I am not totally following what you all are discussing (undergraduate EE was a long time ago), but bottom-line it sounds like Andial's $600 splitter could be replaced by $50 of standard electronic components? Thereby reducing the cost of a twin-plug conversion by 25% or so? Is that correct?

Yupp.
Andial splitter is nothing else but 25$ of electronic components.


rick:
I don't have schematics of DME but woulnd't it be a good idea to rather intercept signal before it goes into single Darlington in the box itself and just connect it to two Darlingtons on a cooler in separate box - connected to it's own coils.

Anyway, it's a simple hack. HW cwould cost something like 30 bucks...

I think the Andial splitter has about $150 of components in it. Two Bosch ignition modules "ignitors" (~$50 each), connectors for them ($10 each?), two 65 amp airplane pull switches ($10 ea) and about $15 worth of Leds, connector strips, regulator, and some descrete components.

If you replaced the $100 worth of Bosch ignition modules with power transistors you could reduce the cost significantly.

My own thoughts are that I want the splitter to reside in the engine compartment to avoid hacking the harness up and running another wire. I intend to spring for the Bosch ignitors because of their proven robustness in the engine environment.
-Chris

Is the signal into the darlington a 5v square wave?

Darlingtons are just two cascade-connected transistors. You cannot feed them with TTL-logic levels, but i believe there are components that can be switched directly with TTL (maybe those Bosch "ignitors" Bennet is talking about). That way, you could make your own splitter. 7205 for 12-to-5 volt downpull for TTL logic Vcc, 7400 as inverter, couple of condensors to get rid of EFI and two "ignitors" to hit the coils with.

Dunno what "ignitors" cost but other components total cost is aound 12 bucks, not counting the box and heat-sink.

Loren: yeah, 7400 has four gates but it's dirt-cheap...something like $0.95. Electronic compontent pricing is weird and has often no correspondence with device's complexity.

You can pay 2 bucks for 10 000 gates VHL circuit and 10 bucks for one single stupid transistor, just beacuse IC is being made in bigger series.

PC motherboards are real-life examples of it....they are book-typical proof of how availability and competition cuts prices....we are talking about 5-million gates of IC, hundreds of components, multi-layered PCB and whatnot...for $90.

i was just on the phone with Nology and they have a 2 channel ignitor that will fire 2 coils but it uses a 5v square wave signal. Warner (the owner) ws very helpful he drives a 930 daily (woo hoo) and had a lot to say about twin vs. single plug.

Great! Tell us what he said then!! http://www.pelicanparts.com/support/smileys/wat3.gif

I was afraid you'd say that. :rolleyes: Didn't want to highjack my own thread but here goes. (I still hope to complete this discussion)
Warner doesn't think that twin plugging is still required given the progress in ignition systems recently. He cited examples including CMW racing's 4 and 4.5 (yeah they have a 4.5 in development) and several Baja racers who use 911 motors converting BACK to single plug using high power CDi, with nology coil, hotwires and silverstone plugs. They also have BBC (big block chevy for the uncultured;) guys running 7 to 8 liters with bores that are huge and no problems.

Given what I know about 911 combustion chamber shape etc. I'm not sure it overcomes the problem of having a big honking hi-comp piston dome dividing half the mixture from the flame front. I'd like to see some dyno sheets and get some real world exp.

I believe you will still need the Bosch modules for Dwell control.

The entire splitter could be built with $15 worth of components, a $5 Radio Shack breadboard and $7 box/enclosure ... for a total of under $30! Selling it for $100 would be ... [fill in the blank] ...

That depends, Bosch makes both smart and dumb ignition modules, some ECU's control dwell, others dont. I dont know whether motronic controls dwell.

I have aftermarket EFI that can be set for either module

Ok, so do any of the EEs in the audience know if at any point the DME system uses the 5v square wave or it is not required in the design? It seems that if there is the equivalent of an ignitor in the DME box then it's triggered by X?? kind of signal?

I found the schematic and, well maybe after a few years of EE classes this will make sense ;) Seriously though, I can trace 1 and 21 back and find the components. Where does the crank signals come in?

..an excellent way for you to make a little money on the side Warren. ;)
-Chris

Has anyone replicated a splitter box as yet?

Why can't one just run two ignition systems (MSD or Crane) off the single OEM trigger signal to drive two high powered coils?

Bump! Chris, have you engineered a cheap splitter box yet, to drive two ignition coils and a 964/993 Distributor?

I'm not to sure I'm willing to spend $600 on an Andial unit, or ~$1k on two Crane/MSD ignition systems :eek:

Won't a Electromotive XDi crank-fired ignition easily solve what you're trying to do without reinventing the wheel?

Yes, but how much is the Electromotive setup going to cost, inc. installation?

How about something like this TWIN FIRE Ignition Coil (typically used for Harley's etc)?

http://www.mpsracing.com/products/Dyna/ig01cd.asp

40,000 Volts per output.

I came up with something that worked - on the bench at least. Between losng my "test car" back in 2003 and the new business I haven't had a chance to do anything further with it.
-Chris

Would this work?

http://www.mwignitions.com/pdf/Pro12_S3.pdf