Using Megasquirt to display and log Turbo Adiabatic Efficiency and Intercooler efficiency

4 January 2006 - My dad gets diagnosed with terminal cancer. 8th January 2006

In order to get some meaningful data on efficiency of my turbo setup, I've added two additional temperature circuits to my MegaSquirt. They are simply a duplication of the existing coolant circuits feeding into X6 and X7 on the MegaSquirt respectively. When duplicating the circuit, omit the 5.1v zener diode as the ECU already has this internally - even the original circuit omits this component. If you leave in, the probes wont read below 17'c.

The thermistor itself is from RS part number 151-215 (sometimes known as a 'sperm') .I made up an extra stimulator using the same pots as the actual stim for the two temp input circuits to test/prove the maths (thank's Mat!)

Temperature probes inserted into turbo outlet and water circuit (to calc IC efficiency)

Then you modify your megatune software to grab the value and create a graph. I changed the variables from egt and fuel pressure to a more universal x6ADC and x7ADC, then done a search and replace on all occurences.

Click here to download my modified msns-extra.ini file which has the changes. The file is for Megatune 2.25b717, running the "extra" firmware. You should be able to cut and paste into any other flavour of megasquirt without issue.

Assuming you place a one temp probe pre-turbo and one post turbo you will now have a turbo adiabatic efficiency gauge (which you can also datalog). For the Intercooler efficiency, I hard coded the ambient temperature because my turbo inlet temp doesn't match the ambient temp (something I will need to address later on.)

Here's some results; My turbo is about 65-70% efficient (once the temperatures settle down), my charge cooler is only about 50% efficient. I'm going to move the temp probe into the water circuit to establish if the cooler pre rad needs increasing.

Here's the results for the Chargecooler. I fitted a temp probe to the water circuit on the CC. Show's that CC is 70% efficient, but less than 50% efficient overall (i.e. compared to ambient).