Engine mapping

[jonamacg83]

Generally when it comes to 'proper' engine maps there seem to be a couple of ways of doing it.

The first being adjustable 'on the fly' via a laptop etc, so that it can be adjusted real time whilst on a rolling road or on track.

The second being one which you can adjust on a PC or laptop, but then have to program into the ECU before running. This method of inputting the map into the ECU also applies to 'off the shelf' maps.

My question is, why would you bother with the second method over the first (excluding the 'off the shelf' chip/map example). If you have the ability to change the fuelling etc, why bother to do it prior to running the engine rather than doing it realtime?

Just trying to get a better understanding of these things. Any comments would be appreciated.

Thanks

[anonymous-user]

Typically it would just depend upon the type of memory that the ecu in question uses. Most "aftermarket" ecu's have a memory that is programmable on-the-fly, so you can make real time changes and just "store" them immediately. Most OEM ecu, although having memory that can be "electrically" reprogrammed, typically cannot just run from RAM (too many variables) so require either 1) changes to be made off line then "flashed" into the memory when the engine is not running, or 2) extra memory "emmulation" to be added (effectively more fast access RAM) to which real time changes are made and then saved to the "std" memory.

For any engine control system, a significant amount of the basic setup (and even mapping if your good;-) can be done as a "desktop cal". i.e. done first without being connected to the ecu. This at it's most basic includes things like setting up firing order or injector constants etc. Doing this offline saves time (and hence money) during things like rolling road or track testing etc.

[ringram]

In a nutshell flash memory vs dynamic ram.
One has to be written as a complete block, the other is by nature dynamic you can reference any particular memory location and change it by itself.

So its usually down to the ECU as to which means of alteration it supports. Most aftermarket ones use battery backed ram so you can tune on the fly.

OEM's usually run flash as you dont need battery backing so they are non volatile.

In the case of Ls1 ECU's a dude in the states (Moates.net) swaps the flash ram out for dram with the result that you can tune the OEM ECU on the fly.. well albeit in modified ECU form.

Maybe some news types of flashram can support dynamic addressing these days..?