SuperMID installation - help needed! - Page 2 - Fuelly Forums

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Old 12-11-2006, 03:41 AM   #11
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How accurate is the pulse width on your car?. If you are driving at e.g. 50mph, then *very slowly* release the accelerator, until you aren't pressing it down, what happens to the pulse width?. Does it go e.g. 4, 3.9, 3.8, 3.7, until it gets to 0, *or* does it go 4, 3.5, 2.9, 2.7, 2.0, 1.4, 0.5, 0 (meaning that it isn't that accurate)?. If it is the first, then I have to wonder why my SuperMID is showing that petrol is used but is reporting no injector pulse width at all (because, you would expect, if the software says pulse width = 0, then fuel consumption should also be 0).

If your car is 4 to 6 at normal cruise, then mine should show minimum 1-1.5, at cruise, and higher when I put my foot down, to get the 25% fuel consumption I get.
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Old 12-11-2006, 06:47 AM   #12
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Hi Matt,

Let me explain how it works.

- When fuel injector is ON, the signal goes to 0V, and when it is OFF, the signal goes to 12V.
- The interface circuit has transistor buffer/inverter, so the output pulse becomes 5V when injector is ON and 0V when it is OFF.
- The SuperMID counts the pulse width by 0.005 msec unit.
- The count number is 1300 when the pulse is 6.5 msec, then SuperMID displays the 6.5 value.
- We know about 0.5 msec mechanical delay between pulse width and mechanical open period.
- The SuperMID subtracts 100 (0.5 msec) from the 1300 count, then the count number is now 1200.
- The SuperMID accumulates the number pulse by pulse, then the accumulated number exceeds the fuel parameter, 7000 in your case, the 1 cc count number +1.

So, I was saying you can't see fuel usage unless you see some pulse number.
Then, I thought the fuel usage number was caused ny some noises.

Is the 25% is always proportional to your actual fuel usage?
Do you know a friend who has an oscilloscope?
If yes, he'll be able to help you, maybe.

Regards,
Yoshi
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Old 12-11-2006, 06:57 AM   #13
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Quote:
Originally Posted by landspeed
My speed sensor is not used on my car - it is meant for cars with the digital display!. It basically pulses between 0-12V. It stays at 12V 66% of the time, dropping to 0V 33% of the time. It does this twice in one revolution.
If the signal swings between 0-12V, the interface of the SuperMID should detect that.
The signal goes to the pin#5 of the processor chip.
Would you please check the siganal at pin#5 swinging between 0-5V?

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Yoshi
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Old 12-11-2006, 07:34 AM   #14
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I don't know how the injectors work on my car, but, I can say, that one pin is connected directly to the battery +12V. The other pin is connected to the ECU, and this is the pin that the ECU activates to activate the injector. Could this have something to do with my problem?.

The speed sensor - is disconnected on my car - but I am going to modify it
to be compatible with the SuperMID - but, at the moment, it is the injector problem I am worried about.

I have made two videos showing the strange findings I am getting (including the fact that it stays at 0.0 pulse and yet the fuel used goes up), and the driving tests, where hard acceleration gives 0.0 pulse (and fuel goes up), and deceleration engine braking causes a 0.5-1.2 pulse (but fuel goes down more slowly, or not at all). I will put them on youtube tonight for people to maybe
guess what is wrong?

Thanks for all the help!

Matt
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Old 12-11-2006, 08:49 AM   #15
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Hi again,

I believe we can't solve these problems without seeing an oscilloscope view.

Regards,
Yoshi
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Old 12-11-2006, 08:53 AM   #16
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The way it sounds is that your ECU uses a switched ground to activate the injectors, not a power signal, which makes sense, as I think that's how most do it.

If that's worth anything.
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Old 12-11-2006, 09:52 AM   #17
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Quote:
Originally Posted by SVOboy
The way it sounds is that your ECU uses a switched ground to activate the injectors, not a power signal, which makes sense, as I think that's how most do it.

If that's worth anything.
I agree. Give that a shot.
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Old 12-11-2006, 11:37 AM   #18
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I *may* have found out the problem with regard to the injectors not being detected (although it doesn't make sense). Will post back later!
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Old 12-11-2006, 11:40 AM   #19
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Oh you tease.
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Old 12-11-2006, 12:26 PM   #20
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It has an 'injector cutoff' thing, which basically cuts off the injectors, while still making the ECU think the injectors are firing.

When this little box has cut the injectors 'off', then the ECU is still sending the pulses to the injectors, but the box is stopping the pulse getting to the injectors.

When the injectors are cut 'off', the SuperMID works perfectly fine (although, in reality, the voltages are exactly the same!). Although, of course, the car is slowing down because there is no fuel!.

When the box is letting the signal go through normally, then the SuperMID does all the bizarre things it was doing, as above.

If I remove this box from the wiring completely (which I have just done), then
the SuperMID only works in the 'faulty' mode as described above. Meaning that it doesn't like my injectors, and that the only way to make it work is to use the LPG cut-off box.

It seens that Nissan ECCS is different from other injector systems somehow?

Thanks for all the help!

Matt
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