hall sensor on a '85 4kq? (5 window type?)

[Ken Keith]

Quoting JShadzi at aol.com:

> << Now I'm wondering how the stock 4kq hall sensor works.  I know
>  the hot ticket for some EFI conversions are to use the NF/NG
>  ignition system, which has a 5 window hall sensor.  Is this is the
>  case with the 4kq as well?>>
>
> Yes, basically the same distributor save for the vacuum advance

Hi Javad!

Meaning they both have some form of vacuum advance, but they are different from each other?  Or, one of them has vacuum advance and the other one doesn't.  If I were to guess (here I go), I would say the 4kq has the vacuum advance, since I recall my past Coupe GT's as having that little shift light that is affected by a functional vacuum advance.

Where do I tap into the hall signal?  Is it at the wires at the distributor?  I read in the archives that you tapped into yours at one point, but I was wondering if I can find anywhere (online) which actual wires they are, like as far as color and so forth.

> << I remember the NF/NG system is preferred over the 4kq system,
>  but that's because of the knock sensor. >>
>
> That's not the only reason.  The CIS3 uses ignition maps based on load,
> which  the 4kq does not do, just a fixed retard per RPM.  Because of this the
> CIS3 system can advance or retard timing within the curve based on load, a
> very nice feature.  Similar to the MC ingnition system.

Yeah, that makes sense too.

Does the hall signal itself change with the vacuum advance, or is the hall signal constant?

I think I would still have to incorporate the timing reference pin in the flywheel for my system to function correctly.

I was thinking this morning that if I have a choice between using components from the MC-1/MAC11 ignition system, or parts from the 4kq ignition, I would prefer to use the 4kq.  That way I can retain a more complete wiring harness for the MC-1.  The idea would be to maybe use those extra parts for some kind of low-to-midrange turbo conversion on a cheap Coupe GT if I ever come across one that's cheap.

I suppose since I would be using the distributor, hold it...  I just had a thought.  So, if I use the 4kq hall sensor, does that mean I'm using the distributor from the 4kq in the MC-1 long block?  I suppose it does mean that.  Are there any special considerations for doing this?

Someday in the future, I have the option of going with direct ignition with 5 coils.  At that point, I don't need to use the distributor for distributing spark.  But I guess I still have to have one physically in the head to provide for the hall signal, if that's where that stuff is.

I think I may have to provide them the length of the flywheel teeth and gaps.  Does anyone have this information?  I have my flywheels still off the car, but I don't have those type of measuring tools (calipers?).  I've been wanting to get a set of inexpensive calipers, but if there's an official spec for the teeth, I'll go with that one.

I have a fax that shows how "motronic triggering" is (can be) handled with this system.  It's a bit hard to read, but the different notes on it say, "camshaft sync, show degrees of leading and trailing edges", "no of teeth", "direction of rotation", "length of tooth", "length of gap", "no of missing teeth".  I don't know if this will be of any value to me.

I think the system will require both crank and cam reference signals, if not just a cam one.

Anyhow, enough typing for now.  I would really appreciate any further comments or suggestions on this.

Thanks,

Ken