"Big Bore" Exhaust - serious question needing good answers

Started by HandsomeDan, April 05, 2007, 09:55:26 AM

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NZPOM

I'll add my two penny's worth ,firstly Jason whether it be exhaust upgrade , inlet u/grade or chipping they all claim to give you better fuel consumption based on the false conclusion that you do'nt have to drive the car so hard to achieve the same speed. torque,revs or whatever which might add some marketing/sales value to those who are looking to buy such items, but we all know that in the real world thats not the case because we want to feel the benefit of those purchases so we give it some, then usually the consumption increases MORAL drive like a granny save money/drive like schumacher and it'll cost a lot more than if you did nought.

Secondly,correct me if i'm wrong but i think you've a VR6,just in case your thinking of tinkering with the exhaust system DONT unless your willing to pay big bucks.I've read on a lot of forums (both usa and euro) that the system on the virus is finely tuned especially the headers/extractors and theres not much out there to better it .If you want a better noise take out the suitcase box that will save you money as well as it weighs 20kg.         

mark2 golf

what would be better for a 8v Mk2 2-1/2 or 2-1/4 and what sort of power gain can you expect if you talk out the cat and go from the down pipes back 
89 mk2 1.8t
97 mk3 gti 1.8t
90 190e 2.6
17 Amarok v6
09 golf gti

BB

Glen T is right but so is golfboy, its true a bigger than standard exhaust can help upper performance but if you go drain pipe all the way its silly and makes less probibly as glen and others says.
A big bore is pretty much just wank factor boyracer crap and annoying to anyone with ears and taste. 
The end is nigh, but the end of what is the question?

Filx

Exhaust systems for NA cars is certainly an interesting subject and the manifold (aka extractor) selection is critical to where in the rev range the power is made. But there's tonnes of variables that can affect the primary and secondary pipe length and size (e.g. cam lift, duration, overlap, etc) and then also whether you select a 4-1 or 4-2-1 (for a 4cyl) manifold.

For turbo engines from a power perspective from the turbo back there is no such thing as "too big"! There might be bigger than you need for your power level, bigger than you can fit under the car, bigger than is bearable from a noise perspective - but for power and torque everything I have read and experienced on my cars says there is no such thing as too big. Back pressure is the enemy of turbos and I believe also should not be an element of ANY exhaust.
FAIL - First Attempt In Learning

BB

Except a two stroke, because if they have a wee bit of backpressure it stops the fuel charge just rushing through the chamber when the exahust port is still open along with the inlet. Is this correct?
The end is nigh, but the end of what is the question?

qta4

Different reasons for NA versus Turbo.
Turbo requires zero back pressure post turbo.
NA require a system engineered to collectively scavenge exhaust.
There is much info on net re-exhausts.
Sorry but bigger exhausts work with turbo, but i would suggest many systems go over thetop to create profit. The standard RS4, or RS6 system is not huge ,also quiet, aftermarket,ie miltech engineer performance with quietness.
My 1.8t , i used a 3" turbo back to one of 3 x2.5"coby muflers, straight through type.
May not be scientific but works well and is quiet, ask anyone who has heard at TAUPO.
I will use same system when i do turbo upgrade.

Big drainpipe systems are mostly for posers.

At the end of the day we only have 1.8 litres, not 7 litres
Skill is, sucessfully tightrope walking across the Niagra Falls.
Intelligence is, having the sense not to do it.

mark2 golf

so if i did a 2-1/2 system with as two cobys and a dtm free flow muffler ant the end. it would be alright for a 1.8 and if i do a 9a conversion it will still be sweet.
or is it to big
how quiet would that be.
i currently have a standard exhaust with 3" tip and that sounds good but not to loud
89 mk2 1.8t
97 mk3 gti 1.8t
90 190e 2.6
17 Amarok v6
09 golf gti

qta4

Quote from: mark2 golf on April 22, 2007, 07:24:59 PM
so if i did a 2-1/2 system with as two cobys and a dtm free flow muffler ant the end. it would be alright for a 1.8 and if i do a 9a conversion it will still be sweet.
or is it to big
how quiet would that be.
i currently have a standard exhaust with 3" tip and that sounds good but not to loud

Believe me you can have an effective exhaust system with stealth, stealth seems to be what most exhaust shops want to remove.

25 years ago i built a 107e prefect with a 3 litre Capri engine (google to see what a 107e prefect is) fabricated exhaust with huge v8 muffler, was quieter than stock, never got a ticket for noise, but huge fun, even towed 15ft caravan around NI. Stealth is good
Skill is, sucessfully tightrope walking across the Niagra Falls.
Intelligence is, having the sense not to do it.

RobClubley

#28
Agreed - stealth is the way to go.

I was thinking about de-catting mine - what's the best way to do this? Buy one of those $300 Ebay decat pipes? Have it cut out and replaced by an exhaust shop?
I'd kinda like to retain it in case I ever need to re-fit.

What do you guys think?
1985 ur quattro
1992 Ford Courier - the sensible daily

BB

I have about 30 stainless Miltek cat replacement pipes for $30 each.
I thought the law was changing tho and you will need your cat for a WOF?
The end is nigh, but the end of what is the question?

Turbo

Quote from: BB on April 26, 2007, 10:08:28 AM
I have about 30 stainless Miltek cat replacement pipes for $30 each.
I thought the law was changing tho and you will need your cat for a WOF?

any for a B5 S4?
2000 S4, MTM stage 1, Oettinger RE's, Bilstein Sports, Vogtland springs, H&R Swaybars, DBA 4000 rotors, EBC Yellow stuff pads, 710N DV's, F1 tints, RS4 clutch

RobClubley

Quote from: BB on April 26, 2007, 10:08:28 AM
I have about 30 stainless Miltek cat replacement pipes for $30 each.
I thought the law was changing tho and you will need your cat for a WOF?

What are they going to do without emissions testing equipment? Physically check if it's there?

Does the CAT unbolt from the downpipe separately? $30 sounds well cheap :D What about postage?
1985 ur quattro
1992 Ford Courier - the sensible daily

Fizz

Hey BB u have any pics of these milteks? i wouldn't mind coming 2 pick up one now that i know where's your place :)

BB

The end is nigh, but the end of what is the question?

Turbo

Quote from: BB on May 10, 2007, 05:52:02 PM
Probibly :) There all the same about 30 of them.

i might bags some. if i ever get around to getting the rest of the zorst. ::)
2000 S4, MTM stage 1, Oettinger RE's, Bilstein Sports, Vogtland springs, H&R Swaybars, DBA 4000 rotors, EBC Yellow stuff pads, 710N DV's, F1 tints, RS4 clutch

BB

So anyone still interested in these pipes ill post up a pic if people want and just text me.
if you want a full exhaust i only have a few certain ones. pm me
The end is nigh, but the end of what is the question?