To wrap or not wrap exhaust?

[Dave 53]

My 818 ran great all day at Thunderhill East last weekend.

After I got it all packed up for the drive home, I heard an exhaust leak. It was easy to spot where it burned through the heat shield wrap.

Thunderhill East has long WOT sections and everything gets worked harder on that course than anywhere else I go. Worst gas milage too. Only track I can't get 3 - 20 minutes sessions on a tank of gas.

I'm wondering if the pipe failed because I had it wrapped and between the long sections of WOT and the wrap, it just got too too hot.

I've got the replacement part and I'm ready to install it, but I'm wondering if I should leave it unwrapped to allow it to run a bit cooler. Thoughts?

exhaust crack.jpg

[DanQ]

I hope that is not the case as I just got done wrapping my entire system. ('33 hot rod)Image - 2024-03-12T133357.288.jpeg

[Dave 53]

I don't think my failure would have happened on a streetcar. It failed on a racetrack after many cycles of pushing the car to its absolute limits.

Due to the tight 180* radius of the manifold, the area that cracked was probably 4 layers thick with insulation wrap.

Pending further research, I'm not going to wrap it again.

[JimLev]

You guys have 2 different types of metal. The 33 hotrod uses stainless steel. I have my complete system wrapped too, no issues at all.

[RoadRacer]

I have no real data, but I started out wrapped but discarded it when fitting new mufflers 10k miles in. The pipes and old mufflers were in good shape externally but certainly blued. As I understand it, this bluing happens at pretty high temp, like 600° or so.

[Dave 53]

I thought replacing the cracked manifold with a new one would take an hour which means 3. Unbolt the cracked one, bolt in the new one. Easy access to all the bolts. Easy peasy. Nope.

The first step was getting a replacement part. The junkyard has them for $25, when they have them. What I discovered is that Subaru turbo engines go fast. I can tell it's pro's pulling the engines the way the wires and exhaust were cut. If you're not there the day the car gets put out, you missed it and the parts will be on eBay.

So, I bit the bullet and bought a new one for $360. Ouch. Plus new gaskets. It has these tabs that are used for a heat shield that I don't have, so I cut them off to be able to wrap it.

I bolted it in and it's not the same as the old one! It's just enough different that no matter what I did, 2 of the 3 flanges leaked. And I cut the tabs off, so now I can't return it.

I'll skip the details, but about 30 hours of time later including running around to junk yards and sourcing new gaskets, cutting, welding, fitting, pulling the turbo off which is no small job in itself, etc., I got the part to fit. The key was to cut the cross over pipe and reweld it and a product called Remflex gasket material. I had to call Remflex to ask if it's okay to stack the gaskets and he said Subarus are notorious for the issues I was having.

The moral of the story.... if you have to replace a Subaru OEM exhaust part, just get an aftermarket header. All the work to get this new manifold installed was not worth it. I spent over $550 in parts and gas and fought it for 2 weeks. A $650 aftermarket header would have been well worth the extra $100 and install would have taken 2 hours tops. I did call my tuner to ask him if I needed a new tune if I put on a header. He said I didn't need a new tune, but the turbo boost would be cut. Which means I would need a new tune. I didn't ask if he could just look and some data logs and email me a tune or if it required a dyno.

[lance corsi]

Dave, this is a bummer. Ace Race Parts offers stainless steel flanges for those building their own exhaust systems which are specifically made to accommodate 1 1/2” schedule 10 pipe. This is what I used, stainless of course. The schedule 10 pipe has a wall thickness of .09 and is more durable than thin wall tubing. I wrapped mine. The only down side to using schedule 10 pipe is that nobody makes v-flange connectors for pipe so I had to make my own. Little things like this is why it takes so long to build these cars.