My engine has sounded raspy ever since I bought it. Most FDs have a nice deep growl when you get on them, mine sounds like a lifelong Camel smoker. Anyway, I've pulled the turbos and exhaust manifold, had a pinhead-sized leak fixed in the main cat, and replaced the downpipe and studs.

The only known thing wrong is some cracking in the turbo manifold around the wastegate door. The turbos boost fine except that the 10-8-10 is sometimes 10-6-10. Could this be the source? Anyone ever change to better turbos and have the engine sound change?





Dave

 

They shouldn't change the sound. I have worse cracks then that, and didn't have a boost issue. I patched them up not long ago because I am in the middle of a non sequential conversion

 

The boost issue is probably unrelated.

So then your experience is the sound of the engine was entirely unaffected?

 

The engine's sound isn't affected by that. What kind of catback do you have? There is a good possibility that the packing has been blown out. My car's exhaust note grew more and more raspy as the muffler got older.

 

could also be the cat getting clogged. i noticed my exhaust sounding a bit differently when i had some boost issues and one of the issues wound up being a clogged cat. i got a used low mileage cat and that fixed it.

 

Collapsed exhaust? Saw it on rennlist(porsche forum). A lot of them noticed boost issues, never mentioned a sound though. Then again the car it was regarding has a very buzzy engine :/

 

I have a stock cat-back, 62k miles. But the sound appears to come from the engine bay near the turbos.

The stock cat looked solid when I had it off this summer - not a speck of rust/dust fell out when I shook it to check.

Dave

 

That's the pre-control door, not the wastegate. I doubt it would make a noticable difference in the sound the car makes. And it is likely that most of the other FDs you've heard also have cracks there.

Make sure the 10mm bolts that hold the turbine housings onto the turbo center housings are tight. It is possible to have leaks there, and they make a lot of noise. If you take them apart and find a carbon "trail", you probably had a leak.

-Max

 

Thanks. Crap, I unbolted everything EXCEPT the turbine/center housing joints.

Yes, indeed the first pic the pre-control door. But I have cracks in the wastegate area too. And maybe a leak on the pre-control cover gasket.



Dave

 

how did you repair it?? Weld?

 

well the sound with my oem exhaust was very very bad. I ahd clogged cats as well as a hole in the muffler. I then swapped to a trust resonated mid-pipe and a trust sp exhaust. ... So I can't really help you with the exhaust tone sorry man.

 

I bought some hi-temp steel that is used to repair manifolds. it is good until 6000 fahrenheight. finished patching up the cracks.. now I am going to sand it down and then do one more coat.. then sand it down again. Just to make sure I get all the spots covered. After that is all said and done, I am going to get my exhaust manifold, turbo manifold and downpipe ceramic coated if possible.

For welding cast iron, that, as far as my welding knowledge goes, is not possible and not very good for the cast iron. you need to get it payned.. or pained however it is spelt. That could run you a good chunk of cash.
Hope that helps

 

Care to share where you got this from?

 

2900F melts cast iron. Whatever you used is probably rated for 600F. The turbo manifolds sometimes get orange-hot (~1000F), so I'm not optimistic it will last. I looked into having mine welded when it was off, (those pics are from Sept). IIRC, welding cast iron is done with proper preheat and some zinc alloy weld wire. But it's very difficult to do and it's unlikely to be worth the effort.

Dave

 

oops I was TOTALLY off. It is good until 2000 fahrenheight. still good enough imo. I picked it up at a Canadian tire, and found it at other places like home hardware etc. I believe that with proper heat cycling it will become stronger. I have attached pics

 

I would be careful using that anywhere before the turbines in the flow path. The concern is having a very strong chunk of cold weld visit your turbine after it heat cycles its way loose. However, maybe it does work. Perhaps you could try it on the wastegate hole first (since it is not before a turbine) and then see how it holds up in a few months. If it looks good, try it in other locations.

-Max

 

It's possible but not for the far majority of welders out there. I know guys who weld aircraft parts for a living and they know how to do it. I have no idea what kind of rod they use but they explained that the key is in preheating the cast iron to the proper temperature before welding it. I'm sure there's more to it than that as well but I'm no expert.

I would not put anything coming out of a tube anywhere near the turbines...

 

I picked up some of this stuff at Autozone today when disposing of oil. Permatex makes some, the stuff I got is 'CarGo ThermoSteel'. Both promise 2000F.

It does come with some detailed instructions to ensure proper bonding and strength to the iron
- bevel cut the crack and drill out the tip to 1/8"
- solvent clean the surfaces
- sandblast, wire brush, or grind surfaces clean
- apply in layers no more than 1/4" thick, allow 3-4 hours air dry. Then gradually heat repair 10-15min to full cure.
- Machine/drill/sand if required using no cutting oil (expect dust)

It looks promising, but like radiator block weld I wouldn't consider it except for turbos that will be scrapped otherwise. If I get a chance this winter I'll pull my turbos and do it. I'm gonna google a little now for more info.

Dave

 

Well guys here is my plan. Put the stuff on heat cycle it with a tagger torch and the get the entire piece ceramic coated (inside and out). I'd imagine that nothing would fall out into the turbine.. I'd hope at least.

Max,
getting proper rods for that is very hard to find. From my years of welding experience I have never seen a rod rated to cast iron. I even made sure by asking a welder who has been working industrial for his lifetime and told me it would be a bad idea to try to weld it.

Well, we'll see next year if you see a thread about my turbos blowing because of this stuff .. you can laugh at me
Edwin

 

OOPS! I mean the second part to DamonB
Sorry
Ed