I had an idea to hook up to the intake air temperature sensor to the Xede to permit compensation for air density changes thus calibrate out changes in boost with differing inlet air temperatures. Note that the Karmen frequency is not a function of air temperature or air pressure, only volume flow. Such an implementation avoids the cost of a 3 bar MAP sensor by in theory adding only one wire and a very small map.

That said I need a free analog input on the Xede to make this work. Consulting Xmap's Xede connector screen seems to indicate that with the SMART system there are no (zero) free analog inputs.

Can someone from Vishnu confirm my read on this?

 

True. With the smart system, All analog inputs are used. We already do bost compensation as a function of MAF values, sounds like a cool little experiment though.

 

I posted such a map in the last few weeks that works rather well over a 50F range of temperatures, but I found that it wasn't sufficient when we were hitting the 5 to 15F weather in the last few weeks.

Basically in reading today the Karmen vortex flow meter measures volume flow. Computing mass flow requires air pressure / temperature measurements in combination with the volume flow number. The Evo's ECU uses all three parameters, as measured within the flow sensor, to compute the mass flow. The Xede is currently only working off of the volume flow, which is sufficient for the fuel/timing load axis but in practice isn't for boost control.

So lets try a different approach. I think PWM0 is a free input, assuming one isn't using lauch control. Can you confirm?

Basically I would need to build a 0-5v input to PWM output converter and use the PWM0 as the Xede input. I was hoping that this would be a simple Xmas project, but maybe I can still pull together the parts...

 

I assume then that you have found this link: http://www.annagarrison.com/MAFS.html

Very cool info on the MAF and others.

l8r)

 

Confirmed! Now get to work

 

That input is free given that you dont have LC. However, its pulse width, so there isnt going to be much you can do in terms of an analog wave form, unless you can convert it to an on/off almost digital type signal, and even then its questionable if you could get the results you wanted.

 

Yea and a few others as well. Good reading.

 

I need to know what frequency, or range of frequencies, that the Xede wants to see on a PWM input. The idea is to vary the duty cycle in the spirt of pulse width modulation as a function of the input voltage.

There is a simple little circuit that will work if the frequency is allowed to change, but the duty cycle is a direct function of the 0-5v input. If the frequency can't change I will have to look a little bit further.

Edit: I'm going to guess that that the PWM input frequency should be rather low given that it is normally looking at something like the waste gate control or the like. Perhaps in the range of 25 to 50 hz?

 

I believe I answered my own questions. The new version of Xmap has more detailed information in the help file.

As such I ordered a prototype card to test this out and it should be in hand by the end of the week.

 

So I have a prototype completed, but not fully integrated into the car. I'm waiting for a connector and enclosure.

I decided to implement two different configurations based upon the one available Xede input (PWM0) and a 8 pin connector on my box.

In the first configuration the box looks at the inlet temperature / atmospheric pressure and generates a PWM output. Connections to the Xede's break out board are: temp, pressure, +12v and ground. In addition there is an output that connects to the Xede's black connector, pin 1 (PWM0).

At this time the mapping between temp/pressure and the PWM output are fixed. In the Xede a small map (e.g. 20x1 cells) is user tunable, where the y-axis corresponds to a combination of temp and pressure and the contents are the correction factors. In reality we can now have mass flow rather than just volume flow in the Xede.

Also notable is that a MAP sensor could be connected as well to do closed loop boost, but that could be $100 additional cost for the sensor alone. The scheme cited above really does the job without the extra cost by looking at mass flow for the first time.

A video of a test of the PWM output is attached. The temp input is ramped over its full range, followed by 1/2, 1/4 and 3/4 scale input for a short periods of time. Sorry for the poor image, but I had to compress it a great deal to upload it here.

Additionally I added an additional function that uses the Xede water spray output to disconnect the air conditioning compressor on high load / RPM. Thus there are three more wires, one which goes to the Xede and two to the ECU harness much in the same way as the boost bypass on the standard Xede harness.

The second configuration is yet untested, but it looks at the clutch switch and the vehicle speed sensor. Electrically it is there, but a little more work is needed. As there is only one PWM input on the Xede this configuration cannot be used at the same time as the temp/pressure compensation.

 

...maybe off topic but where did AN2 In go? I dont see it in the "M" xede pin diagram

Are you going to use the closed loop boost control built in xmap 3.2?

 

It appears that AN2 and maf are exclusive of each other. In other words with the Evo's air mass meter the AN2 pin is used for the maf / freq0 input. I'm going to guess that AN2 is still a possible input, but it is inside the box and no one is saying anything about that.

It is obvious that the Xede's limited number if inputs and outputs is starting to become an issue. To be honest I wish that there was a way to do away with the Xede's LED outputs and use those pins for additional inputs.

It isn't clear if ChipTorque finished the firmware for the Xede's closed loop boost control. That said I'm not sure that they were thinking when they developed that feature. It looks like they want to change boost as a basis of an Xede input. For example one could reduce boost on detection of knock.

To be honest I wasn't planning on the built in closed loop function to make this work. Here is the implemenation in short,

 

There is pin 3 on the black connector, could that one be used?
I'm really interested in this development!

 

The only responses I have received from Vishnu are within this thread, where it is stated that AN2 is no longer open with the Evo version of the Xede.

 

This is getting really interesting...