S2/968 Exhaust manifolds/headers RHD

[Tam Lin]

Looking for the next demon tweak for the car. Primarily, the reason is "heat management", as with a lot of glass fibre up front, my engine bay gets seriously warm. So ceramic coated manifolds they need to be. If they make the engine sound less anaemic, even better. If they add 0.001 BHP at RPMs I never reach, well, that would be the icing on the cake.

Sooo..Does anyone have fitted/has (had) made/has seen right hand drive 968 or 944 S2 exhaust manifolds, ideally equal length, without silly tight corners, made from something better than scaffolding?

 

[Jonny944CS]

Not too sure about your options for an S2/968. I thought the standard manifolds were pretty efficient..., no?

My experience, so far, concerning coatings:
Whilst rebuilding my 2.5 8v, I decided to swap the early type cast iron manifolds (8kg+) for the later fabricated tubular steel type (~4kg).
For the same reasons as you mention, I also decided to have a ceramic coating applied by a local company. After several thousand miles and three track days, the verdict is certainly good in terms of reduced stand-off temperatures; however I seem to be encountering some issues"¦

It may be an issue specific to my car, but I have been struggling to get a good seal at both the head->manifold and manifold->down pipe flanges.
Having inspected the manifold it seems the flanges are warping when hot, causing the gaskets to fail. I spent a long morning sanding them flat, only to find they warped again "" although not quite to the same degree.

I am starting to wonder if the thermal barrier is creating a larger temperature gradient across the mounting flanges, causing warping to occur.

 

[Alexw]

I've been looking at this recently, there are several in the US that make a few extra bhp each:
Stahl
Racers Edge, which I THINK are Stahl anyway
and SFR if you really don't like your wallet.

To get the best out of it I'm pretty sure you would need a rolling road remap though. The racers edge ones appeal to me the most, although I have no idea on the price direct from Stahl, I've never bothered to contact them. You could probably order them with some sort of coating or get it done in this country. Try some local exhaust places, I got a quote of ~£700 for a manifold at a place a few miles from me.

 

[Alexw]

BUMP, Has no one else go anything to say on this?

 

[Big Dave]

Yes,
Save your money....
And get the car live mapped .

 

[Tam Lin]

ORIGINAL: Big Dave

Yes,
Save your money....
And get the car live mapped .

Well, yes, the point in my case of getting a MAF and piggy back was to make live mapping easier..however chucking on a manifold before live mapping sort of seems to make sense to me, as scavenging will affect the amount of advance that can be dialled in.

I am not 100% on this, but I think the SFR does NOT fit a RH car, world please correct me if I'm wrong. At least they didn't think it would when I called them in the States. The LHD doesn't have a steering linkage exactly where one of the pipes wants to go..

Any input, or even better, experience welcome.

 

[nick_968]

ORIGINAL: Tam Lin

ORIGINAL: Big Dave

Yes,
Save your money....
And get the car live mapped .

Well, yes, the point in my case of getting a MAF and piggy back was to make live mapping easier..however chucking on a manifold before live mapping sort of seems to make sense to me, as scavenging will affect the amount of advance that can be dialled in.

I am not 100% on this, but I think the SFR does NOT fit a RH car, world please correct me if I'm wrong. At least they didn't think it would when I called them in the States. The LHD doesn't have a steering linkage exactly where one of the pipes wants to go..

Any input, or even better, experience welcome.

Scavenging may well improve it. But how do you know the manifold you are buying scavenges better or worse than the one Porsche designed for your car with many hours of testing? None of the after market manifolds have been back to back tested on an independant dyno to my knowledge so you are probably better off just flushing your money down the toilet on an NA car. SFR headers definately do not fit a RHD car either, they will hit the steering column. You do not need a piggyback or a MAF to map your car, just someone who knows what they are doing.

 

[Tam Lin]

ORIGINAL: nick_968
1) But how do you know the manifold you are buying scavenges better or worse than the one Porsche designed for your car with many hours of testing?

2) You do not need a piggyback or a MAF to map your car, just someone who knows what they are doing.

1) Well yes, hence I was looking if anyone who had actually changed the manifold to after market, and what their experiences were. From my TVR days, where the Cerbera needed manifolds as the quality items TVR designed for my car with many hours of testing had fallen apart, we learned that ceramic coating anything except new manifolds is a waste of time. I suppose I could get new Porsche manifolds coated, but that doesn't seem to be in the spirit of adventure..plus there is fairly well documented evidence on rennlist that 928s respond well to a changed manifold design, and 1/2 a 928 32v is not that dissimilar to the S2/968 family of engines.
2) Agreed. And I'll probably be visiting Mr Schofield at some point, who, I understand, is reputed to know what he's doing. However until then, a bit of tinkering and a few runs on my reference rolling road help pass the time []

 

[944 man]

Id add that careful wrapping will always help gas flow, whether the manifold has been ceramic coated or not.

 

[Hilux]

it seems the flanges are warping when hot

They will if Ceram coated internally as the flange moves more than the headers when hot and will need webbing to keep square

Big Dave and 944man are right...................

I`d wrap them instead as Ceram coatings do not adhere to old manifolds internally even when cleaned (how do you know they are clean) believe me.

The originals are pretty good anyway so I`d expect a better result from a good chip`n tune and heat wrap.

 

[JamesO]

Would a 968 inlet manifold and throttle body help with your power chasing? It bolts right up to the S2 head.

 

[Alexw]

JamesO: Pretty sure they are the same parts tbh

How does wrapping help with gas flow? Never even considered that, even though I have some on a shelf in the garage.

 

[Hilux]

ORIGINAL: Alexw

JamesO: Pretty sure they are the same parts tbh

How does wrapping help with gas flow?  Never even considered that, even though I have some on a shelf in the garage.

Helps contain the heat (and thereby aids the designed pulsing)

 

[DivineE]

ORIGINAL: Tam Lin

ORIGINAL: nick_968
1) But how do you know the manifold you are buying scavenges better or worse than the one Porsche designed for your car with many hours of testing?

1) there is fairly well documented evidence on rennlist that 928s respond well to a changed manifold design, and 1/2 a 928 32v is not that dissimilar to the S2/968 family of engines.

Just to add my 10penith in on this discussion. When I was asked to look into the benefits of a new exhaust manifold for a project 944 turbo I sat with a wise engineer and a book on turbo tuning and exhaust design looking at the measurements, lengths you'd want. What diameters you'd need at the various points and whether it would be beneficial to change from a 4-2-1 to a 4-1 system. The book and the engineer both agreed with each other and the measurements and design for using the standard exhaust for a 2.5 was slap bang in the middle of the sweet spot.

The exhaust design requirements for a turbo are different from an N/A car and according to the book it is suggested through testing but not stated as a fact that a 4-1 equal length design is less well suited to turbo applications.

Adding the advice of two turbo guru's to the discussion the only possible areas for improvement that came up were

1. The exit pipe for the wastegate that comes off at the wrong angle on the 944, it creates a V shape rather than following the direction of flow, and encourages boost spikes (making it harder to control boost accurately).

2. The theory (disputed somewhere else on this forum) that putting the turbo on the other side of the engine and so much closer to the cylinders would encourage faster spool up.

If I were you I'd concentrate on the restrictive sections of exhaust after the turbo especially the downpipe from the turbo and just heat wrap the standard manifolds.

Edited to add: when I was doing this research it wasn't even my money I was spending and I had freedom of thought to 'suggest' any design I thought best so cost/difficulty weren't even factors.

 

[sawood12]

This is a typical example of what engineering is all about - there is no one solution that will tick all the boxes so you have to make compromises here and there to achieve what you want, and even then you often can't achieve 100% of what you want. You make a change to the manifold to achieve one desired characteristic (e.g. improved spool up or power at high revs will all come at the expense of other aspects) and it will be at the expense of others. Therefore before you spend any money at all you need to be clear what it is you want to achieve.

Porsche designed the manifolds with a very specific requirement in mind. And for that purpose they cannot be improved upon. If you take your car racing for example, then clearly the original manifolds wont be right for the task.

You need to approach this from the right angle. Reading books and talking to experts is all well and good to understand how specific design characteristics affect things, but you need to be clear about what you want to achieve to end up with a manifold that is going to give you what you want. Then you can start burning money! because although empirical engineering theory is correct - making it work in the real world is often not as easy as translating an on paper design to a real part, and requires many prototypes and much testing to verify you are getting what you designed for - that is what testing is for and even though car manufacturers know how to make engines they still need to test them. And don't expect too much from changing one aspect of the car. A manifold on its own is not going to give you much - in fact it might even provide a detrimental change initially. You then need to start modifying other areas of the engine to compliment the manifold to really unlock the benefits.

 

[944 man]

More guerrilla posting: if you re-site the turbo then thats the time to ditch the 1970s tractor turbo and move into the 1990s, or maybe even the 2000s... The original turbo is so desperately out of date now, that if I was having to fabricate a new downpipe, then Id certainly be looking at something that didnt have the spooling characteristics of the SS Great Britains turbine! A modern (not a twin-scroll, and without tricky vanes) turbocharger should spool / reach peak pressure far sooner and be able to generate substantially greater boost. It should also be substantially cheaper. A Mitsubishi TD04 (for up to 300bhp) or a TD05 (for more) would be more than adequate, cost relatively little and be far more durable. A TD06 monster with an external wastegate could flow enough air to generate 500+bhp and itd still make nasty American 944 turbo replacements look expensive!

 

[nick_968]

ORIGINAL: DivineE

ORIGINAL: Tam Lin

ORIGINAL: nick_968
1) But how do you know the manifold you are buying scavenges better or worse than the one Porsche designed for your car with many hours of testing?

1) there is fairly well documented evidence on rennlist that 928s respond well to a changed manifold design, and 1/2 a 928 32v is not that dissimilar to the S2/968 family of engines.

If I were you I'd concentrate on the restrictive sections of exhaust after the turbo especially the downpipe from the turbo and just heat wrap the standard manifolds.

Edited to add: when I was doing this research it wasn't even my money I was spending and I had freedom of thought to 'suggest' any design I thought best so cost/difficulty weren't even factors.

I think the original question relates to an NA engine not a turbo setup....

 

[nick_968]

ORIGINAL: Tam Lin

ORIGINAL: nick_968
1) But how do you know the manifold you are buying scavenges better or worse than the one Porsche designed for your car with many hours of testing?

2) You do not need a piggyback or a MAF to map your car, just someone who knows what they are doing.

1) Well yes, hence I was looking if anyone who had actually changed the manifold to after market, and what their experiences were. From my TVR days, where the Cerbera needed manifolds as the quality items TVR designed for my car with many hours of testing had fallen apart, we learned that ceramic coating anything except new manifolds is a waste of time. I suppose I could get new Porsche manifolds coated, but that doesn't seem to be in the spirit of adventure..plus there is fairly well documented evidence on rennlist that 928s respond well to a changed manifold design, and 1/2 a 928 32v is not that dissimilar to the S2/968 family of engines.
2) Agreed. And I'll probably be visiting Mr Schofield at some point, who, I understand, is reputed to know what he's doing. However until then, a bit of tinkering and a few runs on my reference rolling road help pass the time []

Re the 928 manifold success, is someone actually making a similar and proven product for the 3.0 NA engine? As others have pointed out buying untested products (as most of them are) puts you in the position of being someone elses free R&D testbed! This can be an expensive and frustrating road to go down....also with a 3.0 NA the upside will be limited as to get the best you need to tune the intake, head/cams & manifold as one. Tuning NA engines is much more of an artform than boosted engines.

 

[DivineE]

Oh well in that case is it worth worrying about? Surely limitations from the exhaust would be non existent and gains would be marginal. Better to concentrate your efforts on removing the barn door sensor into the engine and getting the most out of what you already have?

 

[Alexw]

Well the racers edge website claims gains and I've read the same about Stahl on Rennlist. Depends if someone has the money to put one on then get a live remap. Or better yet, one before, one after []