openecu.org

I've read that to convert from MAF to engine load the formula is:

Engine Load (cylinder charge in grams) = (MAF * 120) / (4 * RPM)

However this formula doesn't seem to work out correctly.

For example if the MAF is 300g/s @ 6000RPM, Engine Load calculates to 1.5g. This is clearly not right when the factory ECU goes up go 5.6g in load.

I'm thinking perhaps the factory ECU expresses load in terms of the charge in all four cylinders, rather than a single cylinder, which would mean 300g/s @ 6000RPM calculates to 6g (4 * 1.5). This would be more consistent with the factory load values.

Or do I just have the wrong formula?

I'm pretty sure it is (120*MAF)/RPM. That is, with the units in g/s for maf.

Some ECUs represent it in g/4cyl and some do it in g/cyl so remove the 4* at will depending on which ECU you are going for.

cdvma wrote:Some ECUs represent it in g/4cyl and some do it in g/cyl so remove the 4* at will depending on which ECU you are going for.

Well mine is a JDM MY06 Spec C ECU, which is similar to 2002-2003 USDM WRX ECUs...

It makes sense that mine is in g/4cyl otherwise the load figures from what I've seen would be too low...

RICK SCHU wrote:I'm pretty sure it is (120*MAF)/RPM. That is, with the units in g/s for maf.

Just to clear that up..
It's actually (60sec * 2revs per charge) / rpm
Not important, but I was scratching my head wondering where 120 came from for quite a while.

qoncept wrote:

RICK SCHU wrote:I'm pretty sure it is (120*MAF)/RPM. That is, with the units in g/s for maf.

Just to clear that up..
It's actually (60sec * 2revs per charge) / rpm

Yep

Non-dbw Ecu's (2.0) used to convert grs/sec readings into grs per cycle load scaling.
(1 cycle is 2 revs on a four stroke )

New generation (dbw 2.5) switched to grs per rev, so that the load scaling we were familiar to is now divided by 2.

NB : DbW can actually read MAF up to 350grs, while previous 2.0 where 300grs only.
Unfortunately, 350/2500cc is less than 300/2000cc (0.14 compares to 0.15)