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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Not sure if anyone is interested in profiling cams but I built one out of a stepper motor and dial indicator with digital serial output.
Pic 1 The device
Pic 2 The software
Pic 3 The results.. It's a TW55 cam. The report shows the cam is very close to the publlished specs.
Pic 4 Lobe analysis showing Lift, Velocity, Acceleration and Jerk in Excel
Pic 5 Lobe analysis can be read into MegaLogViewer and 2 files can be compared.. Nice thing about MLV is that you can shift one file referenced to the other so that you can compare ramps etc..
Not that one would ever know when selecting cams considering selection is usually based on lift, duration, intake close and LSA, how important is velocity and acceleration when comparing cams and why did you choose to measure those data points?
DLJ, while in most cases the card specs are all that is needed, the main reason for looking at the profiles was to see what the pick up and set down ramps look like.. The velocity curve seems to show them pretty well.. Acceleration and jerk are supposed to be good for looking at valve train dynamics but the main reason why they were added is that other cam profiling systems have them. Once you've done the calcs for Velocity,, Acceleration and Jerk are real easy to add in..
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Now you need to be able to chart the head flow to the valve lift. That will open some eyes for sure.
Nice job as always Max.
That can be done easily.. It actually brings up a pet peeve of mine. Guys that say you need to port heads to because of some cam that has a bit more lift and duration.. Not true.. Only real issue is whether the flow drops at higher lift. Other than that you can increase overall flow by simply increasing duration and lift.. Going higher lift actually lowers issues for ramp's on open and close. No need to kick the valve hard and have lifter loose contact with the lobe. You can make some really nice numbers with longer cams and higher port efficiency as the longer cams help to control CCPs..
It's all about matching flow to the motor then figuring out if/where you can optimize resonate properties of intake and exhaust tuning. Also it's an iterative process.
That's one of the things real interesting about the new M8s. The low lift flow way up from the 2 valve twincams and So HD was able to cut the cam timing way down.. I suspect that there will be a few junk cams for M8s out there due to guys not understanding this and not matching the cam to the required flow.
Going higher lift actually lowers issues for ramp's on open and close.
I agree with what you're saying. This is used to get the valve train under control after you decide on what you're opening side is going to be. If you design your cam based on what the head flows [among other things] where & when the valve opens & the lift where the demand is greatest sets up the opening side. Now you might need more lift to get it under control. Now you want to decide how fast you're going to close it. Then how you're going to catch it before it crashes into the seat.
My point was that low lift flow is more important on small cams & not on big cams & showing the flow relationship between the cam & the head would help you see what's happening. In Dynomation it will run thousands of iterations to pick the cam timing for the inputs given. With your cam test stand graphing the lift against the crankshaft degrees & the head flow #'s you can see where a change a few degrees one way or another can have an effect that would help explain why some cams look the same on paper look totally different in action.
Crystal ball when looking at cam profiles.
We've had a cam profile program here for some time, but not one that physically measures the lobe.
Next will be solenoids/electrics to open/close the valve?
Scott
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Profiling cams
