Exhaust Manifolds Compared - Saxo

[dobboy 231 2 Cars]

 

Above is a pic of two exh manifolds i have for my Saxo VTS.

 

My car had the bigger looking one on it, but i felt where it sat where it met the system was quite low to the road and it also obstructed/fouled me fitting my lower strut brace.

 

The smaller one is looks to be cheaper made but ok.

 

Few Q's

Do you think the bottom bend/four pipes of the good/big mani could be absolutely roasted with gas gear to allow the bend to be tightened up, to lift the flange up to a height similar to other one?

 

Would there be noticeable different outcomes on the performance characteristics between them, due to the different designs/pipe lengths?

 

(The smaller one (Raceland) has a few PITA fitting issues at the head, as one stud has to be chopped due to the tight bends, and also not all nuts can be got from the top, the alternator needs to be slackened off to get into one nut, etc etc)

 

Whereas the bigger one is very straight forward.

 

TIA

[welshpug 1,621]

wtf is going on with the platea welded to the manifold?

 

What brand is that one?

 

the raceland is very good for the price, work well on a standard engine.

[dobboy 231 2 Cars]

Not sure WP. They were on it when i got it, and thought it came like that. I think it's a Piper or Janspeed but not sure.

 

It is a far better manufacured mani compared to the Raceland one. The raceland one's pipes bend far too early when it leaves the flange/head, making it a pain to fit.

[dobboy 231 2 Cars]

Anyone, could the bends on the manifold (on the left) be roasted to tighten them up? (and lift the exhaust mating flange up off the road a bit)

 

TIA

[welshpug 1,621]

I would start by cutting off the plate, the manifold should bolt to the gearbox near the sump

[dobboy 231 2 Cars]

To see if there is anything untoward with the pipes under the plates?

 

Yeah, i'll need to make up a little hanger bracket for the mount you mention no matter what one I use, both are broken.

[dobboy 231 2 Cars]

Somebody

 

Could the pipes be bent with plenty of heat? or would it be asking too much as it's 4 pipes that would need to be bent together?

[dobboy 231 2 Cars]

Right, today i got the heat on. I never got it to bend much if any but i think it will be possible with another gas torch and another pair of hands. The pipes seem to be cooling down too much as it's impossible to keep the 4 pipes glowing at the same time.

 

Will be having another go at it.

[welshpug 1,621]

did you remove the plate?

[dobboy 231 2 Cars]

did you remove the plate?

Nope. Frightened of what i might find!

 

It looks to be leak free the way it is and i don'thave a welder if something needs attended to underneath it.

Edited January 31, 2016 by dobboy

[stebbs 5]

One is a 4 into 1 the other is a 4 into 2 into 1. The 4-2-1 is much better for drivability and torque whereas the 4-1 is much better high up the revs. I preferred the 4-2-1 after my 4-1 got squashed to death in multi story carpark.

[dobboy 231 2 Cars]

So for a track based car the 4-1 is the one i should be using?

[jamie_1992 66 1 Cars]

the bigger 4-1 looks home made (and badly at that) id use the 4-2-1

[stebbs 5]

For high revs the 4-1 is better yes but the mid range torque offered by the 4-2-1 helps.

[dobboy 231 2 Cars]

For high revs the 4-1 is better yes but the mid range torque offered by the 4-2-1 helps.

 

I've decided/been convinced to go with the Raceland mani. I got a m12 washer welded on to the broken bracket last night which should allow it to be fixed underneath at the Gbox.

 

I notice a lot of the 106/VTS'rs with these mani's heat wrap them, but the opinion is mixed whether or not it actually does anything.

 

Did you do yours? if so did you think it made any difference?

[Batfink 201]

So for a track based car the 4-1 is the one i should be using?

The text books say that but when both are not optimised for power and torque its the best you can get when the manifold has to stop at a certain place, the 4-2-1 will make similar power. In fact the Supersprint 4-2-1 makes the most power on these engines from what i've seen. (bar a complete custom race job)

Most common damage on the saxo manifolds is from bottoming out on the road and flattening the tube.

[dobboy 231 2 Cars]

Thanks.

 

Last night I fitted the Raceland one (4-2-1), I got the mounting hole fixed the night before, by welding a washer on to it.

 

I must have been 3/4hr trying to tighten one of the nuts.... 1/8th turn, turn the spanner, 1/8th turn, turn the spanner......

 

Crap design.... there is no need for the pipes to turn so quick as they leave the head/flange. In fact one of the studs has to be cut down, and if you don't start all the nuts before bringing it into the head you wouldn't be able to get them all on.

 

But it's on now and fits nice under the car, and should allow me to fit my lower strut brace no probs.

 

cheers all.

[welshpug 1,621]

I think they were made to give as much clearance as possible, they fit in a s1 106 which is shorter.

[dobboy 231 2 Cars]

I see WP, but if you look at the pics above, the end pipe on the photo is heading down as it leaves the flange, and that isn't the worst pipe, the far OS pipe is the difficult one..... some of them you can't get a ring key on too, as the studs are that close to the pipes, (and as I said one of the studs has to be chopped.)

 

Whereas, on the other mani, everything can be tightened from the top using a knuckle/bar/ratchet.

 

I maybe should have heat wrapped whilst it was off as all the 106/VTS'r seem to, but hey ho If I want to duct cold air up to my induction kit in I can, or take the front off the car to make wrapping easier.

[welshpug 1,621]

I would not wrap them, you wont see a proper car with them wrapped

[dobboy 231 2 Cars]

found this on the GMC website

 

 

"Exhaust Manifolds

 

Regarding manifolds many things are said about the merits of 4-2-1 as compared to 4-1 as to the performance properties each has. The basic facts are that a 4-2-1 will give more low down power at the expense of a bit of top end and the 4-1 is the opposite, slightly less bottom end but more top. The problem for someone choosing which manifold to buy are not as simple as this, as the above comments are based on the manifold being built to set physics principals, that do not change, no matter who has built it.

 

The principals are too complex to go into fully, so below are the basics.

 

When you burn the fuel and it escapes from the exhaust valve is has a pressure wave, this wave has energy and it can be harnessed to suck more gas than normal from the cylinder, this is the reason for performance manifolds. These waves have a natural harmonics and pulses and you have to get these right to make them do their job. To their job the exhaust pipe diameter has to be correct and more importantly the length of the pipes between joints. To be correct, the length of the exhaust manifold before the gasses from the 4 cylinders come together should be about 32 to 34 inches from the head flange, assuming it is a 4-1 manifold. If it is a 4-2-1 manifold the first 2 pipes should join at between 16 to 17 inches, this is called the primary length, the next 2, the secondary pipes are the same length. The distance to the first silencer or Cat, should be the same distance away from the place the pipes all join. So why are these distances so critical? The pulses of gas move down the pipe until there is a junction and then reverberate back up to the back of the valve, if these lengths are correct the wave pattern exerts a suction behind the valve head. If these lengths are wrong the pressure wave gets distorted and so looses it’s suction power and in some cases it can actually be worse than the standard manifold, as the waves clash against each other ruling out any suction and even providing positive pressure to hold the gas in the cylinder.

 

I know many will say, how is this possible, the standard manifold is not anything like the lengths you have quoted. Yes, quite true, here comes a bit of the technical stuff again. The harmonics of the gas and pipe lengths are to do with multiples and divisions of these lengths stated. Lets take 32 inches as the correct length. If you made a manifold that the 4 pipes joined at 64 inches, no problem, if you made one that they joined at 16 or 8 no problem. If the first silencer was 8 or 16 or 32 or 64 inches from where the 4 pipes join together, no problem. Therefore the standard exhaust manifold will have been designed by the manufacturers to coincide with one of these lengths, even though it does look crap.

 

OK, so where is the problem. The problem is that a lot of exhaust manifold manufacturers do not follow these rules often due to space limitations under the bonnet or for ease of manufacture due to complicated bends and junctions, this being particularly applicable to 4-2-1 units.

 

So yes on paper a 4-2-1 should give you more bottom end power but if it is not built to the correct lengths it will not and may even be worse than the standard one. A particular car that was built that no one could really improve on the standard manifold was the 205 MI16. It was made of course cast iron but was worked perfectly. One reason I am mentioning all this is that some people were contacting us saying a manifold was available for the Saxo that was stainless steel and cheaper than our mild steel one. I rang the company up to ask details and, yes they could supply it cheaper but only if I bought 10 at one time, so the price problem disappeared. I then went on to ask technical specification as it was a 4-2-1, when given the dimensions of the lengths of pipes, I had to laugh, there was no way this manifold could work."

[jackherer 543]

"A particular car that was built that no one could really improve on the standard manifold was the 205 MI16. It was made of course cast iron but was worked perfectly."

That is incorrect on so many different levels I don't even know where to start.

[welshpug 1,621]

that website would not be my first choice for reading.

 

there are worse though!

[Reebmit 51 4 Cars]

wtf is going on with the platea welded to the manifold?.

Straight to the point Mei, I had to chuckle....