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Old 07-28-2014, 12:36 AM   #1
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Default Low MAP kPa @ key on/engine off and Full throttle. stumped!!

I have a 94' with a 99 engine with MS PNP. running the latest 029y4 rev, and tunerstudio beta. I have had this issue since Ive had the car.
the MAP kpa is low, its max is at 84. thats as high as it will go KOEO and wide open throttle.
i noticed it when i started scaling my tables for boost for the upcoming mods, and realized while running VEAL the cells @ 84 would become super rich and everything above that was untouched.
i have a vacuum boost gauge mounted in the cab, and it LOOKS like it hits the "0" mark on the boost side when i slam the throttle open, but the gauge in TS and the tables top out at 84.
I really have been searching all over the web and i have found several started threads were the guys had the same issue and had no answer, or it was something like a kinked line. i have checked all of this.

What settings in tuner studio could i have not set to allow it to not read the map right? or do i just need a new sensor.

Last edited by zacktrotter_uncc; 07-28-2014 at 12:49 AM.
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Old 07-28-2014, 10:49 AM   #2
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What is your altitude where you live?
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Old 07-28-2014, 11:04 AM   #3
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Quote:
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What is your altitude where you live?
748ft /223m
ambient air pressure today = 99 kpa
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Old 07-28-2014, 12:10 PM   #4
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Then something is not right.

With MS1, you must change the MAP sensor settings under:
File > project > project properties > settings > MAP Sensor
AND
Basic settings > engine constants > MAP Type

If you have a MSPNP Gen1 for 94-95 Miata, the correct map sensor type is 4-bar. Also, your MAP and baro sensors should read within a couple kPa of each other.
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Old 07-28-2014, 12:29 PM   #5
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Quote:
Originally Posted by Ben View Post
Then something is not right.

With MS1, you must change the MAP sensor settings under:
File > project > project properties > settings > MAP Sensor
AND
Basic settings > engine constants > MAP Type

If you have a MSPNP Gen1 for 94-95 Miata, the correct map sensor type is 4-bar. Also, your MAP and baro sensors should read within a couple kPa of each other.
yes. exactly, and i have been troubleshooting for a week or more and still cant find out why

the barometer gauge in TS reads like it should. (99kpa)

the engine is reaching "0" on boost gauge @ wide open throttle

the sensor on the MSPNP is a 4 bar, project properties say 4bar, engine constants have 400mapkpa

and i have reloaded the base tune, i have reloaded firmware, i have reverted back to 029y3 and back to 029y4

but.......NOTHING.

the only other thing i can do is get a new map sensor.
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Old 07-28-2014, 04:18 PM   #6
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Is it the stock map sensor? Is there a separate map sensor for barometric calibration?

Reason I ask - lets say that on key-ON before you start your megasquirt takes a sample BARO pressure reading. If the MAX your map sensor will read is 80kpa, then your barometric pressure will be listed as 80... BUT - if you look in your general settings there is a max and minimum BARO setting. So your BARO isn't really 99kpa or whatever, it is just reverting to whatever your minimum baro settings are.

You may have a failed sensor. You may have something shorting on your board. You may have an open on your board. I dealt with nearly the exact same issue with a MapDaddy4 just last week.

Last edited by Chiburbian; 07-28-2014 at 04:52 PM.
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Old 07-28-2014, 04:51 PM   #7
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Ensure that you do not have any liquid trapped in the map sensor or its line. But it sounds like your map sensor is faulty.
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Old 07-28-2014, 05:09 PM   #8
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Ben, do they use the same map sensor as the Mapdaddy? It's funny that I had almost the exact same problem last week.
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Old 07-28-2014, 05:21 PM   #9
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These are in the engine bay. I guess one is a barrometer and another is a map sensor. one leads to the other that leads to the intake, then the line splits to a vaccum/boost gauge and the other end to the MSECU which i guess has a map sensor on it too.

i took the line off and blew through it. nothing changed, the engine map stayed at 86kpa

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Low MAP kPa @ key on/engine off and Full throttle. stumped!!-cam00312_zpswwc42wlu.jpg   Low MAP kPa @ key on/engine off and Full throttle. stumped!!-cam00313_zpswddqvjht.jpg  
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Old 07-28-2014, 05:24 PM   #10
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Quote:
Originally Posted by Chiburbian View Post
Ben, do they use the same map sensor as the Mapdaddy? It's funny that I had almost the exact same problem last week.
Yes.
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Old 07-28-2014, 05:31 PM   #11
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Zach, I don't think the megasquirt uses those sensors in the engine bay (unless I am mistaken).

Ben?

I think you have a bad map sensor.
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Old 07-28-2014, 07:36 PM   #12
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Quote:
Originally Posted by Chiburbian View Post
Zach, I don't think the megasquirt uses those sensors in the engine bay (unless I am mistaken).

Ben?

I think you have a bad map sensor.
that makes some sense if they dont even work.

but how am i supposed to fix the on-board map sensor?

i have zero computer crafting skills, never soldered a thing in my life.
let alone have ever seen the inside of my ecu
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Old 07-28-2014, 08:12 PM   #13
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What does it read with the engine off?
If it's around 100kpa, you have a kink in the hose.
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Old 07-28-2014, 08:29 PM   #14
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Quote:
Originally Posted by Chiburbian View Post
Zach, I don't think the megasquirt uses those sensors in the engine bay (unless I am mistaken).

Ben?

I think you have a bad map sensor.
An MSPNP would use its own, on-board sensor, not one under the hood.


Quote:
Originally Posted by zacktrotter_uncc View Post
but how am i supposed to fix the on-board map sensor?
i have zero computer crafting skills, never soldered a thing in my life.
let alone have ever seen the inside of my ecu
You can send an email to [email protected] for an RMA. This one should be well beyond warranty, so you're looking in the neighborhood of $100 parts and labor.
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Old 07-29-2014, 10:03 AM   #15
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Quote:
Originally Posted by Ben View Post
An MSPNP would use its own, on-board sensor, not one under the hood.
You can send an email to [email protected] for an RMA. This one should be well beyond warranty, so you're looking in the neighborhood of $100 parts and labor.
Ben,
is it possible to wire up and run an external map sensor to this ecu?
- the car is my daily driver, i cant just send off my ecu.
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Old 07-29-2014, 10:13 AM   #16
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Just wire up, no. Modify the board for it, sure, but the scope would be about the same as replacing the map sensor.
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Old 07-29-2014, 10:53 AM   #17
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Provided you have the right sensor, could this be a user level repair? Reason I ask is I am thinking of salvaging my old mapdaddy to use as a spare.

provided you are sufficiently competant with a soldering iron, do you think OP or I could pull it off and have it work?

Any idea where I can get a replacement map sensor?
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Old 07-29-2014, 11:44 AM   #18
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Quote:
Originally Posted by Ben View Post
Just wire up, no. Modify the board for it, sure, but the scope would be about the same as replacing the map sensor.
what about the 2.5 bar sensor?
i dont even need 4 bar. the supercharger build that i want to do only will result in about 9-10 psi of boost.
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Old 07-29-2014, 02:18 PM   #19
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Quote:
Originally Posted by Chiburbian View Post
Provided you have the right sensor, could this be a user level repair? Reason I ask is I am thinking of salvaging my old mapdaddy to use as a spare.

provided you are sufficiently competant with a soldering iron, do you think OP or I could pull it off and have it work?

Any idea where I can get a replacement map sensor?
Replacing the entire mapdaddy is not all that difficult. Replacing just a sensor on the mapdaddy pcb is much more difficult. Not impossible, but it's a surface mount part so takes more skill. I would rate the required level of skill as, "if you have to ask..."
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Old 07-30-2014, 12:21 PM   #20
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Quote:
Originally Posted by Ben View Post
Replacing the entire mapdaddy is not all that difficult. Replacing just a sensor on the mapdaddy pcb is much more difficult. Not impossible, but it's a surface mount part so takes more skill. I would rate the required level of skill as, "if you have to ask..."
so whats the deal with the GM-3 Bar sensor then?
or the 2.5bar sensor?

the gm looks different and is still able to read way more pressure than i will ever need. and it looks like it has a pigtail connector and wires
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