MegaJolt power wiring

pavel5 · Post by **pavel5** » Tue Mar 09, 2010 2:02 am

Hello everyone: I'm wiring up MegaJolt components in our OHC straight six Jeep engine (bronze age engine). I am using 14 gauge wire for the 12v input for the MJLJ, Coilpack and EDIS units. Should this be supplied through a single fused circuit - if so what is the recommended fuse capacity? I am assuming that all three can run off the same fuse, but is this correct?
Sorry to ask such simple questions but....

Cheers and thank you-

Pavel in BC

NITROPIXIE · Post by **NITROPIXIE** » Tue Mar 09, 2010 9:43 pm

Hi Pavel

The option is yours to fuse or not. Some vehicles i have worked on don't have a fuse fitted (old style minis) but then more modern cars do. I don't personally.

As for a fuse size, try a 10 A to start with. This should be an ample size and i really believe they are used in case the wire shorts to protect the wiring from melting. The whole circuit doesn't take up too much current with the coil sinking most of the current through the positive side of the circuit. You could if you wanted have a seperate fuse for the megajolt unit, for this an 0.5 A fuse would be plentiful.

At the end of the day its your choice but with a fuse there is less chance of a fire catching in your vehicle due to a shorted wire or less of a headache replacing a melted loom. On the other hand if a fuse keeps blowing then you have just stalled your engine whilst driving. What i would consider is, is the wiring in the car upto the job and is it secured safely its not going to cause problems. Safety says yes to a fuse.

The choice is yours.

pavel5 · Post by **pavel5** » Wed Mar 10, 2010 6:32 am

Thanks Nitropixie - I'll start out with no fuses then and possibly add 'em (10 amp and 1/2 amp) later.

Cheers

DannyP · Post by **DannyP** » Wed Mar 10, 2010 5:33 pm

I have a 10 A for the Megajolt/EDIS, and a 15A for the coil power. One 10 gauge wire feeding the whole thing, itself fused at the battery with a 30 A ATO type fuse. Remove a fuse to create a nice ignition kill! In fact, replace the fuse with a blown one, no thief would ever figure that out, I'm guessing.

Everything in my car is fused, except the ignition switch. I wouldn't recommend not using fused circuits.

pavel5 · Post by **pavel5** » Wed Mar 10, 2010 8:22 pm

DannyP: Yes, your fused electricals sound much better than just hoping for the best/being lazy. I'm curious however... if you take power directly from the battery (through a 30A fuse), and not from the ignition switch, how do you turn the power to the ignition system on and off from the driver's seat? Surely you don't open the hood and stick in a fuse before starting up....? I must be misunderstanding your set up. I'll apologize for failing brain syndrome later - old guy here!

NITROPIXIE · Post by **NITROPIXIE** » Wed Mar 10, 2010 8:52 pm

I believe he has power direct from the battery to the ignition switch, but then ignition switch to the fusebox and then fusebox ignition parts. Or at least i should think so

BRUCEROE · Post by **BRUCEROE** » Thu Mar 11, 2010 2:59 am

Fuses have some voltage drop, esp as they get older. And they add some unreliability to a critical circuit. I prefer to use fuseable links in engine stuff, like the OEM does. A pretty light link would handle this load. Bruce Roe

pavel5 · Post by **pavel5** » Fri Mar 12, 2010 12:42 am

OK gentlemen, thanks, but permit me to ask the question from a different perspective...

I should run a new 14 gauge supply from the "run" terminal on the ignition switch straight to the MJLJ/coilpack and EDIS with or without individual fuses (fuseable links)?

I can't use the factory wire that supplies the OEM coil, because it may have a resistor involved that decreases the current once the engine is running....

Hope I'm not beating a dead horse...

Pavel

DannyP · Post by **DannyP** » Fri Mar 12, 2010 1:55 am

I switch the power to the 'Jolt/EDIS from a 30 amp fused, 10 gauge wired OE Subaru RELAY. The 30 amp fuse is right at the battery.

The voltage loss of fuses is negligible, I've been using them in auto wiring for 30 years! No failures in my wiring ever, it's all soldered/heatshrunk or crimped AND fused. Done countless stereos, amps, alarms, remote starters etc......

Look up Porsche 550 Spyder Replica in the "powered by" section. I reused a Subaru relay strip with three relays. One for EDIS/Megajolt, one for coil power, and the last for an rpm-controlled crankcase-evac solenoid.

pavel5 · Post by **pavel5** » Sat Mar 13, 2010 12:32 am

Thanks everyone, I'll go the whole route then - with fuses and relays. My little attempt at stimulating the economy...
Appreciate all the advice!

DannyP: Couldn't find the Porsche Spider Replica relevant info...

Pavel

DannyP · Post by **DannyP** » Sat Mar 13, 2010 2:42 pm

http://www.autosportlabs.org/viewtopic.php?t=1753

There you go! On page 2 of "powered by"

pavel5 · Post by **pavel5** » Sat Mar 13, 2010 4:27 pm

Thanks DannyP... your three Subaru relays look very tidy - I'll look for similar ones the next time I take the wife to the wrecking yards near us (she thinks I'm such a hopeless romantic!). Read somewhere that Subarus have excellent shielded cable too - must check.

Pavel

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MegaJolt power wiring

MegaJolt power wiring

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