? 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]
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.
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
The engine installation in the car has much to do in noise too.
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
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.
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.
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
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
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?
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
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?