| I'm a little surprised at Nissan's negligence in not developing a robust system up front. The decision to go with 360 slots (1° = one slot), although very accurate, seems rather arbitrary. The engine dynamics folks should have refuted the decision to go with so many slots as the additional scatter is obvious and was easily predictable even in the stock setup from the get-go. Seems the control nerds won that battle based on accuracy but the Z lost the war in terms of a robust system. For anyone reading my posts the below excerpt out of everything linked above is what sold me. It's an unheralded but serious concern for the Z. "Since the ref input from these sensors has 360 slots (1 per degree), the resolution of the sensor is exceptionally high. The ECU will see 180 ref trigger inputs per engine cycle which ‘should’ give very accurate control of ignition timing. In stock form this sort of works out (actually the fact that they work at all in a stock car says a lot for how well the factory Nissan ECU can decode the input!). Many aftermarket ECUs (admittedly mostly lower end ones these days) struggle to decode the trigger input at high rpm as the frequency of inputs is so high. So far this all relates to a stock engine though. When you start fitting aggressive cams and heavy duty valve springs, the valve train harmonics mess with the sensor and can cause havoc. While you might assume the cam (and hence CAS) rotates smoothly as the engine turns, what you will actually find is that in certain parts of the rev range the valve train goes through a resonant frequency, the cam actually ‘vibrates’ backwards and forwards a few degrees. It sort of bounces back and forth a few degrees at a very high frequency. The result is that the pickup in the CAS may register more ref inputs as they bounce backwards and forwards across the sensor. If the ECU registers more ref inputs than it expects, it can cause a trigger error resulting in a misfire or simply the ECU will lose track of the actual rpm and then the timing and fuel delivery are no longer accurate."
OverZealous (CT) My General posts (click)
My Technical posts (click) |
14:27:02 10/22/14
