Motoring sound on accerelation

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Motoring sound on accerelation
#1
This is a hard to describe sound but low in the rev range there is a "motoring" sound sort of like a V8 sound mixed with gurgling. I don't know whether the manifold is blowing but it shouldn't be because I've got a new gasket on it. There also seems to be a pressure building up sound higher up in the rev range, I'm not sure whether they are linked or not.
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#2
(20-12-2012, 06:11 PM)306Puggy Wrote: This is a hard to describe sound but low in the rev range there is a "motoring" sound sort of like a V8 sound mixed with gurgling. I don't know whether the manifold is blowing but it shouldn't be because I've got a new gasket on it. There also seems to be a pressure building up sound higher up in the rev range, I'm not sure whether they are linked or not.
When you replaced the manifold gasket did you replace the raccoon filter on the breather system?
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#3
(20-12-2012, 06:15 PM)Scott Wrote:
(20-12-2012, 06:11 PM)306Puggy Wrote: This is a hard to describe sound but low in the rev range there is a "motoring" sound sort of like a V8 sound mixed with gurgling. I don't know whether the manifold is blowing but it shouldn't be because I've got a new gasket on it. There also seems to be a pressure building up sound higher up in the rev range, I'm not sure whether they are linked or not.
When you replaced the manifold gasket did you replace the raccoon filter on the breather system?

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#4
Has it started since the new gasket went on?
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#5
are you certain that your engine hasn't bifurcated into a V8 all of it's own accord? you know, evolution?
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#6
(20-12-2012, 06:11 PM)306Puggy Wrote: This is a hard to describe sound but low in the rev range there is a "motoring" sound sort of like a V8 sound mixed with gurgling. I don't know whether the manifold is blowing but it shouldn't be because I've got a new gasket on it. There also seems to be a pressure building up sound higher up in the rev range, I'm not sure whether they are linked or not.

The first bit is what's called an "engine", it sort of goes chuggachuggachugga low in the revs, often mistaken for a V8 that's been dubbed into 70's chase scenes.

The second bit we call a "turbo" and you're pretty close in that it builds up pressure and, in the words of Jeremy Clarkson, "witchcraft happens" and you go faster.

HTH.
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#7
Clarkson knows best. /thread
Doesnt even own a 306.
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#8
(20-12-2012, 06:15 PM)Scott Wrote:
(20-12-2012, 06:11 PM)306Puggy Wrote: This is a hard to describe sound but low in the rev range there is a "motoring" sound sort of like a V8 sound mixed with gurgling. I don't know whether the manifold is blowing but it shouldn't be because I've got a new gasket on it. There also seems to be a pressure building up sound higher up in the rev range, I'm not sure whether they are linked or not.
When you replaced the manifold gasket did you replace the raccoon filter on the breather system?

A very common problem hmm.......... Are you sure you've done up all the bolts on the manny? Sorry stupid question.
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#9
Yeah I have cleaned the manny and put the new gasket on perfectly and done all the bolts up in the correct sequence.
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#10
Blocked air filter?
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#11
Split turbo/boost pipe?
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#12
The gurgling doesn't sound good! Confused

However that other noise is usually a leak on the intake side somewhere, my previous car sounded awesomely grunty with the mani direct to air......
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#13
I had a look today and I am fairly certain that it is the downpipe. I revved it to the rev range where it makes the noise and a small puff of exhaust fumes came from somewhere (I couldn't determine whether it was the downpipe or not) but that is the area where the sound seems to originate from, which would also make sense because it is more noticeable in the cabin.

Fairly pissed TBH as I am sure I did that up properly when I put in the new manifold gasket but I guess the wire gasket on the downpipe hasn't seated properly which is quite possible since I had to have the engine wedged forwards with a block of wood to work on it. I think the pressure noise higher in the rev range is due to the exhaust gases escaping from the leak which is confusing as I thought the exhaust gases where free flowing, i.e. not under pressure. There is also a possibility that the main sound at low revs is caused by one of the washers on the exhaust bolt rattling if the nuts have worked loose.
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