Optimum Exhaust Manifold
Turbo Mini Forums

Before I start cutting and welding a manifold I would like to ask a few questions to the people who know.
This if for a 998 turbo hill climb car and I need to mount the turbo over the clutch housing and I am prepared to put up with an awkward installation if there is some improvement to be had.
1) is there any benefit to be had by keeping the proportions of the LCB manifold as used in N/A motors?

2) will 2mm wall thickness steel tubing get the job done? I cant weld stainless and prefer to use steel initially.

3) Any words of wisdom regarding mounting the turbo in respect of expansion rates?

4)I am told that tubos like pulsed exhaust flow into the housing so would there be any advantage in joining the three collector pipes at the turbo flange or would it be better to join them earlier?

5) I have looked back through earlier posts and have seen, what on the face of it, look like really bad set up's in terms of flow but they have obviously produced excellent results so I am missing something here? Is it less important on a turbo installation?

Thanks in advance for any comments and help
Regards
Dave

The only reason that I would be doing this is if my mini was left hand drive. I find it very difficult to get equal corner weights across the front on my hillclimber. And sticking the turbo high up and on the off side would make it even worse IMO.

Sorry that this dosen't really answer your questions, but I thought that it was worth mentioning.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Will, Take your point.
If it was for circuit use I would agree entirely but for the hills I think I would prefer more BHP and accept a few Kilo's mismatch in corner weights.
Matter of opinion I suppose.
Regards
Dave

stick an a fat passenger LOL

There's only so much power you can put down on the tarmac, this is limited by corner weights.

I would of thought twisty, slower corners would need better corner weights to get traction out of them (even with low-ish power) than anything else.

Don't you want to fit a bulkhead box?

Garrett recomendations:

"General design tips for best overall performance are to:

Maximize the radius of the bends that make up the exhaust primaries to maintain pulse energy

Make the exhaust primaries equal length to balance exhaust reversion across all cylinders

Avoid rapid area changes to maintain pulse energy to the turbine

At the collector, introduce flow from all runners at a narrow angle to minimize "turning" of the flow in the collector

For better boost response, minimize the exhaust volume between the exhaust ports and the turbine inlet

For best power, tuned primary lengths can be used"

If you can tick all of the above boxes, you are doing well.

I think the only one that would be difficult to achieve with the turbo over the clutch is "minimise the exhaust volume".

Reality is that although the Mirage setup breaks most of the above rules, it has been proven to work well.

Material wise, I seem to recall TD recommending the use of 321 stainless and to forget anything else.

Edited by Paul S on 31st Jan, 2007.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Maybe so Iain
Yes i fitted a bulkhead box when I did the shell (just in case) as I was doing a 1380N/A at that time.
I am doing the 998 as a project just for the technical challenge of it. Which is why I don't want to buy all the bolt on bits.
I want to try something different to see if I can.
It may all end in tears who knows
Sorry about the quality of the picture it was taken some time ago and was for reference only not to use on the net.
Regards
Dave

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Axel Thank you,
Great information.
As this will be a DIY effort I will have to use steel for the pipes as it's easier for me to do. If it works then it will be stainless.
Any wise words on mounting the turbo and supporting the manifold?
Regards
Dave

You could always make your own manifold but keep it central?

Make it for something like a T2 sized turbo. (but a more modern turbo as these are much more suited!)

Similar to mirage manifolds but you have a lot more room with the bulkead box.

If its for the challenge though then fair play

I'm planning on my next turbo being higher on a 16v head in the weber bulkead box area as the inlet is at the front. Red hot turbo just under the bonnet will be fun!

The plan for my bros 998 turbo hillclimber is to mount the turbo over the flywheel by using the metro manifold with an extention on it. The extention will use a bit of 'flexi-hose' in it to reduce any expansion problems.

The current 998 turbo hillclimber has a standard netro turbo manifold set-up (and that's the way its staying).

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

If you are looking for a technical challenge, why not try Assymetric turbocharging.

If you use a turbo that actually only needs half the exhaust gases to drive it, as I think most of them do, such as a GT1752 on a 1275, then you would only need to connect the exhaust from the centre port to the turbo.

Not sure of the effect of two cylinders seeing higher exhaust pressure than the others but the piping is so simple.

I think that a couple of guys on here are thinking about this, but are keeping it under their hats at the moment.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Axel, The assymetric thing looks interesting but it's not for me. Initial thoughts are it might be good for road use but anything more would MAYBE give detonation problems on the two cylinders driving the turbo due to the greater amount of exhaust residuals if the turbo is driven hard.
I have a fairly clear idea of what I want to do but I am a little reluctant to go on about it on here as I don't want to sound like the guy on Minifinity who carried his mini engine for 40 miles because someone else had carried theirs for 5 miles.
I am very grateful for all the help from this forum and all I can say is that as I pogress anything of interest I will post up for others.
Regards
Dave

Think you'll find everyone on here more than willing to help out

Most peoples reasearch is via testing so its always good to see different alternatives.

Idea's are there to be bounced around with good and bad input

On such a small engine, I dont think there would be enough energy to spin even a small blower, to make it worthwhile ??

Saab did something similar with a V6 a few years ago though

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will