Problem with Measuring Camshaft Profile

[zning4]

Hello everyone, I am Zhen Ning from the National University of Singapore, FSAE team, working on the engine.

Our current engine is a 07/08 CBR600RR and I have been trying to measure the profile of the camshaft. So far, the results of my measurements gave me profiles that are way off from those mentioned in the specs; the duration of the camshafts do not tally. I have tried a few methods of measurement:

1) Measuring the camshaft by itself with a protractor stuck to the axis of rotation and measuring the cam lobes with a dial gauge
2) Measuring the camshaft while it is fixed inside the engine, attaching a protractor to the crankshaft to turn the engine and measuring the lobe with a dial gauge

The results of both measurements are similar in a sense that both produce cam durations that are not according to the spec of the manufacturer. I had the luxury of measuring the cam shafts from another 07/08 CBR600RR engine but the results were the same.

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Results of Measurements
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For the intake, both results show that they have a duration of around 210 degrees, measured at 1mm lift, which is off from the manufacturers spec of 245 degrees. For the exhaust, I only measured about 200 degrees for its duration when it should be 225 degrees. The timing at which the exhaust shaft opens and closes is also wrong; what I did was to adjust the timing of the intake shaft to open at the correct timing and apply the same offset to the exhaust shaft.

Am I doing something wrong when measuring the profile of the camshafts? Any inputs is greatly appreciated (:

Zhen Ning
NUS FSAE
Engine Department

[Z]

I have tried a few methods of measurement:

1) Measuring the camshaft by itself with a protractor stuck to the axis of rotation and measuring the cam lobes with a dial gauge
2) Measuring the camshaft while it is fixed inside the engine, attaching a protractor to the crankshaft to turn the engine and measuring the lobe with a dial gauge

...

Am I doing something wrong when measuring the profile of the camshafts?

Zhen,

You sure are.

Your second picture (seems to) show the dial-gauge with a small diameter ball at the end of it, with this ball in direct contact with the cam lobe.

The valve has a large diameter, quite flat surface on its "bucket-tappet", with this flat surface in direct contact with the cam lobe.

Therein lies the difference!

Repeat your measurements with the dial-gauge in direct contact with the top of the bucket-tappet. This will tell you how much the valve itself is actually moving.

Z

[Jay Lawrence]

Hi Zhen,

Excellent first post.
Think about the surface you are measuring with (the ball end of a dial gauge) vs. the surface that the cam is touching. Imagine how the 2 different cases might interact

edit: Z beat me

[zning4]

Hi Z and Jay,

Thanks for your quick replies!

I have been thinking of how can I make the measurements directly on the top of the bucket-tappet and searching online for ideas of doing the measurement but its all to no avail. There is no space for the shaft of the dial gauge to pass by the cam shaft and reach the bucket-tappet.

Do you have any suggestions on performing this measurements?

Thanks!

Zhen Ning
NUS FSAE
Engine Department

[DougMilliken]

Look through this long detailed thread,
http://www.r3vlimited.com/board/showthread.php?t=148000&page=17
About 1/2 way down are a couple of drawings with yellow background that show the problem. Followed by pictures of a special holder to keep the dial gauge lined up with the tappet axis. Also, a long thin extension for the probe, to reach past the cam.

[Jonny Rochester]

a duration of around 210 degrees, measured at 1mm lift, which is off from the manufacturers spec of 245 degrees.

It seams like you have a clean workshop, clean engine, engine stand, tools, measuring stuff, data... Your a long way ahead.
As said, your dial gauge should be measuring valve movement, not the cam itself. Ideally, get the dial gauge to touch the cam bucket if you can, however this does not entirely explain your duration problem.

The factory spec maybe the full duration from open to closed. This is tricky to measure as you know, so when we setup cams we only start measuring duration after an arbitrator amount of lift (say 1mm) which makes our duration measurements more consistent. But then we have the problem of different duration's quoted for different lifts. Make sure to know what lift your factory spec is quoted at.

210 degress at 1mm seams reasonable, so you maybe not that far off.

[Jay Lawrence]

Zhen,

Personally, when I performed this experiment, I just machined up a little flat faced follower out of nylon that had an interference fit onto the end of the dial gauge. This then replicated the action of the bucket and was easier than trying to measure the bucket itself.