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Old 03-05-2019, 08:19 PM   #1
GoochE30
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Megasquirt questions

Hey R3v,

I'm new to megasquirt and using my 2.7i engine to learn to tune.

I have a couple issues right now.

My car goes all the way through the rpm range fine at a good AFR but when I hit the throttle hard the engine instantly dies. If I let off the throttle the engine will come back to life. I took a log of the issue. My Accel Enrich is 100% MAP based

Another problem that I noticed is that I've been driving on a tune and had no issues but when I started the car today (warm) suddenly the idle AFR was somewhere around 10 and the car's idle load was much higher (48kpa). The weather is a little bit colder. Could this be an ICV issue?


Anyways I realize that I am painfully inexperienced at megasquirt but I hope I can learn.

https://drive.google.com/drive/folde...1K?usp=sharing
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Last edited by GoochE30; 03-06-2019 at 08:23 AM.
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Old 03-05-2019, 08:47 PM   #2
e30davie
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Welcome to the fun.

Do you have a variable TPS? if so you want to be running TPS dot based enrichment. I or someone an share the TPS settings to get you in the ballpark.

I don't really understand the second part of your question. but what are you doing for idle control? running PID closed loop? and what are you doing for intake air temp? where is it located?

I found idle control, warm up enrichment, and intake temp compensation to be a ridiculously tedious process to get close to right.
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Old 03-05-2019, 09:06 PM   #3
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Welcome to the fun.

Do you have a variable TPS? if so you want to be running TPS dot based enrichment. I or someone an share the TPS settings to get you in the ballpark.

I don't really understand the second part of your question. but what are you doing for idle control? running PID closed loop? and what are you doing for intake air temp? where is it located?

I found idle control, warm up enrichment, and intake temp compensation to be a ridiculously tedious process to get close to right.
I'm running off the stock AFM with a whodwho plug n play ms2. I was thinking that this would be okay because there is a IAT in the AFM correct me if I'm wrong. I have the e30 TPS. Haven't upgraded to the variable yet which is why my enrichment is all MAP.

My second issue is that my Kpa fuelload at idle was 28 but suddenly started idling at 48kpa and running rich. I turned on the autotune feature and it dropped a part of my VE table significantly and got it running at a good AFR. I'm wondering if this is just a cold weather thing. I guess I don't understand what could cause my MAP to read so differently at the same warm idle.
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Old 03-05-2019, 11:33 PM   #4
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please share the MSL, not just an image. In this case, it might help to also share your MSQ.

The temperature should not have an effect on how the motor runs once it is up to temperature.
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Old 03-06-2019, 08:24 AM   #5
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please share the MSL, not just an image. In this case, it might help to also share your MSQ.

The temperature should not have an effect on how the motor runs once it is up to temperature.
Thanks for your help man. I couldn't figure out how to share the files on here so I linked to a google drive folder in the original post
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Old 03-06-2019, 08:31 AM   #6
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Something caused your megasquirt to restart when you nailed the throttle. It comes back on, orients, then attemps to inject fuel again.

I would try to replicate the issue and log it. It isn't sync loss, so it is probably something to do with the megasquirt ground or 12v power to the ecu.


edit: your fuel table is quite lumpy as well, but that's another issue. You should also disable EGO correction when you are tuning the car. The ECU is currently pulling 8% fuel in some areas, adding a bit in others. Your numbers will always be off if you have EGO fighting you as you tune the fuel table. Also keep in mind that a misfire will read as "lean" on your O2 sensor, because uncombusted fuel + air are in the exhaust.
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Old 03-06-2019, 08:46 AM   #7
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Something caused your megasquirt to restart when you nailed the throttle. It comes back on, orients, then attemps to inject fuel again.

I would try to replicate the issue and log it. It isn't sync loss, so it is probably something to do with the megasquirt ground or 12v power to the ecu.


edit: your fuel table is quite lumpy as well, but that's another issue. You should also disable EGO correction when you are tuning the car. The ECU is currently pulling 8% fuel in some areas, adding a bit in others. Your numbers will always be off if you have EGO fighting you as you tune the fuel table. Also keep in mind that a misfire will read as "lean" on your O2 sensor, because uncombusted fuel + air are in the exhaust.
Thanks a ton. I wonder what would cause the ECU to shut off because I do not have this problem on the stock ECU. Would that mean it is internal? I'll make sure to disable the EGO correction. What should my Kpa be at idle. Previously I was idling at 28kpa and suddenly i'm idling at 48. What could have caused this. I have an older log that shows the idle. It shows a CPS issue that I fixed in the log but would be an example of how the idle has changed. I'll upload it.
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Old 03-06-2019, 08:59 AM   #8
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Thanks a ton. I wonder what would cause the ECU to shut off because I do not have this problem on the stock ECU. Would that mean it is internal? I'll make sure to disable the EGO correction. What should my Kpa be at idle. Previously I was idling at 28kpa and suddenly i'm idling at 48. What could have caused this. I have an older log that shows the idle. It shows a CPS issue that I fixed in the log but would be an example of how the idle has changed. I'll upload it.
Idle will depend on the car. With the engine up to temp, I would expect 30-40kpa on a stock cam. Ignition tuning and fuel tuning will dictate where idle rpm and vac sit.

Re: megasquirt resets... I would inspect your grounds. If you look at battery voltage in your log, it comes down from 30 volts after the restart. If you want, grab some jumper cables and ground the motor to the chassis and see if helps.
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Old 03-06-2019, 01:57 PM   #9
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Jax thanks again for your help. The jumper cables did not solve my problem but I discovered that with the ignition on and the engine off, my megasquirt goes offline when the throttle pedal is fully depressed. The megasquirt does no come back online until I release the throttle. I'm thinking that a variable TPS might solve the issue?
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Old 03-06-2019, 02:27 PM   #10
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Have you still got hte throttle position sensor plugged in even though its still the oem switch style? I would unplug it and see if it helps. The MS might not like the switch style throttle sensor.
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Old 03-06-2019, 03:15 PM   #11
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Have you still got hte throttle position sensor plugged in even though its still the oem switch style? I would unplug it and see if it helps. The MS might not like the switch style throttle sensor.
When the TPS is unplugged the car wont start. Probably because when it is unplugged it reads at 150% thus activating the flood clear. But when it is unplugged I can floor the pedal without going offline
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Old 03-06-2019, 03:47 PM   #12
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what does the TPS read when its plugged in? and what does it read when you go full throttle? (when its plugged in)

I would get a variable TPS asap, you can do alot with a variable TPS.

In fact im not sure how how you do some features without a variable TPS. Idle control is activated by TPS < X% etc.

Or for now you might need to trick megasquirt into not doing what its doing by calibrating it so it always reads ~50% or something and thus isnt used.
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Old 03-06-2019, 04:55 PM   #13
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Sounds like you're pulling the entire 5v megasquirt rail to ground when you close that switch. Probably doesn't like that very much.

Unplug the tps and put a 1k or 10k resistor across the tps pins. If you simply leave it open and recalibrate the tps, the % value will creep up slowly as the car runs. I ran my car without a TPS for years, but yes--more sensors is generally better. IMO MAP based AE is hard to get right compared to TPS enrich
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Old 03-06-2019, 05:32 PM   #14
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Sounds like you're pulling the entire 5v megasquirt rail to ground when you close that switch. Probably doesn't like that very much.

Unplug the tps and put a 1k or 10k resistor across the tps pins. If you simply leave it open and recalibrate the tps, the % value will creep up slowly as the car runs. I ran my car without a TPS for years, but yes--more sensors is generally better. IMO MAP based AE is hard to get right compared to TPS enrich
I'll go ahead and run the resistor for now and see how that works. e36 TPS is ordered. Thanks
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Old 03-07-2019, 11:15 AM   #15
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You should also disable EGO correction when you are tuning the car. The ECU is currently pulling 8% fuel in some areas, adding a bit in others. Your numbers will always be off if you have EGO fighting you as you tune the fuel table. Also keep in mind that a misfire will read as "lean" on your O2 sensor, because uncombusted fuel + air are in the exhaust.
While I would still recommend disabling EGO control while tuning, it is my understanding that auto-tune accounts for ALL corrections already, so it wouldn't necessarily be detrimental to leave it on. Same with MAT correction, etc. etc.

OP why leave the AFM in there if you have a MAP sensor? Add in a variable TPS, it's cheap and easy and much more suited for Megasquirt.
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