Me han comentado de ajustar el juego de válvulas en vez de a 0,30 admisión y escape a 0,25, que así suena menos en un M30... pero no sé yo...
¿qué opinas?
nuestro debate, mi argumentacion
thank you Charlie,
My guess is that only valve noise is involved in my comparison
in a conventional world heat decreases clearances, but this M30 might not be a linear system, i mean there are a lot of elements involved, made of different materials, so relative termal elongations might go one way or the other in the final system, i do not know all the details, i am only presenting a fact, valve noise increases,...
1- only my case ?
2- if general, what does that mean ?
clearances must be set with cold engine, yes, but that is only for having a common reference, it does not mean that warm engine will go in one direction or in another
we could set clearance in a hot engine if bmw provides the right figures to do so, i have not found such figures,...
y continuo,
thank you for your post
see the news, it is true, do you understand that clearances may increase with heat ? it is not a linear system, so why not ?
proof is not only your own link, but the blue manuals (a note in the footpage), and even mercedes manuals saying that for a warm engine gap should be fitted at +0,05mm with respect to cold engine setting
why do you refuse these facts ? metal expands when heated ? (not all of them, i.e. zirconium tungstate exhibits the so-called "negative thermal expansion,", yeah irrelevan, but...), so what ? it is a combination of metals and geometries, it is not only posible, it is true !
i did understand what you said about valve stems, but my valves are almost new, so no case here
despues de mucho procastinar alguno empieza a buscarle la logica,
Didn't curiosity kill the cat?
As DQ mentions, the manual's spec sheet includes a footnote for setting valve clearances when hot that is
larger than when cold. .014" versus .012. Although the manual is hardly infallible,
there should be an obvious reason for this recommendation. Presumably, the hot setting is in the manual as advice for professional mechanics, working on an hourly rate, who may not care to charge for the time it takes an engine to cool. A quick look at the owners manual and the relevant Autobooks guide only mentions setting valve clearances when cold (below 95 degrees Farenheit). (From long ago personal experience, I have measured valve clearances on M10 and M30 engines when hot when dealing with reground cams. For the most part, I found negligible variations between cold and hot settings. This was not for the direct purpose of measuring any thermal impact on valve clearances as opposed to making sure that everything was operating within acceptable limits.)
For those dubious of DQ's observation and the shop manual's recommendation, perform your own careful test by simply measuring cold versus hot. In the large scheme of things, the differences are negligible. especially since the vast majority of us DIY'ers adjust our valves when cold.
I tried to offer a lay-explanation by focusing on the various angles involved in the mechanical linkage that controls each valve. Per the illustrations, assuming that normal thermodynamic principals apply, the metal expands with heat although some of it expands at different rates and in different directions, allowing for deflection with expansion. (See bowden cable illustration ^^^^.) But there was an equally plausible explanation in one of the linked sources mentioned in this thread: "As the aluminum gets hotter it expands and moves the rocker arm away from the valve."
The design of the aluminum alloy M10 and M30 cylinder heads suspends and supports the cam and rocker shafts securing the rockers. From the illustration below, the aluminum bosses would likely expand upward and away from the heat source (combustion chamber), thus causing a slightly increased valve lash clearance when hot. Being steel, the cam and rocker shafts will not expand at the same rate as the aluminum and this might explain why, all things being equal, all of the heated metal parts do not result in a decreased valve lash clearance. Additionally, the rockers are isolated from the cylinder head and therefore the cylinder head's heat and are therefore less likely to expand at the same rate as the cylinder head material. (Someone handy with a pyrometer and a spare head could measure the expansion of the bosses that carry the cam and rocker shafts to confirm this theory.)
finalmente me autocito,
the manual says 0,25 to 0,30mm
i set them to 0,25, car runs good, and i have a bit of tickling noise, nothing exceptional
i recall some "old school mechanics" here saying that better 0,30, engine runs better and so on
i have recently met with 2 people that say 0,20 and 0,15 respectively, the later drives the coupe in the track every weekend
o sea que si, yo las ajusto a 0,25 y al final la arena concluyo que era adecuado hacerlo asi
