Motec - going from 1 coil to 8

[750hp]

Every now and then I have to admit defeat and admit that my Google search skills aren't what they used to be. For that matter, I'm so clueless about search engines I got excited when Alta Vista was talking up its IPO all those years ago...

Anyway, an EFI question. My 351W currently has an M800 Motec with a crank trigger and an MSD distributor modified to run as a cam sync (7 of the 8 reluctors removed). I then have an MSD Digital 6 running a single MSD coil.

What do I need to buy to convert to coil near plug? Current plan;
Convert magnetic pickup to Hall effect in distributor.
Blank the dist cap as the dist body will now simply be a cam sync and an oil pump drive.
Buy 8 new Delco GM LS coils.
Run M800 in waste spark so I don't need to buy an ignition expander.

So here's where I lose my way. Do I need anything between the M800 and the coils to boost/control spark? If not, can I remove the MSD Digital 6? Is it optional to either run an ignition booster or not? It seems that the coils are running in a squillion cars with 15 to 20lb boost (which for me will be about 900 to 1000ish engine hp and 700 to 800lb/ft if power/torque somehow factors into the equation but I guess boost pressure would be more relevant for the coils).

Am I missing anything else?

Thanks!

[spookypt]

Call Ozvenom Craig!!!lol

[albanycobra]

Normally LS coils connect straight to the Ecu as they have built in modules as I understand it. As usual check with Motec before you wore up.

[SydneyChris]

or go to the Motec forum.. its manned by their tech staff.. will sort you out promptly..

[boxhead]

I have a few buggy mates running Motec in there LS powered race cars.
If needed I can put you in contact with them.
One just had a freshen up in preperation for Finke.
https://www.facebook.com/rsrc.php/v2...PAXP-deijE.gif

[damage]

You need the Motec ignition expander to run 8 coils, the M800 only has 6 ignition outputs as standard. If you use the expander then you can drive the 8 coils of one output. You shouldnt need a booster because the coils will have sufficient output, just need to make sure you get your axis tables correct so you get your dwell times right so you dont burn the tips off your plugs.

[Aussie Mike]

Could you run 4 ignition outputs and run a wasted spark? i.e fire the ignition on both the compression and exhaust strokes. One output triggering 2 coils.

Cheers

[damage]

No you would end up with spark all over the place each output is one reference signal so wont work on sequential firing. It would have been easier if they had designed them with more ignition outputs. Also you cant run wasted spark on CDI system which is what your require for individual coil. You need to run crank sensor for RPM and cam sensor for phasing, the expander then decides timing of spark to each coil.

Something like that anyway ages since I've played with these.

[Aussie Mike]

Thanks for the clarification Damage. I only thought of it because it's pretty popular technique with the old motorcycles I mess with. They are often have coils with dual secondary windings and dual outputs.

Cheers

[750hp]

I asked the question elsewhere and got all of the same information with one key difference.
Damage, the popular option for tightarses like me is to run 8 coils in wasted spark configuration and configure to sync once per 2 revolutions which still allows sequential ignition trimming with wasted spark when combining the cam phasing (cam sync) with my crank trigger.

The GM Gen4 coils are proven to 1200rwhp in wasted spark (keeping dwell under 5ms so they don't prematurely fire!). To prove a point, a guy with a shop in NSW ran one single LS coil on a blown big block and it made 1000hp at the engine. Nuts!

I can ditch the MSD CDI which I'm happy to do as I'm a bit suss about MSD Digital 6&7 quality.

The Mercury Marine IGN-1A smart coils are an even better product (and Damage I'm sure you know all about this brand ) with the built in ignitors, but they're a bit more exxy than the pov LS coils.

The thing I need to do is power up my ECU to remind myself what outputs I had previously configured. If I use 4 of the 6 for ignition, I think I only have/need elec fans and the second fuel pump that comes on above a preset boost pressure. If there's anything else I've forgotten, then I'll need to open my wallet and get the ignition expander...

Thanks for your comments; it's fun getting my head back into EFI conversations after only stuffing around with Holleys for the last few years.

[albanycobra]

I'm very interested in this as I am converting to Motec one day and want to ditch my MSD 6AL and MSD dissy and use an AU falcon TDC cam sensor.

[750hp]

I'd use a factory cam sensor, but unfortunately Ford never made one for a 9.5" deck motor.
My distributor is out and it turns out the dist shaft is slightly bent, which explains why the bronze gear is wearing even quicker than they normally do (it's a billet steel solid roller cam combo).

I could get someone to make a hybrid body/shaft/sensor as a custom piece, but a place in the states makes a nice billet piece that will bolt straight in. Camshaft Synchronizer

[albanycobra]

I have a 302 and 351 version of the same msd dissy and there is not much difference. shaft diameter and oil pump drive shaft diameter was only difference. So you can run a 302 dissy in 351 with a 302 oil pump.

I'm thinking this may be the way forward for me, means dropping sump and changing oil pump and drive shaft but that's easy.

[damage]

I guess it depends on how long you want your coils to last as far as I'm aware if you run wasted spark through a CDI coil set up it overheats the coils and you end up with capacitor failure and or premature coil failure, the other issue is excess temperature also causes spark break down.

I suppose it's a budget toss up as to what's worth more replacement coils or the expander unit.

The other option you can also look at if a cam sensor is an issue is 2 opposing crank sensors and then tell the computer what it needs to listen too.

To be honest we couldn't ever run wasted spark on 2 stroke applications at all so I haven't had a great deal to do with it.

If you set them up correct on CDI I know they will run 15,000 rpm and never miss a beat. A pulse input of 350-400 volts to the Mercury coils produces a nice fat 40,000 volt spark so you know your alive when those suckers bite you.

[750hp]

Bloody hell I hate when people dazzle me with logic! You're right that a one-off cost for the expander would prevent ongoing replacement coil costs...

Originally Posted by damage

If you set them up correct on CDI I know they will run 15,000 rpm and never miss a beat.

I won't try that sort of rpm with my motor. It might not miss a beat, but it might be missing a few conrods afterwards!

[damage]

Out of interest why not just run the MSD dual sync distributor?

[damage]

We could only run that rpm because our dwell time for coil charge was a lot less then what your looking at.
At 8000 rpm the time between firing cycle on wasted spark is 7.5ms in a 4 stroke so if your required dwell time for peak charge is 5ms your coil isn't getting much break. On sequential your firing cycle is 15ms so your duty cycle on the coil is 30%. Also don't forget every time a j gap plug fires you are also removing electrode metal, so in theory your halving your spark plug life too.

[750hp]

Yep everything you're saying makes sense - thanks.

Now that I need to replace the distributor, the much lower profile of the cam sync plug will allow me to run intake pipe from the intercooler down lower and keep it under a standard bonnet. This is going in the XY.

Here's the height I'm looking at reducing...

[damage]

Looks good

[albanycobra]

Craig
I have an Edlebrock lowline 90deg throttlebody to 4 barrel that would drop down your current set up a bit.