Rattle in head at 3200

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09-07-2008, 01:43 AM

#16

PorscheG96

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Quote:

Originally Posted by 968workaholic

Raj, you have the operation wrong. The cams are retarded at idle to around 1500, then ADVANCE until around 5000, when the vario cam deactivates and the timing is RETARDED to achieve top end power. Anyone will tell you reatarded cam timing will produce more top end power, while advancing the cam timing will give you better midrange power.

What you say about cam timing in general might be true, but this system only changes the intake cam timing. By opening the intake valves earlier there's more valve overlap between exhaust/intake phase, resulting in some recycling of exhaust with intake charge at low revs for cleaner emissions and more power at high revs. I think Raj has it right about 968 Variocam functionality.

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09-07-2008, 11:30 AM

#17

AZ968Cab

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Quote:

Originally Posted by 968rz

+1 on inspecting your cams and chain, also look at the heat shied by the header, mine cracked at a bolt near #1 cyl and would rattle at certain RPMs.

My S2 had the same thing, turned out I was missing 2 teeth on one of the cam gears.... Caught it just in time. Mechanic identified it by putting the tip of a long screwdriver on the the head cover and put his ear to the handle.... Not very high tech but saved my engine