Deceleration Exhaust Rattle, Pickle muffler on a 2.0 TIV Options

[avidfanjpl]

OK, thinking caps, please.

The car sounds great and is strong on acceleration, but it is like there is a slight, and I mean almost not audible, snap/pop on high rev deceleration. And it does not occur such that it is rev related. It might be some kind of post-ignition detonation in the exhaust system.

I had the valves lashed 400 miles ago, and there is no obvious sound of tapping or leaks. I know burned, bent valve sounds, and the engine would not perform like it is with a valve or a burned piston. I know those effects.

I have good hoses to the decel valve, which is tested and working. I have no exhaust leaks that I can hear. It idles perfectly.

This is a Dansk correct 2.0L muffler. Nearly new. Finished in Wurth Zinc Silver.

My detailer and I took off the muffler and reinstalled it perfectly to fix the detent bolt on the speedo. We used new bolts on the headers/muffler, and the gaskets are not new but almost new and not even worn. I checked all the head exhaust bolts. No sign of a leak. No loose anything. Shook the pipes to see if one was loose.

I am thinking it could be tin inside the Dansk???

Would once-used almost new exhaust gaskets cause a minor leak? They were bolted to correct torque specs.

Also does not seem like the heat shield is loose above the Dansk.

Any ideas?

Anything?

Thanks!

John
avidfanjpl

[Tom_T]

John - IIRC it's new exhaust system gaskets whenever they come off, but I'm not certain. If you want to come by tomorrow or Friday or weekend sometime for a "team listen & (IMG:style_emoticons/default/idea.gif) session", give me a call on the cell.

BTW - I'd be careful about shaking the exhaust pipes due to 38 yr old studs in 38 yr old alloy heads! (IMG:style_emoticons/default/blink.gif)

[avidfanjpl]

I can do something Saturday, Tom.

Any other ideas? It does not seem to be that serious, but maybe I should change the decel valve? I have a spare. I think all the decel valves are the same regardless of engine size in the TIV variety? Can you confirm?

And what was that tool that you took off the cheeseheads with? I really need to understand that.

Saturday may work. Maybe we should have lunch?

J

[Ferg]

I would first pinpoint location of the sound, if it truly is coming out the tailpipe it could be any number of things, engine tune related.

Since you said it's not rpm dependent, and on high rpm decel it could be some tin or other loose item that only makes contact when the motor/trans move/rock on their mounts?

Ferg

[avidfanjpl]

Thanks, Ferg!

There is no doubt in my mind that it is coming out of the muffler. or within the exhaust system. I have to check, but if my spare decel valve matches the one in the car, I will replace it and take it for a test drive tonight.

I don't think it is something related to the engine mounts, although that is a GREAT idea. I checked the motor mounts while on the lift at the detailer, and we both agreed that they were "new and in good shape."

And the belt on the alternator is new dunlop, and I checked that 2 weeks after installation. I may drive the car by Steve's Independent Porsche repair to see if they have an idea.

Thanks!

John

I would first pinpoint location of the sound, if it truly is coming out the tailpipe it could be any number of things, engine tune related.

Since you said it's not rpm dependent, and on high rpm decel it could be some tin or other loose item that only makes contact when the motor/trans move/rock on their mounts?

Ferg