Pelican Parts Forums - 3.2 distributor mechanical advance, why???

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- - 3.2 distributor mechanical advance, why??? (http://forums.pelicanparts.com/porsche-911-technical-forum/638421-3-2-distributor-mechanical-advance-why.html)

Quote:

Originally Posted by 911pcars (Post 6357479)

"A couple Pelicans have tried locking their distributors to run the MSD-6AL-digital....."

It appears these owners were using distributor-based points or reluctor to trigger the spark. These distributor-based signals are all dependent on the advance mechanism of the distributor, thus "phasing" must exist between signal and rotor. If the signal is performed externally, rotor "phasing" is no longer an issue.

Sherwood

No, those guys were using the MSD 6AL Digital, which boasts independent ignition maps just like an electromotive Xdi. The timing is independent of the advance mechanism of the distributor. However, the limitation arises when you try to use that box (basically a progammable ECU) to trigger the spark. Those guys were trying to lock the distributor and I think the consensus was, bad idea, because of the possibility for misfires.

Rotor phasing is absolutely the issue, otherwise those advance mechanisms would not have been included.

Quote:

Originally Posted by BURN-BROS (Post 6357627)

Maybe Porsche did not want to spend money creating a new convention. As far as the advance components go, It looks as though Bosch supplied them generic components from their most commonly used parts lines reducing the overall cost. Perhaps there was quite a bit of inventory left @ Bosch that mandated the utilization of the remaining inventory(housings,shafts,etc.

The 3,2 distributor and the SC are different designs, the SC incorporates the reluctor while the 3,2 doesn't have anything other than the phasing. Even if it were true that they had several thousand extra parts on the shelf, that doesn't explain the 964/993, which used TWO small distributor caps and a belt. I have to tell you , the dual distributor idea looks like one of the most Kludgey setups I've ever seen! But it was probably driven by packaging and not wanting to do a complete redesign.

Ford introduced EDIS, a crank-triggered waste spark design, in 1990, on such unremarkable vehicles as the Mercury Tracer. Are we to believe that Porsche's partnership with BOSCH could not yield anything more fruitful than a twin distributor setup?

Do your beautiful twin plug setups trigger externally? I seem to recall they use a reluctor. Do they incorporate rotor phasing?

Quote:

Originally Posted by 304065 (Post 6357674)

The 3,2 distributor and the SC are different designs, the SC incorporates the reluctor while the 3,2 doesn't have anything other than the phasing.

The Euro SC dizzy was the same casting as the 3.2. The shaft is the same dims but assembled/machined for CW rotation. The advance piece is from a 4 cylinder application without the lobes ground. The weights are nothing special. Who knows, the amount of inventory may not have been enough for the whole 3.2 run but enough to warrant the decision. It's pure speculation. Think about the 906 suspension in design vs production.

Quote:

Originally Posted by 304065 (Post 6357674)

.., that doesn't explain the 964/993, which used TWO small distributor caps and a belt. I have to tell you , the dual distributor idea looks like one of the most Kludgey setups I've ever seen! But it was probably driven by packaging and not wanting to do a complete redesign.

No it doesn't, But it does fit with their stubbornness not to jump into new technology.

Quote:

Originally Posted by 304065 (Post 6357674)

Ford introduced EDIS, a crank-triggered waste spark design, in 1990, on such unremarkable vehicles as the Mercury Tracer. Are we to believe that Porsche's partnership with BOSCH could not yield anything more fruitful than a twin distributor setup??

Ha! 1989 Ford Taurus SHO :p

Quote:

Originally Posted by 304065 (Post 6357674)

Do your beautiful twin plug setups trigger externally? I seem to recall they use a reluctor. Do they incorporate rotor phasing?

My dizzy is triggered by the stock pulse generator found in the SC and incorporates Rotor phasing. But the original Marelli units were fixed. I widened the blades on my rotors with the anticipation that one may want to run ecu controlled timing with the Marelli twin plug Dizzy