Map sensor reading low, 99kpa at sea level

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Map sensor reading low, 99kpa at sea level

Postby kaneda774 » Wed Feb 14, 2007 11:01 am

Hi,
After building and testing my MS my kpa is reading low, should be 103 ish for sea level, I live right on the water can't get any close to sea level than that.
I checked the manual for this problem and found this,

-----------
If the MAP sensor doesn't appear to read correctly, you can check:

* If your MegaSquirt MAP sensor is reading too low, but responds to vacuum and pressure, then you have the wrong ".inc" files in your MegaTune folder. Copy the files (you need are "kpafactor.inc" and "barofactor.inc") from the "Turbo" sub-folder into your MegaTune folder, and everything should work. Place the correct files in your MegaTune directory (for older versions), or in the mtCfg folder (if it exists). (The "turbo" files refer to the ability of the MPX4250 MAP sensor to sense boost, not to the actual configuration of the engine.)
* If your MAP sensor reads low and doesn't respond to vacuum or pressure, it is likely in backwards. Verify that it is in correctly. If it isn't, unsolder it, turn it around, and solder it back in. You will have to bend the pins the other way - be careful not to break them. You probably haven't damaged any components by installing the MAP sensor backwards.
------------

So I have a responsive map sensor, but it's reading low. There isn't a turbo sub folder in the megatune directory. Also the files "kpafactor4250" and "barofactor4250" are in the megatune folder, are these the correct files? Do they need to be altered? Do I need to activate something within megatune?
I have searched this forum

MS-1 V2.2, using MSnSE from the Mega CD,
Thanks
-George
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Postby PSIG » Thu Feb 15, 2007 1:10 am

George,

99kPa is fine. If you check Step 55 of the assembly section, you'll see that 101.3 is the sea level target and it can have a variation of 4 to 5 kPa and still be within tolerance. So if you're getting 96 to 106 kPa (depending on how severe the weather is that day!) you're all set.

Note that you can overtighten the screws, or solder the sensor in while stressing it or the board, and get different values. Try holding the board and gently flexing it. The MAP pressure will change! Anyway, don't worry about it, the output is well within tolerance and will function fine.
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Postby LT401Vette » Wed Feb 21, 2007 10:57 am

Sea level is 101.3 kpa, so 99 (2% error) is within the accuracy of the MAP sensor.
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Postby dieselgeek » Sat Mar 10, 2007 1:47 pm

there's more than just altitude to a MAP reading. Figure in the relative barometric pressure, no?
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Postby MattKab » Mon May 21, 2007 4:52 pm

Absolutely, I see a 3-4Kpa swing here in the Mersey valley.

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Re: Map sensor reading low, 99kpa at sea level

Postby leogc » Fri Jul 31, 2015 5:31 am

Hi,

I know that this topic is very old, mas i'm having a problem very similar to that and I'd like to know if somebody can help me.

I was using megatune and my map was marking correctly. On last 3 weeks I had to change the fuel of my engine (from ethanol fo gasoline) and I changed (computer substitution) to tunerstudio (licensed version), but now the map is marking 60 kpa (I'm on the sea level) when the engine is off. I saw that I can change the inc files, but i'm in doubt if i should use 4115 or 4250 file. Can somebody help me?

thanks
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Re: Map sensor reading low, 99kpa at sea level

Postby Matt Cramer » Fri Jul 31, 2015 1:31 pm

leogc wrote:Hi,

I know that this topic is very old, mas i'm having a problem very similar to that and I'd like to know if somebody can help me.

I was using megatune and my map was marking correctly. On last 3 weeks I had to change the fuel of my engine (from ethanol fo gasoline) and I changed (computer substitution) to tunerstudio (licensed version), but now the map is marking 60 kpa (I'm on the sea level) when the engine is off. I saw that I can change the inc files, but i'm in doubt if i should use 4115 or 4250 file. Can somebody help me?

thanks
Leonardo


What MS version is this?
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Re: Map sensor reading low, 99kpa at sea level

Postby leogc » Fri Jul 31, 2015 5:19 pm

ms1.

Actually, I noted in Tunerstudio/Basic Settings/Map Sensor Warning that I should setup the map sensor. But I don't know where I can find the cited "Megatune Configurator". I'm using the last version of Tunerstudio.

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Re: Map sensor reading low, 99kpa at sea level

Postby Paul_VR6 » Sat Aug 01, 2015 3:04 am

Its in project properties now.
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Re: Map sensor reading low, 99kpa at sea level

Postby leogc » Mon Aug 03, 2015 5:41 am

thank you paul, it's worked.

Now it's marking 86 kpa instead 60 kpa. I think it's little bit stranger (i'm around 50m above sea level)...but its better than before.
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Re: Map sensor reading low, 99kpa at sea level

Postby WestfieldMX5 » Mon Aug 03, 2015 8:06 am

That's still too low. 50m hardly makes a difference. You should have at least 20kPa more than that.
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Re: Map sensor reading low, 99kpa at sea level

Postby leogc » Mon Aug 03, 2015 9:39 am

I agree, but what can I do? I tried change the inc files and configurations, but didn't work.
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Re: Map sensor reading low, 99kpa at sea level

Postby dontz125 » Mon Aug 03, 2015 4:01 pm

Please put up your .msq tune file, and confirm which MAP sensor you're using.
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Re: Map sensor reading low, 99kpa at sea level

Postby leogc » Tue Aug 04, 2015 5:59 am

follows attached the msq file and a little datalog made driving on parking lot.

the mega is running in a I-4 gm engine, very similar to IronDuke.

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Re: Map sensor reading low, 99kpa at sea level

Postby dontz125 » Tue Aug 04, 2015 6:33 am

What sensor are you using? MPX4250AP, GM 1-bar, ... ?
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Re: Map sensor reading low, 99kpa at sea level

Postby leogc » Tue Aug 04, 2015 11:50 am

400 kpa, model 6400.
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Re: Map sensor reading low, 99kpa at sea level

Postby jsmcortina » Tue Aug 04, 2015 12:01 pm

7 seconds of datalog isn't very helpful.

Key on. Start datalogging. Pause.
Start the engine. Let it idle.
Wait at least one minute, then stop the datalog.

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Re: Map sensor reading low, 99kpa at sea level

Postby leogc » Tue Aug 04, 2015 12:07 pm

sorry. wrong file.

I'm goingo to make another one today, begining before the start of the engine.
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