Small Changes, Big Results
Everything we learned with both our two ADCOLE gauges and three Spintron systems has made its way back into the design and manufacturing side of COMP Cams. Without being able to measure the camshaft profiles and the affect of a profile change on dynamics, I’m certain that our progress would have been drastically stymied. Even in systems that are very stable, we can see changes in duration of 5-10 degrees at 0.050 at the valve throughout the operating rpm due to component deflection. A small change in acceleration or the shape of the acceleration curve can reduce the speed limit of the engine by 200 rpm, and sometimes much more in high-speed applications. While I am not sure even a good Pro Stock engine builder could measure the performance change from even 1 degree of duration, I am 100 percent certain that they could find a way to use an extra 200 rpm if it can be provided without a loss of torque or power at lower rpm.
COMP Cam’s Valvetrain Engineering Group has done an amazing job of streamlining the cam grinding process in the last few years. After a new profile is designed, the information is loaded into our main computer database. From there, COMP’s proprietary software converts the profiles over into a computer code that the Okuma machine can read. Afterward, the cam grinding program can be adapted for any engine family given the desired profile and centerlines. Those part and profile files are then loaded onto our network before getting transferred to the grinding machines by COMP’s expert machinists. It’s important to point out that the same machinists who operated the manual production of our NASCAR cams when they were still being ground on Berco grinders moved across the hallway to our new CNC grinders. As always, the people are far more important than the machinery. Furthermore, the efforts our personnel have made to streamline the process can’t be overemphasized. We have even had guys call about a new cam design and fly down the next day to pick up the cam at one of the local airports. You can now call us on Thursday, build and dyno the engine with a new cam on Friday, and then be on the track Saturday and Sunday.
On a typical run of off-the-shelf camshafts, the variations from cam to cam are extremely small. We allow the duration to move around just over a degree from the original design, but we don’t use any error correction software. The error correction software takes the actual measured specs minus the design profile and then multiplies an error correction coefficient back in. This can get your profile accuracy down into the tenths of a degree of duration, but it can adversely change the acceleration curve. The errors we do measure come mostly from compliance of the camshaft during the grinding process, and this remains extremely consistent from cam to cam. On the manual side, we hold lobe separation within about plus or minus 1/2 degree. On the CNC side, the lobe separation is typically within a few hundredths of a degree from design. Hence, the easiest way to tell if a cam was ground on a CNC or a manual machine is by looking at the ADCOLE report and checking the lobe separation on each cylinder. For instance, if the design calls for 108 degrees and the measured range is from 107.97 to 108.01, then it was ground on a CNC machine. If you measure 107.81 to 108.12 degrees, then it was created by someone doing a very good job on a Berco grinder.