Why does the noisyness of diesel vehicles vary so much for identical makes/models.
Some cars are quiet and subdued at tickover whilst other examples of an identical car can have a sharp percussive clattery sound to them.
Any views, driving style, fuel brand etc ?????
Edited by Dynamic Dave on 03/04/2008 at 15:05
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None of my diesel cars have had a "sharp percussive clattery sound" but I have not owned a transit, PD VW, or black cab. My cars have all been slightly quieter after an oil change. Perhaps neglect is a factor.
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My Passat PD was pretty quiet inside. As have all VW group diesels I've been in.
Indeed a passenger recently commented that my new Hyundai coupe petrol was noisier inside at least.
The answer is 42.
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I am on my second PD Audi A4 and indeed they are well soundproofed inside, in fact they are less dieselly than some of the more refined common rail motors inside, its just the external tickover noise thats the issue. Also, Passats with the exact same engine as the A4 tend to be quirter externally - wierd eh !
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The answer is 42<<
Why not just ask Marvin?
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Missed the edit, engine temperature?
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At high mileage? long service oil change intervals contrasted with ever 6 months, 6,000 miles?
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Engine temperature has to be a big one. Even the most refined diesels are still clattery when cold, and unrefined ones even more so.
I notice it as a pedestrian though - most commonly with Mondeo TDCI's and VW PD engines. Some are significantly noisier and rougher sounding than others. My mother-in-law had a mk4 Golf PD115 which was written off. We found another - same year, same spec, similar mileage and history, yet far smoother and quieter. A little quicker too.
The latter is not a new phenomenon. The old 2.0 8v Vauxhall petrol engines used in the Cavalier SRI and Astra GTE used to vary wildly in performance terms.
Cheers
DP
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I have noticed that Shell diesel in my HDi 110 results in a much more quieter tickover and cruising compared to say Esso diesel. Additives can have quite an effect on noise from combustion.
Naturally some of these noise factors will be down to the nature of diesel itself and the compression ignition engine model.
There are tools in the industry such as OpenFoam (which im currently working on though unrelated) that model engine combustion through a solver called engineFoam so its definately possible to factor in from an engineering side.
However naturally its a very complex situation for diesel. When they switch into lean burn mode (50:1 ratio ?) thats when they become quite efficient, but recent generations of common rail injectors and their nozzles have to then deal with another issue - swirl patterns in combustion.
Companies such as PSA spend lots of time per generation adjusting these to get the best match of performance , economy, and environment consideration.
Thats just the combustion process, nevermind surpressing the rest of it...
So i'm just going to agree with the other poster for now - 42!
Edited by smokescreen on 03/04/2008 at 15:58
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My Passat was not noticably noisier than any other vehicle. Unless you drive a van, these days most diesels are pretty quiet. Of course that could be due to the insulation packed in the engine bay - but same result.
Ultimately, 42 is the answer.
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When the engine is good & hot, diesels are much much quieter.
Common rail motors tend to sound a bit less "clattery" than DI diesels IMHO
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>>As have all VW group diesels I've been in.<<
It's funny you say that glaikit cos I have never been in a quiet VAG diesel yet.
I find them very course - only really becoming bearable at about motorway speeds.
I have been in quite a few both as a passenger and a driver so I thought it was typical of the design - but maybe not ?
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In my experience, the A4 or Passat are quieter inside than the C class Merc diesels and pretty much as quiet as the super quiet BMW 4 pot diesels. However, I went in a golf plus the other day and there seemed to be no soundproofing at all.
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"I went in a golf plus the other day and there seemed to be no soundproofing at all. "
Yes - that's strange, isn't it: I had a test drive in a Golf Plus and found the same. The estate is much better - at least mine is....
Noisy only when cold or during hard acceleration, and particularly quiet and restful at motorway cruising speed (in my case, an indicated 75-80).
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I have noticed that Shell diesel in my HDi 110 results in a much more quieter tickover and cruising compared to say Esso diesel.>> >>
Surely this is just your imagination. What on earth could account for the difference?
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Personal observations:
VW diesels are definitely pretty unrefined but make up for it in sheer grunt, whereas many smoother and quieter rivals lack their torquey feel.
I've found that using 'designer' diesel fuel results in coarser, not smoother running.
Diesels tend to be pretty noisy at low speed but seem quieter and smoother as revs increase. The reverse is true with petrol engines.
Edited by AlanGowdy on 04/04/2008 at 00:23
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The torquey feel is the way the PD delivers the torque, which then dictates how the power is delivered.
If you look on rri.se, you'll see the power delivery curve isnt that smooth compared to say a HDi of the same power, as it delivers it in one lump rather than smoothly over the range.
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I used to think that myself. Then I had a passenger notice the same thing.
I think it has something to do with the additives Shell use.
I have noticed a difference between Esso and Shell diesel in my case. It's quicker warming up from cold, you can clearly hear the idle clatter is subdued using Shell diesel.
Also other HDi users have also noticed its possible to get better MPG using Shell diesel than it is others as well as a little quieter, so I wasnt the only one picking this up after all.
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Oh forgot to add, the engine is much less grumpy below 1.5k rpm when on Shell too, unlike Esso.
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