how restrictive are the standard exhaust systems

[cptkirk 10]

ive got the new system on today and by looking at the standard system they must be poor

 

 

[MurphG60 0]

There designed for a good all round system also mostly made cheaply to keep costs down

[fendervg 30]

The Corrado one isn't cheap! About £600 cat back. They were long life and it's not unusual to see them lasting 10 years or more. My 93 was on it's original exhaust until 2 years ago, and when I replaced it there was very little wrong with it.

[VR6Pete 0]

Still on my original! Had replace front section other month though but rest is still ok! :)

[cptkirk 10]

hopefully the stainless system will last long tiime

[Wild-Animal 0]

I have been working on designing an exhaust system for a race car at uni. From having no exhaust then having a highly tuned exhaust system to a car will only give 4 Hp of difference, it also depends on the of headers as to where the power will be. a 4-2-1 header will be better for power through out the rev range compared to a 4-1 header which is normally tuned to top end power.

 

A friend told me that a trial was tested on a MK4 golf with varoius different exhaust systems on a dyno, everysingle system they put on the car made the car loose power compared to the original exhasut apart from one system had a gain of 1 hp.

[fendervg 30]

I'd believe that - a custom exhaust will get you very little apart from more noise without serious changes to the engine and the intake - it all needs to be built as a system.

[Rams 0]

New systems tend to be lighter than the old so will shave some weight. But agree with above comments.

 

Often sound can be mistaken for horse power! Lol

[Yandards 0]

Worst bit is the downpipe, the pipe of the pair that is covered by the heatshield has a large 'dent' in it.

 

No doubt this is to improve exhaust performance but it does seem a bit back to front.

 

Exhausts, manifolds and intakes are complicated pieces of engineering and depending on the state of tune of your engine the exhaust length and bore may need to vary - it is also worth considering that an overbore exhaust often removes performance in a N/A powered car and can delay boost in turbo powered cars.

[fendervg 30]

I'd spend the money on a VSR first if I could find one! I just checked the price of the VR exhaust in Germany - €960 euros! My Milltek was about €500.

[cptkirk 10]

|^^^how much!!!

 

only got this sytem because the old one was gone..it had been repaired at some point...

 

 

i just cant understand how the large box would make the gases flow nicly...no lamba on mine eva?? thought it would have one

[Redfox 10]

On my Laverda motorcycle, it is very important, that the downpipes are as big as the inlet tract diameter in the cylinderhead, and the diameter in the exhaust port - 36mm. Then secondly the downpipes should have as little or no bends to prevent the burnt gasses "standing" in the tubes, waiting for the valve overlap to be sucked in again, which in turn gives bad performance.

Next on list is the collector which connects the three downpipes into one. This is oversized, but only to a limit, not just overly big, conical shaped, then split into two pipes of bigger sizes, into finally two silencers with the correct back pressure.

the shape of the conical collector is very important, as is helps the spent gas from one cylinder extract the next portion of spent gasses and so on, leaving the complete system. This tuned system gives a lift of about 8 hp on a rolling road compared to standard system, which is only built for being silent and with little emission. The tuned system only works if you upsize the inlet tracts from the carbs and eventually also the carbs themselves. The cylinderhead is already tuned to max per factory on this particular model - 36mm from 32 mm normally. So are valve sized, shaping, angles, length, stems and weight. On top of this can be chosen two other set of cams. This description is based on lots of development and testing and is optimal. The factory 3-1 race system is absolutely crap in comparison. So is the original 3-2 compared to this described system.

Enough about that. But I just wrote it to demonstrate, that it works as a system, and that one thing is not always relevant for performance in middle range as used on road driving/ top end for race driving.

Weight is surely always a nice thing, and lots of kilos can be saved by chosing a specific system. I would or rather will also bolt on a banana manifold when I get around to it. I personally would prefer to save a lot of kilos all the time. But not to the point of it breaking though.

The original second rearmost silencer on my G60 is enourmously heavy... ;( for example.

 

So, what is the lightest and best system for a G60 with a better cam (not race, more like tuned road cam), and a little better tuned system, cooling, and intake plus 70mm wheel or little bit modified G-lader?

Not wanting and exploadable motoer in a season ;)

 

Is 2,5" all the way plus cat enough? Two or three silencers?

 

Cheers,

Redfox.

Edited February 20, 2012 by Redfox

[Kevin Bacon 5]

Don't know about the valvers but my VR6 was pushing well over 300hp through it's standard exhaust at one point, so they can't be that restrictive. An off the shelf exhaust rarely gives any additional power over stock but gains can be seen with a proper custom one.

[steveo29 0]

i went from a 2.5" jetex on my g60 back to a vag system , no power loss that i can tell at all , might be my thinking but i feel theres more mid range on it

 

lovely and quiet and no booming at motorway speeds , well worth it to me to sound like a halfords chav

 

and theyre mostly stainless anyway , should last many years

Edited February 21, 2012 by steveo29

[Yandards 0]

As Mr Fishwick has said and others have touched on the standard exhaust does flow very well.

 

The other plus point for the original items is that they last a very long time, you will always get 10 years plus of regular use from a genuine exhaust and around 100k before they start to fail and its usually due to high loads on the pipe joints/welds thanks to worn exhaust rubbers not being replaced.

 

KR (1.8 16v) powered cars never came with a lambda and the 9A 2.0 16v unit is a emissions bodge to get it to meet the 1992 emissions regulations - it was never intended to refine or improve peformance. The 16v block that has a proven record of producing a lot more power is the ABF derived unit as fitted to mk 3 Golfs etc, these blocks have all the sensors that the VR has to ensure optimum efficiency but when coupled with aftermarket ECU managment regularly produce in excess of 160 bhp and lbft across a wide band of the rev range.

 

Restrictions in an exhaust system will produce more torque and having a system open to atmosphere does not produce more power - a custom exhaust built for your engine specification might release a couple of bhp but this is unlikely.

 

Most power gains come from removing the CAT (pre 1992 cars only or its an MOT fail) the Corrado exhaust manifold is of a good design on all varieties of engines used which is where most performance gains can be found.

 

So if you want a new exhaust, get a custom one from a supplier that knows how exhausts work and what they need to do (its all about pulses of flow and tuned lengths of pipe) or just stick with the factory one - VW/Karmann did seem to understand how to build a good exhaust system.

[davidwort 0]

It's true that 1980's era 8v golf GTI's do see a performance improvement from all-in-one manifolds and downpipes, particularly if the engines had headwork and cams, but I think that's where the performance exhaust myth stems from. It's in the same category as 'performance' air filters, i.e. most of it is bunkum but plenty of companies make money out of it, so there's plenty of reason to perpetuate it!

A blowing OE exhaust or one that has broken baffles or rusted through sound deadening inside is also not going to help the problem, how many people actually compare a new OEM exhaust with a new aftermarket one?

I've never actually bitten the bullet and shelled out for new VAG items, like a lot of people I guess it's easy to get blinded by shiny stainless systems for half the price of OEM ones, but looking back I wish I had gone for VAG ones on a number of occasions!

I've quite a list of short lived pattern exhausts, cracked stainless system brackets and ill fitting parts and all the best rolling road plots were on OEM parts :lol: