Dual pickup phasing.

[Chickenman]

I have a Federal Dizzy with dual pickups on my 1976 280Z. On cold start-up the advanced pickup is actuated and specs call for an additional 6 degrees of advance over fully warm specs.

 

I have a fairly big cam in the car and wonder if any one has experimented with increasing the " Phase " split on cars with big cams?

 

The car is pretty snarky when cold even with the static advance bumped to 12 degrees BTDC. First thing to do is to actually check if the advanced pick up really is set to +6 degrees additional advance. I know someone has messed with the dizzy before. If that checks out I'm going to bump the " advanced " ( cold running ) pickup to +10 degrees of advance and see if the engine responds.

 

I know engines with big overlap like lots of advance down low. Having the dual pickup design should give me some tuning capability for cold warm up.

 

I'll report back with results.

[Chickenman]

Well.. I did a quick check last night, and found that the PO had the pickup coil phasing completely out of whack. Had the adjustment slot bottomed out the wrong way so that the Timing was actually retarded when warming up. Will have to re-adjust things and reset Timing.

 

As it's the " Retarded "  pickup that has the adjustment on it, and that is what the car runs on when at operating Temp, it will require two adjustments to set the Ignition Timing correctly. First adjust the phase split, then reset static timing with engine warm ( or thermal time switch disconnected ). Why Nissan didn't make the advanced PU the adjustable one I don't know.  Then your base timing at operating Temp wouldn't be changed when you adjust the phase split. Oh well.... 

 

I'm going to use a white Paint Pen to mark the relationship of the reluctor Teeth to the Retarded pickup. Then I can change the Phase split, and then line up the marks on the Retarded ( Primary ) PU coil again. Should get me in the Ballpark for initial timing. Then do fine tuning with T/Light.

[Chickenman]

Wow!! What a difference changing the phasing made. Car was super snarky when cold and you had to play a " tap Dance " on the accelerator pedal just to keep it running.

 

I just did a rough adjustment on the phasing , but now car runs at 1,500 rpm when cold and then slowly settles down to a nice " rumpety " 1,000 rpm idle as it warms up. ( 280 duration cam in car ) . Will check timing figures tomorrow. Was up til 2:00 AM trying to figure out why AC is intermittent.

[Mark Maras]

Good job. It's always a great feeling when one figures "it" out. "The thrill of victory".

[Patcon]

Chickenman,

How do you set the phasing? And what exactly do you mean by phasing? I don't really understand what you did. Glad you made progress though.

[Chickenman]

Chickenman,

How do you set the phasing? And what exactly do you mean by phasing? I don't really understand what you did. Glad you made progress though.

The Federal Sate distributors on 75 and 76 Z's, have two sets on pickup coils inside. Just like the early 510's with dual points. One pickup coil is mounted on a slotted plate, so that it's orientation to the reluctor can be " Phased " or " Off set" from the Primary pickup coil.

 

This " Secondary " coil PU is adjusted so that it Advanced approx 6 degrees from the Primary set. The advanced PU is only used during the Cold Run  period and is controlled by its' own separate Water Temp switch, with bimetallic contacts.   After certain coolant Temperature, the WTS switches over to the Primary or " Retarded " PU coil, for emissions purposes. The extra ignition advance when the engine is cold stabilizes the idle and aids Drive-ability.

 

It has an added benefit for us " Hot Rodders ", in  that big cams like more advance at idle than a normal cam, and tend to be " snarky " when cold. So you can play with adding more Cold Running advance by adding a bit more " Phase split "  when the engine is cold.  

 

Ignition timing will vary depending when you set it. Hot or Cold. Something you must be aware of.

 

Still experimenting with mine as I didn't get it right last night, and I have a different issue going on with excessive richness at Cold startup. Slowly getting there though.....  

Edited June 8, 2015 by Chickenman

[Patcon]

Thanks

[Chickenman]

Well.. I finally got things set right. The extra advance when cold does help the car idle better. Ended up going with the factory recommended 6 degrees of extra advance when cold, as I had already bumped the timing to 12 BTDC ( 7 BTDC stock ) . 

 

Car is still too rich when cold. New ECU CTS. But it's an aftermarket part, so I'm going to check the resistance values when cold. Might be out of spec???  The CTS is definitely working though, as the engine runs fine after about 5 minutes.  Unplugged CTS as a quick check and car would barely run and belched out black smoke.

 

AAR valve is new and works fine. 78 style AAR hose routing.

Edited June 17, 2015 by Chickenman