rusefi.com

I have a '95 Jeep Grand Cherokee Laredo that came with the 4.0 liter inline 6 cylinder. A popular engine package is to use the 4.0 block and the older AMC 4.2 liter (258 CID) crankshaft for 4.6 liters, with a 0.030" overbore. I built mine a bit different than most. The build requires custom pistons. Fortunately, they are available in mild forgings with different dish volumes. I used a 1996 block for the main girdle support, 2004 TUPY head for the smaller exhaust ports, and it measures out to a 10.5:1 static compression. Furthermore, I'm using Comp Cams Rock Crawler camshaft with more lift and less duration and overlap than stock. Stock dynamic CR is around 7.5:1 and mine is around 9.0:1. I heavily modified the cylinder head to promote a faster burn. Sharp edges were seriously radiused in the combustion chamber. I added Somender Singh Grooves. There is mild port biasing to promote better in-cylinder swirl. Finally, I added what I call Powre Lynz to the intake ports. It's like 16 pitch screw threads to excite the boundary layer. My objective is low-end torque for towing, and fuel economy. Ultimately I want to take it to Roush Labs in Livonia, MI and have the FTP-75 Emissions and Fuel Economy test done on it.

Going from 8.8:1 to 10.5:1 CR, I loaded the fuel tank with 91 octane before the swap. In the heat of late summer, it detonates on a flat doing 45 MPH. Stock timing goes up to 46 degrees BTDC. My best guess is that this engine doesn't need any more than 34. I need serious ignition timing control, which is why I bought into the rusEFI program. In the past I've worked with a MOTEC, Link PC, and MegaSquirt. My UAEFI arrived yesterday, so I'm just getting started.

Welcome to the forum! Please make some cool progress and move this project forward!

uaEFI gives your one knock channel, one EGT and one WBO. Do you think you need two/three/six of either of these advanced sensors?

Do you have a photo of your trigger wheel? Do you see it on https://github.com/rusefi/rusefi/wiki/All-Supported-Triggers#jeep?

I will need the WB O2, but not EGT or knock. Your link went to the Jeep 18-2-2-2, which is what I have. Here is a scope shot I took this morning. Blue trace is CPS, red is CMS, and yellow is cylinder #1 firing. I captured one of these images for each of the 6 cylinders. The stock '95 ECU has 1 ignition coil output, because it uses a distributor. I want to use GM LS Coil-Near-Plug. I cut & welded the coil bracket using 2 factory LS coil brackets. Still have to put legs on it (then sand blast and powder coat it, of course). "scfrontier" loaded his tune for his '98 Jeep 4.0 (installed in an older CJ). I've been looking over the choices he made to jump start my journey.

Just shelled out $70 to upgrade TunerStudio MS. I'm going to need the data logging feature at a minimum.

I got the ignition trigger Offset dialed in. Used the scope to determine CMS polarity to get coil #1 firing when the distributor was firing #1. Swapped from the distributor ignition wire to the LS coil, one at a time, and the engine ran the same. Waiting for a shipment of ignition parts -- including the secondary wires -- to start driving & tuning.

I'm waiting on an AquaPulser ignition delivery. Meanwhile, I configured the UAEFI as single coil, output on Coil1. To drive my "dummy" coil, and so I didn't have to modify the PCB, I rigged up an IGBT. I could't get the engine to start, with a range of Dwell and timing settings. Frustrated, I cleaned the plugs (wet from fuel), disconnected Connector B (the one with the coil outputs), and jumpered from the stock ignition coil- wire to the coil terminal. Still wouldn't start. OK, I'll remove the IGBT from the coil terminal and make a solid connection with the stock wire. SNAP went the coil terminal stud! Now I have to get the rusEFI working (or replace the coil I won't be using anyways). Jumpered in an LS coil, and with a little fiddling in TunerStudio got it to start and idle smoother than it did stock! Great! Then...CRAP!! The laptop battery hit critically low, disconnected from the rusEFI before I could Burn the latest tune, and shut down. Ran great until I shut it down, then wouldn't start.

While the laptop charges, I made the LS coil more permanent. Also decided to update this thread. Hang on, just checked, the laptop is charged. Back to work.

If anyone is working on something similar and trying to follow all of the bouncing balls I'm volleying, here are 2 other threads I started with questions:

https://rusefi.com/forum/viewtopic.php?f=17&t=2806

https://rusefi.com/forum/viewtopic.php?f=17&t=2811

That said, I know I had the engine running in Single Coil mode on an LS coil yesterday, using B15 Coil #1 output. The battery in my laptop hit the critically low shut down and I hadn't burned the latest settings. The engine ran until I shut it off... then wouldn't restart for anything. After the laptop charged, I went back out and loaded the last tune. Still wouldn't start. Slept, then today checked my connections in my custom LS coil harness. I had Signal Return on cylinders 4-6 but not 1-3. Pulled the harness apart and sure enough, I never spliced that wire! Now I'm wondering how the bleep it ran yesterday with no Signal Return!?! Anyways, now I get to do fun stuff like tuning.

After about 10-15 minutes of fiddling with idle settings, the engine quit -- like I turned the key off. Verified no output on B15 - Ignition Coil #1 Output. I changed the setting from Single Coil to Individual Coils and checked for output on all 6 coils. I got output on 2-6, but nothing on #1. Took it into my electronics lab, found #1 output was 30 ohms to ground and about 1k ohms to Signal Return. Traced it back to U103, SN74LVC4245APWR logic level translator. Maybe I weakened it when I fiddled with that MOSFET. When powered down, all of the I/Os should be in a tri-state -- or open condition. Circuit A8 (IGN_OUT1), pin 10 was in a grounded state. All other I/Os were indeed in tri-state. Ordered 5 since they're only $1.26 each on Mouser.

I think I'm done with rusEFI. I had an ignition output failure. Diagnosed it, ordered replacement part, soldered it in, and got running again. I made a few rookie mistakes and blamed it on myself. Now everything seems to be in order. With the new logic level translator installed, I DIDN'T MAKE IT OUT THE DRIVEWAY BEFORE ANOTHER IGNITION #1 OUT FAILURE!! This time instead of failing to constant ground, it failed with a constant 5 volt output! I'm surprised I didn't blow the fuse.

Sorry to hear that you are having a bad experience.

All hellen-family ECUs are using more or less same ignition control circuitry, I would assume that LS coils were used successfully.

Both other designs - proteus and microRusEFI - use tc4427. Please consider adding tc4427 between the board and smart coils.

After sleeping on it, I ordered the Ignition IGBTs for dumb coils. The Jeep came stock with a single dumb coil and distributor. For now, I'll replace the logic level translator (again), remove the 0 ohm resistor, and add the driver.

Do you still have the exact URL of where you've purchased your LS coils? I would love to reproduce your issue here in NJ.

My friend does a lot of major engine work. He swapped a JY LS in a truck. The JY engine came with coils. He gave me the rails off the bad engine. Coils were good when removed. In other words, they are OEM used.

mpgmike wrote: ↑

Fri Sep 20, 2024 6:11 pm

He gave me the rails off the bad engine. Coils were good when removed. In other words, they are OEM used.

Does it mean that you had qty 8 at some point? Any chance you could ship me qty 1 or 2? Happy to DM my address.

There are 6 physically good coils and 2 that got damaged around the HV wire terminal. I can send you one with a chunk of connector for testing. PM me an address.

I boxed Qty 1 GM LS Ignition Coil with damaged tower (but tested and functional), and Qty 1 coil connector with about 4" of wire. It's labeled (AndreyB sent me a PM) and ready to ship. Post Offices around here close at noon on Saturdays, so if I don't make it tomorrow, it will be in Monday's mail (pending some cataclysm like another instant ice age). I must say, I couldn't get this level of support from Jegs, MSD, or even Chrysler Corporation. I feel comfortable sticking with rusEFI and doing what I can to make it work; aside from my frustrated venting.

Don't give up, I burned up my ms3 trying to directly control the alternator. I'm using an ignition coil driver from diyautotune on my wasted spark setup.

Take 2. Ordered a new UAEFI board to try again. Due to arrive Tuesday. I'm going to install the IGBT dumb coil driver & remove the 0 ohm resistor so I can use the stock coil & distributor for now. I'll try the individual LS coils later, but with a better driver set-up.

New board arrived in the mail today. I removed the 0 Ohm resistor on Ignition #1 driver circuit... ...and soldered in an ISL9V3040D3ST IGBT. Since I want to keep the factory ECU for tachometer, cruise control, and other non-performance functions, I'm sharing sensors with the UAEFI. Digital signals like crank & cam sensors aren't an issue. However, CTS & IAT are variable pull-down thermisters, whereas the ECU has a pull-up resistor creating a voltage divider. The UAEFI has a 4.7k pull-up for these sensors. I removed the UAEFI pull-up resistors so it doesn't alter the voltage back to the factory ECU. I'll just have to calibrate them with TS. Now it's time to do the configurations and load the last tune from the old board.

Yesterday I ran wires for CTS & IAT, as well as a new wire for Cyl #1 Ignition to drive the factory coil. Couldn't get it started. Today I hooked up the scope and found factory cranking dwell was 63 ms! TS only lets me go to 30 ms. I bench tested the coil for optimal dwell and came up with around 2.8 ms at 14 volts. Factory idle dwell was 5.0 ms. Made some dwell adjustments in TS and it started. Spent a couple hours on back roads getting the lower end tuned. I'm liking it! No pinging now and it seems to have even more throttle response.

After I get the ignition timing tables as good as I can with the butt dyno, I'll rig up the 5-gas and see if it can tell me anything more.

It has been hard to start. It runs quite well once started, and if I turn it off and immediately restart it, it starts. Let it sit and it just doesn't want to start. Started digging in TS and found a setting for Cranking Dwell. It was set to 3.6 ms, probably from when I was playing with the LS coils. Again, I physically measured the stock ECU delivering 63 ms during cranking. The Dwell settings won't go above 30 ms. However, Cranking Dwell allowed me to take it up to 50 ms (it may go higher, I stopped there as it is working). So far it is starting as good as or even better than stock.

Crongratulations, glad to hear you are one step closer to your goal! FYI I have settled on open loop idle control. I could never dial in PID on the close loop side, but open loop sounds and runs great. I uploaded my latest tune: https://rusefi.com/online/view.php?msq=1729

The next thing I want to incorporate is IAC. I have looked at a couple uploaded files and whereas the uploaded files offer hardware configuration, mine is just greyed out. I looked at the uploaded tune from scfrontier and again, what he was able to configure was greyed out. Ask me questions, send me on a research mission. I can't seem to be able to configure the UAEFI to control a 4-wire Chrysler IAC motor! HELP!!

mpgmike wrote: ↑

Thu Feb 27, 2025 2:04 am

I can't seem to be able to configure the UAEFI to control a 4-wire Chrysler IAC motor! HELP!!

update uaefi to latest snapshot
in popular vehicles click "Small Block Chevy"

that would wipe out your tune but set 4 wire stepper idle settings

you would have to restore your tune manually

I uploaded my current tune, Jeep_46s_1 (Jeep 4.6 Stroker, Version 1):

https://rusefi.com/online/view.php?msq=1731

Not Github literate. Still struggling with swimming through the vast information posted there.

Added a knock sensor. My vehicle didn't originally come with one. Came off a 2012 Jeep 3.6.

I suspect it may be necessary to switch between stock and UAEFI as I work out the bugs. I cut the 6 injector wires and added Amphenol connectors with a 6" extension. I have a matching connector coming from the rusEFI. Did the same thing for the IAC wires. Eventually I want to run the Bosch 4.9 WB, so I ran the wires to where the Bosch connects. Sunday I spent some time setting up the knock sensor settings: sensitivity, how many degrees it can pull, how quickly it can pull timing, and post recovery rate. I'll probably fine tune that a bit later, but I'm happy with the initial settings.

Got the Bosch wide band functional. Initially I changed the connector from factory ECU control to rusEFI control of the injectors. Couldn't even get the sucker started. Used my shop scope and got the idle zone IPW to closely match stock. Swapped again and it idled! I pulled it into gear and it chugged and stalled. The NB gauge was absolutely no help. SO...

I swapped out O2 sensors and tried again. Got idle, and all the cells I could reach inside the shop without moving. The cat was starting to get hot (I could smell it) so I called it good for the day. Maybe tomorrow I'll take it out on back roads to dial in the lower-load fuel cells. Progress!

what's the markings on yours?

i have some boards which could be newer PN but I am confused for sure