darrens
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| posted on 9/3/07 at 07:50 PM |
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Renault dCi engines
? for thee,
I have a Laguna dCi 120, which is quiet as a mouse, I have just purchased for work a Renault Trafic dCi 100, same engine but 20 less HP, anyone know
why the engine diesel knock is louder on the dCi 100 van than on the car. This is listening on the external of the car/van.
It is quite considerably louder as well. For ref car has 128K on it, van has 75k on it
Pondering as this has me confused, could it be anything to do with compression ratios.
Cheers
[Edited on 9/3/07 by darrens]
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coozer
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| posted on 9/3/07 at 07:52 PM |
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Its normally the diesel pump that makes the knocking noise, not the engine.
It might be the van pump timing is different that gives you 20bhp less and causes the noise.
1972 V8 Jago
1980 Z750
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tegwin
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| posted on 9/3/07 at 08:06 PM |
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I know that some of the modern diesel engines in high end cars are fitted with electronic engine dampers.....could this be the difference? the car has
them and the van doesnt?
Dunc
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Aloupol
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| posted on 9/3/07 at 08:35 PM |
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The engine installation in the car has much to do in noise too.
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froggy
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| posted on 9/3/07 at 08:43 PM |
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the higher power engines have a number of "injection events" to make more power which also reduces the knock, so instead of a couple of
squirts for each firing there can be up to seven with the higher output engines
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darrens
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| posted on 9/3/07 at 09:29 PM |
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mm! I'm more likely to agree with the injection events, as engine insallation is virtually identical. Could possible be the diesel pump, as
these are a high pressure pump driven off the cam belt.
So next, thought, how do I reduce the knock, wouldn't av thought you could simply swap pumps as this would muck up the timing etc.
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COREdevelopments
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| posted on 9/3/07 at 10:39 PM |
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doubt it will be the pump, diesel knock is in the engine itself. there would be many differences in the car and van engine, like different mapping of
the ecu, new cars have alot of engine insulation etc.
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froggy
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| posted on 9/3/07 at 11:15 PM |
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the "pump" is just that ,a high pressure pump delivering monster pressure to the fuel rail , its the ecu and injectors that time the
injections just like a petrol engine. this is why there are so many chips available for modern turbo diesels as the boost is electronically controlled
too so power increases can be controlled on the fuel and boost side by re mapping as there is never going to be a shortage of fuel and plenty of scope
to widen the time span of the injection without changing any hardware either.the problems i see with modern common rail diesels is rarely down to
electronic faults but problems with the pump and injectors , you will notice that the price of pumps and injectors has halfed over the last twelve
months for 4+ year old cars using common rail systems, i paid £650 for a pump for a scenic 18 months ago which is now under £200 from europarts
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Chippy
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| posted on 10/3/07 at 12:09 AM |
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The knock on old standard injection engines was produced by the pump, as it was/is a set of pistons that fire diesel through the injector by
mechanical timing. Common rail engines should have no pump knock, as the whole thing works in a totaly different way, the pump produces its pressure
as a constant, not in spurts. The injection process is taken care of electonicaly, with, (usualy) the injector being fired several times per intake
valve opening. Have you tried listening to both engines with there bonnets open, as the sound proofing on cars is somewhat better than vans, (which
usually have none at all). HTH Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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nick205
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| posted on 10/3/07 at 09:09 AM |
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I bet the car has much more sound proofing around the engine. Does the van bonnet have the 1/2" thick "lagging" as the car bonnet?
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Jasper
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| posted on 10/3/07 at 12:03 PM |
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Get them tuned by Angel Tuning - they did my 2.2dci Espace and it's like a completely different vehicle - drives like a 3ltr AND the fuel
economy is better - wish I done it when I bought it 
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Aloupol
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| posted on 10/3/07 at 12:49 PM |
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quote:
Originally posted by nick205
I bet the car has much more sound proofing around the engine. Does the van bonnet have the 1/2" thick "lagging" as the car bonnet?
This is what I mean as "engine installation", which is obviously different in car and van.
This includes the foam parts in the chassis beams, all the stuff reducing noise.
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