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3 BAR MAP Giving me 109 kpa at idle

 
Old 01-05-2019, 04:51 PM
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Default 3 BAR MAP Giving me 109 kpa at idle

Just installed an EFI Source 3 Bar MAP. Flashed PCM to 3 Bar OS using the linear of 305 and offset of 10.33

With the engine idling, if I pull the sensor out of the manifold (the sensor will not give me a reading it I just do key on.. engine has to be running) HPTuners scanner (logging 3 Bar MAP PID) shows me 109 Kpa

Atmospheric pressure in Houston right now is 101.5597 kpa.. 109 kpa to 101.6 kpa is a difference of about 1 psi

Anyone know if I should mess with the linear and offset? Or just leave it as is?

Anyway I can get it to read exactly correct?
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Old 01-05-2019, 11:15 PM
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Originally Posted by TXjeepTJ View Post
Just installed an EFI Source 3 Bar MAP. Flashed PCM to 3 Bar OS using the linear of 305 and offset of 10.33

With the engine idling, if I pull the sensor out of the manifold (the sensor will not give me a reading it I just do key on.. engine has to be running) HPTuners scanner (logging 3 Bar MAP PID) shows me 109 Kpa

Atmospheric pressure in Houston right now is 101.5597 kpa.. 109 kpa to 101.6 kpa is a difference of about 1 psi

Anyone know if I should mess with the linear and offset? Or just leave it as is?

Anyway I can get it to read exactly correct?

I don't understand. You say the sensor does not give a reading, but then you say what the sensor reads?
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Old 01-06-2019, 10:52 AM
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engine idling it should read like 40-50 kPa

KOEO is should read ambient baro aka 101 kPa at sea-ish level
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Old 01-06-2019, 04:13 PM
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Originally Posted by gametech View Post
I don't understand. You say the sensor does not give a reading, but then you say what the sensor reads?
The sensor doesn’t give a reading with key on engine off. Only will show me a reading when the engine is actually running
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Old 01-06-2019, 04:15 PM
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Originally Posted by truckdoug View Post
engine idling it should read like 40-50 kPa

KOEO is should read ambient baro aka 101 kPa at sea-ish level
Key on engine off it won’t give me a reading

if I pull the sensor while the engine is running (same as key on engine off, since the sensor is out of the intake) I get 109kpa which is decently off from right.

Wondering if I mess with the offset I can get it to read right
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Old 01-06-2019, 04:36 PM
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Did EFI Source give you the parameters for the sensor? Are those the right ones?

My DPE 2.5 Bar, they gave me the offset and linear...
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Old 01-06-2019, 06:04 PM
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do any of your sensors read at KOEO?

but yeah usually you subtract or add offset until it reads 101kPa as ambient baro at sea level
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Old 01-06-2019, 11:27 PM
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y-y1=(y2-y1/x2-x1)(x-x1)

Offset linear can be found with above formula or simply laid out y=mx+b

I've had instances where KOEO the 3 bar map pid does not read, its a OS glitch. I suggest adjust the offset.
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Old 01-07-2019, 07:53 AM
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Originally Posted by subeone View Post
y-y1=(y2-y1/x2-x1)(x-x1)

Offset linear can be found with above formula or simply laid out y=mx+b

I've had instances where KOEO the 3 bar map pid does not read, its a OS glitch. I suggest adjust the offset.
Yup, reading through HPTuners posts, one of the actual programmers posted that it WILL read 0 KOEO.. annoying glitch lol

Thanks!!!!
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Old 01-07-2019, 08:19 AM
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Make sure your 3 bar OS applied correct (you did a write entire, not just write calibration).
Also, double check your MAP sensor. A 1 bar MAP on a 3 bar OS will read around 100 KPA while idling.
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Old 01-08-2019, 09:19 AM
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I hate those junk chinese sensors
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Old 01-08-2019, 10:52 AM
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2 Bar / 3 Bar MAP sensors with Custom OS don't give a reading at KOEO (it will show 0 in the scanner), the engine must be running to give a reading.
What I do is start the engine then use bi-directional controls in the scanner to kill the engine without closing ignition. This way it will keep reading MAP then you can check if it matches BARO
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Old 01-16-2019, 08:43 PM
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Well, for anyone who cares, I did some testing

I got a digital pressure gauge that reads down to the tenth psi, an air tank, etc. I plotted a few pressure points vs the voltage the pcm was seeing. I plotted those lines in excel and had it put an equation on the line.

The equation it spit out was y = 0.0162x - 0.0428

Using this equation, I got the offsets of 0v=2.60 kPa and 5v=306.33 kPa. I input those into HPTuners and uploaded the tune. My KOEO now is 100kPa, way closer than the 109kPa using the offsets provided via other sources(10.33kPa and 305kPa).

After looking at it, I think the 315kPa value is a lot better to use than the 305kPa. If I plot the line for using the offsets 0v=10.33kPa and 5v=315kPa, I get very close to the line slope I found doing testing. The slope ended up being y=0.0164x - 0.1695 so only .0002 off from the slope of the actual test data. The Y-axis intersect value can be increased/decreased. I plan on doing this to get my KOEO dead on to 101.5kPa

I also plotted 0v=10.33kPa and 5v=305kPa, the line slope had a much more aggressive slope than the 315kPa value and the data I found testing.

Pretty much, how you find the offsets is plug in Y=5v and Y=0v. X is the offset you input into HPTuners

Last edited by TXjeepTJ; 01-25-2019 at 08:34 PM.
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Old 01-23-2019, 03:13 PM
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Sounds like some good usable info!
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