Ignition Upgrades and Such

I have searched and didnt really find what I was looking for. Most of the posts refer to stock 4.0Ls and the general idea was that a hotter coil, new caps and bigger wires dont do much for power and increase mileage very little.

What about a stroker motor? I figure that a built 4.6L stroker with higher compression and more displacement could use a hotter spark and better igniton components.

So what brands are out there and how well do they work? What would you stay away from and what would you run.

Thanks,

AARON

An ignition upgrade like the Performance Distributors kit make for a smoother running engine without adding much performance, but will make the most out of intake and exhaust upgrades.

What year? MSD makes a coil for distributor XJ's 1991-up that will probably help your stroker, and they also make an adapter harness that I'm trying to get more information on, but I think it's designed to adapt a 6-series ignition box to the RENIX ignition as well.

If you as this sort of question, it really helps to give us more information - like year of vehicle, year of electronics (if you've swapped them,) and what other modifications you've done already - like telling us you're working with a stroker. There's information out there, but it takes info to get info in this world, and that's going to be anywhere you go. Otherwise, you're just working off of other people's guesswork, since we need more specific information to work with :laugh3: !

Meanwhile, once you let us know more, we'll be able to give you better and more useful information for your purposes...

5-90

I guess I left this part out: I have a '91 XJ with a 4.6L stroker

The block is a '96, with a 4.2L crank and rods, Sealed Power H802CP .030" pistions, rotating assymbly ballanced, Mopar preformance head gasket, high flow oil pump, Flowkooler water pump, Crane #753905 cam, Crane lifters, springs and retainers, custom K&N header, bored T-body and spacer to 60mm, FMS #24 injectors, portmatched intake to head, ported and polished 91 head, Banks header, new 2.5" downpipe, high flow cat and flowmaster with a 2.5" catback. Compression is calculated at 9.5:1 or 9.6:1 depending on the formula used.

I also plan on running an Apexi SAFC so I can tune the fuel curve on a dyno. I want to run a better ignition to get the most out of the motor and also help with more gain from the Apexi air fuel controler.

AARON

You can use MSD #8228 coil as an upgrade, and with just a little wiring changes you can use a 6-Series box without too much trouble. MSD #32233 or 32239 should work - they are listed for 93-98, and I don't recall any changes for 91-92 and 93 - they'd probably work for 87-90 as well; although I usually make my own.

When you select your cap and rotor, make sure it has brass terminals rather than aluminum, since brass is a better conductor. I usually use Borg-Warner since they are consistently easier to find with brass terminals, but visually check before you accept the thing - I think most of the OEMR caps are aluminum, and about half of the aftermarket ones as well.

I'd also use Autolite Platinum plugs with that stroker - the electrodes are less susceptible to high-voltage erosion, and the electrode tips on those plugs do a better job of keeping themselves clean. You can usually find them for about $2 per plug, and I change mine every two years (just in time for Smog.)

Bear in mind that most rotor ends tend to be coated with something, so give it a quick pass with some very find sandpaper or emery cloth to clean it up - you don't want to remove any material, just make sure you have bare metal at the end, and that there aren't any burrs left over from manufacturing (those terminals are also usually stamped.)

Last and most critical - make sure you are getting a full 12VDC voltage to your ignition control - more is better. You should get full battery voltage there, which is supposed to be in the range of 13.6-14.5VDC. Take some time to make sure your ignition supply wiring is sound, or any mods you do are worthless.

Could you email me info on the header and the AFM you're using? I didn't know K&N made headers now, and Apexi isn't one of the AFR people I'd turned up. You might also want to look into the Adjustable MAP sensor mod, which will give you a little fine-tune control over AFR - and maybe relocating the IAT to the airbox to measure actual intake air temperature rather than manifold air temperature - which is higher. The lower temperature reading will result in slight fuel enrichment, which may help with your higher compression (since you don't mentione anything about quench.)

It would help you with fuel selection to know the Dynamic Compression Ratio of that setup - I can help you with that if you email me (I'll explain the whats and whys and how I got that number for you, if you decide you want it...)

5-90

5-90 said:

The lower temperature reading will result in slight fuel enrichment, which may help with your higher compression (since you don't mentione anything about quench.)

It would help you with fuel selection to know the Dynamic Compression Ratio of that setup - I can help you with that if you email me (I'll explain the whats and whys and how I got that number for you, if you decide you want it...)

5-90

Click to expand...

Aaron's built an exact copy of the 4.6L low buck stroker option 1 recipe on my stroker page apart from the cam. It's also virtually identical to mine, except I used +0.020" 677P pistons (slightly lower CR) and Mopar springs/retainers.
My ignition is stock apart from the 100+k mile old Splitfire plug wires which still work great. I even dropped in Champion copper plugs without gapping them. I do have an MSD 8228 coil in my spare parts bin to use when my stock coil eventually takes a dump.
________________________________
Dino's "Mean Green Machine"
1992 XJ Laredo 4-dr - 4.6L I6 HO Stroker - 180k miles - AX15, NP231, D35c, D30

263hp@4900/321lbft@3300-3800, 1/4 mile = [email protected], 0-60 = 5.8secs
Websites - Jeep 4.0 Performance, 4.6L Stroker Build-Up, Dino's Jeep Tricks

The MSD will help, especially if the fuel curve ends up a little rich...if the quench is too large and creates areas of low turbulence around the cylinder perimeter, excessively rich conditions will cause detonation especially under high load/low rpm conditions where the effective compression ratio will be the highest. If you have those conditions, and reducing the quench clearance is out of the question without pulling the motor back apart for further machine work, try advancing the cam a couple of degrees to reduce the low rpm effective compression ratio.

I goofed when I was typing :dunce: I ment I have a custom intake and heat shield that uses a K&N cone filter. I have a Banks header.

What does the MSD 6-Series box MSD #32233 or 32239 do that the coil doesnt do? What are the benifets of this? As Dino said, I have the 4.6L option #1 on his stroker page.

I have an adjustable MAP sensor and found it to not work very well. The adj MAP sensor will adjust the entire fuel curve up or down. I need to be able to adjust the fuel curve per RPM. On my old 4.0L which was built with all mods execpt the stroker crank and rods, it ran lean under 3k RPM and rich over 3K RPM. I could richen up the lower end and gain power down low but I would loose power up top. If I leaned out the upper end, the power down low droped. I know this because I was on a mustang dyno with a wideband O2 sensor.

The Apexi SAFC 2 is an air fuel controler that works much like an adjustable map sensor execpt it can add and remove fuel at 200 RPM intervals. This means I can add fuel to the curve as well as remove it from other spots depending on what is needed. I dont have it right now but I plan on getting this and installing it in the next week or so.

AARON