DFI revisited

[Bruce]

Simple gate logic for when the sensors phase right to start the count to X
chip.
I the ought the dewell was figured in the coils electronics.
I don't have my eDIST running yet,  so I can't say for sure.
What a minute, it just uses the ecm for firing the plugs, I'd just about bet
the dwell control is in the coil
Bruce

----- Original Message -----
From: "Howard Chu" <hyc at highlandsun.com>
To: <diy_efi at diy-efi.org>
Sent: Thursday, October 25, 2001 7:54 PM
Subject: DFI revisited


> I've had some time to re-think my previous approach. One of the problems
I'm
> trying solve by going to direct-fire ignition is insufficient dwell time
at
> high RPM. My previous design doesn't solve that problem. I started looking
> at how I could rig up a timer with my switching logic, but I think I'm
going
> to give up on the switches altogether and just use a PIC16F84 or
something.
>
> And, having made that decision, I now realize I don't need to buy any new
> sensors at all; the stock setup already has two CKP sensors and a CID
> signal. I just need to tap off the CID and one of the CKP sensors to keep
> track of which cylinder needs to fire next. The control logic will be
> something like this: run a countdown timer set at a 5ms interval. If the
> timer runs down before the next ignition pulse from the ECU, just activate
> the current coil by echoing the ECU spark signal to the coil. If the pulse
> comes before the counter runs down, then we have to start charging the
next
> coil while the current coil is operating.
>
> So, the questions - has anyone done something like this before? It looks
> like I need 3 inputs - CID, CKP, and SPARK and 6 +5V coil outputs (These
are
> LS1 "smart coils", remember). Any recommendations on how to do this with
the
> absolute minimum number of components? As another alternative - how smart
> are these coils anyway? If I always tell them to dwell for two cylinder's
> worth of time, will they operate correctly? (Someone please correct these
> specs if I'm wrong: I believe the LS1 coils are 1Ohm resistance, charge
time
> of 4.4ms. I'm working with a maximum engine speed of 7500rpm, or 2.667ms
per
> cylinder. I guess the practical limit is 7000rpm, or 2.857ms per cylinder.
> And with idle at 650rpm, 30.769ms per cylinder.)
>   -- Howard
>
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