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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old April 1st, 2002, 20:54   #1
eidie2
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Join Date: Dec 2001
Location: CA
TDI(s): 05.5 Jetta
Fuel Economy: 36
Default What causes diesel chatter?

I have always wondered what is it that causes all diesels to chatter. I thought I read somewhere that VW found a way to reduce the noise by creating a swirl pattern during the injection into the cylinder. It is obvious VWs are quieter than any diesel truck or the old Mercedes, but why do diesels chatter and gassers don't? Just Curious.
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Old April 1st, 2002, 21:11   #2
veedub_tdi
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Location: Scarborough, Ontario
Default Re: What causes diesel chatter?

check this site out
http://www.howstuffworks.com/category.htm?cat=Auto

the diesel engine is covered, and so is gas,as well as rotary and a bunch of other stuff too.
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Old April 1st, 2002, 22:00   #3
eidie2
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TDI(s): 05.5 Jetta
Fuel Economy: 36
Default Re: What causes diesel chatter?

Read the link, which was great info, but it did not necessarily say what causes the chatter. Is it soley the higher compresison and the explosion that i am hearing, or is it the force of the explosion on the piston, rods, or valves?
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Old April 2nd, 2002, 04:58   #4
SkyPup
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Default Re: What causes diesel chatter?

Crappy USA diesel fuel causes it, get some good 50 Cetane fuel and you'll never hear it.
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Old April 2nd, 2002, 05:45   #5
Metro
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Default Re: What causes diesel chatter?

SkyPup is playing.. even with B100 you get plenty of clatter
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Old April 2nd, 2002, 05:50   #6
SkyPup
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Default Re: What causes diesel chatter?

Quote:
Originally posted by Metro:
SkyPup is playing.. even with B100 you get plenty of clatter
<font size="2" face="Verdana, Helvetica, sans-serif">lol, you cannot even hear either one of our TDIs from inside the car, no one who is a gasoholic even knows that they are riding in a DIESEL! [img]images/icons/grin.gif[/img] They are all shocked and absolutely amazed when they are told they are riding in a high performance turbodiesel passenger car, since it is so quiet, so smooth, so powerful, and so economical. [img]images/icons/shocked.gif[/img] Blows their minds every time.

But fill up with some low life rot gut diesel puke fuel and everyone thinks you are hauling waste out to the landfill. [img]images/icons/frown.gif[/img]

Get some 50 cetane and forget about smoke, clatter, crud, and all the other hassles garbage truck fuel brings...... [img]images/icons/wink.gif[/img]
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Old April 2nd, 2002, 06:03   #7
jasonTDI
 
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Location: Madison, WI
Fuel Economy: 13.7 c, 12-18 towing hwy
Default Re: What causes diesel chatter?

skypup is right there is a huge difference in interior noise with the good diesel. I can now tell if an amoco dealer is lying about fuel grade, you just drive a couple of miles and you can hear the difference.
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Old April 2nd, 2002, 06:25   #8
chopchop
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Default Re: What causes diesel chatter?

You can certainly tell ours are diesels on startup on a cold Canadian morning, such as today (-24deg C..), if you forget to use a block heater, but other than that, most folk around here who have been passengers in our Golf TDi don't even realise it's an oil-burner.

I reckon that with my additive, and the best diesel I know of round these parts, my effective C/N is about 49/50.

Even my "agricultural" old TDi Discovery doesn't make anything like the clatter of most American diesels using my diesel mix, but, as I've said before here, it IS noisier here than it was in the UK, and that can only be down to the crap diesel, since NOTHING else has been altered. DIs are also inherently noisier than IDIs, remember.

Diesel fuel quality DOES make a difference in the decibel stakes!

- Richard
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Old April 2nd, 2002, 07:18   #9
MITBeta
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Default Re: What causes diesel chatter?

Quote:
Q. What causes diesel chatter?
<font size="2" face="Verdana, Helvetica, sans-serif">A. Good gossip.
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Old April 2nd, 2002, 08:59   #10
think diesel
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Default Re: What causes diesel chatter?

I believe what causes diesel "chatter" is the rapid increase in pressure. Compression ignition is essentially knocking. The knocking you hear in an older gas engine with octane that is too low is sometimes called "dieseling" It is basically the same thing, fuel igniting without a spark.

The diesel chatter is the combustion happening, I think it is louder in a diesel because the process is slower and occurs with more force/pressure.

Volkswagen TDI's are quieter in part because of pilot injection. The swirl you refer to helps the fuel combust more efficently, but it is the two stage injection, that breaks the combustion up into a little bang followed immediately by a bigger one that quiets things down a bit.

Something like a Dodge Ram with the Cummins engine is not even trying to be quiet. One big bang in cylinders than displace a liter each! [img]images/icons/shocked.gif[/img]

Now, listen to the new Chevy Durmax diesel truck motor and you'll be amazed. Much much quieter than the Cummins. One reason is that it uses pilot injection like the TDI (it also has a few other soundproofing tricks, like rubber coating on stuff and insulation.)

Hope that helps [img]images/icons/wink.gif[/img]
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Old April 2nd, 2002, 11:53   #11
peter pyce
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Default Re: What causes diesel chatter?

In gasoline engines you have spark plugs. So, before the piston reaches the top, there is a spark that in a way generates good amount of light (a flash), so the piston can see the coming-soon wall (the head) and slows down, then turns back ....

In diesels, there's no spark plugs, so it's dark inside the cilinder and the piston can't see when to stop, so it hits the wall (the head), therefore you have the sound......

Well, it's not 1 April, but it was few hours ago [img]images/icons/smile.gif[/img]
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Old April 2nd, 2002, 13:31   #12
Metro
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Default Re: What causes diesel chatter?

SkyPup,

With B100 it is quieter, and I had a person say they did not know it was a diesel just yesterday, but I can still hear it.

It still sounds like a diesel, and it still clatters, but it is quieter.

why would you have your windows up when you can hear the engine with the windows down so much better [img]images/icons/grin.gif[/img]
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Old April 2nd, 2002, 21:54   #13
nuke
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Default Re: What causes diesel chatter?

With 50+ cetane diesel, it still clatters and makes some smoke and soot.

It's just how diesels work.

It's not real bad on the TDI and better fuel is nicer but it won't magically go away with 50 cetane fuel.
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Old April 2nd, 2002, 22:34   #14
Dorado
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Default Re: What causes diesel chatter?

To my ears, the volume of the TDI engine idle sound stays about the same, but the pitch is noticeably lower when using biodiesel (B5 and beyond). I take that to be the effect of its high lubricity. [img]images/icons/smile.gif[/img]
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Old April 3rd, 2002, 10:14   #15
think diesel
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Default Re: What causes diesel chatter?

Actually I would attribute that to the very high cetane value in Biodiesel. That means faster combustion which equals less noise.
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