Exhaust manifold design

[Uberderv]

There is nowt I like more than a turbo sitting over the gearbox. A. Cos it looks fantastic B. Cos if you want to swap it, work on it or modify it etc... its alot easier than the standard position.

Equal length manifolds are great and obviously the best but I think for the Dw10/Xud a log manifold with a side exit would still yeild great results. So after many hours using CAD software I've drawn this up -

Anyone tried such a manifold?

[306Dan]

A common one ive seen is taking the standard manifold and making a pipe that comes of the flange to relocate the turbo on the gearbox.

[Danny2009]

as above, make a plate that bolts onto the standard manifold, weld a pipe to that fetch it to battery area weld a plate onto that end and bolt your turbo to it job done

[Niall]

Moved this to the correct section.
As said above, it will be much cheaper and easier for you to just make a pipe up to go over to the battery which bolts onto the original manifold.

[Uberderv]

I've seen that before too but the above design could be made quite cheap/easy and would probably work quite a bit better than the extension pipe method. Just thinking of making the best solution at a reasonable cost.

If made from SCH40 mild steel pipe it would make the Id 35mm which is perfect for a HDI manifold. I made a manifold years ago and the flange was the most expensive part, group buying could bring that reet down though.

[Piggy]

That design wouldnt be all that great

Check out Steedspeed

[Jenkosowls]

You made that on cad? Sure it wasn't ms paint?

The ease and cost of the original manifold extension that few people have done, out weighs the cost of makin a new manifold as you've designed laser cutting, material cost, welding, development soon not as easy as you'd think.

[Rippthrough]

If you're going to the expense of having a manifold plate made you may as well just make a proper manifold.

[Paul_13]

SCH40?! Blimey we're using that on steam pipework at work!
SCH20 would be more than adequate

[Tom]

Lol i hope you didnt pay for that software!

[londondan86]

Good cad work there, I may pay you to design my rods where the tolerances are less important! :Lol:

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But as above, don't bother mate. Get an extension pipe, proper manifold or leave the turbo down the back

[C2K]

Glad to see you all missed his Sarcasm. Guess it really is dying.

Lol at sched 40, your manifold would weigh a crazy amount.

[Piggy]

^^^^I know! He was only being funny about his cad
Now I see how my sarcasm falls flat

[Ruan]

There's guys out there making 1200hp+ on log Manifolds... There's not much point IMHO in going for equal length and I just never trust tubular Manifolds, they always crack unless you spend an insane amount of money on them...

As piggy said, check out SteedSpeed - that's the sort of idea I'd be going for, two halves of machined steel and then just welded together, no issues with cracking, strong, you know what the internals look like... Perfect, there's people making insane amounts of power with them and they aren't massively expensive and with some work you could design one yourself, no point in worrying about primary lengths, the cam profile of a diesel and the fact they don't spin that fast means that it has little effect, especially on the exhaust side..

That's my opinion anyway...

[Piggy]

And we all know that Ruans opinion isnt worth much.....

[Uberderv]

I am open to generate any CAD drawings like the manifold

I would use 1.25" sch40 pipe only because I had to buy 6m of the bloody stuff last time, it would be heavyish but not alot more than the cast items already fitted.

I know there are far better designs out there but this seems like a good compromise between original mani with extension and custom equal length etc.....

The Steedspeed manifolds look great and if you had access to a CNC you could design one for our engines. Im just looking at this from a DIY point of view and what tools I have in the garage. A tuner made 250hp using the original manifold but I bet the EMP was through the roof.

[zx_volcane]

There's guys out there making 1200hp+ on log Manifolds... There's not much point IMHO in going for equal length and I just never trust tubular Manifolds, they always crack unless you spend an insane amount of money on them...

As piggy said, check out SteedSpeed - that's the sort of idea I'd be going for, two halves of machined steel and then just welded together, no issues with cracking, strong, you know what the internals look like... Perfect, there's people making insane amounts of power with them and they aren't massively expensive and with some work you could design one yourself, no point in worrying about primary lengths, the cam profile of a diesel and the fact they don't spin that fast means that it has little effect, especially on the exhaust side..

That's my opinion anyway...

Have been discussing this with Paul for my next turbo, prob going for a log manifold if he can knock one up

Know all too well about cracking though, my current gearbox manifold has cracked twice which is annoying, but its under all sorts of heat cycle and vibration stress.

But for something you can do in your garage with a welder and some scraps of metal its a great way to go.

CNC machined mani looks amazing, its just getting access to the tech or having know how to design one and knowing someone that would put it on their machine for cheap rather than having to pay a company setup just for one run.

[Uberderv]

Would you go for the side exit design? You can get directional tee joints, lateral tees I think there called. 3 of them, a long radius 90 and the flange and your sorted. I would shotblast the inside once its welded or acid dip it. Out of interest where is your manifold cracking and have you got pics of it?

[darrenjlobb]

A log manifold will more more than surfice for just about any application on cars like these.

However you cant beat the noise a properly designed stinless tube equal length manifold produces..makes the engine sound much more in tune when its on song, its something you cant do without once you have had imo.

As for cracking...the only time ive ever had issues is when things arnt supported correctly / welded to close and heat has no where to go expantion wise.

My manifold i have now has caused no issues at all.

But a simple log manifold up the side of the block will quite happily flow all you need for mega hp all day long, the head will become a restriction along time before the manifold!

[Rippthrough]

There's guys out there making 1200hp+ on log Manifolds...

And they'd probably make it with less boost on a decent tubular manifold

And who the hell CNC machines a manifold? Even F1 manifolds are welded by an old bloke in a shed out of tube...

[Piggy]

Tubular manis that actually do anything would need to tuned to match and for an XUD which doesnt really rev high enough isnt really worth it...plus it costs a LOT of money.
Plus when you consider what bhp those big diesels get on those manifolds, IE about 175bhp per litre, I wouldnt argue with their methods

[Kezzieboy]

Yeah, t'is lovely inconel tube though! I assume he means CNC mandrel bending, which is how I'm getting an exhaust for a formula student done, the joys of peddling for sponsorship means we only pay cost price though.

[Rippthrough]

Tubular manis that actually do anything would need to tuned to match and for an XUD which doesnt really rev high enough isnt really worth it...plus it costs a LOT of money.
Plus when you consider what bhp those big diesels get on those manifolds, IE about 175bhp per litre, I wouldnt argue with their methods

The whole point of a pulse tuned manifold is that it's tuned to the correct RPM range.
A rotary bent manifold will give you everything bar the last nth percent as compared to a mandrel bent, you usually only need to use mandrel bent stuff when your struggling for packaging.
175bhp per litre from a big turbo....so basically bog standard Evo power then.....

[Martin306]

I've got an NA petrol engine that does 172hp/litre

It's only 10cc though

A log mani would sound epic, just because it's not in tune doesn't mean it won't be entertaining to listen to!

[Ruan]

I've not got much to go off here, but what I can refer to is current "High Performance" diesel manifolds...

Mazda Skyactiv-D



It's not going to crack at least...

450hp ish 2.2l diesel.

[Rippthrough]

908 diesel....



R10 diesel:



R15 diesel:



R18.....




Spotting a trend yet?

[Ruan]

Yes, on incredibly expensive, high performance applications where longevity isn't so much of a concern... Tubular manifolds are better, but in the real world, where cost, longevity and packaging is a concern... Log style manifolds are preferred...

I'm saying log manifolds are still a viable option, not that they're better... You don't HAVE to have a tubular, yes it's preferable, but it's not the be-all and end-all of manifold design...

IMHO anyway.

[Piggy]

Yeah if you wana spend 10k on making a one off racing mani for your xud....then carry on

[Rippthrough]

The most expensive/time consuming bit of DIY'ing a manifold is making the flange, the bit after that is easy, so why wouldn't you just make a tuned tubular if you're making one anyway?

[Piggy]

And fyi:
R15 Audi v10 makes 107bhp per litre vs the mazda 2.2 making over 200bhp per litre on a 'rubbish' manifold

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The flange is the easy bit