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Old 07-16-2010, 10:41 PM   #26
turboge
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Cool thanks for the info. I am using the COBB adapter as well but I have only logged with MRP corrected and not the sea level compensation. I started with the settings lance posted and MRP was about .75psi off of what the boost gauge read. Going to give yours a shot tomorrow and see how things line up.
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Old 07-27-2010, 05:16 AM   #27
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How about using cheaper map sensor like found here?

Auberins
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Old 07-27-2010, 12:37 PM   #28
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Quote:
Originally Posted by imppu2001wrx View Post
How about using cheaper map sensor like found here?

Auberins
If it works, its works. What's your question?

I've never used that brand so I don't know how the accuracy or linearity is.
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Old 07-27-2010, 02:12 PM   #29
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I got their egt gauge set and it is super accurate.
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Old 07-27-2010, 03:38 PM   #30
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Quote:
Originally Posted by kellygnsd View Post
If it works, its works. What's your question?

I've never used that brand so I don't know how the accuracy or linearity is.
Just figuring out other options than AEM map sensor with cobb adapter. I found out that omni power makes plug&play map sensor for Subaru (3 bar / 4 bar) and it should be super accurate too like gaby said about the auberins egt setup. I am just one of those persons who tries to think and find a good balance between price and quality
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Old 07-27-2010, 03:59 PM   #31
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I will be way more accurate that the stock one, that's a fact.
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Old 07-27-2010, 09:26 PM   #32
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Quote:
Originally Posted by imppu2001wrx View Post
Just figuring out other options than AEM map sensor with cobb adapter. I found out that omni power makes plug&play map sensor for Subaru (3 bar / 4 bar) and it should be super accurate too like gaby said about the auberins egt setup. I am just one of those persons who tries to think and find a good balance between price and quality
Looks like a good find then. I'll try the 4 bar model and let you know how it works. For the price I have to try it.
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Old 07-31-2010, 01:24 AM   #33
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Quote:
Originally Posted by turboge View Post
Cool thanks for the info. I am using the COBB adapter as well but I have only logged with MRP corrected and not the sea level compensation. I started with the settings lance posted and MRP was about .75psi off of what the boost gauge read. Going to give yours a shot tomorrow and see how things line up.
Your boost gauge is not corrected for relative pressure
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Old 07-31-2010, 01:41 AM   #34
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Also, to anyone using the OEM sensor as a reference to "calibrate" an aftermarket sensor -- the factory uses a single calibration value based on the sensor's theoretical calibration, regardless of sensor to sensor variation, sensor variance or drift over time, etc. You may very well be "calibrating" to the same slightly incorrect values you're seeing from the OEM sensor.

Stating that the values I posted are incorrect is, well, misleading...the values are exactly as stated in the calibration data by AEM. It's a simple y=mx+b calculation that works out to m=12.5 and b=-6.25. If you have an accurate pressure gauge to calibrate against, great...just remember that from then on you're dependent on that calibration gauge's accuracy, which again, may be every so slightly off.

Using the calibration data as stated by AEM will at least be consistent. Regardless, anything close will be good enough for government work, as kellygnsd mentioned.

One of the best ways to sanity check your calibration is to simply compare it to the barometric pressure sensor in the ECU with the key on and the engine at rest. If they match within less than a tenth of a PSI, move on

I can provide AccessTuner calibration values for any linear 0-5v sensor on earth with two known points. Feel free to contact me if anyone needs help or guidance on this issue

Last edited by lancelucas; 07-31-2010 at 01:48 AM.
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Old 07-31-2010, 09:01 AM   #35
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Quote:
Originally Posted by lancelucas View Post
Also, to anyone using the OEM sensor as a reference to "calibrate" an aftermarket sensor -- the factory uses a single calibration value based on the sensor's theoretical calibration, regardless of sensor to sensor variation, sensor variance or drift over time, etc. You may very well be "calibrating" to the same slightly incorrect values you're seeing from the OEM sensor.

Stating that the values I posted are incorrect is, well, misleading...the values are exactly as stated in the calibration data by AEM. It's a simple y=mx+b calculation that works out to m=12.5 and b=-6.25. If you have an accurate pressure gauge to calibrate against, great...just remember that from then on you're dependent on that calibration gauge's accuracy, which again, may be every so slightly off.

Using the calibration data as stated by AEM will at least be consistent. Regardless, anything close will be good enough for government work, as kellygnsd mentioned.

One of the best ways to sanity check your calibration is to simply compare it to the barometric pressure sensor in the ECU with the key on and the engine at rest. If they match within less than a tenth of a PSI, move on

I can provide AccessTuner calibration values for any linear 0-5v sensor on earth with two known points. Feel free to contact me if anyone needs help or guidance on this issue
It states in black and white on the spec sheet that comes with the aem 3.5 bar sensor that at 1 volt the sensor should read -8.24. With the offset posted I was getting around -7.4. I am on speed density and it was clearly affecting my fueling at low map. Yes close enough for gov work might be ok if your map sensor does not affect fueling, but in my case the gov work isn't good enough.

The multiplier posted was spot on up to 25 psi, my hand pump gauge will only read to 25 or I would have tested higher. I'm just showing the actual facts I found trying to use the offset posted and the actual aem 3.5 bar sensor I was working with. It had nothing to do with trying to match what aem sensor with the same readings as the stock sensor. I was stating how close the aem sensor readings where to the stock after being calibrated correctly.
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Old 07-31-2010, 09:51 AM   #36
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Quote:
Originally Posted by fastblueufo View Post
It states in black and white on the spec sheet that comes with the aem 3.5 bar sensor that at 1 volt the sensor should read -8.24. With the offset posted I was getting around -7.4. I am on speed density and it was clearly affecting my fueling at low map. Yes close enough for gov work might be ok if your map sensor does not affect fueling, but in my case the gov work isn't good enough.

The multiplier posted was spot on up to 25 psi, my hand pump gauge will only read to 25 or I would have tested higher. I'm just showing the actual facts I found trying to use the offset posted and the actual aem 3.5 bar sensor I was working with. It had nothing to do with trying to match what aem sensor with the same readings as the stock sensor. I was stating how close the aem sensor readings where to the stock after being calibrated correctly.
Actually, in black and white, it's -8.45 PSI when the sensor is outputting 1 volt:

http://www.aemelectronics.com/Images...e%20Sensor.pdf

Not sure where you got -8.24 unless you referring to a different AEM sensor that I'm not aware of.

I fully believe your real-life results may vary from the stated calibration values from AEM. There are a number of possible causes for this -- manufacturing variance between sensors, too high/low input voltage, poor grounding, etc. But once again, regardless, the numbers I posted are 100% correct per AEM'S instructions and stated calibration data. YMMV.

Also, the offset value (b) you posted is like .3 PSI different from the stated cal values (6.575 - 6.25 = .325). y=mx+b. Since you used the same multiplier (m), this means your sensor will read a scant .325PSI higher across the board. You said you observed almost a full 1 PSI of error, so I'm not sure I follow how you corrected with 1/3rd of PSI increase to offset.

Last edited by lancelucas; 07-31-2010 at 10:03 AM.
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Old 07-31-2010, 10:32 AM   #37
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Quote:
Originally Posted by lancelucas View Post
Actually, in black and white, it's -8.45 PSIg when the sensor is outputting 1 volt:

http://www.aemelectronics.com/Images...e%20Sensor.pdf

Not sure where you got -8.24 unless you referring to a different AEM sensor that I'm not aware of.

I fully believe your real-life results may vary from the stated calibration values from AEM. There are a number of possible causes for this -- manufacturing variance between sensors, voltage offsets, too high/low input voltage, poor grounding, etc. But once again, regardless, the numbers I posted are 100% correct per AEM'S instructions and stated calibration data. YMMV.
You are correct, it is -8.4 I was just remembering but not correctly it seems. It may be variance. In fact my gauge (ashcroft digital psig calibration gauge) was reading a psi under at 1 volt sensor output using the posted offset. We have a calibration lab where I am employed. I am fixing to tune a car with the omni 4bar sensor so I plan on taking that sensor to work with me and getting some data from it.

When I say a psi it could have been a true .3?? To .5?? As the gauge jumps around some and I was looking mostly at the whole number when I noticed the values didn't match.

Last edited by fastblueufo; 07-31-2010 at 10:39 AM.
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Old 07-31-2010, 12:52 PM   #38
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My issues could also be off due to a leak at the MAP sensor housing, along with other various parts of my motor
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Old 07-31-2010, 01:24 PM   #39
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Ok reading through this, I noticed that some people are using pre-distinguished numbers and being done with it and others are making further adjustments. Is everyone just supposed to use the numbers that cobb provided or is every car going to be different? Also what role does altitude play in this? I'm assuming that if it requires a specific change at sea level the specific change will stay the same at any altitude above sea level?

It just seems like there are quite a few variables that could make everyone's calibration of these go differently. If you are calibrating the aem or whatever map sensor the variables could be: the stock sensor could possibly sway over time reading slightly different, your boost gauge could be off, altitude possibly, and any test gauge you could be using could be off. Or am I just being to anal about this? I am using a gm 3bar and currently trying to figure it out, but the problems all seem to be the same whether you are using an aem or whatever. I guess ideally everyone just wants a set it and forget it number to use right?
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Old 07-31-2010, 03:10 PM   #40
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As you know these sensors are mass produced and probably some are not even produced in the same facility even though its the same brand. Same for the parts they are made with so I'm sure there has to be some variance. A .5 psi variance + or - really won't matter on a maf subaru as the map sensor has nothing to do with fueling. But on speed density it affects fueling so I chose to fine tune the sensor readings.

The gauge I was using is calibrated and certified twice a year to a set us standard and is used to calibrate other gauges that are used by the company I work for so it is fairly accurate to a set standard. As for atmospheric pressure, the map sensor reads the same for how ever many psi you are over the atmospheric pressure of your area. So if your psia is 13 and you get 1 psi gauge pressure, then you will have 14 psia. Sea level with 1 psi gauge pressure is 15.7 psia.
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Old 08-02-2010, 11:30 AM   #41
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Quote:
Originally Posted by 2gnt2wrx View Post
Ok reading through this, I noticed that some people are using pre-distinguished numbers and being done with it and others are making further adjustments. Is everyone just supposed to use the numbers that cobb provided or is every car going to be different? Also what role does altitude play in this? I'm assuming that if it requires a specific change at sea level the specific change will stay the same at any altitude above sea level?
Well....the difference is that the AEM unit comes with the scale. They give you a low MAPV = MAP value and a high MAPv = MAP value. So getting the numbers from y = mx+b isnt hard.

Im unsure about the altitude comps. I know there are altitude comps for the 02 sensors.....IE it changes the whole scale by a certain % based on atmospheric pressure. but i cant recall off the top of my head if the same comp exists for the MAP sensor.

Quote:
Originally Posted by fastblueufo View Post
A .5 psi variance + or - really won't matter on a maf subaru as the map sensor has nothing to do with fueling. But on speed density it affects fueling so I chose to fine tune the sensor readings.
Actually there are boost related fuel trims in the ECU. In the 06 STi they are around a 20x20 cell table.....in the 08's+ they are ~30x30. They are also in the AP.

See this thread in romraider about it. Many 08 cars experience a hesitation that can be tuned out via this table.

Spreadsheet to generate fuel trim pivot table (RPM v. MRP)
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Old 04-09-2011, 07:36 PM   #42
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Didnt want to make a new thread so...

Can you move the stock map sensor somewhere without effecting things?

I need to lose mind for various reasons.
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Old 04-10-2011, 06:43 PM   #43
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Originally Posted by 25rsti View Post
Didnt want to make a new thread so...

Can you move the stock map sensor somewhere without effecting things?

I need to lose mind for various reasons.
You can mount the sensor wherever you like just as long as it is reading actual manifold absolute pressure correctly. Where are you planning on moving it?
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Old 03-05-2012, 02:08 AM   #44
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Just installed the AEM 3.5bar. I report my results tomorrow.
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Old 10-28-2012, 08:04 PM   #45
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Gentlemen, I didn’t want to start a new thread but I need some help. I installed a AEM 3.5 bar MAP and also changed the scaling under “Manifold Pressure Sensor Scaling”. When I log I am still pegging 22.35 psi. Is there another parameter I need to change within RomRaider?
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Old 10-28-2012, 08:23 PM   #46
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Log map

Log atm press

MAP - Atm = boost

U shouldn't have to do that though. U might just be logging the wrong mrp parameter
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Old 10-29-2012, 02:59 AM   #47
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Originally Posted by gotsugg View Post
When I log I am still pegging 22.35 psi. Is there another parameter I need to change within RomRaider?
There are a couple different logger parameters for boost, and one of them has an upper limit of about that much. Try logging one of the 2-byte parameters. I think "Manifold relative sea level pressure (2-byte)" is the one that I use. It's just MAP minus 14.7, which is good for logging if you also have RomRaider set up to show target boost as MAP minus 14.7 (aka "psi relative sea level" which is what almost everyone in the US uses).
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Old 06-07-2014, 09:49 AM   #48
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so don't change the definition in romraider logger for the map sensor. doesnt make sense. or am i missing something. sorry for the long bump. just need clarity
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