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EDIS again - signals
02GF74 - 2/4/08 at 07:52 AM

1. pin 8 is power - is this 12 V? or 5 V?

2. what is signal level for SAW?

3. is SAW pulse positive (i.e. mark) or negative (i.e. space)?

4. same questions (2. & 3.) for IDM and PIP

5. IDM is generated when coil is fired (used for rpm) so this will give 2x actual rpm, correct?

6. SAW should be sent 10us after 10 ATDC but EDIS mentions it can be sent anytime but is ignored at a certain points. Can I make SAW equal mark/space square waveform? this will update timing in the EDIS more often than is necessary so will that cause problem?

7. posiiton of VR: engine at TDC for cyl 1, VR at 9'oclock, missing tooth at 3 o'clock - correct? (looking from front)

coozer - 2/4/08 at 08:12 AM

Sounds like your getting too deep into the workings there marra, not got the wiring diagram from Megajolt?

There was enough explanation on there for me to wire mine up using the loom from the car and get it working. I used this site for info when i was setting mine up...
http://www.cate1.co.uk/megajolt/

Only one I can be sure of is 12v to power it up.

Steve

[Edited on 2/4/08 by coozer]

[Edited on 2/4/08 by coozer]

02GF74 - 2/4/08 at 08:16 AM

quote:
Originally posted by coozer
Sounds like your getting too deep into the workings there marra, not got the wiring diagram from Megajolt?


indeed, that is because I am going to make my own megajolt.

why? same reason why people make their own sevens instead of buying cateringhhamvans and:
a) becasue I think I can
b) I should be able done it for tenner.

I realise I won't have any support but then I can't seem to access any of the magajolt/squirt and related sites anyway.

coozer - 2/4/08 at 08:37 AM

Ah, nice study program

02GF74 - 2/4/08 at 02:54 PM

woo hoo!!! some answers here!! seems SAW is square wave - that makes it easier!!

FYI - sorry it is a bit big but I did not draw it!

paulf - 2/4/08 at 07:11 PM

I would do some searching for Edis on google .Theres a lot of info on the workings of it on the web.
If i was going to start from scratch i would look to build something that was self contained rather than relying on the availability of edis parts as then it would be possible to build further units without being reliant on supply of Edis etc.
The next version of megajolt is going to be self contained apparently.
If you want to buld a megajolt using the existing design I have a flash programmer for the processor so could program a processor for you.
Paul.

ken555 - 2/4/08 at 07:32 PM

I have a bare version II board if needed.

MikeRJ - 2/4/08 at 08:11 PM

quote:
Originally posted by 02GF74
woo hoo!!! some answers here!! seems SAW is square wave - that makes it easier!!


Think about it...it can not possibly be a square wave at all engine speed/advance combinations assuming you send the SAW once per ignition event.

Sending it multiple times might work, but is fraught with danger IMO. The EDIS does ignore the SAW at certain points, so if you send a long SAW whilst it was ignoring it, it may see it half way through and interpret it as a much shorter SAW. This is why megajolt (and the Ford ECU) sends the SAW synchronously.

Why would a square wave would be easier? If you are going to use a micro such as an 8051 variant, PIC or AVR, then generating arbitrarily long pulses is very simple.

In terms of component value a Megajolt work-a-like could quite easily be cobbled together for under a tenner. What you pay for is a nice PCB with tinned tracks, solder resist and component mask, and the rather high cost of components when bought through RS or Farrell in small quantities.

quote:
Originally posted by paulf
If i was going to start from scratch i would look to build something that was self contained rather than relying on the availability of edis parts as then it would be possible to build further units without being reliant on supply of Edis etc.


A very good point, though this puts far more emphasis on the reliability of both the code and the hardware. The VB921's have been found to be sadly lacking in any demanding applications, and their internal protection doesn't seem to stop them burning to crisp if you use extended dwells (to compensate for the lower spark energy you get from using them). This makes the only sensible choice to roll your own coil driver using an IGBT with external current limiting and voltage clamping, just as the OEMs do.



[Edited on 2/4/08 by MikeRJ]

02GF74 - 3/4/08 at 08:02 AM

quote:
Originally posted by MikeRJ

Think about it...it can not possibly be a square wave at all engine speed/advance combinations assuming you send the SAW once per ignition event.

Sending it multiple times might work, but is fraught with danger IMO. The EDIS does ignore the SAW at certain points, so if you send a long SAW whilst it was ignoring it, it may see it half way through and interpret it as a much shorter SAW. This is why megajolt (and the Ford ECU) sends the SAW synchronously.



According to the documentation about the EDIS the there is no limit on the frequence it can be sent other than if EDIS does not receive it withing 5 ignition evnets, it reverts to defualt advance of 10 degrees. Likewise, as you stated, there is a period where EDIS ignors the SAW.

The EDIS sould not misinterpret the SAW since if designed properly it would be looking for a low to high transition before counting the high period.

But anyway, I take on board what you & others are saying and am learning all the time - it does appear to be easier to send the SAW after the PIP and seems to be the way MJ does it.

As for doing away with the EDIS, not considered that but for the time being it should make things simpler for me to use this.

quote:
In terms of component value a Megajolt work-a-like could quite easily be cobbled together for under a tenner. What you pay for is a nice PCB with tinned tracks, solder resist and component mask, and the rather high cost of components when bought through RS or Farrell in small quantities.


I don't have a laptop that I can use to program so my controller is going to use push buttons to set the advance map.


[Edited on 3/4/08 by 02GF74]

ken555 - 7/4/08 at 01:22 PM

Also worth having a look at the Ford Patent for the EDIS

Patent