MSD rev limiters

John,
Just started the same process with my '85 Euro, but haven't checked the RPM difference between the dial and the dash. My problem is the throttle response is terrible compared to the Magnetti.
Did you just block off the vacuum?
Any other hints based on your experience so far?
Thanks

 

Phil,

I believe that John is doing the MSD conversion on an earlier car...with dual distributors that are very different than what's on your car. His units have an advance mechanism built into the distributor bodies, whereas yours don't.

The 1985 Euro or USA distributors have no provisions for an advance mechanism, as it (advance) is done through the Magnetti ignition module via engine vacuum. By replacing these units with the MSD spark boxes, you'll get spark but no ignition advance, as the MSD units are strickly for generating spark. They cannot advance or retard the ignition. Hence, your timing is fixed at the initial settings, based on the position of the sensors for 1-4 and 5-7, which are approximately "zero" advance.

I am not aware of any MSD vacuum based unit that you could use in conjuction with the 6-AL units to create ignition advance.

Short of going back to OE, or using a crank fired Electromotive unit, I just can't see how you'll get your 308QV to run properly.


Regards,
David

 

oooooops

 

FWIW I've found a Haltech brain will read the factory triggers and will control the factory coils with their ignitor .. then you can dial your own advance curve which can liven these cars up but 4V maybe not so much (they run better than the "detuned" 2Vi's) . .. haltech has an ignition only brain but the fuel and ignition brain isn't much more if you're contemplating that. . . .don't you hook the 6al's up to the output of the digiplex? if so it's reading the advance correctly I would think.

 

Dave/John,
Thanks for the inputs...
When we got the two MSD units (based on recommendation from a Ferrari parts dealer, because he said Magnetti's were no longer available), it didn't make sense that they didn't have a vacuum sensing capability. Once installed only one bank fired, so we swapped units and it changed banks, so we had a bad unit and had it replaced. It now runs on all 8 but no power. I've started to review the Electromotive units on their website, and I'll look into the Haltech unit as well.
Thanks again.

 

Phil
I think Davis (Fastradio) sums it up. So, I have no idea how you are triggering the MSD box to fire the coils.

The MSD 6 boxes were designed to be used with a trigger (most always a distributor) which already had the advance mechanism.

I put a MSD box on my 3.2, but required a Mallory unilite trigger distributor with adjustable advance to do it. I chose to do one, but you can do two I suppose.

 

Ah ha!

But...you can trigger, as likely Phil did, the MSD units with the TDC sensors using the Violet/Green inputs. The problem is/was that there's no advance/retard capabilities.

Phil: We've had some good successes repairing the Magnetti units. Drop me a note if you'd like to explore this avenue.


Regards,
David

 

David,
Thanks for the input. And you're right about the hookup.

I would definitely like to persue repairing the Magneti unit. I have kept the car as original as possible since I bought it ten years ago, and it has always had good throttle response with the stock setup. And it has always done very well on emissions checks except for recently.

How do you want to proceed? I can ship the unit to you anytime. Would you like to have both of them for reference? I'll tag the bad one.
If you could troubleshoot and give me an idea of the cost, and if it makes sense to repair, I can pay you prior to shipping back to me.

Thanks again for all your help.

Phil

 

David,
It just dawned on me.... I saw you at Verell's get together. I had the '89 Testarossa at the end of the line. Would have brought the 308 also if it hadn't been for the problems I've had with it.
Loved your 365 bb, always liked the red/black combo.
And if that's any indication of the work you do, I certainly feel comfortable having you look at fixing the Magneti.

Thanks,
Phil

 

Phil,

Which units do you have: MED803A or MED803?
What was the symptom that caused you to determine that the spark box was the specific problem?

Thanks,
David

 

David,
MED 803A.
The problem started out as the engine would run for a short period, sputter, and then one bank would drop out. Several tries would show the same thing... short run of 1 - 2 minutes then 1 bank cut off. Then running time decreased to 15-30 seconds before cutting out. Led me to think something was heating up and failing.
Not being the best at diagnosis, checked for coil output once it failed and the one bank showed nothing. First thought it might be the crank sensor and replaced it, but no change.
Swapped positions of the 2 modules and the problem moved to the other bank.
I have no EE capability, so asked a friend what he thought, and he took the bottom covers off and checked some meter readings and saw a big difference between the two units. (He's an EE from Italy who was visiting and is leaving to go back to Italy tomorrow.) His opinion was it was heating up and failing.
Didn't see any apparent heat discoloration in the unit though.
That's about all I can contribute.
Thanks,
Phil

 

Thanks Phil!
Yes, the BB is my pride and joy, although she was once, many years ago, a "problem child"...However, now, she's extremely reliable, with very few issues. I replaced the very troublesome Magnetti ignition unit with an MSD unit many moons ago. On the BB, the advance unit is in the distributor, so there were no issues with compatibility. As my electronics were potted in epoxy, the repair was not feasible.

The common problem with repairing these units is sourcing the often obsolete semi-conductors. New units do pop up from time to time, but are very costly.

I'll PM you later on today....I need to do some digging on the parts situation, as we had a very rough time on a couple of units that we (successfully) repaired last Spring.

A bit of trivia....I also had a Euro 308QV, though it was an 83. I sold it back in 85-86. A great, great car...

Regards,
David