MSD Question....
 

Hey guys... Its time for hotter...sharper spark.... I am looking to upgrade my ignition to a MDS or Malory set up...

From what I understand I will need two boxes...two coils...

Can someone who has installed a setup give me an idea of how its done... Wiring...exc...

Thanks -

Here you go

https://www.rx7club.com/attachment.p...1&d=1197245556

Which is better.... One MDS Box or two?

This is going in my racecar...

Two. Even distribution of the spark to both coils.

It's a rotary, you only need one box for the leading. Trailing is a waste of money.

I learn something new everyday. Thanks for the clarification. :icon_tup:

+1 for what the troch says, i upgraded to a single MSD box about two years ago and have had excellent results

3 msds
 

Im really new to the rotaries but in sbc v8s it is rare to see more than one msd. I have seen RX7s with 3 MSDs what the point,does it make it spark more?

the little quote ive hurd was, 1 box gets you 90% of the way, the other 2 get the other 10%

So... Two boxes it is... 6A or 6AL?

doesnt matter. 6al has a rev limiting capability, the only difference. run one box through the leading with a 2nd gen leading coil and be done with it. simple install too!

Can you explain this a little more about the 2nd gen coil..... Thank you....

Use a 2nd gen leading coil with either the MSD 6a or 6al box....i perfer the 6al because of the rev limiter.

Woah, whats with wiring the leading and trailing coils in parallel in that diagram...Why would you want to do that?


The reason you see 2-3 MSD boxes is the guys who are using the rev limiter...cant be done with 1 box.
The guys who run 3 are either tired of replacing the cap and rotor from the multiple sparks burning them out, or want to run complete directfire.

Trailing seems to need 2 boxes for some reason. Jeff or Addict can explain it better, (waste spark?). Also need 3 boxes to even have rev limit capacity, unless trailing is disabled and the power for the tach and fuel pump are switched to the leading side. Trailing is no where near 10% of the power, much less.

Keep it simple, 1 box, 2nd gen coil optional.

IIRC 2 boxes can be used for rev limiting, trailing just has to be run through the cap..

People who run 3 boxes usually have a CAS and run direct fire (4 coils), Im not sure how or if you could run 3 boxes with a distributor.



Anyways, that aside...Am I the only one who thinks that first MSD diagram is a bit fishy??...
Seems to me the person who made that diagram has no idea about rotary ignition, or the flame propagation of the rotary engine...
Looks to me like that setup completely ruins the theory of leading and trailing ignition.

Yeah, shouldn't that wye to each coil instead?

I agree. 1 MSD + 2nd gen coil on leading. Trailing does so little, it is kind of pointless to use another MSD on trailing. Technically, you would need a pair of 6ALs for the rev limiter (running trailing through the cap). However, based on others experience, you can get away with just the 6AL on leading. Once the leading cuts out, you'll have a big drop in power which will help keep from over-revving.

On that diagram, the 1st setup will give 0 split timing. Whether this is good or not is debatable. I know that some, if not all, of the Mazda factory race cars ran 0 split. Other racers also run 0 split. For the street, it is best to leave the split in place, though (IMO).

Yeah, you don't need the trailing ignition. Only reason they're there is bored engineers wanting to entertain themselves and of course the accountants didn't complain... more spark plugs/wires for you to buy!

God I forgot how hilarious the first gen section was. Back to ignoring it.

False, you, in theory, dont even need to run a trailing plug with MSD. I run a MSD 6AL through the leading 2nd gen coil with no trailing ignition. Simple. Nothing running through the dizzy cap. It runs just as smooth as with the trailing in, no notice between the two actually...

Contact MSD and tell them that. They were the ones who gave me that diagram. I just give what I'm given. I went to them after I did my own searching on how to wire up an MSD ignition on my car (haven't done so, expensive, but I have 2nd Gen coil) and then I called them up to see what the deal was, since I didn't really find it on their website.

So is it ok to wire the MSD box like the first illustration suggests? Or is it a safe bet to wire it directly to the trailing coil? Also I remember seeing a tutorial on another site about wiring through the dizzy. How do you guys have your MSD box installed in your cars?

This is the way I have always done it:

One box.
Remove igniter from leading side of dizzy
Trigger the msd with the wires inside the dizzy that went to the igniter.
Black and orange wires to Leading coil #1
Jumpers from positive and negative of Leading coil #1 to Leading coil #2
Plug wires from Leading coils to Leading plugs

Ignition voltage to positive side of the trailing coil
Wire from top of "T" trailing igniter to the trailing coil negative
Wire from bottom of "T" trailing igniter to the trailing coil positive
Move trailing plug wires to leading side of dizzy cap.


Never had a problem and 6al limiter works

-billy

OK I am just a little confused. Should the jumper wires from positive and negative of Leading coil go to Trailing coil? Or do the Leading coil have 2 coils? I hope somebody makes a tutorial for this because I really want to learn how to install a MSD box in my FB before next autox season.