MSD for Twin Plug

[randywebb]

Duh.... I was trying to think of German words...

[cameron.arnott]

Bump for an old thread.

Did anyone try running the single then dual MSD's to see if there a noticeable difference in performance?

Cheers

[tom1394racing]

I've been running my 3.0 RSR clone with the twin plug/twin coils/single MSD for 2 years now.

It put down 285 HP at 7500 RPM on the dyno and has been running strong with no ignition problems.

[JohnJL]

Can I get some more pics of engine compartments with twin ignitions with 2 MSD, 2 coils and 12-plug distributors? I am looking to finalize my layout. I've got webers too...

thanks

[RWebb]

I have a few - there will be more if you search.

this might be Iris...



single box in stock position on a '75 I used to have; note the early style fuel restrictor for CIS pump with carbs...

[RWebb]

[mjshira]

Great thread, and very helpful. Man I love this forum.

[LJ851]

Hmmm... Very interesting.It seems one could have a fairly inexpensive twin plug set up with a 993 distributor , MSD , twin tower coil,and something to create an advance curve. ( with the slightly reduced energy at the plugs) Does anyone have back to back dyno proof of the difference between single MSD twin plug and dual MSD twin plug ?

[Brando]

MMSD may only reccommend 1 box per coil... but Iknow for sure Mallory specifies one box can drive 2 coils and run just fine. Mallory Hyfire VIAL (rev limiting).

[Eclectic911]

Hi Tom,

You have a PM.

Mel

[iamchappy]

2 coils 1 MSD

[RoninLB]

i may have missed it but

what does MSD have to say on this 1 box + 2 coils

twin plug isn't covered in their tech manual and a search on their site for "twin plug" is ng

[kent olsen]

I'm looking at the same thing. My 3.0L was run on J&B Racing's engine dyno. With 1 MSD and single plugs it turned 233hp. With 2 MSD's and twin plugs it turned 245hp. Mike Bruns at J&B Racing says I'd give up some HP with only 1 MSD and 2 coils. I have a spare Mallory MSD that I used on my old 2.7L for years so I think I'll mount it with the MSD unit and run 2 coils. No use giving away free HP.

One other thought. While running both MSD's and coils, how do you confirm that they are all working? Maybe so sort of light?

[kenikh]

The old race cars had switches for dual Bosch boxes in the cabin that could turn each box off/on. You could tell by how the car ran when flippin switches as to how they were operating.

[Steve@Rennsport]

Originally Posted by kent olsen

I'm looking at the same thing. My 3.0L was run on J&B Racing's engine dyno. With 1 MSD and single plugs it turned 233hp. With 2 MSD's and twin plugs it turned 245hp. Mike Bruns at J&B Racing says I'd give up some HP with only 1 MSD and 2 coils. I have a spare Mallory MSD that I used on my old 2.7L for years so I think I'll mount it with the MSD unit and run 2 coils. No use giving away free HP.

One other thought. While running both MSD's and coils, how do you confirm that they are all working? Maybe so sort of light?

Kent,

Mike is right; you do give up some power when triggering two coils from one CD box. To what degree depends on the engine's configuration.

Be aware of spark timing differences when running two types of CD boxes. Sparks need to occur at the exact same time and there are circuit differences between Mallory and MSD that may slightly delay one of them. Caveat Emptor on this.

One checks ignition functionality just like on piston A/C engines: by shutting off the supply voltage to each CD box and observing RPM drop.

[kent olsen]

Well since I have the Mallory and a mallory coil I'm going to try sharing it with the MSD and MSD coil.

The MSD will run the top plugs and the tach. The Mallory will just run the bottom plugs. I'll check with Jegs, Mallory tech and MSD tech once again to see if they can envision any compatability issues.

The next question is location. I'm not to sure about mounting one box on top of the other, especially in the heat of Florida. Remember this is basicily a street car.

The dual coils on the fan looks good until I use a tape measure and see how much space it takes. So I think I'll leave the one coil there and hide the other behind the little cover on the left that covers the voltage regulator and a couple relays.

I thing I'll try to mount the Mallory forward of the MSD, which is already in the old CDI position.

[Brando]

This is an inaccurate comparison, kent. From what you said, you had single plug with a single box, upgraded to twin plug with dual boxes. An accurate comparison would be twin plug with a single box vs. twin plug with dual boxes.

Originally Posted by kent olsen

I'm looking at the same thing. My 3.0L was run on J&B Racing's engine dyno. With 1 MSD and single plugs it turned 233hp. With 2 MSD's and twin plugs it turned 245hp. Mike Bruns at J&B Racing says I'd give up some HP with only 1 MSD and 2 coils. I have a spare Mallory MSD that I used on my old 2.7L for years so I think I'll mount it with the MSD unit and run 2 coils. No use giving away free HP.

One other thought. While running both MSD's and coils, how do you confirm that they are all working? Maybe so sort of light?

[kent olsen]

Maybe a little explanation.

After I built this twin plug 3.0L engine we ran it on J&B Racing's engine dyno. We ran it first with twin MSD units and twin coils. After all the tuning the engine made 245HP and 228 lbs of torque. We then ran it with one MSD/Coil with just the top plugs. 233 HP and 214 lbs of torque.

I then took the engine home, installed it in the car and ran it for a couple months on just one Mallory MSD and one Coil and the top plugs. I had some difficulty with the tach so I sent it to Palo Alto speedo to convert it to digital. Then I had difficulty with the Mallory driving the tach so I bought an MSD unit.

Now I'm installing J&B's Twin plug distributor. And all of this is why I'm trying to convince myself to match the MSD and Mallory units together to run the twin plug setup!

[Cornpanzer]

Anyone have any issues with solid copper wires and MSD. I know that MSD doesn't recommend it, but I am putting my boxes up under the front seat - far away from the engine. Any concerns about RF interference?

[kent olsen]

Randy Jones and anyone else who have stacked the two MSD units.

Have you had any issues with heat buildup? I know they are mostly transistors but there are cooling fins. I'm strongly cosidering the stack for my installation. I live in Florida so heat is always an issue.

Thanks