Can't get past 2500 rpm

[AlanJ]

At my wit's end. Here is yet another problem...

Quick details
92 Dodge Dakota
3.9l v6
Ms3x using stock sensors except,
36-1 crank wheel from diy
Crank sensor from diy
Ms3 v3 main board - no stim to test with.
Stock half moon cam sensor
Ms3 controls; fan, torque converter, overdrive, AC, tachometer.
Raspberry pi 3 built in dash running tuner studio and mega log viewer.
No sync loss issues noticed.

Issue #1, can't get engine to rev past 2500 rpm. Except in neutral, and it hates it in neutral.

The first attempt in the log is me sneaking up on it. The second is an all out full throttle attempt. The full throttle one is short because some how it's running lean and that's bad so I kept it to a minimum. The ve table is all jacked up now from my attempts, I have added what I believe to be twice the required fuel but it still runs lean.

Issue #2, the pwm out to the tach gives up at this time and goes to 0. Witch is weird because tuner studio still shows the correct rpm.

What am I doing wrong? I'm at my wit's end and about to trade the ms for a stock computer. My frustration is endless at this point. It's a great product and I can't talk bad, except for my own tunning ability.

Please help

[slow_hemi6]

I see you still distribute spark by distributor. How is the rotor phasing? You want the rotor tip centered on the No1 cap tower with the crank at 20 to 25 degrees BTDC. If it is losing spark to the dissy body or another tower and misfiring, then your AFR will show lean because it is not burning that cylinders oxygen and it is going into the exhaust and fooling the WBo2.

[billr]

Another way to say pretty much the same thing: Use a (simple) timing light to check spark advance on every cylinder, right as the engine hits that rpm limit.

[AlanJ]

Yes, i'm still using the distributor. I have the cam phased as follows;
On phase 1 the cam signal is low from tooth 1 to tooth 11 then transitions between tooth 11 and 12 to high
phase 2 the cam signal is high for 360 degrees then transitions between tooth 11 and 12 to low.

First i rotated the engine its rotating direction to 5 deg past TDC on no 1 compression.
I then removed the distributor cap and marked the outside of the distributor to the area of the rotor contacts.
I then made sure the post for cyl 1 was just inside this area, Assuming this (5 deg ATDC) would be the least timing used.
I then set timing by the software, then verified by timing light. I experienced little drift while blipping the throttle (Less than 2 deg) but never revved it out.

I never noticed this but the spark is completely dropping out at the 2500-3000 limit. Minor drops starting as low as 1800 RPM, Thanks for the tip. I adjusted the dwell time to increase the dwell and decrease it and no change to the limit. Here is a tooth logger while its hitting the limit, I don't feel comfortable doing a full throttle log of it. What can cause the spark to drop out if there is no sync loss? So this is related to the tach output dropping to 0 as well during this period.

Thought: Can this be considered accurate as the timing light I don't think can fire the xneon bulb properly at this rpm.....

What are the next steps?

[slow_hemi6]

rotor tip centered on the No1 cap tower with the crank at 20 to 25 degrees BTDC.

Rotor Phasing.

[AlanJ]

Mine is set up as follows at TDC. The the roater is in contact from approx 110 degrees BTDC to 5 degrees ATDC.

the rotor contact is very wide on my setup. But that is stock for this truck.

Should I shave that down or readjust the timing? I think it might miss at high advance settings if I move it more.....
I haven't noticed any cross arching, unless this is the cause of the problem......

PHASE-06.jpg

[billr]

Has the dizzy been "locked", no centrifugal or vacuum advance at all? The timing light should work at any speed, if it stop flashing that is a big hint there is no spark... However, that may not apply to a dial-back type light. Use a simple light.

[AlanJ]

yes, its locked. From the factory there is no previsions for vacuum or other advancement. I only own the cheap timing light. tonight I will play with the timing light some more. i just cant do it much because my neighbors call the cops (They know me by name now, and just call instead of show up.... )

ill just move it a tad in both directions and see the effects and let you know when I get home.....

[AlanJ]

No change in the limit when it's moved, I hooked a test light to the ms output and the ms is not sending a spark trigger during this period. Are my settings for the coil correct. Dwell time etc.? I looked again and didn't see anything wrong.....It has to be a settings issue.....

[slow_hemi6]

What is the hardware, wiring and connections for your spark? Your msq has LED spark configured so by rights that will be D14 driving a BIP373 through pin 36 of the mainboard connector to a std coil or perhaps a logic signal through pin36 for an external ignitor or logic coil.
You also seem to have Tacho out (pin26) of the ms3x configured as pwmA and turned on. It's set as variable frequency with a load of RPM but the curve values are garbled. I doubt it would work right.

[AlanJ]

I'm using LEDs spark out to the neg side of a single coil. The positive side is fed by the fuel pump relay.

Board mods;
Q16 installed, igbtout jumpered to ign, jumper from igbtin through 330ohm resistor to r26, r57 removed.

The tach built in the dash requires a variable frequency to operate. When the load axis is switched to tps position I can sweep from 0 to 6000 with no jumping or dropouts. Even random changes and movement does not cause it to drop out. I then changed the load axis to rpm and evenly decided them among the slots available. It works great except when I get close to the ghost rev limit. Then it drops to zero. I can tell when the limit is approaching because the RPM will drop to 0 then the missing spark happens. Then if I release the pedal it jumps back to the proper rpm and the engine catches at the same time.

If I drop gears the tach will jump up to the rev limit then to zero. And the spark will drop out as well. As soon as it gets below it it jumps back up, and the engine catches.

No matter what i do I can't get the tach out to keep from dropping to zero. It seams the ms is giving up at that rpm for some reason. I just moved my crank sensor and re adjusted timing. No change. If I change spark output to js10 then it will Rev just fine but timing is all over the place and I can't get it stable even at idle. I also enabled the filtering on the crank sensor input, that did not help and the RPM is delayed too much to be useful.

I just moved the ignition over to the msx output and reset timing. Timing is good, but the ghost limit is still there...

[billr]

Try powering the coil from some other 12V than the FP relay, even direct from battery temporarily. Do you have good grounding for the MS?

[billr]

How did you move the coil drive over to the MS3X? Those spark outputs are completely different from what you get from Q16 on the mainboard; they should work at all for driving a basic coil.

[AlanJ]

How did you move the coil drive over to the MS3X? Those spark outputs are completely different from what you get from Q16 on the mainboard; they should work at all for driving a basic coil.

I assume you meant "shouldn't".....

I ran a jumper from the pin 14 on the msx through the 330 ohm resistor to igbtin on the main board. Basically I did it with the intention of ruling out that particular output on the ms3.

Long story short. I'm still using the same hardware, just different output type in case there was an unknown issue with the LEDs spark out pin.

I ran the jumper as suggested and no change. I didn't mention it because earlier because It didn't change anything. I also tried the spark out test of 2ms dwell and 3ms intervals. That is one hot spark! Sounds like a bug zapper from ... To my eye and ear no skips. Also jumps 1/2 inch with out a problem.

Also I should have said earlier and I apologize but it was a previously fuel injected engine. The original computer caused preignition on hard acceleration in the summer, and I want more power and a supercharger... . I cut the old computer plug off and added the ms3 and ms3x harness to that location. Only new wires run so far are crank trigger wires.

[billr]

"I assume you meant "shouldn't"....." Ah, yes, I meant should not... I hate typos, yet am not immune to making them myself!

"I ran a jumper from the pin 14 on the msx through the 330 ohm resistor to igbtin on the main board. Basically I did it with the intention of ruling out that particular output on the ms3." Understand. That was a rather good thing to try.

[slow_hemi6]

Was there a reason you could not just use the standard tacho out function/setting under the Basic/Load Settings tab?
Have you tried another coil? What about running it in the dark and looking to see if spark is arcing out anywhere?

[AlanJ]

Was there a reason you could not just use the standard tacho out function/setting under the Basic/Load Settings tab?
Have you tried another coil? What about running it in the dark and looking to see if spark is arcing out anywhere?

Yes, I couldn't get the regular thacho function to be anywhere close to correct, its some special dodge computer controlled dial thing.....

I Used the Spray bottle method. (Spray Rev, listen repeat)

I will try the new coil thing this weekend, An update so far......

I changed the position of my crank sensor, checked timing. and changed a bunch of settings. I can finally get past that ghost limit. But Not like it should... I'm leaning towards some sort of tuning problem now. As soon as I can get conformation I will change the heading to indicate such... There is definitely an issue going on with the megasquirt though. The Thacho i have set up is dropping out just as the spark or injectors are starting to shut down. Is has proved a very reliable indicator thus far. Can anyone explain what is going on in the programming of the megasquirt here?

New Logs And Tune attached.

[AlanJ]

Okay, definitely it's the mega squirt. I just spliced in a factory computer plug. Plugged in my old computer and it starts right up and revs just fine. Lots more power than the mega squirt has. So it's down to that black box called mega squirt....

Differences between stock run and Ms;

Different crank sensors (stock vs 36-1 for Ms)
Different map sensors. (Same vac port though)


No other changes. Literally none. Same wires. One set 12 inches longer than the other. No check engine light on stock computer.

Tried to change over to not use the map sensor, same issue. Removed map sensor from stock computer. Runs rough but still revs just fine. So is it a bad mega squirt?

[slow_hemi6]

The tacho shutting down is not shutting the MS down. It's not loosing sync and I cant see the fuel or spark being commanded to cut. The tacho out is hitting 100% duty cycle around you trouble area but I just don't know what type of signal your factory computer supplies the tach. Still 100% should mean your out of range on that output. It does seem short on timing for those rpms. Mid 20's I would have thought even at no load. I think about this point I would put a scope on the spark output. Sometimes I do a quick check with a timing light on each plug lead and just look for irregularity or weirdness with the flashing.

[AlanJ]

The tacho shutting down is not shutting the MS down. It's not loosing sync and I cant see the fuel or spark being commanded to cut. The tacho out is hitting 100% duty cycle around you trouble area but I just don't know what type of signal your factory computer supplies the tach. Still 100% should mean your out of range on that output.

The tach uses a variable frequency signal. 0 for 0 and a flat line to 200 Hz to display 6000 rpm on the tach. I just checked again and in my runner studio it shows its set to "Variable Freq" I thought this setting uses a 50% duty cycle for this option and only changes the frequency.....

It does seem short on timing for those rpms. Mid 20's I would have thought even at no load. I think about this point I would put a scope on the spark output. Sometimes I do a quick check with a timing light on each plug lead and just look for irregularity or weirdness with the flashing.

This I'm having an issue with. I pulled a bunch of timing so I don't destroy something because this is my daily driver. I have to drive 15 miles to work every day. When I first installed the ms it had terrible predetonation. I know there is an effect on the amount of fuel required but I am waiting to get the rev issue fixed first.

I originally thought my spark was dropping out at that rpm as well, but I'm not sure now. The only timing light I have currently can not properly strobe above 2000 rpm. I have verified this by trying to rev to there and then just setting the test mode to spark there. It seams to max out at 1500rpm. I'm looking for another but I don't want to spend a couple hundred on something I'm going to use once.... I'm on Amazon now....