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downpipe/exhaust track car #1628801
21/01/2019 07:28
21/01/2019 07:28
Joined: Aug 2017
Posts: 233
Surrey
J
jonnyboy54321 Offline OP
Club member 1630
jonnyboy54321  Offline OP
Club member 1630
Making a profit
J

Joined: Aug 2017
Posts: 233
Surrey
Gents
I will preface this with the comment that I have a fella who can do stainless exhausts. However, on we go:-

My track car - engine wise is standard apart from a gtec1 - I have loads of bolt-on bits for it in stock inc fmic, bigger injectors, fpr, walbro, gt28 with 3" flanged downpipe and blueflame exhaust. But the nature of the beast is that we want to track it roughly as is then slowly evolve it. Only to a point though - not going forged etc.

Cambelts and waterpump are done, I have the gearbox half out to do a kevlar clutch. The downpipe is pretty shabby as is the middle section of the exhaust (I think the rear looks like a newish cybox but will check). The dp has had an upper part 3" welded in then grafted (badly) to the lower part. Horrible. But as it's a standard turbo its v band. I do have a standard spare downpipe in stock. If you were me, would you bother re-doing the downpipe in 3" at this point? May want to do at least a couple of track days before the big blower goes on, because at that point its fmic and remap time etc. More interested in making it stop well and go around corners initially..... Or should I just chuck the standard one on and look at the centre section of the exhaust as it is minging too?

All responses appreciated, bit of a crossroads moment.

Re: downpipe/exhaust track car [Re: jonnyboy54321] #1628809
21/01/2019 12:10
21/01/2019 12:10
Joined: Oct 2008
Posts: 6,583
In the coupe.
magooagain Offline
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magooagain  Offline
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In the coupe.

You won't need anything but standard for your stock turbo .




If you are going the gt route then a new 3"complete system with the five hole flange is what's needed. No silencers needed if it's a dedicated non mot track car.



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Re: downpipe/exhaust track car [Re: magooagain] #1628826
21/01/2019 20:32
21/01/2019 20:32
Joined: Aug 2017
Posts: 233
Surrey
J
jonnyboy54321 Offline OP
Club member 1630
jonnyboy54321  Offline OP
Club member 1630
Making a profit
J

Joined: Aug 2017
Posts: 233
Surrey
Originally Posted By magooagain

You won't need anything but standard for your stock turbo .




If you are going the gt route then a new 3"complete system with the five hole flange is what's needed. No silencers needed if it's a dedicated non mot track car.


In that case I will dig out my spare downpipe, and see if I have a centre section somewhere. It is a track only car but do want it to pass mot.

Thanks

Re: downpipe/exhaust track car [Re: magooagain] #1628844
22/01/2019 12:36
22/01/2019 12:36
Joined: Jan 2006
Posts: 9,873
SW London
suba Offline
Je suis un Coupé
suba  Offline
Je suis un Coupé

Joined: Jan 2006
Posts: 9,873
SW London
I would not go without silencers unless you only plan on doing 102db days - most are 98db, and it's not worth being right on the limit as you'll get booted off without warning.

I put two straight through silencers on the RX7 for this purpose - lost 3bhp, and only slightly higher EGT's.

Goes without saying that official MOT needs a CAT in the exhaust...


Rotary fun - 370 bhp per ton. GT30's are small you know?!??!?!?!
Re: downpipe/exhaust track car [Re: suba] #1628857
22/01/2019 19:56
22/01/2019 19:56
Joined: Aug 2017
Posts: 233
Surrey
J
jonnyboy54321 Offline OP
Club member 1630
jonnyboy54321  Offline OP
Club member 1630
Making a profit
J

Joined: Aug 2017
Posts: 233
Surrey
Originally Posted By suba
I would not go without silencers unless you only plan on doing 102db days - most are 98db, and it's not worth being right on the limit as you'll get booted off without warning.

I put two straight through silencers on the RX7 for this purpose - lost 3bhp, and only slightly higher EGT's.

Goes without saying that official MOT needs a CAT in the exhaust...


Agree - I do have that cybox back box....

And a blueflame for when the gt goes on

Re: downpipe/exhaust track car [Re: jonnyboy54321] #1628865
23/01/2019 10:07
23/01/2019 10:07
Joined: Oct 2008
Posts: 6,583
In the coupe.
magooagain Offline
Club Member 259
magooagain  Offline
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Forum is my life

Joined: Oct 2008
Posts: 6,583
In the coupe.
Straight through 3" stainless steel including down pipe purrs like a cat. It won't get anywhere near 95dcb.

I do understand that it's no good for an mot road going coupe mind.

The blue flame will be louder than a straight through I reckon but still ok for track noise limits.



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Re: downpipe/exhaust track car [Re: jonnyboy54321] #1628869
23/01/2019 12:25
23/01/2019 12:25
Joined: Dec 2005
Posts: 17,082
Staffordshire
Nigel Offline
Club member 123
Nigel  Offline
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Joined: Dec 2005
Posts: 17,082
Staffordshire
My 20vt gave 98db with a straight through 3" system with just one small backbox

However, it got very boomy under load, so I had a big centre silencer fitted (still 3" straight-through) which made a lot of difference

Back to the OP's question - its the first section of exhaust that is critical - as the gasses travel down the pipe, they cool and need less volume.

If you still have the stock V-band adapter fitted, this is the limiting factor - you could fit a 6" exhaust from the V-Band back and it wouldn't improve anything

Don't fit a bigger downpipe until you're about to fit a turbo with a 5-bolt flange - you won't see a benefit until then


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Re: downpipe/exhaust track car [Re: jonnyboy54321] #1628871
23/01/2019 12:51
23/01/2019 12:51
Joined: Oct 2008
Posts: 6,583
In the coupe.
magooagain Offline
Club Member 259
magooagain  Offline
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In the coupe.
Strange mine is nowhere near that amount. Mind you I have a hybrid so still on VBand. What was the turbo you were using Nigel.



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Re: downpipe/exhaust track car [Re: Nigel] #1628881
23/01/2019 18:08
23/01/2019 18:08
Joined: Aug 2017
Posts: 233
Surrey
J
jonnyboy54321 Offline OP
Club member 1630
jonnyboy54321  Offline OP
Club member 1630
Making a profit
J

Joined: Aug 2017
Posts: 233
Surrey
Originally Posted By Nigel
My 20vt gave 98db with a straight through 3" system with just one small backbox

However, it got very boomy under load, so I had a big centre silencer fitted (still 3" straight-through) which made a lot of difference

Back to the OP's question - its the first section of exhaust that is critical - as the gasses travel down the pipe, they cool and need less volume.

If you still have the stock V-band adapter fitted, this is the limiting factor - you could fit a 6" exhaust from the V-Band back and it wouldn't improve anything

Don't fit a bigger downpipe until you're about to fit a turbo with a 5-bolt flange - you won't see a benefit until then


Nigel - presumably yours was a road car that you track with? This one is a track car that I occasionally road with....keep MOT up etc. At least that's the plan....

Re: downpipe/exhaust track car [Re: jonnyboy54321] #1630975
24/03/2019 10:06
24/03/2019 10:06
Joined: May 2006
Posts: 149
Surrey Hills, U.K
G
godders Offline
Club Member 1575
godders  Offline
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On a journey
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Joined: May 2006
Posts: 149
Surrey Hills, U.K
I’m on a similar “journey” to you but perhaps a year/year 1/2 ahead.

My car started (came with) with a basic Flea remap ~240bhp ish.

I focussed on suspension and breaking initially.
I’ve now got Flea’s stage 2 and hybrid Turbo, FMIC etc and around 300BHP - i’ve also lost a lot of weight (the car not me unfortunately) which is equivalent to adding power and better brakes.

The car now is plenty fast enough (I know is there such a thing) the limiting factor now is me and possibly some at the limit handling - which i’m working on, the latter is easy the former not so!!!!!

I would recommend focusing on suspension, brakes and good tyres (I love the Toyo R888R’s) and building up the performance as you learn to drive the car on circuit and understand the handling limits - which are much further than you think!

Re: downpipe/exhaust track car [Re: magooagain] #1630988
24/03/2019 18:28
24/03/2019 18:28
Joined: Dec 2005
Posts: 17,082
Staffordshire
Nigel Offline
Club member 123
Nigel  Offline
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Forum veteran

Joined: Dec 2005
Posts: 17,082
Staffordshire
Originally Posted by magooagain
Strange mine is nowhere near that amount. Mind you I have a hybrid so still on VBand. What was the turbo you were using Nigel.


When I first went to a 5-bolt flange, I was using a GT2871 - I'm now on a GT3071


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