My Megasquirt adventures over the years
****DISCLAIMER: THE VAST MAJORITY OF POSTS BY ME FROM THIS POINT ON ARE MY OWN EXPERIENCE/OPINIONS/UNDERSTANDING ON HOW THESE SYSTEMS OPERATE BASED ON THE INFORMATION I COULD FIND. ALL VALUES ARE FROM MY PERSONAL TUNE AND SHOULD BE TAKEN WITH A HEAVY GRAIN OF SALT. I HAVE A PRETTY WEIRD ENGINE SETUP THAT I HAVE NOT SEEN ANYWHERE ELSE, SO I WOULD NOT EXPECT THEM TO WORK FOR YOU OUT OF THE BOX. IT IS ENTIRELY POSSIBLE THAT SOME OF THE INFORMATION I WILL GIVE IS INCORRECT. IT'S GOING TO GET TECHNICAL. I APOLOGIZE IN ADVANCE.****
So that being said, let's start from the top and follow in Uhcoog1's footsteps and walk through the main MS settings. I also plan to put some HP Tuner info side by side to explain where I got my values from and how I adapted them for use on the MS. I spent way too much time searching for stock values only to find them right under my nose (HP Tuners includes some example files, I was incredibly fortunate that a 2006 5.7 just happened to be one of them). All of the below is based on my current tune as of today (Aug 7, 2025) running firmware 1.6.0.
Basic settings - these define the very basic values of your engine, like how big it is and what sort of control algorithm you want to run. I tried to highlight some of the key values here in red boxes:
The required fuel value is the basis from which all MS calculations are done. Technically speaking you can get this "wrong" and still tune the car to work fine (ask me how I know...), but it might make your tables look a little funny. The control algorithm defines what formula MS uses to calculate how much fuel to inject and determines what kind of sensors you need for your installation. Speed density is what most Dodge products run as far as I'm aware. That setup relies on knowing the pressure and temperature of air in the manifold to estimate the mass. The other main algorithm used by OEMs that I'm aware of is Mass Air Flow. It measures the air mass more directly via a MAF sensor. If you were feeling fruity you could probably retrofit a MAF sensor onto your engine and run this way, but I have a carb style throttle body setup on mine, so I kept it speed density. MS will calculate the required fuel value based on the information put in the box on the far right of the screenshot. This was more of a struggle for me than it should have been and goes back to my lack of information regarding OEM injectors. I searched high and low for values, but never got the full story anywhere I looked. The main caveat is that a lot of places list injector values at 43 psi as that is one of the "standard" pressures that fuel systems run at. Dodges tend to run at 60, so unless the data you have specifically states flow at 60 psi, be wary. I pulled the 30 number from injector data in HP Tuners (more on that to come). The air fuel ratio here depends on what fuel you want to run. Conventional wisdom says to pick 14.7 for pump gas, but a lot of pump gas nowadays is 10% ethanol (E10). The stoichiometric AFR for E10 blends is typically closer to 14.4. The HP Tuners information backs that up:
It's weird, but for some reason Dodge likes to use the reciprocal value for everything. 1 divided by 0.0694 equals 14.41, so that seems to be what Dodge is expecting you to put in the tank for base values. I changed my value to 14.4 to calculate my required fuel, then changed it back to 14.7 later without recalculating (for other reasons I'll mention later).
The rest of the settings on the page are fairly straightforward and the tooltips provided do a good job of explaining things.
****DISCLAIMER: THE VAST MAJORITY OF POSTS BY ME FROM THIS POINT ON ARE MY OWN EXPERIENCE/OPINIONS/UNDERSTANDING ON HOW THESE SYSTEMS OPERATE BASED ON THE INFORMATION I COULD FIND. ALL VALUES ARE FROM MY PERSONAL TUNE AND SHOULD BE TAKEN WITH A HEAVY GRAIN OF SALT. I HAVE A PRETTY WEIRD ENGINE SETUP THAT I HAVE NOT SEEN ANYWHERE ELSE, SO I WOULD NOT EXPECT THEM TO WORK FOR YOU OUT OF THE BOX. IT IS ENTIRELY POSSIBLE THAT SOME OF THE INFORMATION I WILL GIVE IS INCORRECT. IT'S GOING TO GET TECHNICAL. I APOLOGIZE IN ADVANCE.****
So that being said, let's start from the top and follow in Uhcoog1's footsteps and walk through the main MS settings. I also plan to put some HP Tuner info side by side to explain where I got my values from and how I adapted them for use on the MS. I spent way too much time searching for stock values only to find them right under my nose (HP Tuners includes some example files, I was incredibly fortunate that a 2006 5.7 just happened to be one of them). All of the below is based on my current tune as of today (Aug 7, 2025) running firmware 1.6.0.
Basic settings - these define the very basic values of your engine, like how big it is and what sort of control algorithm you want to run. I tried to highlight some of the key values here in red boxes:
The required fuel value is the basis from which all MS calculations are done. Technically speaking you can get this "wrong" and still tune the car to work fine (ask me how I know...), but it might make your tables look a little funny. The control algorithm defines what formula MS uses to calculate how much fuel to inject and determines what kind of sensors you need for your installation. Speed density is what most Dodge products run as far as I'm aware. That setup relies on knowing the pressure and temperature of air in the manifold to estimate the mass. The other main algorithm used by OEMs that I'm aware of is Mass Air Flow. It measures the air mass more directly via a MAF sensor. If you were feeling fruity you could probably retrofit a MAF sensor onto your engine and run this way, but I have a carb style throttle body setup on mine, so I kept it speed density. MS will calculate the required fuel value based on the information put in the box on the far right of the screenshot. This was more of a struggle for me than it should have been and goes back to my lack of information regarding OEM injectors. I searched high and low for values, but never got the full story anywhere I looked. The main caveat is that a lot of places list injector values at 43 psi as that is one of the "standard" pressures that fuel systems run at. Dodges tend to run at 60, so unless the data you have specifically states flow at 60 psi, be wary. I pulled the 30 number from injector data in HP Tuners (more on that to come). The air fuel ratio here depends on what fuel you want to run. Conventional wisdom says to pick 14.7 for pump gas, but a lot of pump gas nowadays is 10% ethanol (E10). The stoichiometric AFR for E10 blends is typically closer to 14.4. The HP Tuners information backs that up:
It's weird, but for some reason Dodge likes to use the reciprocal value for everything. 1 divided by 0.0694 equals 14.41, so that seems to be what Dodge is expecting you to put in the tank for base values. I changed my value to 14.4 to calculate my required fuel, then changed it back to 14.7 later without recalculating (for other reasons I'll mention later).
The rest of the settings on the page are fairly straightforward and the tooltips provided do a good job of explaining things.