the back OK with an extra 45 degree bend added.

They reduce in size, so sleeve nicely onto a 2" middle section.

On 11th Feb, 2015 robert said:
i tried putting soap on it , and heating it to brown , then slathered my new lube on it

*hehe!*


cossierick

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wakefield West Yorks

Mines 2.5

Rick


stevieturbo

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Northern Ireland

There are few negatives other than fitment for a larger pipe in a turbo car, especially close to the turbocharger.

But even at 300+ 2.5" wont be posing much of a restriction worth worrying about.

Ive changed exhausts on cars making 400+ from 2.5 to 3" and never noticed any difference.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


Carlzilla

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Quarry Bonk

I'm just wondering if there is any advantage to keeping it 2" up to past the selector then increasing the pipe to 2.5" to ease gas flow?
Not that it matters for me as I'm having internal, but what about after the downpipe?

Edited by Carlzilla on 26th Feb, 2012.

On 26th Jan, 2012 Tom Fenton said:
ring problems are down to wear or abuse but although annoying it isn't a show stopper

On 5th Aug, 2014 madmk1 said:
Shit the bed! I had snapped the end of my shaft off!!

17.213 @ 71mph, 64bhp n/a (Old Engine)


dig-mini

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Rotherham

Mines 57mm which is what saab down pipe is and I'm going to carry it on all the way through. I don't think its worth risking not doing it if your spending a lot of money and wanting big power.

Edited by dig-mini on 26th Feb, 2012.

Craig

my mini van http://www.turbominis.co.uk/forums/index.php?p=vt&tid=448248


Carlzilla

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Quarry Bonk

Well, I'm gonna be running a T3, but I've had Phil work his black magic on my exhaust elbow and manifolds, Just trying to make the setup as 'stress free' as possible.

On 26th Jan, 2012 Tom Fenton said:
ring problems are down to wear or abuse but although annoying it isn't a show stopper

On 5th Aug, 2014 madmk1 said:
Shit the bed! I had snapped the end of my shaft off!!

17.213 @ 71mph, 64bhp n/a (Old Engine)


JT

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Hertfordshire

im going for 2.5" all the way from the turbo (gt17) on my build. i might have to flatten it a bit to get it past the subby and pot joint.

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985


stevieturbo

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Northern Ireland




On 26th Feb, 2012 Carlzilla said:
I'm just wondering if there is any advantage to keeping it 2" up to past the selector then increasing the pipe to 2.5" to ease gas flow?
Not that it matters for me as I'm having internal, but what about after the downpipe?


Absolutely none whatsoever. If you are changing size, the larger size should always be close to the turbo.

The gasses cool as they get further away, so take up less space anyway, so you could downsize near the back rather than go larger.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


Miniwilliams

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Proven 200+bhp & Avon Park 05,06,07 Class D 3rd place

nice post stevie, I think people go far to big some times! all it does is make lag and noise!

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

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stevieturbo

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Northern Ireland




On 27th Feb, 2012 Miniwilliams said:
nice post stevie, I think people go far to big some times! all it does is make lag and noise!


Going big on a turbo car will have few downsides other than noise and packaging. So I'm not saying not to do it.

But even though theory does suggest a certain size is smaller than ideal, it really doesnt have a huge impact on performance even making power well beyond that ideal.

But going from turbo-small-large is totally pointless.

If anything it needs turbo-large-small, or turbo-large-large ( noise and space permitting )

Bigger downpipe etc will assist spool, not hurt it, as you want as much of a pressure drop across the turbine as possible.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


dig-mini

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Rotherham

Thanks for that Stevieturbo this helps a lot with my build and and clears a though is-hoses on my build which I've been pondering on

Craig

my mini van http://www.turbominis.co.uk/forums/index.php?p=vt&tid=448248


bennyy

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Doncaster, yorkshire

I am in two minds whether to go 2.5" downpipe to 2.25" at the pot joint, is there a noticable difference to when it spools?

Audi s4 b5 - 470bhp & 486ft lbs

On 15th Mar, 2012 wil_h said:

Yes, Carl says he gets requests for rimming all the time

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble *wink*


stevieturbo

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Northern Ireland




On 28th Feb, 2012 bennyy said:
I am in two minds whether to go 2.5" downpipe to 2.25" at the pot joint, is there a noticable difference to when it spools?


I'd say as 2.25" will already be more than adequate, any difference would be very small. But it cant do any harm if you're able to package it.

Ive never done a stepped size, always just one size the entire way through.

Although in saying that....one 2.5 Subaru with a GT30 and 1.8 bar boost did have a 3" DP and 2.5" system and we swapped this for 3" the entire way. Didnt make any noticable difference.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

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