WHY 2800 RPM
#1
Racer
Thread Starter
WHY 2800 RPM
I read a few days ago on here a post that Jake wrote. Can't remember what the topic of the post was. Jake said 2800 rpm was the hardest rpm on the cam chains. WHY?
#2
Rennlist Member
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Maybe this - http://en.wikipedia.org/wiki/VarioCam
For more detail - https://rennlist.com/forums/996-foru...-a-primer.html
However, these explanations do not say anything specifically about 2800 RPM being a changeover point, so maybe ask Jake directly.
For more detail - https://rennlist.com/forums/996-foru...-a-primer.html
However, these explanations do not say anything specifically about 2800 RPM being a changeover point, so maybe ask Jake directly.
#3
Race Director
I suspect it has to do with when the intake valve timing is changed.
Now my info is that for some engines the valve timing is changed around the 1400 RPM level and then again at a bit over the 5K RPM level.
However, later M96 engines with VarioCam Plus may have a different cam timing change profile. After a quick search of my references I can't find any specifics on this.
#4
the only explanation that I can think of is only for vehicles with "variocam plus". At approx. 2800 rpm to 3200 variocam plus switches from small lift to large lift. The stroke of the intake valves changes from 3.6 mm to 11 mm. The timing chains will be required to do a little more work in this mode.
#6
Racer
Thread Starter
the only explanation that I can think of is only for vehicles with "variocam plus". At approx. 2800 rpm to 3200 variocam plus switches from small lift to large lift. The stroke of the intake valves changes from 3.6 mm to 11 mm. The timing chains will be required to do a little more work in this mode.
#7
Race Director
My info is timing is changed at around 1400 RPMs and again at something over 5K RPMs.
Even with VarioCam Plus my info is the transition from low life to high lift occurs at a much lower RPM than 2800. More like half that, around 1400 or so.
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#9
Yes, your 3.4L engine didn't come with VarioCam Plus, just plain ol' VarioCam.
My info is timing is changed at around 1400 RPMs and again at something over 5K RPMs.
Even with VarioCam Plus my info is the transition from low life to high lift occurs at a much lower RPM than 2800. More like half that, around 1400 or so.
My info is timing is changed at around 1400 RPMs and again at something over 5K RPMs.
Even with VarioCam Plus my info is the transition from low life to high lift occurs at a much lower RPM than 2800. More like half that, around 1400 or so.
#10
Rennlist Member
Interesting that the Variocam-Plus 3.6 engines is when the IMS failures make a big jump. If fact it could be that it is the cam chain end of the IMS shaft where the failures begin.
#12
Yes, your 3.4L engine didn't come with VarioCam Plus, just plain ol' VarioCam.
My info is timing is changed at around 1400 RPMs and again at something over 5K RPMs.
Even with VarioCam Plus my info is the transition from low life to high lift occurs at a much lower RPM than 2800. More like half that, around 1400 or so.
My info is timing is changed at around 1400 RPMs and again at something over 5K RPMs.
Even with VarioCam Plus my info is the transition from low life to high lift occurs at a much lower RPM than 2800. More like half that, around 1400 or so.
#13
Pro
Hartech mentions this on one of their documents as well, but I want to say they specify 3K RPM's. I do believe they say its related to the Variocam change over point
The list of documents is here -
http://www.hartech.org/porsche_996_9...ers_guide.html
The list of documents is here -
http://www.hartech.org/porsche_996_9...ers_guide.html
#14
Pro
My wife has been instructed to run the motor 3K RPM's or more. Never lug it (had to explain). and Every on ramp should be done in 2nd gear until she reaches freeway speeds. 1st time she did it she called with OMG!!!! this car can get a ticket in 2nd gear!!!!!!!!!!!
#15
you may be correct, the switch to large lift is not at an exact rpm and it occurs at different rpms depending on several factors. the attached is for the 996 turbo, i could not find anything for the carrera. i ran fister modded mufflers for a while and noticed the switch at about 2800 rpms but with stock exhaust it was nearly seemless.