Map shows 122 kpa when the engine is off
 

Does anyone have an idea what might cause my Map to read 122 kpa when the engine is off. It reads this way both in Mega Tune and Tuner Studio. I just swapped injectors and had to replace the o-ring on the air valve. I wouldn't think it was the air valve because it does this when the engine is off. I also pulled off the source line going to the Map Daddy Sensor and the results were the same. The car of course is close to undrive able. Anyone have an idea what could have caused this.

I stepped down from 726cc injectors to 460's. I'm just wanting to drive the car with the 460's until I have enough cash for my swap.

(Posting from my phone.)

Its either the map sensor is bad, you live below sea level, or the calibration is wrong

Did the sensor ever read correctly? If so, what changed between then and now?

Does the reading from the sensor still move "normally"? Eg: if you were to stick a tube from the sensor into your mouth and blow or suck into it (there's no non-suggestive way to say that) does it do what you'd expect?

It does sound a tad like a miscalibration. Specifically, the voltage output from a normal MPX250 at 100kpa (atmospheric) would produce an indicated reading of 120kpa if the software were configured for an MPXH6300 (300kpa) sensor.

I guess it could be a miscalibration or a bad sensor. I was having issues with my larger injectors so I pulled them and but the 460's back in. When I pulled vacuum line going to the Map off and blew in it I didn't see a change on the display.

I change a few things, the tune as I went down from the 726's. I also replaced the o-ring on the air valve and put a new adjustment bolt on the alternator. I don't think either of those could cause this but I'm not going to say it can't happen.

After I started to car to see what it would do, it idle around 66-75 kpa. One other thing I noticed was the Fuel Map did not automatically rescale when I changed the Map sensor as I used the original 93 Non AFM Map as my base.

I went into the configurator in Megatune to change the MAP as well as select my wide band, but I will take a look again just to make sure. I changed the Map in Tuner Studio under projects.

Thank you both for looking at this.

I checked the previous settings and everything seemed fine. Just to be certain I reuploaded the firmware and reloaded an MSQ. I checked everything except the Dwell on my coils because I forgot the proper settings.

My Map is now reading 143-144, the current barometric pressure here is 30.15 in. Maybe it was in some other application but I thought you had to set the base Kpa in MegaTune, but I can't find that setting anywhere. I also looked at tuner studio, and again I cannot find a similar setting.

Looking at the mega manual it make a reference to an .inc file. Its said to be sure the proper .inc is loaded. Any idea which .inc it could be, or is that even the cause?

(Posting from my phone.)

Three actually. But that has to do with clt and ait tempps not map sensor

Do I have to specify map while the engine or give a base line anywhere during setup. I don't remember doing this in the past, but again I could be missing something. Is it maybe in the firmware update? The car will start but it behave very strangely.

Could the air valve effect this, or should I try refreshing the firmware once again with a different version.

The air valve is not going to create 6 PSI of boost.

Something is very wrong, and I'm honestly at a loss here.

Pop the lid off of the MS. With the engine off but the power on, take a voltmeter and measure between pin 23 of the CPU and ground. This is where the voltage from the MAP sensor enters the CPU.

Assuming that the MSPnP uses the standard 250kPa sensor (I think it does) you should see about 1.8 volts (the specified error for that sensor would put the acceptable range between appx 1.7 - 1.9 volts at 100 kpa.)

I'm using a 4 bar map, should I reset to a different sensor? Maybe set it two 250, and then test the voltage.

Ah.

Changing the software config won't change the sensor's output, it only changes how the CPU interprets that output.

But no worry, you can do the same test, just look for 1.2 volts (+/- 0.1v) at the pin, assuming 100kpa ambient.

Here's the scale of pressure to voltage for the 400 kpa sensor:

https://www.miataturbo.net/attachmen...ine=1319938482

You need to set your config for 4 bar map sensor. I'm guessing you set it for 1 bar.

i can confirm, on MS1 if you set it to the 250kpa sensor with a 4bar it reads about 120-130kpa.

If that's config as in configurator under megatune > file >configurator > MSPNP 9093 without AFM > settings.ini > settings> MAP_SENSOR i'm using MPXh6400A -- 400kpa

I went through everything again and now change. Then I removed all of the tuning software off my laptop redownlaoded everything and started from scratch just to make sure I wasn't uploading a corrupted file. So now I'm seeing slightly better but not great results. When I set the configurator to the 400 kpa sensor I'm seeing 110kpa in megatune. When I set the sensor to 300kpa, I see 82kpa. When I set the map under configurator to 250, I see 73kpa. Setting it to 115 shows nothing. Could I have a 350kpa sensor, and I don't have a setting for it?

crack open the case and try what joe suggested, also posting a pic of the sensor will allow everyone to identify it for you

dont use megatune. use tunerstudio.

I use MegaTune because the last few times I needed help from the guys at DIY they needed logs from MT. I also use MT to update firmware but thats only because I don't know of a way to do it in TunerStudio.

So this situation is anything but stable. With the engine not running and ignition off pin 23 to ground i get .988 or .989 at 106kpa. I also saw .991 at 104kpa. With the engine off, and the ignition on the meter shows 0.000.

https://www.miataturbo.net/attachmen...ine=1319997633

I was really confused so I went to pick up a new multi-meter. While going though the instructions I realized I was measuring resistance not voltage. It explains somethings but not others. So with the new meter set to measure voltage, I'm seeing 5.06-5.07 on pin 23 on the second board closest to the connector for the harness. And to answer Joe's earlier question, yes it sensor did seem to read correctly before, this is new behavior. Since it worked in the past should I just go through the boot jumper process and reload everything with the hope that maybe something was corrupted previously. BTW map kpa is listed as 106 now.

So under Basic Settings, Engine Constants, MAP sensor is set to 400kPa?

How close does the BARO sensor gauge read to your MAP sensor gauge?