Turbo Support

Just remembered something I've been meaning to ask for ages. How come Escort and Sierra Cosworth engines have a support bracket for the turbo? Nearly every other turbo engine I've seen doesn't have supports.

Is it because the Cosworth manifold is particularly long and prone to flex or something?

Just thinking about rigging something similar up for mine as I'm starting to wonder if I have support issues, having cracked 2 manifolds now.

An example of what I mean.....

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I can see why you would want a bracket, but, with the thermal expansion and contaction of the exhaust manifold, you could end up putting it under more stress.

Basically I haven't a clue.

The support they made up for that turbo looked a bit odd by the time they'd tied it all together.

Toad wrote:Basically I haven't a clue.

I know what you mean though. I think support is necessary where the turbo is quite a long way from the engine and liable to cause flexing in the manifold. My ATP manifold is a stumpy little thing, as are quite a lot of modern engines' manifolds now I think of it, so I think I just answered my own question

Kev,
The old RS-500 cosworths used a turbo damper 'cos there was a possibility that the exhaust mani. studs could snap or work loose and apparently at certain rpm's there was a kind of resonance created that caused a simuler problem,you also had to from time to time re-build the damper.
The old Alfa 2.0 75 turbo also had that same bracket on a T3,i'm also using that bracket up side down on my newly aquired T4 in order to hold the wastegate penny shut along with steel wire.

When you brace a turbo to the cylinderhead/engine/rocker cover you create a situation where as the manifold heats up it has nowhere to expand, putting it under phenomenal stress making it prone to crack. In the same token if you have a turbo hanging of a manifold and not got a proper flexi in the downpipe the manifold ends up supporting the full weight of the turbo and exhaust system again making it prone to crack.

Long and short of it it's ot whether a manifold will crack but as to when it will crack.

When we designed this manifold it was designed with thermal expansion in mind creating a slip joint between the collector and the runners. Allowing a very heavy turbo to be bolted down to the head. All of the mani is made from cast stainless 4mm thick but again it is a matter of when not whether it will crack.

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That is 1 big bastid of an exhaust,must be 4inch at least?.
Come on JNL,spill the beans,what's it goin into?.
How much $ for a corrado 16vt manifold built like that?.
That's 1 nice piece of work mate.

Thanks for the explanations JNL and Veedubbed. Think I'll leave the bracing then!

That is one very nice peice of work JNL!!

I think if you take the precautions to avoid cracking, it should take longer to crack than it normally otherwise would, great work!

VEEDUBBED wrote:That is 1 big bastid of an exhaust,must be 4inch at least?.
Come on JNL,spill the beans,what's it goin into?.
How much $ for a corrado 16vt manifold built like that?.
That's 1 nice piece of work mate.

Just finishing of the wastegate take of from the collector today so will upload another pic. Exhaust is indeed 4". Straight thru with single muffler side exit. As seen here.

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As for making another one wouldn't even contemplate it. The collector was custom made in the US and together with all the bends straights and flanges the material costs came to £1200 incl welding gas and consumables for just the manifold. + On and of labour over 2 months 1 evening a week and a couple of saturdays. Only reason we made it ourselves (owner of the car helped grind all the insides smooth and made all the cuts) was because there was nothing else on the market that flowed enough to support the headwork. We got qouted from £2000-3000 with no gaurantee it would flow enough so thought bugger it make one ourselves checking it on the flow bench as we went along by bolting it to the prototype head and see f it dropped flow at any point. Fortunatelly it didn't as it couldn't have fitted any other way.

As for what it's going in the car will be out some time mid this year.

Kev, I could just pop into Geoff Goddard's office on Monday and ask him why he used a bracket on the YBs if you like. He is one of my lecturers after all.

Jon thats awsome.....

JP thats awesome.....

He's not in today, so I've fired off an internal email to him.

JNL, does the downpipe have a reducer in it to drop it to the right size for the turbine, or am I seeing things?

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If so, wouldn't that hurt gas flow rate through the exhaust, as it's a kind of bottleneck?

Yes the reducer is 4" to 3"

As for bottleneck, No. Remember the outlet on the turbo is 3" so by expanding to 4" all you are doing is offering sudden expansion to help reduce back pressure much like you get on a 2 stroke exhaust. This helps pull away gasses from the turbo quickly and allow for smoother spool up and less spool loss inbetween gearchanges.

I like the sound of that! Thanks for the explanation.

Does that exhaust system come with ear defenders! Looks Incredible!

Email attached below from the God' as we call him!

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Hi

Ford were responsible for the installation of the engine in the car and came
up with the requirement and design of this crazy bracket which as you say
was then fitted to all the early Cosworth versions of the Sierra.

The lunatics in the Ford asylum did not ask us to look at the problem they
were trying to solve and only fitted this appendage immediately before the
production car was launched without passing it back to us for development
testing. We (Keith Duckworth, Mike Costin, and me) all fell about laughing
when we saw it as it was meant to be a friction damping device rather than a
mere support using loaded washers as the friction face. Needless to say
these had a life of about a fortnight where upon it simply became a jangly
bracket doing absolutely nothing. We then asked Ford what it was for and
they said it was to cure the horrendous "body boom" that occurred half way
up the rev range that was being exited by our manifold design!

We thought that this was hilarious because by the ashtray they had fitted a
shallow trough which we thought was meant to hold the ear plugs for use if
you objected to the noise but Ford insisted this trough was for parking
meter coins. However we still thought it was hilarious because the natural
frequency of the manifold was so far removed from the body modes with such
low high frequency amplitude that it could not act as a driver for their
problem so asked if we could go and look at the final production version of
the car to see if it needed some chassis mods.

The requirement for chassis mods was based on the fact that the original
Cosworth BDA Escorts had such a weak front end on the chassis that the
engine mountings could tear off the top hat section lower chassis rails on
the 285bhp versions with a decent torque output, and we cured that by sledge
hammering a second top hat rail over the first one and welding it in place
hence doubling the stiffness of the rail as a production specification
change and solving that entire problem. Hence we expected to find a similar
problem on the Sierra. However looking at the Sierra it immediately became
apparent where their mistake lay as they had failed to attach the sump to
the bell housing so the engine and gear box were only held together around
the top half of the circle. Hence the whole powertrain was going into
rotating bend at max torque and the bell housing was becoming a bell at the
critical "body boom" speed. We pointed out that the missing link was this
connection and later Cosworth's including the four wheel drive versions had
this link and no silly manifold "damper"

Regards
Geoff

-----Original Message-----
From: [You must be registered and logged in to see this link.] [mailto@brookes.ac.uk]
Sent: 16 March 2009 14:50
To: *REMOVED*@brookes.ac.uk
Subject: Reason for turbo support bracket on Cosworth YB engine

Good afternoon Geoff,

I was having a conversation with some friends about why the YB Engine made
by cosworth in the 80s and 90s had a bracket fixing the turbo to the
manifold, and you are the man to ask about it.

I was thinking that maybe the manifold was prone to flex or movement, or
perhaps the turbo was too heavy to be held in place purely by its flange
mountings and needed an extra support? I guess that the weight of the
turbo would have a large effect on the structure of the exhaust manifold
through its heat cycles, and as such it warranted a bracket being used.

Many thanks for your time.

Jon Clark

BEng Motorsport Engineering.

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question answered. I'm the king of the world.

That verifies my oppinion that supports do not prevent cracking and it's a myth

Good work.

I would love a job figuring these kind of things out. The things some clever people pay a lot of attention to, that are completely ignored by lesser mortals, never ceases to amaze me!!

I love history lessons on iconic cars, keep em coming Mr Monkey

kevhaywire wrote:

I would love a job figuring these kind of things out. The things some clever people pay a lot of attention to, that are completely ignored by lesser mortals, never ceases to amaze me!!

I love history lessons on iconic cars, keep em coming Mr Monkey

I concur, awesome!

Does Geoff want to join Oddunit?

Good idea! Another bloke as knowledgable as JNL Racing can only be a good thing for the forum!

Ha ha! He's quite eccentric, giggles to himself a lot etc etc but knows approximately 7.5 shíteloads about anything car-related really.

I've just applied for my final year project - intake manifold and plenum design run by Geoff....fingers crossed.

Toad wrote:Does Geoff want to join Oddunit?

That's a great idea. Invite him along Mr Monkey

I have said it before and i will say it again, just pure awesomeness going on in this thread.

Maybe we need the definative awesome thread, just purely for awesome pictures and stuff.