ktech
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« on: March 16, 2010, 03:52:31 AM »
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I have been trying to figure out how to change the software to adapt to a mapsensor that can measure higher values than the stock one (1,5bar) Tony do you have any input on this.? I want to use the AEM 2,5bar sensor.
I have been looking at these maps.
DSLGRAD. think this could be the one to make the direct conversion i Volt vs Hpa
But again alot of other maps need to be changed also. Factors and offset need to be adjusted in other maps so the software will convert the values the right way.
Please type in you inputs on this.
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Tony@NefMoto
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« Reply #1 on: March 21, 2010, 01:16:38 PM »
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I spent a while looking into this myself.
The main problem is that the MAP sensor value is stored in an 8bit variable. This variable has a maximum value of 2550mbar, because it has a scale of 10, and the maximum value an 8bit variable can hold is 255. So even if you change the sensor to one that reads higher and update the sensor voltage to pressure conversion map, the ecu can't store any value higher than 2550mbar.
If you want to change the variable scale or offset to another value, then you will have to find every other pressure value in the ecu and update them as well. You could also change the 8bit variable into a new 16bit variable, but then you woul have to update all places using the old 8bit variable to the new 16bit variable, and change the 8bit assembly instructions into 16bit instructions. Both of these approaches would be very labour intensive.
The other option is to not rescale the sensor voltage to pressure convesion map after upgrading to a higher reading MAP sensor. If you do this the ecu will believe you are running less boost than you actually are. You can get away with running this way if you tune any important maps referencing the MAP variable to be in line with your new sensor. There may be unknown side effects to underscaling and having the ECU belive you are running at a lower pressure than you actually are.
Hope this helps.
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spen
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« Reply #2 on: September 22, 2010, 08:38:45 AM »
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Tony
I've not looked at this closely enough but I'm surprised by this. Internally the ADC is 10bit IIRC. Most of the output from the scaling functions (in my d box there are two functions for MAP ADC scaling - one appears to be a relic) is as words. One output is a byte. I assumed the byte was going to be used for comms - a little like the MAF cannot report more than 364.08 g/s via VAGCOM but internally the ECU can go higher.
Have you got the function decoded?
Spen
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Tony@NefMoto
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« Reply #3 on: September 23, 2010, 10:38:31 AM »
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I have disassembled just about every function that reads in sensor data in the ME7. I was also very surprised that the MAP value was being stored in an 8 bit variable. The main problem I found was that the internal scale of the MAP variable limits the maximum value to 2550mbar. If you were to rescale the variable to allow for storing a higher pressure, you would then need to rescale every pressure constant in the ECU. All pressure constants in the ECU seem to use an implicit scale of 10.
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spen
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« Reply #4 on: September 23, 2010, 04:15:37 PM »
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Thanks Tony, your comments make it worth investigating! ME7 is well constructed and I'd like to see if I can understand why the designers accepted such a limit. I'll post my disassembled output once I have it.
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spen
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« Reply #5 on: September 28, 2010, 03:33:19 PM »
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Tony, you are correct. The map sensor goes through a y=mx+c normalization and then is stored as a byte.  What is worse is that "requested boost in front of the throttle body" is a byte too All in, that is a lot of work to change for minimal gain. |
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Tony@NefMoto
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« Reply #6 on: September 28, 2010, 04:45:09 PM »
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Exactly. It is going to be a major pain to make the ME7 handle more than 2550mbar. You would need to rescale every pressure value in the ECU. I think there may be some short cuts you could take, but at this point I don't see it being worth the investment in time to support pressures higher than 2550mbar.
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Drehkraft
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« Reply #7 on: September 28, 2010, 05:07:11 PM »
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This would be why the APR 3+ files all clip at 2550 and then just rely on the maf readings after at high boost. But then again, they just run it pig rich to be safe anyways....If it were easy, I'm sure they would have done it.
On a side note, I see many TDI mappers swapping the pressure sensor.
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Tony@NefMoto
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« Reply #8 on: September 28, 2010, 05:30:17 PM »
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You could swap the sensor, and not rescale the values in the ECU. This would cause all of the pressure values in the ECU to be underscaled. It can work, but you will be running at a higher pressure than your ECU thinks.
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hammersword
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Revlimit ECU tuning
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« Reply #9 on: November 02, 2010, 07:26:06 PM »
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Here are the maps to rescale a MAP and install anything you like gradient for manifold pressure sensor - DSSGRAD - hpa/Volt offset for manifold pressure sensor - DSSOFS - hpa In my car I have install 300Kpa maps instead of 255Kpa stock!  |
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99pwr
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« Reply #10 on: November 03, 2010, 12:56:04 PM »
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So, for install a 350-400Kpa map sensor must be decreasing dsxgrad and increasing dsxofs?
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turboskipper
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« Reply #11 on: November 03, 2010, 02:25:24 PM »
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Here are the maps to rescale a MAP and install anything you like gradient for manifold pressure sensor - DSSGRAD - hpa/Volt offset for manifold pressure sensor - DSSOFS - hpa In my car I have install 300Kpa maps instead of 255Kpa stock! Tony says above that the value is stored in an 8bit value though so I don't see how you could just toss in a new sensor and change those calibrations. Seems it would just clip at 255. |
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Tony@NefMoto
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« Reply #12 on: November 03, 2010, 05:52:31 PM »
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The ECU can't read above 2550mbar no matter what sensor you put in it. I am 100% sure of this on the B5 Audi S4.
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hammersword
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Revlimit ECU tuning
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« Reply #13 on: November 04, 2010, 07:53:23 PM »
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in 1.8T engines works perfectly!
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Tony@NefMoto
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« Reply #14 on: November 05, 2010, 02:41:01 PM »
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in 1.8T engines works perfectly!
If you datalog the boost pressure, does it ever read higher than 2550mbar? If you rescale a map using an 8bit boost pressure on it's axis, do map cells with axis values higher than 2550mbar ever get accessed? The main problem with the S4 ME7 is that almost all maps in the ECU use the 8bit boost pressure variable which has a limit of 2550mbar. |
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