It appears that an AEM/Honeywell 5 bar sensor will do the trick. Using this sensor will get you approximately 2.5-3 bars of range. I have yet to test this in car but it works on paper.
We confirmed 2 things at DDozier's shop in September.
#1 . The ECU will never be able to see over 2.8volts on the map sensor channel.
#2 . The ECU clips the lower end of the MAP sensor voltage and you must use a MAP sensor that doesn't go below .5 volts at full vacuum. The 4 bar map sensor we were using was around .07 volts at full vacuum and this is why couldn't get it to work
The issue is in the ECU's hard coded, un-modifiable MAP sensor volts to internal LOAD translation routine. It not only clips the upper end of the MAP voltage (~2.8volts), it also clips the lower to .5 volts. (I don't have my notes with me, so those aren't the exact #s but they're close). Here is what happens:
Engine LOAD is specified as a percentage. Engine LOAD is not direct representation of MAP sensor voltage since some filters and delta's are applied to it but for most purposes it's damn close to it. The stock load % value also translates approximately to KPA.
0% LOAD = 0 BAR / 27 inHg = .5 volts
50% LOAD = .5 BAR / 13 inHG = 1.4 volts
100% LOAD = 1 BAR (Atmosphere) = 2.8 volts
With the AEM 5 bar:
0% LOAD = 0 BAR / 27 inHg = .5 volts
50% LOAD = 1.2 BAR = 1.4 volts
100% LOAD = 2.9 BAR = 2.8 volts
There are literally 100's of parameters in the ECU and they all need to be re-scaled to match. So if a parameter was for instance, set to engage the ejection seat at 100% load (atmosphere) it now needs to be set to 48% LOAD since that is the new map sensors value for atmosphere.
The fuel, ignition and other LOAD referenced maps also need to be scaled. Depending on your preference for resolution (the stock ECU's tables are 16 LOAD x 20 RPM) you modify the load scale appropriately. This is a bit complicated to explain so I'm going to use 10 columns for simplicity's sake.... let's say you wanted to allocate 4 columns for boost.
Stock Columns:
10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100*
Add 4 Boost Columns with 5 bar sensor, tuning up to 2BAR of boost
8 | 16 | 24 | 32 | 40 | 48* | 53 | 58 | 65 | 70
Add 4 Boost Columns with 5 bar sensor, tuning up to 2.9 BAR of boost
8 | 16 | 24 | 32 | 40 | 48* | 68 | 78 | 88 | 100
*= Atmosphere
-Matt
