[Gmecm] a question of timing

[Rick McLeod]

I didn't see quite enough (maybe there, just didn't see) but when replacing mechanical spark distribution w/ electronic (which it appears you're doing) there needs to be 2 signals, one is per cylinder and the other is per revolution of cam, so that the beginning of the 8 cylinder firning sequence is initiated. (unless using twin-cylinder coils, then a crank position is appropriate) I've seen both addition of a crank position wheel that sends both cylinder and position references, and I 've seen conversion of the mechanical dizzy to do that, which I believe I like better, easier to time base mechanical as long as your electrics allow, otherwise static may be easier to set up on a crank wheel.
   
  Just my 2Cents worth, but am interested in how you adapted TPI to a Buick intake/head?

Don Brown <gs455tpi at comcast.net> wrote:
  My question below is about the reference signal. The application is

buick 455
90 corvette TPI (vin 8)
electromotive hpv1 dis


The tpi to buick is bridged by an adapter that connects the two.

My corvette manual comments that the reference signal provides both rpm and crankshaft position. It doesn't say what the amplitude of the reference signal is.

Since the hpv1 has it's own advance curve I'm going to use it for the timing. But can I use the tach output from the hpv1 for the reference signal into the ecm?

My original plan was to just plug the distributor hole with a fixture that would still turn the oil pump. But as I was thinking (a painful process for me), the tach output is not going to be 8 pulses for each revolution of the distributor that the distributor would provide. I have since modified a distributor to provide the reference output needed by the ecm. 

I think that I've answered my own question here but some comments would be great since I don't think of everything. I believe that I'll need the reference signal from the modified distributor to give both tach and crank position to the ecm (16197128) since the tach signal from the dis won't be giving crank position. I'll still be able to use temperature and map to adjust fuel delivery and will program the ecm to work with the dis

A little additional thougt tells me that If I use the curves in the dis, I don't need a knock sensor. And hopefully I can adjust the hpv1 to eliminate the need for it.

Does anyone know what is the amplitude of the reference signal is?

Thanks in advance for all comments.
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