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200 tdi turbo/ exhaust connection


Corrode Finger
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People may or may not be aware that i am helping twizzle with the install of a disco 200tdi into a 109.

As is seen in the members thread, we have it sat in the engine bay with the turbo on and missing the chassis.

BUT

I have a concern, we have proposed inserting a straight pipe onto the back of the turbo at the exhaust end, to allow the 'normal' cast bend to be repositioned about 6/7 inches further down the exhaust to then allow the normal routing of the exhaust under the truck.

Straight pipe where the tape is, then the normal bend.

post-2166-1193043933_thumb.jpg

Is the 'normal' cast bend directly fixed to the turbo necessary to create back pressure etc to ensure the turbo works correctly? I know that too tight a bend here, 90degrees, restricts the gas flow, and prevents the tdi from performing.

Equally will too little restriction, immediately after the turbo, cause an issue with normal operating.

I may be thinking of a problem that does not exist, but it would be nice to consider the problems before making the solution? :)

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People may or may not be aware that i am helping twizzle with the install of a disco 200tdi into a 109.

As is seen in the members thread, we have it sat in the engine bay with the turbo on and missing the chassis.

BUT

I have a concern, we have proposed inserting a straight pipe onto the back of the turbo at the exhaust end, to allow the 'normal' cast bend to be repositioned about 6/7 inches further down the exhaust to then allow the normal routing of the exhaust under the truck.

Straight pipe where the tape is, then the normal bend.

post-2166-1193043933_thumb.jpg

Is the 'normal' cast bend directly fixed to the turbo necessary to create back pressure etc to ensure the turbo works correctly? I know that too tight a bend here, 90degrees, restricts the gas flow, and prevents the tdi from performing.

Equally will too little restriction, immediately after the turbo, cause an issue with normal operating.

I may be thinking of a problem that does not exist, but it would be nice to consider the problems before making the solution? :)

Yes and no....

I personnally don't think it will cause a problem, and as mentioned it will actually reduce turbo lag....

But it 'can' reduce the life of the seals in the turbo... due to the difference between the intake and the outlet pressures. Standard turbo's are supposed to be used within certain parameters... so reducing back pressure from standard 'might' take it out of this window.

However, if you still have a 90 degree (or thereabouts) bend somewhere near the turbo outlet, back pressure will be similar.

I don't understand what you will gain by using the cast elbow further down... I wouldn't bother - I'd just use a nomal 90 degree bend in pipe, rather than trying to attach the cast section.

If you wanted to go one further, I'd modify the outlet from the turbo so that it seperates the main outlet from that of the waste gate butterfly. This will reduce the disturbance of the exhaust gas from the turbine wheel - which can occur when the wastegate opens. The waste gate outlet can either be vented straight to atmoshpere under the car (will be quite load unsilenced though) or it can be linked back in further down the exhaust.

Ian

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I simply made up a flange to suit the back of the turbo and then used standard pre-formed bends from the motor factor to make up an exhaust to fit. I wouldnt bother trying to do anything with the standard cast bit - I threw mine away and started again. Easy enough to do - just cut and weld the bends to suit until it all fits.

Jon

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I simply made up a flange to suit the back of the turbo and then used standard pre-formed bends from the motor factor to make up an exhaust to fit. I wouldnt bother trying to do anything with the standard cast bit - I threw mine away and started again. Easy enough to do - just cut and weld the bends to suit until it all fits.

Jon

The only logic for using the original casting was that with a inserted straight tube where the tape is shown, the cast pipe fits nicely due to its shape(by chance i geuss) and seemed to send the exhaust system down underneath.

One other thing that has been brought up in the members truck thread, but thought it might get a bigger audience here?

At the moment the g/box shown is a disco LT77, we have a defender LT77 to go on, just not fitted yet, it was suggested that when using the def box, the clutch master cylinder sits where the current starter motor is, they swap sides, and then there will be a heat issue, as its tight there?

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Yes it does move to the other side. Thats part of the reasoning behind making your own exhaust downpipe up so you can make sure you leave clearance for the slave cylinder. You need to get the exhaust down prety quickly if that makes sense.

Bleeding the slave cylinder becomes a piggy too if you make it too tight!!!

Jon

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Just been a wondering?

As i understand things, its the volume of an exhaust that determines its performance and flow rate as opposed to just its shape?

ie: my thought, the current pipe at the turbo is (from memory) 57mm internal diameter, therefore to maintain the performance, it should not be smaller, (ie 45mm for instance).

BUT

Would there be a problem maintaining the 'volume' but creating a flatter shape, ie an oval that allows the exhaust to pass the restricted area. It would be the normal 'tube' at the turbo flange, change shape the return to round below the chassis?

Again, may be flawed but just came to me whilst eating my ham sarny! :lol:

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If it helps - a 300 tdi front pipe flange/front pipe will fit directy on the 3 bolt turbo exhaust housing and is the correct diameter. I bought one to use on my conversion but opted for the steve parker conversion to save time. You would need to do lots of cutting/bending but the flange is a perfect fit, the front pipes are cheap £20 if you dont mind the cutting/welding

I have one here you can have for a £10 but you are a little too far away i think.

dont forget to rotate the inlet housing so it will clear the inner wing and be easier for pipework you will need to re-drill/tap it for the wastegate housing - 6mm metric.

Most tdi conversions appear to sit very low so no need to worry there. if you need to/want to fit the glow plug timer i can send you the wiring instructions if you want them that is?

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Thank you for the offer, we may come back to you requiring bits, depending how things develop.

At the moment, i have been 'exploring' ideas, in a 'simonr' outside of the envelope way.

Just thinking it through as you do.

Also twizzle has got to be happy with the ideas, as its his truck at the end of the day.

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Thank you for the offer, we may come back to you requiring bits, depending how things develop.

At the moment, i have been 'exploring' ideas, in a 'simonr' outside of the envelope way.

Just thinking it through as you do.

Also twizzle has got to be happy with the ideas, as its his truck at the end of the day.

anything to make things a bit easy .I don't mine cutting an welding it wont be the first or last

:wacko: TWIZZLE :wacko:

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Another option is to fit the turbo upside down on the manfold :o and rotate the center bearing secion so it is the correct way up for the oil feed/drain pipes (these need extending). This means the outlet of the turbo faces forwards where there is loads more room for the downpipe to drop and gives loads more room for working on the starter and slave cylinder B) . I am waiting for new oil pipes etc but hope to try it out in a week or so. Will let you know if it works, but I can't see any problems unless someone has tried it before?!!

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Another option is to fit the turbo upside down on the manfold :o and rotate the center bearing secion so it is the correct way up for the oil feed/drain pipes (these need extending). This means the outlet of the turbo faces forwards where there is loads more room for the downpipe to drop and gives loads more room for working on the starter and slave cylinder B) . I am waiting for new oil pipes etc but hope to try it out in a week or so. Will let you know if it works, but I can't see any problems unless someone has tried it before?!!

That's what the photo above shows.

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