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I think it took so many pages because many of us were thinking about vibrations and knocks rather than noise and harmonics. These are quite distinctly different.Quote:
Originally Posted by Lotz-A-Landies
Its all in the way we describe and others interperet.:)
Had the opportunity to help a friend to replace the in-tank diesel pump today (preventive measure as they tend to fail around 130K) and drove his 2004 Td5 with 125K afterwards to check and this engine is much smoother. You can feel a very slight vibration in the 2200-2400 range but hardly noticable. After I have replaced the engine mounts I will report back. If the downpipe should have problems with the flex coupling, how could that be verified? With a running engine one must surely be able to feel exhaust gasses escaping from that area?
no, they dont leak, but they tend to rattle. thats what mine does at 2200 rpm, but thats just part of the noise and vibration i get. when i fitted new non genuine mounts, all the rattle from the flex pipe went away, but the body shook so much it was like a tractor idling. new genuine mounts took it back to smooth at idle, but the flex pipe rattle came back.
but i had the chance to do a bit of thinking yesterday on a 500klm trip. my car sounds almost as if its missing on 1 cylinder at the said revs 2200rpm
diesels need a glow plug to run properly?. TD5's only have 4 glow plugs, could it just be that they dont fire properly on cyl 5 and so aren't as smooth as they could be ?
maybe,, untill warm,,
heh, mine was certainly warm, especially after 5 hours driving. just seems to be a harmonic noise and vibration, that sounds almost like a half missing cylinder at 2200rpm. hard to describe, but on a long climb, you can really pinpoint it.
not really "good" with this harmonics thing,,
lots of 5 cylinders in the world,,
so they must all vibrate ??
To answer an earlier question, my Td5 Manual Defender does it at about 2100 rpm. The "experts" have told me it is the "nature" of the 5 cylinder. It is a little annoying, but I live with it. I have 130,000km with no noticable increase in noise. Very smooth above and below that RPM.
<<sounds like Diana is not a huge fan of the td5:angel:>>
Yep, the Volvo 850 5 cylinder is a bit of a buzz box too. Volvo chucked the 5 cylinder turbo in the V70 for an atmo V6, probably to soothe the American buyers.Quote:
Originally Posted by Pedro_The_Swift
Long live the V8.:)
some interesting reading
"A five-cylinder engine gets a power stroke every 144 degrees (720° ÷ 5 = 144°). Since each power stroke lasts 180 degrees, this means that a power stroke is always in effect. Because of uneven levels of torque during the expansion strokes divided among the five cylinders, there is increased secondary-order vibrations. At higher engine speeds, there is an uneven third-order vibration from the crankshaft which occurs every 144 degrees. Because the power strokes have some overlap, a five-cylinder engine may run more smoothly than a non-overlapping four-cylinder engine, but only at limited mid-range speeds where second and third-order vibrations are lower.
Every cylinder added beyond five increases the overlap of firing strokes and makes for less primary order vibration. An inline-six gets a power stroke every 120 degrees. So there is more overlap (180° - 120° = 60°) than in a five-cylinder engine (180° - 144° = 36°). However, this increase in smoothness of a six-cylinder engine over a five-cylinder engine is not as pronounced as that of a five-cylinder engine over a four-cylinder engine. The inline-five loses less power to friction as compared to an inline-six. It also uses fewer parts, and it is physically shorter, so it requires less room in the engine bay, allowing for transverse mounting.
A disadvantage of a straight-five over a straight-six engine is that a straight-five engine is not inherently balanced. A straight-five design has free moments (vibrations) of the first and second order, while a straight-six has zero free moments. This means that no additional balance shafts are needed in a straight-six. By comparison an inline-four engine has no free moments of the first or second order, but it does have a large free force of the second order which contributes to the vibration found in unbalanced straight-four designs."