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post #1 of (permalink) Old 04-27-2000, 10:03 PM
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YJ coil replacement

I was wondering if anyone had a suggestion for a coil replacement in an otherwise fairly stock (motorwise at least) YJ...
It's a 4.0, 91 i was thinking something like the high vibratoin MSD blaster.. any experiances (good or bad)
thanks in advance
BJ

"If you chose not to decide, you still have made a Choice" RUSH
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post #2 of (permalink) Old 04-27-2000, 11:14 PM
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Re: YJ coil replacement

I used the MSD blaster 2 coil. Got me 2 mpg. Quicker starts and better throttle responce. I also put on a MSD ignition box and new wires also, though. Lost my tach. Can fix it, even have the adapter to do it, just need more hours in the day.

post #3 of (permalink) Old 04-29-2000, 01:07 AM
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Re: YJ coil replacement

thanks Jason.. i was thinking of doing the same.. i think i will now
BJ

"If you chose not to decide, you still have made a Choice" RUSH
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post #4 of (permalink) Old 04-29-2000, 02:54 PM
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Re: YJ coil replacement

The MSD box will do little, if anything, for the fuel ijected 4.0. However I recommend you get the coil and new low resistance wires.

Hope this helps
A.B.

post #5 of (permalink) Old 04-30-2000, 01:32 AM
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Re: YJ coil replacement

Wonder why that is.. every street racer around here swears by them... (MSD 6AL's are like gold) even in newr Camaros. I wonder if it's a "I just spent a hell of alot of money on this ignition, it better damn well work" mod. IS the ignition in the Fuel injected Jeeps THAT good. Every Engine i've ever run a MSD on, has seen a HUGE difference (course they were all carbed, older motors)

I'm not doubting at all.... just wondering why
Thanks
BJ

"If you chose not to decide, you still have made a Choice" RUSH
post #6 of (permalink) Old 04-30-2000, 01:38 PM
 
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Re: YJ coil replacement

A.B. is just plain wrong.

The MSD 6 series module will do more for your ignition than all of the other aftermarket gadgets combined.

You will see the same performance upgrades with the new Jeep that you do with every other new fuel injected vehicle.
It's basic Physics. It works the same way all the time....

Until factories start using Capacitive Discharge Ignitions, and Multiple Spark Discharge Ignitions, the MSD 6 series modules will continue to be the single most cost effective upgrade anyone can do.
Period.
---------------------------------

Don't forget about getting the more useable spark energy to the plugs...

1. That means a good coil,
The MSD Blaster II is a good coil, and it's wound correctly, and it will work fine with your stock ignition.
It probably will only marginally out preform you stock coil in your stock application.

If you are going to use a MSD 6 series module, use your stock coil.
The MSD module will make your stock coil out preform any of the aftermarket coils by 100 to 1,000%.
Your stock coil, and the MSD Blaster II will run almost exactly the same output if you power them with the MSD module.

2. That means a good cap and rotor...
Use a premium cap and rotor, no matter what coil or module you use.
Your cap and rotor is the place where the most ignition energy is lost.
Don't use cheap aluminum terminals, and rotors made cheap, they bleed energy.

Using a good quality cap will get the spark energy to the rotor first, then to plug wire with a minimum of parasitic loss.
Premium distributor caps will have correct terminal placement, so the spark energy goes where it's supposed to.
A good quality rotor will have a brass blade, and the blade will reach out far enough to keep the air gap to the plug tower to a minimum.
A good rotor will have precise distributor shaft alignment guides to insure correct timing.

3. That means a good plug wire set...
Once the spark energy is created in the coil, it's up to a good set of plug wires with coil wire to get it where it needs to go.
NEVER USE SOLID CORE WIRES WITH AN ELECTRONIC IGNITION...

Your best bet is a set of low resistance MSD helically wound wires and coil wire...
---------------------------------

If you are considering using a MSD 6 series module to upgrade to Multiple Spark and Capacitive Discharge, let me know, and I'll send you a wiring diagram for the MSD module that keeps you emissions legal, doesn't defeat the computer controls and will still give you full benefit of the CDI and MSD upgrades...

Good luck, and hope you are not confused,
Aaron.



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post #7 of (permalink) Old 04-30-2000, 09:06 PM
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Re: YJ coil replacement

Aaron... i think you have the mind of a God... that is Exactly what i was looking for... some results, w/ the reasons why. I think that Wiring Digram will be useful, but it will be a few weeks. I think i'm gonna get a 6al box, is there any (reasonably easy) way to Water proof it, or should i just mount it as dry as possible? Thanks Again
BJ

"If you chose not to decide, you still have made a Choice" RUSH
post #8 of (permalink) Old 05-01-2000, 09:26 AM
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Re: YJ coil replacement

TeamRush, You probably know more about the ignition systems than I do, but I talked to at least 2 jeepers with healthy Fuel Injected 4.0 engines who added the MSD 6 box, MSD coil and MSD low resistance wires. They agreed that the performance gain was minimal and fuel economy only improved by 1-2 MPG.

The only thing they didn't do form your list is the cap and rotor upgrade. I know you explained how they work and the explanation makes sense, but does the lack of these premium components simply render the MSD upgrade useless? If so then how come the same upgrade on a carbureted engine makes a huge difference using stock or old cap and rotors?

I'm not simply arguing here, I'd just like to understand better.

In the 4.0 case, what brand/model of cap and rotor do you recommend?

Also I'd appreciate it if you send me the MSD diagram.

Take care

A.B.
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