Head Mods
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The manifold, cut and shut from maniflow LCB

Edited by mikemph on 12th Mar, 2005.

Somebody's handy with the welder ! Nice job mate.

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Cheers mate, I didn't think it was bad myself

looks good...

it'll be interesting to see how long the turbo lasts for...

keep us posted!

Alex

AlexF

I'm more interested to see how long the manifold lasts!

Seriously, My first manifold to take the T2 was a cut/shut maniflow LCB. It lasted around 2 weeks before the first crack appeared. After that, I started chasing my tail on the new cracks. I'd be inclined to source some really thick steel tubing, or decent grade stainless (302??) and start again!

VNT stuff is pretty interesting though! Fab was trying this some time ago, not sure how far he got mind!

Yeah I will do it from 316 stainless when we get some more in at work, don't fancy paying for it at the moment lol. When work get some in stock its free if you know what I mean.

I have got the use of a mandrel pipe bender so should be nice and easy, and a TIG welder so should be sweet as!!


Just liked the idea of the boost coming on nice and early with still plenty up to top.

Edited by mikemph on 14th Mar, 2005.

Dave's right about the risk of cracking. My mate has made two sets of manifolds to date. The first one was very similar to the one Dave made up. Mild steel using the flanges from an LCB, he was forever welding it, but managed to get 6months or so before he gave up.
His latest design is mounted over the clutch housing and he's using high quality stainless tubing. Even this has cracked but only slightly in one place. Though this was subjected to some extreme heat, often glowing red, caused by some "interesting" boost levels.
I would suggest adding some form of bellows to allow the manifold to expand and contract.

Phil.

Edited by Turbo Phil on 14th Mar, 2005.

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Yeah, bellows like the janspeed one had would be good. I am looking for that at the moment. Think I found something that will do in our stores at work.

I think the cracking may have something to do with the heat and the carbon deposites on the inside of the tube, basically hardening the mild steel with the heat and carbon. Just a theory tho

Its more often one of two things:

Support

Expansion

Steel grows a fair amount with temp, and if you don't allow for this in the design it will crack. The support thing is less obvious but a turbo is a heavy lump to support and is subjected to not only vibration but also accelerations in every direction from the movement of the car itself!

alex

AlexF

Stainless comes in a highly stressed form already so i guess it keeps its shape better.

I wasnt gonna hang the turbo on the end lol, but i know what you saying buddy.

Mild steel does expand alot more than the likes of stainless

Don't get me started about manifolds crackink, had a nightmare with my mates old TVR stainless manifold, we welded it and it cracked somwhere else, etc. Stainless absorbs oxygen when it gets really hot and can set up imperfections which add to the fact it's brittle anyway. Mild steel everytime. I would get it blasted and try some novel ideas about stress relieving. I hate cracking manifolds, everytime you fix one, you should stress relieve it. Honestly, the amount of mucking about I've done with home made exhausts/manifolds is ridiculous.

Bugger off, I'm getting there.

Might have to see, might be able to heat in a oven, have to wait and see wot happens. I didn't have any problems with my last stainless manifold for 1.4K-series but like you say its one of the those things you get with the countinuous expansion contraction cycles, and work hardening.

The latest

have you sandblasted the head?

You had a nice beak in the top picture, why did you remove it..Poor beak, poor squish ;(

beak affects the swirl more surely? Squish is a factor of the squish band generally - keeping the combustion away from the bore walls and towards the centre of the piston?

Either way, it's a line between a nice chamber shape and reasonable boost, or an open chamber and lots of boost. I know which i favour!

lots of bosst ............. yeah

Everyone knows that instructions only have to be read if the thing doesn't work....

Rock on Mr Hybrid turbo!

bling bling ,
rock on tommy ,
to me , to you , to me ..

Everyone knows that instructions only have to be read if the thing doesn't work....

AlexF

Sure?

fairly...

unless my understanding on what squish achieves is wrong... which like anything is possible!

The way I understand it:

Squish is an area trapped between the cylinder head and the piston that DOESN'T form part of the combusion chamber.

So you want the actual volume to be very small to prevent detonation in this area which can be caused by cool cylinder walls, the advancing flame front, and the trapped end gasses.

To make this volume small you run the pistons very close to the cylinder head (ie small clearance) and this pushes most of the end gasses into the main combustion chamber.

The BIG advantage to this is that as the piston comes up the bore the squish area forces the gasses at high speed towards the centre of the combustion chamber... this movement can be used to create swirl... which is a shole subject in itself... but the A-series certainly has very high swirl for a production engine!!

Alex

AlexF

Swirl is when gases are coming into the cylinder from the inlet. Tumble or bounce are similar.

arr yes... I mean turbulance I think...

alex

AlexF

Yeah not too worried about the sqish so much.


Anyway pretty much finshed now, check out the ports let me know your thoughts on it as it is.


Exhaust port