Kroon Harness for 944 Turbo

[Tom]

Well great. Now you have me scared.....

They broke out a huge magnet and it almost flew out of his hand onto the flange, so I'm thinking it's mild steel. It's already all welded up. They definitely weren't laying dimes, but it also only cost me their shop minimum ($75).

They also recommended using some copper high temp exhaust gasket RTV. They said in a perfect world the crushable donut gasket should be enough, but I'm not dealing with a perfect world.

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It's my understanding, based on various people who have tested these parts and reported the results online, that the flanges can be either mild steel or stainless, while the pipe itself is Incoloy 800 (or an unbranded alloy of similar content). Sounds like your flanges are mild steel — mine are too.

Try putting a magnet on the pipe itself. Assuming the magnet does not stick to the pipe, it is likely Incoloy 800.

I don’t mean to scare you, just trying to save you some extra work down the road. From the photos, those don’t look like TIG welds to me. They look more like MIG or stick welds, which makes me wonder/doubt whether the correct filler and process were used.

I’d still call and ask exactly how they welded it and what filler rod/wire they used, but I wouldn’t be overly optimistic unless they can give a confident answer. On the other hand, it’s impossible to say from here how long they might last — a month, a year, a decade? It’s not the space shuttle, so you could always install it as-is and cross your fingers. I’d just go in knowing there’s a real risk they will crack.

Well, at this point there's probably no going back regardless. I guess it was a good idea for me to hang onto the original crossover pipe in case I need it. Note to my future self though - if I (or anyone else) is in the same situation in the future, probably better to look for a machine shop to see if they are more knowledgeable in welding those types of metals together.

At least that part is after the primary o2, so I'm thinking if it does crack in the future it will only mess with my WBo2 readings.

Since you’re in the heart of NASCAR country, or at least a lot closer to it than most of us I assume, you probably have a much better chance of finding an Inconel/Incoloy-capable shop than most. Most exhaust shops would consider this “exotic metal” work — the kind of thing more commonly associated with aerospace, F1, NASCAR, a few high-performance cars, and, for some reason, the 944 Turbo. So it’s specialty work you may have to hunt down.

If you have a good spare crossover and don’t mind swapping it in later if necessary, there’s no real harm in trying this one as-is. For that matter, having it welded by a nickel-alloy-capable shop might cost more than it’s worth, for all I know. I just checked, and a 10 lb tube of Alloy 82 filler is over $900 at Grainger, compared with maybe $15/lb for ordinary filler rod. Then add the skill level and rarity of welders who know how to do this correctly, and the cost of re-welding that one might make the spare look pretty good.

Keep in mind, though, that if it does leak — even if it doesn’t throw off your O2 reading — it will reduce exhaust energy reaching the turbine. That means more turbo lag, less efficient boost, lower boost potential, etc. Any exhaust leak before the turbo can reduce performance. So if you get everything sorted and then one day the car starts feeling sluggish on boost, just something to keep in mind.

On the bright side, it sounds like you’re making real progress now. These are exactly the kinds of problems that seem like they “must” be one-in-a-million rare issues, but often turn out to be the same boring old problems most of these cars have — just hard to find. Finding them is 90% of the battle. So despite my relentless reality checks, I think you’re on a well-earth path to success now. Whether these issues were responsible for all your symptoms or just a few of several contributors, they are high-value finds.