Today we did some more tuning on a SR20DE naturally aspirated rally car. We previously had tuned this car and we were testing some different cam timing settings today in the hopes of making some more power. Usually we degree in a motor when we build it but we did not have the luxury of building this customers motor so we did the next best thing and tuned it on the dyno. Keep in mind that most tuners do not mess with the cam gear tuning on these cars because you have to remove the valve cover to change the cam timing. Well, we did it and we found some great results. As you can see from the dyno chart there are 3 distinct curves. All 3 curves were fully tuned with timing and fuel corrections and optimized for the cam settings. We didn’t just change the cam gear, do a pull and call it done. The car was previously tuned with an intake cam advanced 5 degrees and the exhaust cam retarded 4 degrees and this is shown in dyno run #11. As you can see the torque and horsepower were great down low but fell off in the higher RPMS. The customer came in with the cams set at zero and after tuning the fuel and timing we came up with the results that can be found in dyno run #1. We noticed that this was not good enough and changed the cam timing to 2 degrees of advance on the intake and 2 degrees of retard on the exhaust. You can see the results of the fuel and ignition timing tuning in dyno run #9. As you can see from this example cam timing can change the power and torque of an engine significantly and can move the power around.
Another thing to remember is whenever you machine the block or the head you are changing the length between the axis of the crank pulley and the axis of the cams. This requires adjustable cam gears to degree the cams in correctly and to get your motor running optimally. This is something that 99% of shops know nothing about. DEGREEING CAMS IN IS A DISCUSSION FOR ANOTHER DAY SO STAY POSTED TO THE BLOG.
