SuperMID installation - help needed!

[landspeed]

Edit - the outcome of this was that my car had a strange
fuel injection system - the problem was resolved and the knowledge will
be useful for other cars with Pulse Width Modulation injector systems.

Yoshi was extremely helpful throughout, and I cannot recommend the SuperMID more (and the level of support is second to none, which is a
refreshing change these days!



I have got my SuperMID (looks very well made, and can't wait to get it working!). I have sent an email to Yoshi with a description of the current installation problems, but need to wait till Japanese time comes around again (it is early morning there just now). I was wondering if anyone here might have some ideas as to what is going wrong at the present time.

My SuperMID comes with 4 wires : Ground, +12v, Injector, and Speed sensor.

I need to mess around with my speed sensor to make it work, so, at the moment, I have just been using the injector / fuel used measurements.

I have connected the wires as follows:

Ground - goes to the same ground (engine ground) as the injectors.
+12v - the +12v supply that the ECU uses
Injector - goes to one of the 4 injectors:
- The have two wires from the ECU - there is a single common
ground, which they all use, but each injector also has a unique
wire which is used to 'fire' the injector. I have connected the
injector wire to one of these individual injector wires.
Speed sensor - connected to my speed sensor but no signal at all (I will look
into this later).

I *think* I have wired it up properly (at least in terms of Ground,+12v,Injector), and here is what happens:

(1) When I start the car, the SuperMID readings show (when engine is idling)
(1) Injector Pulse 0.00
(2) The 'litres used' starts going up at a constant rate.

(2) If I rev the engine, this happens:
(1) Injector Pulse 0.00
(2) The 'litres used' goes up a bit faster.
- When I let go of the accelerator after revving the engine, this happens:
(1) Injector pulse goes up to 6, for a split second
(2) The 'litres used' keep going up at a constant rate.

(3) If I drive, at 50mph, cruising with gentle, fuel-efficient driving, I get:
(1) Injector Pulse 0.00
(2) The 'litres used' goes up faster then when at idle

(4) If I drive at 50mph, then put my foot down, and go to full boost on the turbo, I get:
(1) Injector Pulse 0.00
(2) The 'litres used' goes up at the same rate as when I am driving carefully at the same speed.

(5) If I coast in-gear down a hill (my ECU does fuel-cut in this scenario, which it says in my service manual) this happens:
(1) Injector Pulse 0.5 (it spikes to 1.3 at the beginning then stays at 0.5 for the rest of the time)
(2) The 'litres used' stops going down (although sometimes goes down v. slowly).

Therefore:

(1) the 'Injector Pulse' only goes up when fuel-cut is active and the injectors are *off*
(2) The 'litres used' is only based on the engine speed, and not on what the injector pulse length actually is
(3) The only exception is coasting downhill, which is when the litres used stops going up (which makes sense), but the injector pulse width goes up (which doesn't make sense).

Can anyone see what is happening where?. The (3) in the sentence above in particular makes no sense, and I can't see how a hardware fault would cause this.

I know I will get it sorted in the end, but perhaps this thread might help someone else in the future when setting up their car

Matt

[SVOboy]

Number one: Props to another MID user, good stuff there.

So, let me get this straight, the Nissan has a common ground and switched power to the injectors? And you're tapping the injector from just the ecu side of things?

It seems like there is something RPM related going on here. What does it do if you take it out of gear and rev it up/down?

[landspeed]

Edit : I formatted post (1) using spaces to make it make sense - it is a little confusing as the leading spaces has been deleted!.

If I rev the engine, it stays at 0.0 injector pulse width, but when the engine is slowing down (therefore with the fuel cut active), the injector pulse width goes above 0 (up to 6.0) for a brief period of time.

If I keep the engine at higher speeds at idle, the injector pulse width stays at 0.0, but the 'total fuel used' display (bottom right) speeds up. This doesn't make sense to me?

Edit : Looking at the circuit diagram, for the injectors, I should have said :

(1) The injectors are all connected to the battery '+' terminal, via a fusible link
(2) Each injector is also connected to the ECU, which turns them on + off when it wants to.
(3) I connected the SuperMID signal to wire (2), which is not the common ground wire.

I'll just go and check my wiring is OK, but I know it is!

[landspeed]

I have connected to the ground to the 'engine ground' (which is the same ground the injectors and distributor use), and there are 4 wires from the ECU to this. The positive supply I am using is the same one that the injectors use (and, it is the one that the ECU uses!). It goes straight to the battery via a fusible link.

Would it make any difference if I used the 'body ground' rather than the 'engine ground'?. Should there be a difference?

Thanks for the help!

Matt

[krousdb]

I used my cigarette lighter for the positive and negative connections for power. I don't know why the pulse width is acting that way. Try connecting to the common injector ground instead of one of 4 injector wires. Just to see what happens.

[landspeed]

If I connect it to the common ground, it will be the same ground as the SuperMIDs ground for power. But, it still might be worth a try!.

I suppose I will have to try taking power from some other source, but still
wonder why that might be causing these problems!.

Edit : Yoshi (if you read this) - what kind of speed sensor does the Prius use?. My car has a simple speed sensor, which basically has infinite resistance, and makes a connection twice for each revolution. It doesn't
have +12v going through it, though. It would be possible to rewire it so that
it connects to +12v twice on each turn of the speed cable, if that was
helpful?

[GasSavers_Yoshi]

Hi,

The injector pulse display is just a raw number measured by SuperMID.
The fuel usage display is accumulated values of the injector pulse.
My bet is that the injector line is not connected properly and the fuel usage count was caused by some noises.
Would you please make sure the injector line connection?

Originally Posted by landspeed

Edit : Yoshi (if you read this) - what kind of speed sensor does the Prius use?. My car has a simple speed sensor, which basically has infinite resistance, and makes a connection twice for each revolution. It doesn't
have +12v going through it, though. It would be possible to rewire it so that
it connects to +12v twice on each turn of the speed cable, if that was
helpful?

The original signal of speed sensor on Prius is from wheel rotation sensors on each wheel, which is mainly prepared for the ABS system. The computer manipulates the signal, then the signal goes to speedometer, other computers and pulse output for external equipment such as Navi system.

What kind of equipment is your speed sensor signal connected to?
I believe an equipment needs pulse signal, so the speed pulse exists on the wire.

Regards,
Yoshi

[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.

I will aim to get the injector signal working first, before looking at the speed
sensor. Unfortunately, I checked the wiring last night - it is perfect, and it is
connected to an injector.

I am going to try a direct connection to the battery for the +12V and ground tonight, to see if that helps! Then I may try connecting to a different injector or something like that!

Matt

P.S. What confuses me is that, when the injector pulse is 0, the fuel usage increases, whereas when the injector pulse is 0.5, the fuel usage stops (that doesn't make sense)

[landspeed]

OK, I know the fuel usage isn't calibrated, but, on the way to work, I noticed

(1) The SuperMID says I used 0.6 of a litre of fuel (about 25% of what I would actually use
(2) The Injector pulse width says 0.0 all the way there.

Does anyone know how it would say 0.0 for the pulse width and still say that I have used a significant amount of fuel (the amount used is equivalent to 80 MPG (US) if it was correct?

Does anyone know what their normal ranges for injector pulse width are, cruising at e.g. 30,40, or 50, when cruising, or when accelerating?

Thanks!

[krousdb]

Well in my case, the pulse width was about 2 at idle and 12 at full throttle. Normal cruising was 4 to 6 depending on the speed.