Jonathan's Audi 20vt Exhaust Manifold Project

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Some car parts are projects all by themselves!

I am modifying this 20vt EM in part to see how far the stock manifold can be taken, in part because I would like to do an upgrade to my 200Q 20v in the future, and in part to test and expand my cast iron welding skills.

First off, I know that the factory manifold will always have limitations compared to a properly designed tubular header. I'm not deceiving myself into thinking that this manifold would match or outperform a header. That's not the point of this exercise. I will be flow testing the manifold when it is finished and comparing it to a stock EM. Dyno results on a car are meaningless because so much else has to change in order to use this manifold.

So, here goes...

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MoAr!

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Taking shape!

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#1

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#2/5

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#3/4

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Lots of nickel-99. Here, I am building up the flange to match the Garrett T3 flange.

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Grinding down the surfaces-up nickel 99 to match the perimeter of the T3 flange exactly.

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Grooves out and welded the inside and outside of the collector crack.

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Finalized collector shape.

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Inside of collector welded up.

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If this isn’t the most extensively worked-over OE 20vt exhaust manifold, I want to see the one that is!

I had some porosity problems on the outside flange welds, so I will be grinding those out and redoing them.

After that, I have to repair the other crack (outside radius of #4 close to the head.

Then I will gasket match the head flange, blend to the best of my ability, and set up a date for flowbenching this against a stock unit.

I have a Holset HY-35 that I plan to bolt to this once ready to install it.

[DE80q]

That is a lot of welding done to that manifold. I hope you are pre/post heating, as well as very slow cooling. I welded my single piece manifold a number of years back with good results, at first. It has recently recracked, and it's right along the side of one of my welds around the runner.

I do look forward to your flow bench results. I'm having essentially a stainless log manifold made for factory placement.

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Oh, yes. That's cast iron welding 101--preheat, postheat, peen, slow cool.