DadTruck wrote:
Doc
do your 'My Experience' rules apply to the UEM calculator when following their instruction of using IVC @ .050 + 15
or to your practice of using observed seat timing?
asking as
when I follow the UEM instructions on a build with over 10.6:1 compression and a 256 @ .050 duration cam I get an effective compression of
8.4 which seems reasonable with a moderate high static compression and a medium sized cam. The medium size cam will not bleed off cylinder
pressure like a really large cam
when I follow your instructions and use seat IVC on the build mentioned above I get an effective compression of 6.8, which is off the scale on the low side.
That does not seem right.
do your 'My Experience' rules apply to the UEM calculator when following their instruction of using IVC @ .050 + 15
or to your practice of using observed seat timing?
asking as
when I follow the UEM instructions on a build with over 10.6:1 compression and a 256 @ .050 duration cam I get an effective compression of
8.4 which seems reasonable with a moderate high static compression and a medium sized cam. The medium size cam will not bleed off cylinder
pressure like a really large cam
when I follow your instructions and use seat IVC on the build mentioned above I get an effective compression of 6.8, which is off the scale on the low side.
That does not seem right.
Agreed.. that a a large difference that does not make much sense.
I base my calculations on "what the engine will see" and that is the point where the intake valve is on the seat... solid on the seat.
There is some judgement on when the true on the seat IVC "moment" occurs because some lobe ramps set the valve down slowly so try increasing the clearance a bit, to get off the "lazy" lash ramp area, then take a new reading.
Use a dial indicator to get a better idea on where the cam's lobe flank movement transitions into the lash ramp. (the lobe flank moves a lot faster then the clearance ramp area)
My guess is that the lash (clearance) you are using for testing may not be correct for the lash ramp ground onto the cam.
DD