[Diy_efi] Re: EMS inputs/output?

[Kent Martin]

Alex,
I have Mitsubishi cam angle pick up at the moment and it outputs two
waveforms.
The signals are digital 0 to 5V signals.
The first goes high 60 DBTC and then low at TDC. This is used primarily for
spark.
Id a distributor is used then this is the only signal you would need for
spark.
The engine I have has two coils (4 cylinder) instead of a distributor. Each
coil
has two outputs and connect two cyclinders1&4 and 2&3. This means that both
cylinders
will have spark at the same time but this is OK because when 1 is firing 4
is on the exhaust stroke so it
only ignites any unburnt fuel in cylinder 4.
The second signal goes high and low half as much as the first but pulses are
not the same time or width.

crank angle    0          180    360     540      720
cylinder firing 1          3         4         2         1
signal 1           ____--____--____--____--
signal 2           _________----________--_
coil 1              _------------__------------_
coil 2              ------__------------__------
injector 1        ___________----------___
injector 3        --_______________-------
injector 4        --------________________
injector 2        _____---------__________

signal 1 and 2 are the input signals and the others are outputs to the coil
and injector driver circuits generated by the EMS from signals 1 and 2.(and
tables and other sensors)
if you sample signal two at the rising and falling edges of signal 1 you can
determine which cylinder is firing or intaking.
The state of signal 2 on the signal 1 rising and falling edges is:-
00110010
If you keep the state of the rising edge in memory and at the falling edge
you can read signal two then you will get the following sequence :-
00,11,00,10
So when you get the previous rising edge value 1 and the current falling
edge value
you know that you are at TDC number 4 firing. If 10 is read then you are
at TDC number one firing. When 00 is read the cylinder is indeterminate.
You can use a counter and set it to the correct value twice during the
sequence
and reset when it gets higher than four. This will allow you to tell which
you are on
all the time.
This only one example of sensors and I'm sure there will be many other
variants.

Drivers are generally just a transistor and take in a digital signal from
micro as shown above. Injector drives may also have peak and hold
current control. This can be done in a number of ways but you
buy integrated devices to do this, but I'm not sure how easy they are
to get hold of. Coil drivers must also have large protection diodes to
protect the transistor from the flyback voltage of the coil.

Anyway there's lots more I haven't said in this as I'm sure
others will feel the need to need or correct me on, but you
are probably best to get hold of a book or some site that
will have more detail on this. Perhaps someone can suggest
a site that has this info?
Kent.

----- Original Message -----
From: "alex averbuch" <averchoob at hotmail.com>
To: <diy_efi at diy-efi.org>
Sent: Friday, July 26, 2002 2:58 PM
Subject: [Diy_efi] Re: EMS inputs/output?


> Kent, you said that to do ignition and sequential injection you need 2
Crank
> Angle sensors. Would you be able to go into more detail about these 2
> inputs?
> When is the signal recieved from each sensor?
> What current/voltage does the average sensor transmit?
> What does each signal represent?
>
> Also, how does an EMS turn the coils off/on?  Is there an intermediate
> hardware driver that the EMS communicates with or can a digital signal be
> used...?  In each case, what signal does the uP itself send (Digital edge,
> Digital Level, etc)?
>
>
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