Snake
Mopar Nut
Hi guys,right now i have the 5 pin ecu with the 4 terminal resistor.I just pick up a new ecu witch is the 4 pin,will this work.Sorry this has been ask a million times.
Ecu 4 pin vs 5 pin
- Thread starter Snake
- Start date
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TrailBeast
AKA Mopars4us on Youtube
I have always heard the fifth pin was not connected to anything anyway, but not positive about it.
Really usefull right?
Del knows for sure.
Really usefull right?
Del knows for sure.
BillGrissom
Well-Known Member
Yes, it has been covered a gazillion times, and yes a 4-pin ECU will work with either system (single or dual ballast), it simply won't use the 2nd ballast (5 ohm). Most 5-pin ECU's you buy today have a dummy 5th pin, probably to not scare buyers. The "5th pin and 2nd ballast" was the original design. The improved design doesn't require it. The single ballast is 0.5 ohm, to keep the coil from getting too hot (and protect the ECU from high current).
Snake
Mopar Nut
ok thanks so the 4 pin is better?
longarm
Car sold back to original owners
..........
I guess Mopar thought so, at least it's simpler. But that IS a good question, which design was inherently better?? "I don't know."
BillGrissom
Well-Known Member
I would guess that the 4-pin is better. The early ones needed the 5 ohm resistor to protect part of the ECU circuit, so it probably wasn't operating up to its full potential, but I don't know that you would see that on an O-scope or in a brighter spark. Kit Calson here does a lot of that, so maybe he will test both if he gets bored.
The fewer ballast resistors, the better the ignition, which is why the GM HEI (which came later) is better. Mopar had later and better ignition drivers, but they are built into the engine controller box (lean-burn and such), so not easy to adapt to our cars. The lean burn was problematic, but I think that had to do mostly with the location on the engine. I had a similar box on my 82 Aries that got erratic. I traced it to the Molex style connector on the box. Today's automotive connectors are much better.
The fewer ballast resistors, the better the ignition, which is why the GM HEI (which came later) is better. Mopar had later and better ignition drivers, but they are built into the engine controller box (lean-burn and such), so not easy to adapt to our cars. The lean burn was problematic, but I think that had to do mostly with the location on the engine. I had a similar box on my 82 Aries that got erratic. I traced it to the Molex style connector on the box. Today's automotive connectors are much better.
KitCarlson
Well-Known Member
The 5th pin was for the power supply part of the box. The power supply provided a regulated voltage for the pickup coil interface. Early units used the external resistor, and internally a zener diode to clamp the voltage. The zener shunt regulator is an inefficient means of regulation. The external resistor put the heat outside the box. Later units used a series pass linear regulator, so no external resistor required. The linear regulator is also inefficient, but the losses are less. The other day there was a thread on what is in a FBO box, it had a few pictures of OEM boxes. One had a tab device in a corner, with a small heat sink, someone said it was a driver, to me it is a linear regulator.
More wires and external connections do not improve reliability, so by choice I would use 4-pin. With that said, and HEI conversion is even better, because it eliminates the ballast resistor, with internal dwell and current limit controls.
More wires and external connections do not improve reliability, so by choice I would use 4-pin. With that said, and HEI conversion is even better, because it eliminates the ballast resistor, with internal dwell and current limit controls.
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