Why Does the Carrera S "Rattle" When Starting Cold?
06-02-2008, 07:01 PM
#31
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Howz a guy supposed to get any work done around here with distractions like that?
06-03-2008, 08:27 PM
#33
Race Director
Some rattle noise, like chains being dragged over big log, is normal..
I've noticed when I start my car & the engine is cold from sitting overnight, it gives sort of a "rattle" sound when it first starts up. I've even noticed a similar "loud "rattle" sound that only lasts for a second or two (which is really irritating) when I leave a light and may be lugging it a little, or in second gear just crawling around a corner such as I'd do in a residential neighborhood. The sound is not always there, but it does always seem to be there when the engine is cold.
I seem to recall the dealer salesperson telling me that the "S" model does that when it first starts up.
Any comments from those of you that know a lot more than I do would be appreciated.
I seem to recall the dealer salesperson telling me that the "S" model does that when it first starts up.
Any comments from those of you that know a lot more than I do would be appreciated.
When the engine is first started these tensioner/guides (which rely upon oil pressure to position them and apply proper tension) is absent. The chains then sort of drag over these guides/tensioners (their surfaces is made up of a composite plastic material).
Once the engine oil pressure is up high enough -- and this should just take a moment or two normally -- the chain guides/tensioners should be pressed against the chains and the chain being dragged over a log noise gone.
As for the rattle you hear when lugging the engine that is coming from misfire (preignition) from subjecting the engine to too much load at too low RPMs, which just so happens to be the definition of lugging. While this isn't as bad as detonation, it is bad enough. It subjects the bearings to higher loads at lower oil pressure and this can lead to early or premature bearing wear which can lead to lower oil pressure which can lead to more wear and so on. Stop it.
Don't lug engine.
Sincerely,
MarcW.
06-03-2008, 08:56 PM
#35
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and to some extent is just what is happening. These engines have long chains that spin the exhaust cams and these long chains require long guides/tensioners.
When the engine is first started these tensioner/guides (which rely upon oil pressure to position them and apply proper tension) is absent. The chains then sort of drag over these guides/tensioners (their surfaces is made up of a composite plastic material).
Once the engine oil pressure is up high enough -- and this should just take a moment or two normally -- the chain guides/tensioners should be pressed against the chains and the chain being dragged over a log noise gone.
As for the rattle you hear when lugging the engine that is coming from misfire (preignition) from subjecting the engine to too much load at too low RPMs, which just so happens to be the definition of lugging. While this isn't as bad as detonation, it is bad enough. It subjects the bearings to higher loads at lower oil pressure and this can lead to early or premature bearing wear which can lead to lower oil pressure which can lead to more wear and so on. Stop it.
Don't lug engine.
Sincerely,
MarcW.
When the engine is first started these tensioner/guides (which rely upon oil pressure to position them and apply proper tension) is absent. The chains then sort of drag over these guides/tensioners (their surfaces is made up of a composite plastic material).
Once the engine oil pressure is up high enough -- and this should just take a moment or two normally -- the chain guides/tensioners should be pressed against the chains and the chain being dragged over a log noise gone.
As for the rattle you hear when lugging the engine that is coming from misfire (preignition) from subjecting the engine to too much load at too low RPMs, which just so happens to be the definition of lugging. While this isn't as bad as detonation, it is bad enough. It subjects the bearings to higher loads at lower oil pressure and this can lead to early or premature bearing wear which can lead to lower oil pressure which can lead to more wear and so on. Stop it.
Don't lug engine.
Sincerely,
MarcW.
Thanks for this very well thought out & very technically oriented reply. It was just what I was looking for.
06-04-2008, 09:05 PM
#37
Three Wheelin'
I get the new bee to stand behind the P-car and make sure I can see thier reaction on start-up with the PSE on! Priceless, I can almost read thier minds, "What the F*&^K!"
