Injector duty cycle
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Injector duty cycle
<center><img src="http://im1.shutterfly.com/procserv?si=00002937301920010424020403992.JPG&ps=0 &rx=640&ry=485"></center><p>Someone on this site was concerned with injector flow (Jenner?). I decided to check duty cycle on the way home today. There appears to be little if any room for more flow (required for more hp) at 5900 rpm & above. The duty cycle does not include the injector's closing time. At 6160 rpm there was only 0.6 milliseconds available. If the injector takes 0.3 to 0.5 ms to close then only 0.1 to 0.3 ms is left. How can you get 25 to 30 more horsepower in this range? APR what am I missing?
P.S. The blip in the air flow at low RPMs is the manifold downstream of the throttle filling with air once the throttle is opened wide.
P.S. The blip in the air flow at low RPMs is the manifold downstream of the throttle filling with air once the throttle is opened wide.
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I wonder if the post processing of the data or the software conversion factors are incorrect...
It doesn't make sense.
One way to check if this is true would be to physically measure the duty cycle (time open divided by time closed) and compare it to the post processing done by the software. I "think" the rule of thumb is not to operate injectors past 80% duty cycle. I wonder if the reason for that is that the output isn't linear past the 80% mark.
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One way to check if this is true would be to physically measure the duty cycle (time open divided by time closed) and compare it to the post processing done by the software. I "think" the rule of thumb is not to operate injectors past 80% duty cycle. I wonder if the reason for that is that the output isn't linear past the 80% mark.
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Injection time & RPM as reported by ECU (measurement block 101)
Close signal is obtained from camshaft sensor, open point is calculated by ECU for each cylinder each time. Graph is average time for cylinders 1-4. Percent duty cycle is = (injection ms)/(1200/RPM). The wastegate control valve (N75) is also run to 95% duty cycle.
As far as linearity, the ideal is regulation of the injection pressure referenced to manifold pressure. In actuality there are pressure pulses in both the manifold & fuel rail that are a function of the operating point. In addition this was an acceleration run, manifold fuel storage is transient. The ECU is programmed to take this into account.
As far as linearity, the ideal is regulation of the injection pressure referenced to manifold pressure. In actuality there are pressure pulses in both the manifold & fuel rail that are a function of the operating point. In addition this was an acceleration run, manifold fuel storage is transient. The ECU is programmed to take this into account.
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