Guest09

I have a 2000 cherokee with the gay coil pack style spark rail. I'm running a stroker and 49 pound injuctors, so I was thinking that a little more spark might be necessary.

What, if any, is available for my application?

When I look it up, they all seem to be universal, but I'm not so sure...

5-90

Unless you've done something silly with the compression ratio (SCR >10.5:1, DCR > 8.5:1 or so,) or you're going to burn something really exotic (112LL, say...) more ignition power isn't really needed.

When it came out, GM's HEI was really new and a truly high-power ignition system. That was 1974 - now, pretty much all ignition systems are on a par with HEI.

Multiple-coil systems also have an excess of spark energy over single-coil setups, simply because each coil is allowed greater time for field saturation - for the three-coil six-cylinder "waste spark" system (like what you have,) you'll have about three-quarters again the spark energy over the single-coil system (it's not a 1:1 increase - it does follow a predictable curve, but it's more "inverse logarithmic" than linear.)

So, there's really not a reason to upgrade past what you have now. If you're having ignition trouble, it may be advisable to go one step hotter on spark plugs (if that's available to you,) but increasing spark energy is something to be reserved for correcting a specific issue.

There's nothing really "gay" about the COP/DIS system - I've been wanting to get my paws on an old GM V6/DIS Waste Spark setup to see if it can't be adapted to the AMC six (it probably can. Why the GM? Easier to programme, easier to find parts for, and you can do rather more with it than you can with the ChryCo setup. If I wanted to do more than I can with the GM, I'd end up having to build it myself.)

Bustedback

Well said and informative, thank you!

M4RK

To many big words for me, but I believe you anyways.

Guest09

Thanks much bustedbak. The reason that I have a particular dislike for the coil rail is because I had 1 go bad. It is a pain in the neck to figure out which one due to the fact that the code only shows that it is a coil malfunction.

I wish I could tell you what the compression raito is, but I forgot. It is a Titan Monster 300ci 4.9 stroker. I've tried to get the most out of it. Cold air, banks headder and full stainless exhaust. 49 pound injectors. I run mid grade and it runs solid. I was told that a "hot" ignition would give it a little more pep. I'll tell ya this. It'll just about roll up the pavement right now. 0-40 I can't be beat. It launches super hard due to the weight to torque ratio.

What I'm looking for, is to make sure that I am every penny of performance out of that 4000 stroker and all the loot it cost to get it right.

5-90

Coils are fairlly simple to test - you have an ohmmeter, right? Or a decent DMM? The typical coil test is to check the primary (12V) resistance and the secondary (HV) resistance. If you suspect a heat-related failure and the coil tests fine at room temperature, either heat it with a hair dryer or put it in the oven at 175-200*F for about twenty minutes and retest (this will "heat-soak" the thing, and point up any heat-related failures.) Failing that, you can just "shotgun" it and replace the whole coil rail, then figure out the parts to salvage later (depends on your skill level - I don't know if you can run this stuff offhand or if you need time to sort it all out. But, it's certainly far from impossible - and my test method is derived from checking out GM's DIS Waste Spark system.)

@M4RK - which words would you like explained? I'll help you as much as I can!



Unless you did some heavy special ordering for your stroker (milled heads, custom pop-up pistons, and the like,) your CR is still going to be well within useful range of the OEM COP/DIS system