85 3.2 MSD Install ?

greglepore · 03-13-2003, 05:12 AM

Ok, I know I may see little to no improvement, but I have an MSD 6AL and a High vibe coil lying around from an ex-autcross car, so I figure I might as well try them in my Carrera, if they don't make any diff I'll sell them.

A search turned up tons of info on pre-DME installs, but couldn't find what I needed for a DME car.

Do I use the mag pickup imput or the standard points imput? What wires in the car go to which on the MSD? (I know where the constant power and ground go, obviously).

I assume the tach is connected to the DME and I can avoid the adaptor, correct or not?

Do I need a ballast resistor on the coil?

Tim Polzin · 03-13-2003, 08:03 AM

The first question would by why? The Motronic system is fully electronic now. The distributer has nothing to do with generating a spark, that's done with the flywheel sensors and the DME.

If you wanted to do this, you would have to replace your distributer with one from an earlier car and likely use an earlier tach.

I suggest you simply should sell the unit since what you already have in the car is superior.

Tim

greglepore · 03-13-2003, 08:11 AM

The only reason as to why would be to get the multiple sparks below 3k and to run the larger plug gap/bigger spark. I understand that this might help idle, and also might be optimal with a chipped car (have an uninstalled chip sitting here).

I practically certain that you don't need to change out the distributor, you simply need to get the signal that normally goes to the coil to the MSD, which then trigger the coil through its electronics. My primary question is do I use the mag trigger leads on the MSD or the standard (points style) leads, and which coil lead goes to which MSD wire.

I don't intend to do anything irreversible, and if there's no improvement I might go back to stock.:

jabb · 03-13-2003, 08:21 AM

I think it would be a lot of work to get this to work with the Motronic, Have never herd anyone doing this, not that it could not be done just never herd of it being done. I have an MSD on my 3.0 motor with webers works good

greglepore · 03-13-2003, 08:40 AM

Well, possibly it is difficult, but in the tech articles section there is an addenum to the MSD install article from a Mike Wadkins who makes it sound like the hard part is finding a mounting location. Anyone know how I can reach Mike?

Tim Polzin · 03-13-2003, 09:30 AM

Oh, now I understand, use the signal from the DME to trigger the MSD box.

Good question, but unfortunately I have no idea.

Tim

Bill Verburg · Bill Verburg's Garage

I'm w/ the folks that wonder why? The DME electronics develop a 25-30 kv spark which contains 60-120 mJ of energy w/ a duration on the order of 12ms. This is far beyond the minimums necessary and employed elsewhere. It is a hot, fat sustained burst of energy.

The multiple restrike feature ends at a relatively low rpm level and if I rememeber correctly the spark may be hot but its duration is minimal.

stlrj · 03-13-2003, 01:02 PM

Why not install the MSD HEI coil that puts out a healthy 40 kv spark. No problem jumping a spark plug gap of up to 0.060" . I have my 86 3.2 with the GM HEI and am currently gapping my plugs at 0.045" but experimented with 0.060 without any problems.

Regs,

Joe

cab83_750 · 03-13-2003, 01:13 PM

I want to buy your unit for the rt $. Not to persuade you to sell, but Bill's words should be taken seriously. Either you sell or install, good luck.

greglepore · 03-14-2003, 03:38 AM

Cab, sent you a pm.

Silveresrty911S · Silveresrty911S's Garage

My 84 3.2 has been running Autolight 64's for about 2 years gapped @ 0.060". It has an Authority chip in it and it idles smooth (15-20 second rpm flucuation @ start up) runs great and when I check the plugs they are whitish/tan and lookfine. My .02

cab83_750 · 03-14-2003, 06:43 AM

Greg,

Sent you a PM!

greglepore · 03-14-2003, 02:54 PM

Cab-for some reason it didn't work. My email is glepore@comcast.net.

chibone_914 · 03-14-2003, 03:59 PM

You won't be able to run solid-core plug wires with the MSD, they'll transmit too much EMF to the MSD unit and fry it out. You'll need to get a set of Magnecore wires. Secondly, you'll need to run a tach adapter (PN# 8910) that, according to MSD "may or may not work" to have the tachometer work.
The factory ignition works great just as it is.

Just my .02 cents

Wayne 962 · Wayne 962's Garage

This is ironic, this is exactly what I was trying to figure out in this thread:

UPDATED: What's your take on this? (Permatune)

I can't see any added benefit to trying to replace this part of the Motronic system...

-Wayne

stlrj · 03-14-2003, 04:37 PM

Trouble with the factory unit is you are limited to the recommended spark plug gap of 0.028". With the MSD HEI style coil you go from 15kv to 40kv and can gap your plugs up to 0.060" without a misfire.

Regs,

Joe

Bill Verburg · Bill Verburg's Garage

Just as a point of reference the Motronic 12ms spark(it's actually a tad longer but that is the duration of the fat part excluding the initial spike) is 4.32&deg of crank rotation @ 1000rpm and 25.92&deg of crank rotation @6000rpm. These #s are theoretical and will be degraded by switching and saturation losses as rpm increases.

stlrj, can the stock Motronic coils just be swapped out for the GM units? and are this #S from a scope or from published data?

stlrj · 03-14-2003, 11:26 PM

Bill,

You might be able to find that technical data on a Delco website.

As far as swapping a Bosch coil with a GM HEI unit, it seems that the grounding transistors in the DME are robust enough to handle the additional current draw of the higher output coil.

Regs,

Joe

Bill Verburg · Bill Verburg's Garage

According to Delco/Dephi published data their systems are typical for a cd type i.e. high voltage ~35-40kV, moderate energy ~45mJ, and short duration .5 - 2.5mS An intriguing concept is Delphi’s ionization current sensing ignition subsystem which consists of one ignition coil per cylinder The spark plug is not only used as an actuator to ignite the air/fuel mixture, but when combined with a detection feature as a sensor to monitor the combustion process. This signal contains misfire and knock information. Interesting stuff!

I repeat my earlier assertion, the Bosch Motronic package is a superior unit.

The MSD is good for its intended purpose to replace weaker oems and the distributorless version looks interesting in the same way that Electromotive or Clewets is(though I am not familiar with the Clewett system)is. They are vague in their specs indicating 20&deg of crank rotation as the duration but also stating the the multiple restrike feature only operates up to 3300rpm. The do not say if there is a hard or soft cutoff of the mrf. If it is a hard cutoff then the duration reverts to cd norms of .5 - 2 mS they do claim a significant increse in spark energy in the 100mj range, though they do not specify if this is peak or variable as the Motronic is.

stlrj · 03-15-2003, 10:59 AM

Let's not confuse one ignition coil per cylinder with the DME one coil for all cylinder ignition system. At least the 40kv HEI coil over the stock 15kv Bosch coil for all cylinders as it was intended is a significant improvement. Also seems quite fashionable these days to utilize higher coil voltages along with bigger plug gaps as is the norm with todays modern engines.

Regs,

Joe