[Matrix89]

I've used to run my it in my miata, until I've moved to Haltech. Given what it's worth speeduino is a killer in terms of price to performance. IIRC I've moved because speeduino being based on ATMega, doesn't allow for high resolution tables, and overall it's quite basic. My friend used to run megasquirt and while it had more features according to him megasquirt was harder to setup right than speeduino

[lubesGordi]

How did you learn how to tune (fuel maps, timing, etc)? I was kind of hoping the speeduino docs would have something in there, alas "it does not cover advanced engine tuning, fuel / ignition strategies etc".

[westmeal]

I can send you some video seminars from this company called high performance academy. They have these paid courses and honestly they've got a lot of free shit on youtube too that is helpful for tuning your VE tables and how to come up with timing figures.

[lubesGordi]

High Performance Academy looks great! Thanks for bringing that up.

[rainbowzootsuit]

Not sure on speeduino, but for Megasquirt, you would start with a best guess fuel map based on engine displacement. These are data that can be shared around.

Then, to tune precisely to the engine, you datalog the oxygen sensor or fuel ratio sensor in closed-loop and process that data to refine the fuel map.

I'm harking back to Megasquirt 1 here so things might be a little different now.

[lubesGordi]

So does the best guess basically just mean estimating a fairly rich mix at first? Then for tuning are you trying to lean it out to the point you start pinging then back off?

[rainbowzootsuit]

Yes, sorry to be obtuse.

The MegaSquirt measures as its most basic inputs Manifold Absolute Pressure (MAP) and engine speed (RPM) and uses a Volumetric Efficiency (VE) [1] in a lookup table to calculate the fuel injection pulse width in order to combust at a stoichiometric air:fuel ratio (14.7g air:1g fuel) or maybe a bit rich (<14.7:1). A VE <100% is implied by all engines under vacuum because their displacement is constant while the atmosphere in the manifold is at a reduced density. Also good add an inexpensive intake air temperature sensor to adjust air density.

An oxygen sensor in the exhaust stream will "switch" between a lean signal —approximately 0.1 volts—and rich signal—approximately 0.9 volts. This acts as feedback to the engine management to add a correction to the theoretical VE.

More advanced is a "wide band O2" or "lambda" sensor that measures the air/fuel ratio over, as the name implies, a range of air/fuel ratios rather than just a nearly binary output at stoichiometry.

Many engine management systems use a Mass Airflow Sensor (MAF) to directly measure the mass of air taken into to the engine through a single point in the intake air piping and don't need to know much about the details of the VE of the engine.

[1] https://x-engineer.org/calculate-volumetric-efficiency/

[millzlane]

Yes, it's how the pros do it. After a bunch of cars with the same mods you can tune in the base map pretty much withing 20% error. Copy that map to a car with the same mods. Then it's just a pull on the dyno and refine the fuel maps, rinse and repeat until all cells are stoic or rich but not too rich at WOT. That's a very simple explanation. But there's also things like timing, VVLT, Boost controllers, torque maps, and clutch friction points for DCT's that can all be adjusted.

[Matrix89]

Honestly I don't know, it's not like I've read some kind of a book. I think it's a combination of reading random articles, docs and watching youtube videos(HPAcademy <3). Obviously having a good understanding of how an engine works is also super useful.