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Old 07-03-2009, 01:57 PM   #1
kellygnsd
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Default AEM 3.5bar MAP sensor scaling

Anybody using one? What are you guys using for the multiplier and offset? Thanks.

KG
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Old 07-03-2009, 04:25 PM   #2
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edited for wrong values

Last edited by fastblueufo; 06-19-2010 at 06:26 PM.
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Old 07-05-2009, 05:02 PM   #3
kellygnsd
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For others information

Multiplier = 12.6875
Offset = -6.34375

That gives you 0 to 50.75psia.
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Old 07-05-2009, 10:05 PM   #4
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Quote:
Originally Posted by kellygnsd View Post
For others information

Multiplier = 12.6875
Offset = -6.34375

That gives you 0 to 50.75psia.
This is the correct multiplier and offset values then?
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Old 07-05-2009, 10:59 PM   #5
kellygnsd
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Yup, flashed it in and verified with an calibrated pressure gauge and a hand pump.
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Old 07-16-2009, 01:38 AM   #6
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Quote:
Originally Posted by kellygnsd View Post
For others information

Multiplier = 12.6875
Offset = -6.34375

That gives you 0 to 50.75psia.
These appear to be correct for me as well. For search, I am using an AEM 3.5 bar MAP sensor with COBB MAP sensor adapter with pigtail soldered into the factory harness.



Thank you!
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Old 07-16-2009, 02:26 AM   #7
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Quote:
Originally Posted by lancelucas View Post
I am using an AEM 3.5 bar MAP sensor with COBB MAP sensor adapter with pigtail soldered into the factory harness.


Will this setup work with the OEM ECU and RomRaider? ie. will it allow me to log and tune for higher boost then the stock MAP limit of around 23psi? Or does this only work with the AP?

Leslie.
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Old 07-16-2009, 03:21 AM   #8
kellygnsd
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I'm using Rom Raider
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Old 07-16-2009, 05:43 PM   #9
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Quote:
Originally Posted by wrxsti.l View Post
Will this setup work with the OEM ECU and RomRaider? ie. will it allow me to log and tune for higher boost then the stock MAP limit of around 23psi? Or does this only work with the AP?

Leslie.
You could have asked me on RomRaider

Yes, it will allow for tuning over 2.5 bar (OEM sensor's limit) -- however, the 16-bit ECU has a hard limit of 24.75 psi. I'm running right around 23psi and my OEM would peak at 22.35psi, so the extra ~2.5psi is worth it for me.
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Old 07-16-2009, 06:37 PM   #10
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Quote:
Originally Posted by lancelucas View Post
You could have asked me on RomRaider

Yes, it will allow for tuning over 2.5 bar (OEM sensor's limit) -- however, the 16-bit ECU has a hard limit of 24.75 psi. I'm running right around 23psi and my OEM would peak at 22.35psi, so the extra ~2.5psi is worth it for me.
What? I can see up to 36 psi relative now with my 3.5bar sensor installed on my 16bit ECU if you log the right parameter.
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Old 07-16-2009, 08:11 PM   #11
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I think he means that the ECU's target boost will not target anything above 24.75 (at least mine doesn't) - but you could still increase wastegate and go over I guess and watch the log to know the actual boost you're running. But I'm not sure how TD will effect things then?


Thanks for the info - but would anyone be willing to explain exactly what I need to get this working? WHere can I buy the sensor, what needs to be cut/soldered and what settings in RomRaider do I use to be able to tune with the higher MAP ability?

ATM I'm running 24psi, although depending on AP it seems to be anything between 23psi-24psi. I really want to run around 26psi and be able to control and tune it properly - what do I need to do to do this?


Leslie.
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Old 07-16-2009, 10:53 PM   #12
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Quote:
Originally Posted by wrxsti.l View Post
Thanks for the info - but would anyone be willing to explain exactly what I need to get this working? WHere can I buy the sensor, what needs to be cut/soldered and what settings in RomRaider do I use to be able to tune with the higher MAP ability?
It's a COBB MAP sensor adapter and AEM MAP 3.5bar MAP sensor. It is three wire (+5V, ground, signal) just like the OEM sensor. The multiplier and offset posted above are correct.

The COBB adapter is for fun's sake; the MAP sensor comes with adapters for 1/4" hose barb as well, meaning you can also tap your BPV vac line like any other boost gauge.
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Old 07-17-2009, 09:24 AM   #13
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The 16-bit USDM ECU only allows for a target boost up to 24.75 psig, even though the ECU's boost control can handle any level of boost you could possibly run (assuming your MAP sensor that could handle higher levels of boost - i.e. aftermarket). This limitation is not a cap, but is due to the way the target boost table is stored, so it couldn't be easily changed.

If you install an aftermarket MAP sensor and after scaling it properly, what you could do is change the offset so that the max boost you are likely to see will not exceed the 24.75 psig target boost limit and then change your target boost table with that in mind.
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Old 07-19-2009, 06:06 PM   #14
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Quote:
Originally Posted by kellygnsd View Post
For others information

Multiplier = 12.6875
Offset = -6.34375

That gives you 0 to 50.75psia.
Quote:
Originally Posted by lancelucas View Post
These appear to be correct for me as well. For search, I am using an AEM 3.5 bar MAP sensor with COBB MAP sensor adapter with pigtail soldered into the factory harness.
To update, I ended up using the calibration data provided by AEM. The exact calculation is:

Multiplier = 12.5
Offset = -6.25

The closest values that can be input into a 16-bit ROM are:

Multiplier = 12.499
Offset = -6.265

Good luck to all!
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Old 08-17-2009, 06:39 PM   #15
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What are the threads on the stock MAP sensor?
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Old 08-17-2009, 07:04 PM   #16
kellygnsd
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Quote:
Originally Posted by lancelucas View Post
To update, I ended up using the calibration data provided by AEM. The exact calculation is:

Multiplier = 12.5
Offset = -6.25

The closest values that can be input into a 16-bit ROM are:

Multiplier = 12.499
Offset = -6.265

Good luck to all!
I was able to input
Multiplier = 12.689
Offset = -6.342

I got my numbers from y=mx+b and have since verified them with a calibrated pressure gauge. Anything close will be good enough for government work.
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Old 09-05-2009, 05:28 PM   #17
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FYI, in the Cobb software the numbers are the OS values * 51.715, so the values for the AEM sensors are

For the 3.5 bar psia (30-2130-50) Multiplier: 646.133 and Offset: -323.218
For the 5.2 bar psia (30-2130-75) Multiplier: 969.655 and Offset: -484.828

It is interesting to note that based on the stock values in the 02-07 cars, at the maximum value of 4.81v you would get 25.2psig. In pratice it seems the sensor itself is pretty non linear above 4.5vs, you get a usage range up to aboue 24psig.

In the new 08 STI+ cars there is a new sensor. At 4.81Vs is is at 27.5psi, so using the same logic at 4.5Vs is would read to about 24.5. It is possible it has a more linear range, but I would not rely on it for boost control above 24psi.

Jeff Sponaugle
Surgeline Tuning
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Old 09-05-2009, 07:40 PM   #18
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Quote:
Originally Posted by sponaugle View Post
FYI, in the Cobb software the numbers are the OS values * 51.715, so the values for the AEM sensors are

For the 3.5 bar psia (30-2130-50) Multiplier: 646.133 and Offset: -323.218
For the 5.2 bar psia (30-2130-75) Multiplier: 969.655 and Offset: -484.828

It is interesting to note that based on the stock values in the 02-07 cars, at the maximum value of 4.81v you would get 25.2psig. In pratice it seems the sensor itself is pretty non linear above 4.5vs, you get a usage range up to aboue 24psig.

In the new 08 STI+ cars there is a new sensor. At 4.81Vs is is at 27.5psi, so using the same logic at 4.5Vs is would read to about 24.5. It is possible it has a more linear range, but I would not rely on it for boost control above 24psi.

Jeff Sponaugle
Surgeline Tuning
Perfect. Thank you, sir.
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Old 12-01-2009, 10:33 PM   #19
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i have an issue.....i have been running the AEM MAP for a while with 12.5 and -6.25.

tonight i logged MAP, mrp, and then did MAP-atm to get mrp2......my MAP is pegging at 37? I dont get it......and the MRP logged isnt matching the MRP calculated. FYI the atm press is 13.49

is there a setting im missing in the ecu.....all i changed was the multiplier and offset. its still capping at 2.5bar (14.7*2.5=37).....im lost.

any ideas?

Code:
RPM	MRP	MAP	MRP2	IGN	LOAD	FBKC	FLKC
2768	-12.2	2.47	-11.02	40.5	0.28	0	0
2810	-7.76	7.69	-5.8	47	0.49	0	0
2844	-2.57	12.19	-1.3	39	1.13	0	0
2914	-1.58	13.2	-0.29	34.5	1.27	0	0
3005	-0.09	14.65	1.16	22.5	1.45	0	-0.35
3106	2.02	16.83	3.34	18.5	1.72	0	0
3244	4.96	19.73	6.24	17.5	2.03	0	0
3443	9.1	23.94	10.45	17	2.57	0	0
3592	15.77	30.76	17.27	17	3.36	0	0
3888	24.28	37	23.51	16	4.34	0	0
4123	24.82	37	23.51	16	4.24	0	0
4380	24.28	37	23.51	16	4.16	0	0
4706	23.85	37	23.51	16	4.1	0	0
4914	23.37	37	23.51	16	4.01	0	0
5208	22.71	37	23.51	16.5	3.95	0	0
5376	22.25	36.85	23.36	16.5	3.88	0	0
5560	21.92	36.56	23.07	17	3.79	0	0
5757	21.69	36.42	22.93	17	3.72	0	0
5976	21.44	36.13	22.64	17.5	3.6	0	0
6194	21.35	35.98	22.49	18.5	3.51	0	0
6336	21.18	35.98	22.49	19.5	3.42	0	0
6516	21.12	35.98	22.49	20.5	3.37	0	0
6608	21.15	35.84	22.35	21.5	3.29	0	0
6748	21.12	35.84	22.35	22	3.24	0	0
6894	21.02	35.84	22.35	23.5	3.2	0	0

Last edited by Phatron; 12-01-2009 at 11:03 PM.
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Old 12-01-2009, 11:13 PM   #20
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^^^ Intresting...^^^
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Old 12-02-2009, 12:15 PM   #21
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Hey Ron is this the WRX or STi? I don't know much about the 32bit ECUs but in the 16bit ECUs there are 4 tables for both the multiplier and offset that must be changed.
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Old 12-02-2009, 01:17 PM   #22
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This is the sti

Another interesting thing.....I was running a 14psi spring in my Tial 38mm ext gate and it would blow off air all the time, it was so loud. Well last night i added the 6psi spring to it and now it doesnt blow off at all and my boost rose 2 psi across the board.

Logging MRP is showing 26 up from 24 psi and my STRI gauge is pegging at 30 psi to redline.

im starting to hate my car.

Last edited by Phatron; 12-02-2009 at 02:46 PM.
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Old 06-19-2010, 06:25 PM   #23
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I wanted to bump this thread again. I just got through installing this sensor and came up with different values. I made a log at full boost and at idle prior to the install. I tried the values listed above but at idle my absolute pressure was off by about a psi. I run speed density and it was affecting my fueling.

I messed with the values until I got the MAP at 1 volt to match what was in the aem sheet which was -8.4. That is exactly what my car was idling at on the stock sensor except it was at 1.4 volts with the stocker.

The multiplier was right on with what was mentioned above (12.499) but the offset is what was off. I ended up with the following values in case anybody else runs into this problem. My before and after logs now match and my fueling is back to normal with these values.

Multiplier= 12.499
Offset= -6.575

Last edited by fastblueufo; 07-14-2010 at 01:48 PM.
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Old 07-16-2010, 04:25 PM   #24
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fastblueofo - How do you have your sensor installed? Using a COBB adapter or barb?
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Old 07-16-2010, 10:08 PM   #25
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Quote:
Originally Posted by turboge View Post
fastblueofo - How do you have your sensor installed? Using a COBB adapter or barb?
I have the cobb adapter, It was worth every penny it cost. The install was easy and very clean looking. The aem sensor would need to be mounted seperately if you used the barb, the shape and size of the map sensor would make it a bigger job to install if you didnt have the cobb adapter. The sensor has a pigtail that wires into the stock harness and plugs into the aem sensor. I def recommend the cobb adapter.....

If the multiplier and offset posted would have been spot on It would have been a 20 minute job max. But as soon as I started the car with the numbers posted my fueling and map pressure where not correct. It took another hour of messing with the multiplier and offset to get things back in line.
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