DIY MS3x hitting limiter 2000 rpm?
 

Hey all, first off I'd like to apologize for my frequent noob post in this MS section.

The issue I am having is around roughly 2300rpm my car is hitting some sort of rev limiter. This happens both in gear and in neutral.

I have loaded the trubokitty 1.6 basemap onto the car with some slight modifications to the VE table. Since installing my ms I have yet to have the car fully functioning. But all sensors have been calibrated and base timing has been set. The car runs some rich but other than that will start and idle fine. Initially I thought this was some sort of fueling issue since the car would start to lean out in this area (2300rpm) but after adding lots of fuel to this portion of the table I am able to see a significant change in the AFR reading but no change in my problem. I have looked through the tune and haven't found any sort of limiter or fuel cut that is turned on... I remember reading somewhere someone having a similar issue that turned out to be the vr conditioner pots. Tonight I reset both r11 and r56, after spinning both pots the number of turns trubokitty has documented. I tested both with a voltmeter. R56 was at 2.7v measuring off of r54. R11 at 2.4v measuring from the zc testpoint. After this the car started and ran as it did previously. I've been pretty stuck on this for a few days now. What further troubleshooting steps can I take?

Some info on the car.
1993 1.6, 2.5" exhaust. no cat
oem injectors, oem fuel pump
vTPS from MK Turbo
DIY MS3x 1.4.1 firmware

Here a short video of what I am experiencing. I added a bunch of fuel in some cells to keep the car from going lean at this rpm.
https://www.youtube.com/watch?v=d8Ja...ature=youtu.be

I have also attached my current tune, a composite log, and normal data log taken in neutral in my garage.

Definitely a rev limiter function. Is launch control activating? CLT-based limiter?

There is no fuel cut in the log. I don't know what spark cut would look like in a log but spark advance is functioning as expected.

Not 100% sure how to check if launch control is activating? CLT based limiter is off. Hard rev limit set to 7200

I am assuming an NA alternator, I have never seen a battery voltage log look like that before. Did you actually measure the battery voltage and calibrate the MS3? It almost looks like there is an overvoltage protection device kicking in or something.

Status2 would indicate spark cut.

This is 100% not spark or fuel cut.

Yes NA alternator from rock auto. I did not measure battery voltage, brand new battery within the last week. Not sure what you mean by calibrating the ms3 for the battery? So no I did not do that.

You better measure that voltage. You could be in the process of killing your MS

yikes. are you saying just measuring voltage directly off of the battery?

while running, yes. measuring at the MS or the alternator would probably be better. Don't rev it anymore until you get this part confirmed.

will do. thanks for the heads up

I had a bad alternator from the parts store, Bosch I believe, that went to 18v when revved. Only ran it a few minutes before figuring out from seriously bright headlights.

While running I measured 14.4v off of the battery with my meter. Voltage does not increase with rpm or anything like that. In the log it shows a constant 14.4v. What should it be looking like?

Does the voltage change when you turn the heater fan on full and the headlights on? IIRC, your idle is high, like 1100, so you may be at an rpm where the alternator voltage is up. I characterized a few NA alternators in detail, and they all had voltages in the 12 range at idle, and rarely hit 14.4. There was also quite a bit of variation in the battery voltage in the log.

NA alternators don't usually regulate that well, especially at idle. I know nothing about the circuitry in your MS, but if there is a voltage limiting device that shunts current to ground, it will conduct current until the alternator voltage drops. They aren't designed to do that normally, only under fault conditions, so they burn up eventually. You can browse around here a bit and see examples of where people have done that.

there may be nothing wrong with your setup, just trying to keep you from bad things if there is.

Just went out and checked, voltage remains the same with heater on full and headlights on. Correct my idle is high around 1100. Looking at my log posted above named "garage" I am seeing a constant 14.4v in megalog viewer. I'm not really sure where you are seeing variation? I am fairly new to MS and tuning, I appreciate your concern to keep me from causing damage to my stuff.
https://cimg9.ibsrv.net/gimg/www.mia...c4abdcf261.png

The point is that there is no variation. There should be. The voltage should drop when you turn the headlights on.

Make sure the 2 pin connector going to the alternator is connected, if it is, tou might want to pull the alternator and get it tested.

Here's another one of home boy's logs from a different thread. Minimal fluctuation but there is some. Still weirdly consistent.

So if the battery is staying at 14.5v all the time wouldn't that entail that the alternator is preforming exactly as it should? I'm not tying to question anybody's wisdom, just trying to understand why this could be a issue.

If it's actually staying at 14.5v sure, but a 3.5+ minute log with zero voltage change is weird. You'll typically see some fluctuation.

If you've confirmed with a meter that it is actually staying at that voltage then the alternator is probably fine.

Does the tach sort of jump around when you hit the limit?

I had a similar issue on a 99 where the pots were adjusted way off and it felt like it had a way lower rev limit. Not sure if this is relevant for the 1.6 CAS.

bottom line is that it is very difficult to diagnose these types of problems from the other side of a computer. Unless somebody has experienced exactly the same thing, we are really just guessing.

As far as the constant 14.5V question, I have already answered that, but maybe I wasn't clear.

There maybe components in your car that prevent the voltage from exceeding 14.5V. This would most likely be done by consuming enogh current to drop the system voltage to whatever voltage the component has as a threshold (14.5V). This consumed energy is dissipated as heat. This is not a good thing.

I can tell you that an alternator that is not regulating properly and is sourcing too much current can result in behavior that looks very similar to what is in your video. The data in your logs, based on the little I know about your hardware, looks... unusual.

Yes tack jumps around. The more throttle it has the more abruptly it jumps around. I have reset my pots and confirmed voltage using documentation from the megamanuel.

Okay that makes sense now. Thanks for clearing that up.

Not sure if this information is relevant but the car ran normally with the stock ecu and same alternator. Does ms3x have some sort of voltage regulating system? You mentioned above to get the alternator tested, is this something that can be done at home? Or where do I get this done.

Apologies on asking questions on nearly everything you guys are saying, this is my first time diving in to a project like this. Seems like I should've studied up more

The MS may have an over-voltage protection device on the input voltage lines. Did you make any other changes when you installed the MS? Will it still run with the stock ECU?

I have not had the stock ecu in the car in a few weeks. I could put it back in this weekend to confirm the car still runs with it. Other than the MS I have put in a vTPS, AEM UEGO, and a new battery since mine was starting to go dead being pretty old.

Earlier today I put back in the stock ecu. I was facing the same issue until I realized I had not put the stock TPS back in. After reinstalling that the car was able to surpass 2300 rpm and rev freely.

I got my vTPS from MK Turbo which is a AIP TPS314 97-122816 throttle sensor. When I was installing this on the car I was having trouble getting the wires out of the tps connector to flip the 5v reference and TPS signal wires. I ended up just leaving this and in result got inverted TPS values in tuner studio. There was a option in tuner studio that asked if I wanted to flip these and I selected yes. I was getting what felt like accurate TPS readings in my logs. Not sure what the culprit is here.

It makes sense that the OEM ecu does not understand the vTPS signal but I am lost as to what is causing to MS to have the same behavior.

TPS was actually the first thing that I thought of, but your logs looked OK. A early NA runs 12V to the TPS pigtail. You have to disconnect this 12V and depending on how you wire it, connect it to GND or VREF. I had a very similar behavior on an AEM based early NA install.

Edit: I might have the WOT and IDLE signals swapped in my head, one of them goes to 12V.

What determines weather you wire the 12 volts into the ground or 5v ref?

Did the MKturbo TPS come with instructions? Wire the pigtail as the instructions instruct. I am sure there are writeups here as well.

you should be able to disconnect the tps with the MS and still run. Does it still "rev limit" with the TPS disconnected?

No instructions came with vTPS, I'll find some and get that sorted. I reconnected my MS and just started car with no TPS and re calibrated the TPS in tuner studio to read zero. Still has that weird limit around 2000rpm it had before.

Out of curiosity, does your ms3 not have the jumper in place to look for a variable tps? I know when I installed my ms3 I had to put in a jumper on the main board to tell it to look for a vtps.

Leave the TPS disconnected - it's primarily used for acceleration enrichment. Slowly rev the engine - that will give the megasquirt time to meter the air - if it passes the 2300rpm wall, it's in your TPS. If not - it's something else. And when I say slow, I mean slowwwwly.

I'll throw this out there as well - I've had my MS3x w/ 3.56 board show errant values for voltage - in the nature of 18v. Verified the voltage with a mutlimeter and ended up reflashing the firmware to fix it.

its the standard SadFab VTPS bracket and KIA TPS. There are directions from Hi_Im_Sean floating around on mt.net in several places.

I would assume so given that I build it using trubokitty's instructions. which jumper is it?

Where were you measuring voltage at? I think just re flash firmware tomorrow just for a piece of mind. I hate this guessing game

Pretty much anywhere, there shouldn't be much drop between the underhood fuse box and battery. What you're really worried about is boiling the battery though, so measure there if you want to be sure. 13.8-14.2v are nominal.

No TPS connected. Re flash of the 1.41 firmware. Applying throttle slowly and still the same problem :td: Battery still measures 14.5 consistently. How can I check that my alternator is working properly?
The car runs normal with stock ecu so that leads me to believe its a issue with the MS itself. Is there anything I could've soldered incorrectly to cause something like this?

The 93 alternator is internally regulated, so no, it's not anything to do with MS. If you want to check the alternator, stick a multimeter on it on the battery and measure with something that's more or less known good. 14.5 isn't going to blow up MS.

I just looked at the video and your tune - you need to remove fuel. You're already rich and then you have a dramatic spike - you're drowning spark. If the video and log were taken at the same time, you need to see if you've set the wbo2 up correctly - MS is seeing 2 points richer.

Secondly - if the issue persists - tune the VR pots. I know you said you already have, but those are starting points. Turn them a half turn clockwise - if it gets worse, turn them a full turn counter clockwise. I had a 5000 rpm limit going off the suggested values, tweaked them a little bit more, and haven't touched them since.

So I went and did some tuning to the VR pots. This is for sure the issue! I was able to get the car revving freely.

After messing with the pots I was able to get the car running all the way up to redline. But I am still having some weird behavior as my tach in car was readying 7000rpm and now as I look at the log I am seeing 7800rpm. My hard limiter in tuner studio is set to 7200 so I don't know how or why it was able to climb this high. Or whats causing my tach and tuner studio to read a differential RPM. After adjusting the pots the car was having trouble staying running on its own. 4.8v on R11 and 1.1 on R56 is where both pots current sit at. This is significantly different than the 2.5v specified in the Manuel which throws me off. Is there a better method I should be using to tune these pots other than guess and check?

Big thanks to everybody who has chimed in thus far. Hoping to gain a bit more understanding of this before I continue or potentially damage anything. Here is the log I took while adjusting r56 where the engine gets to a alarming 7800rpm. My VE table right now is a joke, I haven't really touched it since I have been focusing on this issue. So AFRs are kinda all over the place.

You have a hard rev limit set, but no method as to how - you haven't enabled spark or fuel cut.

And the stock tach is pretty inaccurate.

which is better or more commonly used. spark or fuel cut?

Your basemap had it turned on. Maybe you should look at what it used......

oh... duh. thanks

Fuel cut - possibility of lean condition as you're bouncing off the limiter.
Spark cut - possibility of backfire pop when the spark comes back on.
Retard - high cylinder EGT's.

Pick your poison. I ran spark cut without a cat.

Problem is officially solved. The issue ended up being incorrectly tuned VR pots. As I mentioned above both r11 and r56 had to be moved pretty far from the documented turns specified both on trubokitty and the megamanuel. Big thanks to all of you who have responded to my dumb questions. Now onto tuning!