Cranking RPM and the process of starting
#1
Cranking RPM and the process of starting
My DIYPNP is gradually getting closer to starting like stock, but I'd welcome any advice about the process the ECU goes through when starting the car.
This morning the car took about 2 seconds to fire, but then ran smoothly.
Stepping through the log, it took about 0.3 seconds for any rpm to register and that's when Cranking:Y lights up. Run:Y lights half a second later (but I don't see what triggers that). Fuel injection starts 0.3 seconds later. Another 0.3 seconds later it hits 300rpm and fires up cleanly on the next stroke.
For most of that time, I can see it it was cranking at about 250rpm. My Cranking RPM is still set to the DIYAutoTune default 300rpm. Is there any reason I shouldn't reduce the value to 250rpm to speed the process? (Or is 250 actually rather low, and should I look at my battery, ground wiring etc? When cranking, the voltage drops to around 10V. Is that low?)
This morning the car took about 2 seconds to fire, but then ran smoothly.
Stepping through the log, it took about 0.3 seconds for any rpm to register and that's when Cranking:Y lights up. Run:Y lights half a second later (but I don't see what triggers that). Fuel injection starts 0.3 seconds later. Another 0.3 seconds later it hits 300rpm and fires up cleanly on the next stroke.
For most of that time, I can see it it was cranking at about 250rpm. My Cranking RPM is still set to the DIYAutoTune default 300rpm. Is there any reason I shouldn't reduce the value to 250rpm to speed the process? (Or is 250 actually rather low, and should I look at my battery, ground wiring etc? When cranking, the voltage drops to around 10V. Is that low?)
#5
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It should read the pulses instantly, but it skips pulses (user set) before it does anything, correct?
#6
I see your point, though if I had a weak battery I wonder if the cranking would ever reach 400rpm unless I opened the throttle a bit.
<edit> I think I may have misunderstood. I thought Cranking RPM was the speed at which the MS decided it was time to fire the ignition and start the engine, but that's wrong, isn't it? It's actually the speed at which it decides it has started the engine - the ignition's firing all the time fuel is being injected. Is that right?
<edit> I think I may have misunderstood. I thought Cranking RPM was the speed at which the MS decided it was time to fire the ignition and start the engine, but that's wrong, isn't it? It's actually the speed at which it decides it has started the engine - the ignition's firing all the time fuel is being injected. Is that right?
#7
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yes, because it would catch. The cranking RPM is the point where the motor isn't cranking, but actually running. It needs to be HIGHER than your actual RPM during cranking. 300RPM will work; I used that for years.
#17
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The first couple of pulses might be unstable, given that the engine is still accelerating under the power of the starter motor, so the fuel/ignition delivery might not be optimal. Ideally, you want fuel and ignition to be delivered under stable conditions, ie the engine is spinning at a constant angular velocity.