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[bigboyscottyb]

Hi guys

 

I might be having some problems with the diesel engine in my forester, but then I might not be.

 

Basically I get a noise intermittently when driving, its almost like a bad drone noise that comes on between 1000rpm and 2000rpm, when you sit at idle it sounds like any other Subaru (which is very rare for the diesels). but the noise will only last about 5kms of travel time and then disappear!!!

 

This noise seemed to start when I fitted an my11 WRX cat back exhaust, which of course my misses is blaming the exhaust, but my thinking is that the factory diesel exhausts are so restrictive that the car always made the noise but the exhaust suppressed it.

 

I have checked the oil in the car, besides being as black as the ace of spades the oil level is correct, checked all pipes (intake, headers and exhaust) there seems to be no leaks and all clamps are done up nice and tight.

 

I was going to try get a video of this noise but as I said it happens so rarely that its hard to capture. But the noise is similar to the drone when you fit a cheap cannon muffler and hit the freeway.

 

I have done some searching and there is one fella in the states that has started a thread re this (on his 2010 FXT) but its not a diesel but he seems to be getting a similar issue

 

Any help or direction would be great

[Niko]

Hey mate,

 

I know Subaru have some of the most advanced diesel engines, but could it be soot deposits in the exhaust manifold? Perhaps due to the cat back being off a petrol engine it isn't designed to filter the diesel exhaust as well?

 

Another more likely possibility is that due to the system being of a different model, the cat back system is designed for the pipe resonance of the WRX not the Boxer diesel, therefore you will have wavelengths of the vibrating pipes combining rather than combating each other.

 

Google 'exhaust pipe resonance' and you might find some solution to fixing drone

 

I'm getting a drone at 1500rpm on my STi mufflers, but that's pretty standard for that mod I've been told, I could fix it by matching the rest of my system to the mufflers etc, but CBF, it's not loud enough for other people to hear.