Need info about a camshaft
03-18-2007, 11:44 AM
#2
Hmmmmm...
Just checked one just pulled from a 87 turbo. Number on the part is 155-05
That matches PET for turbo/51 944-105-155-05
The part number listed on the PET for th N/A is 955-105-155-09
hope this helps..
-BB
That matches PET for turbo/51 944-105-155-05
The part number listed on the PET for th N/A is 955-105-155-09
hope this helps..
-BB
03-18-2007, 11:58 AM
#3
Racer
Thread Starter
found a pdf that compares 155.05, 155.09 ,155.9r camshafts but i dont get any wiser.
is the 9r cam for eurocars only or is it for later 944:s like my 1990?
or do i not have the original camshaft in my car????
according to the pdf
turbo cam 155.05
exhaust duration: 220
intake duration: 228
155.9r
exhaust duration: 215
intake duration: 223
what does this mean?
is the 9r cam for eurocars only or is it for later 944:s like my 1990?
or do i not have the original camshaft in my car????
according to the pdf
turbo cam 155.05
exhaust duration: 220
intake duration: 228
155.9r
exhaust duration: 215
intake duration: 223
what does this mean?
03-18-2007, 01:59 PM
#4
Originally Posted by DLS
found a pdf that compares 155.05, 155.09 ,155.9r camshafts but i dont get any wiser.
is the 9r cam for eurocars only or is it for later 944:s like my 1990?
or do i not have the original camshaft in my car????
according to the pdf
turbo cam 155.05
exhaust duration: 220
intake duration: 228
155.9r
exhaust duration: 215
intake duration: 223
what does this mean?
is the 9r cam for eurocars only or is it for later 944:s like my 1990?
or do i not have the original camshaft in my car????
according to the pdf
turbo cam 155.05
exhaust duration: 220
intake duration: 228
155.9r
exhaust duration: 215
intake duration: 223
what does this mean?
I think it refers to the degree? in lift?? for the cam or how long the valve is open during it's power stroke and exhaust stroke??? recalling what I think I remember from shop class.
Also there is a clear difference between the two cams and I would use the cam for the turbo on a turbo.
-BB
03-18-2007, 04:05 PM
#6
The duration refers to the period (degrees from 360)
that the valves are off the seat.
A stock Porsche TURBO cam will tend to have less lift and duration because it is easier to achieve less overlap this way.
When you have high overlap with a turbo, the relatively high backpressure (ESPECIALLY with the tiny #6 exhaust housing) will pull exhaust gasses back into either the chamber OR all the way into the intake (depending on cam timing with a single cam engine).
Obviously, this will light off the fresh charge and cause knock.
You can spend weeks agonizing on this relationship with the 951.....trust me.
that the valves are off the seat.
A stock Porsche TURBO cam will tend to have less lift and duration because it is easier to achieve less overlap this way.
When you have high overlap with a turbo, the relatively high backpressure (ESPECIALLY with the tiny #6 exhaust housing) will pull exhaust gasses back into either the chamber OR all the way into the intake (depending on cam timing with a single cam engine).
Obviously, this will light off the fresh charge and cause knock.
You can spend weeks agonizing on this relationship with the 951.....trust me.
