Where to get 12V key on inc cranking for Holley Sniper EFI
#2763206
04/12/20 09:15 PM
04/12/20 09:15 PM
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Joined: Feb 2006
Posts: 1,179 Canada
demon
OP
super stock
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OP
super stock
Joined: Feb 2006
Posts: 1,179
Canada
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A buddy is installing a Holley Sniper EFI on his 70 Charger. The car has the Mopar electronic ignition using a new engine harness that has the electronic harness built right in. The EFI requires 12 volt key on power for the computer. Needs to maintain constant 12 volt power while cranking. My thoughts were to tap into the hot side of the ballast resistor, but we found the voltage at the input of the ballast resistor drops off significantly while cranking. A friend suggested using this ballast resistor point to run a relay for direct battery voltage. Anyone have suggestions? One simple wire is holding us up.
Last edited by demon; 04/12/20 09:17 PM.
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Re: Where to get 12V key on inc cranking for Holley Sniper EFI
[Re: Andrewh]
#2763945
04/14/20 05:40 PM
04/14/20 05:40 PM
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Joined: Apr 2005
Posts: 4,910 new berlin wisconsin
Mr T2U
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master
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i don't know the exact details of your voltage needs. when i installed a MSD in my 72 road runner. i just attached both the, i think, lt brown and blue wires together at the ballast resistor. one wire has 12V with key on but goes away when you turn the key start position. the other one has no volts at key on but full voltage when you turn the key start. hook both together and you have power at both key on and key start. this worked for my MSD, don't know if it will work for you.
perception is 90% of reality
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Re: Where to get 12V key on inc cranking for Holley Sniper EFI
[Re: Sniper]
#2763973
04/14/20 07:34 PM
04/14/20 07:34 PM
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Joined: May 2005
Posts: 4,681 Florida
BDW
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master
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Been covered before, for ignition with ballast, place a diode across the ballast. That’s the way mine’s set-up for 2 yrs with FiTech and Mopar electronic distributor.
Last edited by BDW; 04/14/20 08:01 PM.
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Re: Where to get 12V key on inc cranking for Holley Sniper EFI
[Re: dvw]
#2764084
04/15/20 06:26 AM
04/15/20 06:26 AM
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Joined: Aug 2007
Posts: 6,089 Valencia, España
NachoRT74
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Valencia, España
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Keeping the stock ignition system, the diode over the ballast terminals would be the correct setup to keep the coil safe in RUN just like it should be with low voltage while allowing full 12 volts when cranking ( from brown to blue wire ) to the EFI being spliced into the Run circuit as must be.
MSD ignition requieres a ballast bypass just on RTR distributors because that's the source for them. MSD ECU modules don't need the ballast bypass because the wire to coil ( with ballast still there ) used for this works just as a remote on signal where the ballast signal is enough to keep it on, not for the source. The load for the module runs in a diff wire.
Need to say, once the diode is set, the ballast wires ( brown end and blue end ) must be connected AALWAYS on that way, being a resistor it doesn't matter which wire is conected on what prong, but with a parallel diode, it must be conected on the correct way. EXCEPT if you link the diode between wires instead at the ballast prongs, which it won't care where you connect the ballast wires just like originally is.
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: Where to get 12V key on inc cranking for Holley Sniper EFI
[Re: Andrewh]
#2764257
04/15/20 02:06 PM
04/15/20 02:06 PM
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Joined: Aug 2007
Posts: 6,089 Valencia, España
NachoRT74
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FBO box doesn't need ballast ( per their instructions ) is a diff deal. The diode solution is for the stock ignition which requires/includes ballast on the game
The relay could be an option DEPENDING on the voltage what the relay operates, BUT also requires more wiring involved to make it work. Remember ballast change the operating voltage range with temperature and load going throught so could be switching on and off constantly. Never have made it but just IT COULD happen
The diode is the easier, no need for extra sources/wiring, just jump out both circuits with it... but correctly done, to keep the ign 2 circuit still isolated from the Ign1 while car is in run, which is the deal on this to keep the coil on the ballast operating range, but just jump out the ballast for the ign 1 circuit while cranking
Now, the value for the diode! I can't tell which one could be the best. I'm not in those numbers
Last edited by NachoRT74; 04/15/20 02:51 PM.
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: Where to get 12V key on inc cranking for Holley Sniper EFI
[Re: Andrewh]
#2764284
04/15/20 03:23 PM
04/15/20 03:23 PM
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Joined: Aug 2007
Posts: 6,089 Valencia, España
NachoRT74
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I got what you meant
30- input from blue circuit 87-output to blue circuit 87a ( if 5 pins )-empty 86-trigger from brown circuit 85 ground
but still, a cleaner way just the diode LOL. And if relay gets activated by the low level ballast ouput, could remain activated. Nothing wrong really thought, but maybe switching on and off constantly with Ballast voltage variations. ( just thinking out loud )
Last edited by NachoRT74; 04/15/20 03:24 PM.
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: Where to get 12V key on inc cranking for Holley Sniper EFI
[Re: BDW]
#2764410
04/15/20 08:05 PM
04/15/20 08:05 PM
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Joined: Jan 2003
Posts: 15,197 Omaha Ne
TJP
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I Live Here
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Omaha Ne
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Re: Where to get 12V key on inc cranking for Holley Sniper EFI
[Re: AndyF]
#2764543
04/16/20 10:31 AM
04/16/20 10:31 AM
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Joined: Feb 2013
Posts: 140 Missouri
randavis
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Hard to do if you're going to keep the ballast resister and the old Mopar distributor. My advice is to ditch the Mopar ignition system and put a Hyperspark distributor on there. Then you can get rid of the ballast resistor and tie IGN 1 and IGN 2 together. Your buddy will thank you later once he understands how much better the Sniper works when it can control timing. Installing a Sniper without timing control is a mistake. I agree with Andy. I originally tried to use the stock dizzy and an old MSD 5C with my setup. After fighting emi for a while, I bought the HyperSpark and and the 6EFI cd box and most of my problems went away. I'm still adjusting the spark and fuel tables, but the car runs so much better.
74 Challenger, bought it new. In 1978 I replaced the original 318 with a 446 and 727. Mild cam, Jardine headers, and Holley Sniper EFI. New engine! 511" RB, Edelbrock Performer RPM heads, Eagle rotating assy, Comp hyd roller cam, Doug's 2" headers.
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