Are 4-2-1 manifolds really worth it

16th February 2012, 09:33

As said above are they really worth it, iv had mine for a while now but never seemed to get any gain.

do makes of manis make a big diffrence as mine is only a sportex 1.

maybe there is a gain but im not really sure as it has been on for a while

thanks

16th February 2012, 09:36

tbh i'm not sure for road use. Going from standard to 4-2-1 raceland i didn't think it was worth it.

16th February 2012, 09:41

Depends what car it's on. On a mk2 VTR it will make a huge difference. On a Vts it doesn't make a massive difference until you've got high lift cams and regularly hit the limiter.

Sportex are pretty poor too tbh, the manifold design isnt great.

16th February 2012, 09:45

Standard VTR downpipe is very restricted - check the pipe diameter compared to say an xsi or rallye 8v version. 4-2-1/4-1 should indeed give some good benefits if you use one atleast on a 8v

16th February 2012, 09:50

its the full saxport 2" race system and decat, dont get me wrong its got the most back pressure iv seen on an exhaust so im guessing the air flow is good am just not sure if i see a huge gain maybe just cant remember how it was without.

16th February 2012, 10:16

what is the best 4-2-1 manifold to buy?

16th February 2012, 10:24

so would it be worth getting a better branded mani if spotex are not great and bad design

16th February 2012, 10:27

Quote:

Originally Posted by j100vtr

its the full saxport 2" race system and decat, dont get me wrong its got the most back pressure iv seen on an exhaust so im guessing the air flow is good am just not sure if i see a huge gain maybe just cant remember how it was without.

how do you know this?

16th February 2012, 10:33

Yes they are worth it, my vtr was shit in low revs after we fitted the high lift cam, a 4 branch manifold made it much better.

16th February 2012, 10:38

Quote:

Originally Posted by Jungle

how do you know this?

i said i have seen

16th February 2012, 10:40

Quote:

Originally Posted by Technics_1210

Yes they are worth it, my vtr was shit in low revs after we fitted the high lift cam, a 4 branch manifold made it much better.

im not running cams u think it would be a good buy, was on my list

16th February 2012, 10:42

Quote:

Originally Posted by j100vtr

i said i have seen

How can you see back pressure?

16th February 2012, 10:44

4-2-1 definitely made a noticeable difference to my 8v! Got a nice kick at 4k, then a bigger kick at 5k.. whereas before, I couldn't feel the pull much after 5k.

16th February 2012, 10:50

Quote:

Originally Posted by j100vtr

im not running cams u think it would be a good buy, was on my list

Up to you really mate, i've done about all i can with my vtr and to be honest i'm bored of it and want something quicker so i've got a 16v engine to go in it. I would personally not bother modding the vtr and save for something better.

16th February 2012, 11:04

To be fair.. I miss my 8v engine. I miss how I could happily be heavy footed and still get 80 miles from 10 litres. My 16v is lucky to see 50 miles from 10 litre's.. with less heavy foot moment's.

And the 8v engine isn't a million miles away from the 16v.

So extra fuel, extra tax, extra insurance cost's, harder to work on engine.. for <20bhp increase... worth it? no.

Without a doubt i'd say I was faster with my 8v engine than my 16v. Whole different power delivery to get used to, and the 16v spins up ALOT easier than the 8v coming out of bends.

same mods on both engines, so the 8v wasn't 'breathed' and the 16v standard.. they both had the same, 4-2-1 / race centre / 3 in backbox / green cotton filter / 1.1 gearbox.

My 2p's worth..

16th February 2012, 11:06

Quote:

Originally Posted by Jungle

How can you see back pressure?

u can feel it from a great distance away, and also when its cold u can seeee it.

16th February 2012, 11:09

Quote:

Originally Posted by saxova

To be fair.. I miss my 8v engine. I miss how I could happily be heavy footed and still get 80 miles from 10 litres. My 16v is lucky to see 50 miles from 10 litre's.. with less heavy foot moment's.

And the 8v engine isn't a million miles away from the 16v.

So extra fuel, extra tax, extra insurance cost's, harder to work on engine.. for <20bhp increase... worth it? no.

the reason im sticking with 8v and low mile engine.

16th February 2012, 11:20

Don't blame you..

Only reason i went 16v is because the 8v needed a new clutch and cambelt.. and was nearly on 100k..

So when i saw a sub 50k miles JP4S with new cambelt and new clutch for £350, It was a no brainer.

Getting a 5 door diesel golf for a daily anyway.. then it doesn't matter how much MPG the 16v get's.. as it'll be just for fun. Not nipping to the shops

16th February 2012, 12:07

Quote:

Originally Posted by j100vtr

u can feel it from a great distance away, and also when its cold u can seeee it.

Do you know what back pressure is?

16th February 2012, 12:26

Quote:

Originally Posted by Jungle

Do you know what back pressure is?

back pressure is the pressure that is in the exhaust pipe before it leaves the exhaust system. ok i worded it badly but u no what i mean.

16th February 2012, 12:33

I have a 4-2-1 raceland and I noticed no difference after fitting it to mine.

Car feels the same as it did before...

16th February 2012, 12:35

ye that was my thinking aswell

16th February 2012, 12:38

Lol at you trying to own him in some way about back pressure. You knew what he ment he didnt claim to be a genious.

Aftermarket manifold is essential on an engine with any sort of internal work, as other people said on a standard engine the most noticeable change from an aftermarket manifold is on the mk2 8v.

16th February 2012, 12:47

Quote:

Originally Posted by Tom5190

Lol at you trying to own him in some way about back pressure. You knew what he ment he didnt claim to be a genious.

Aftermarket manifold is essential on an engine with any sort of internal work, as other people said on a standard engine the most noticeable change from an aftermarket manifold is on the mk2 8v.

thank you. my vtr is a mark 2 but guess im just use to it now, cams and remap next hope to see a improvement.

16th February 2012, 23:51

Quote:

Originally Posted by Tom5190

Lol at you trying to own him in some way about back pressure. You knew what he ment he didnt claim to be a genious.

Aftermarket manifold is essential on an engine with any sort of internal work, as other people said on a standard engine the most noticeable change from an aftermarket manifold is on the mk2 8v.

I didn't and I still don't, pipe down.

16th February 2012, 23:54

Quote:

Originally Posted by saxova

To be fair.. I miss my 8v engine. I miss how I could happily be heavy footed and still get 80 miles from 10 litres. My 16v is lucky to see 50 miles from 10 litre's.. with less heavy foot moment's.

And the 8v engine isn't a million miles away from the 16v.

So extra fuel, extra tax, extra insurance cost's, harder to work on engine.. for <20bhp increase... worth it? no.

Without a doubt i'd say I was faster with my 8v engine than my 16v. Whole different power delivery to get used to, and the 16v spins up ALOT easier than the 8v coming out of bends.

same mods on both engines, so the 8v wasn't 'breathed' and the 16v standard.. they both had the same, 4-2-1 / race centre / 3 in backbox / green cotton filter / 1.1 gearbox.

My 2p's worth..

Mines decent on fuel.

Must be something up with yours.

17th February 2012, 00:08

Supersprint would be your best bet. I had one on my MK2 VTR

17th February 2012, 08:37

Quote:

Originally Posted by Prickle

Mines decent on fuel.

Must be something up with yours.

he's not running a lambda. mine is the same

17th February 2012, 09:02

i personally think they are worth it.

felt more responsive than faster. plus they look way better than the standard shit citron used.

17th February 2012, 12:39

Quote:

Originally Posted by Stuart85VTR

Supersprint would be your best bet. I had one on my MK2 VTR

roughly 7-9 bhp gain with the Supersprint

17th February 2012, 14:09

I got a 5 hp increase at the wheels with the raceland 4-2-1. They do make a difference, but like any modt don't expect miracles

18th February 2012, 14:55

Dont get one on a vtr complete waste of money.
I got a raceland 4-2-1 for my 2002 mk2 vtr and as it also acts as a decat yeah it was a tiny tiny bit better top end but was miles slower lower in the rev range which is what i loved the vtr for. So the cat and standard manifold soon went back on.

It does help high in the rev range but will feel slugish my vtr limiter was only 5.5k revs so by the time u got the gain from the new manifold was time change gear.

18th February 2012, 14:57

Quote:

Originally Posted by devilsadvocate

I have a 4-2-1 raceland and I noticed no difference after fitting it to mine.

Car feels the same as it did before...

Could always sell me it and put your standerd one back on

18th February 2012, 15:05

my vts has a piper 4-1 manifold on from the previous owner, is the much of a difference between the 4-1 and 4-2-1?

18th February 2012, 15:33

noticeable difference on my old MK2 VTR, that was a piper 4-1/Decat and it also had Supersprint 2" system and enclosed induction, it made 111bhp on the rollers. It also had a VTS gearbox on and when i was due an upgrade to a VTS i testdrove a one with open cone and manifold and i swear my VTR wasnt much slower.

Never drove a VTS without a aftermarket manifold but would imagine it would still make a difference like.

18th February 2012, 15:51

Back pressure is the thermodynamic resistance of the entire exhaust system that is dictated by the number and magnitude of velocity changes in the system. The less resistance the faster the exhaust gases. This must be carefully dictated to ensure high thermal efficiency as well as the efficiency gained from the increase velocity. This back pressure is also key in producing resonant exhaust pulses. These are pressure waves that are formed from the exhaust gases and the operation of the exhaust valve. This high velocity wave travels down the pipe and at any point in which it reaches a change in velocity (essentially where the pipe gets bigger or smaller, the biggest of these pressure differentials being at the end of the pipe of course) a pressure pulse is sent back down the pipe in the other direction towards the exhaust port again. If the exhaust is designed correctly then these pulses arrive back at the exhaust port just prior to the exhaust valve opening. Hence the reason that all the primaries on an exhaust manifold must be of equal length, so the pulses of each cylinder reach the collector at equally spaced intervals

18th February 2012, 15:53

Quote:

Originally Posted by adamskiTNR

Back pressure is the thermodynamic resistance of the entire exhaust system that is dictated by the number of velocity changes in the system. The less resistance the faster the exhaust gases. This must be carefully dictated to ensure high thermal efficiency. This back pressure is also key in producing resonant exhaust pulses. These are pressure waves that are formed from the exhaust gases and the operation of the exhaust valve. This high velocity wave travels down the pipe and at any point in which it reaches a change in velocity (essentially where the pipe gets bigger or smaller, the biggest of these pressure differentials being at the end of the pipe of course) a pressure pulse is sent back down the pipe in the other direction towards the exhaust port again. If the exhaust is designed correctly then these pulses arrive back at the exhaust port just prior to the exhaust valve opening.

you are the copy and paste hero

18th February 2012, 15:56

Why do you think i copy and paste. I do assignments on similar scenarios on a regular basis and design exhaust systems, running full simulation on them likewise.

18th February 2012, 15:58

My Vtr is a mk2 and i fitted a supersprint 4-2-1 manifold and full system and i noticed a difference. The main difference was that the revs felt much more free and the engine didnt feel as suffocated. I had to refit my old manifold with cat for the mot and it didnt seem to pick up as well throughout the entire rev range. So it made a difference for me

18th February 2012, 15:59

Quote:

Originally Posted by adamskiTNR

Back pressure is the thermodynamic resistance of the entire exhaust system that is dictated by the number of velocity changes in the system. The less resistance the faster the exhaust gases. This must be carefully dictated to ensure high thermal efficiency. This back pressure is also key in producing resonant exhaust pulses. These are pressure waves that are formed from the exhaust gases and the operation of the exhaust valve. This high velocity wave travels down the pipe and at any point in which it reaches a change in velocity (essentially where the pipe gets bigger or smaller, the biggest of these pressure differentials being at the end of the pipe of course) a pressure pulse is sent back down the pipe in the other direction towards the exhaust port again. If the exhaust is designed correctly then these pulses arrive back at the exhaust port just prior to the exhaust valve opening.

Interesting read to be honest

18th February 2012, 16:13

Quote:

Originally Posted by CitroenSport

noticeable difference on my old MK2 VTR, that was a piper 4-1/Decat and it also had Supersprint 2" system and enclosed induction, it made 111bhp on the rollers. It also had a VTS gearbox on and when i was due an upgrade to a VTS i testdrove a one with open cone and manifold and i swear my VTR wasnt much slower.

Never drove a VTS without a aftermarket manifold but would imagine it would still make a difference like.

The vts gearbox is more close ratio, and is a superb upgrade for a vtr. I recommend all vtr owners to get one of these before anything. You will lose top end but you will accelerate quicker. I drove a vtr with vts box on and that was way quicker than my vtr was when it had a 421 Decat and supersprint. Awesome upgrade and not very much either. I'd buy an sbox over a mani anyday.

19th February 2012, 09:58

Backpressure is a byproduct. Its something you dont want but have to live with.
The primary concern for a normally aspirated car is high gas velocity. Faster gas pulses exit the exhaust and clear the engine of unwanted gases as well as helping pull in air and fuel
As gas velocity increases sadly so does backpressure. Too much backpressure will hold back an engine. By choosing the right bore size for the engine power and characteristics you can get the best out the engine.
A town car will use a small bore to improve low down power, but a track car will use a larger bore to optimise the gas flow at the top end. The trick is to find the balance. Go too large and the gas velocity will reduce and create a 'wall' for the gases coming along behind it.

19th February 2012, 10:22

yeh you just need a spacer if u have a standard manifold