Thread: My first VE tune...

I've covered this here before:

http://www.e30tech.com/forum/showpost.php?p=680504&postcount=5

Holy shіt that map is awful in the bottom right quadrant.

It really doesn't matter. You can't get to that high a load at really low RPM. You won't be on the far right column until about 2k.

I usually stick something like 7 degrees of timing there, but even if you somehow managed to get to that point on the map (which you won't) the ECU is still using the idle timing and not the main timing map anyways.

Tuning with a MAF must be different than tuning with a MAP because I can get to full load (100 kPa, naturally aspirated) at 500 rpm if I want.

I'd like for you to explain this. Clearly I've never tuned with this software before.

I see.

No problem. The load axis isn't in pressure obviously, as there is no pressure sensor. Its 'TP', or 'theoretical pulsewidth'. The numbers (13 to 66) your looking at above are unscaled, which is how most people prefer to view the maps. Here's how it works- the ECU measures some mass of air with the MAF sensor. Then, with the current RPM it calculates the theoretical pulsewidth needed to achieve 14.7:1. This TP value is then used as the load. Its a little odd, but its really just another way of saying 'Volumetric Efficiency'. To see that, think about it like this- the ECU knows the actual mass flow of the engine for a given RPM (via the MAF sensor), and you can calculate the ideal mass flow based on the displacement of the engine (and same RPM). Then the ratio of those two is your actual efficiency (the RPM terms cancel, and you've simply got actual mass flow over ideal mass flow).

Anywho, knowing that the load is really in terms of pulsewidths, its really hard to load the engine enough to need a really long pulsewidth at low RPM, so that part of the map isn't a big deal.

The big difference is with a MAF sensor you can directly compute the actual efficiency. When it gets down to actual tuning it doesn't make much difference though- you've got a load axis and an RPM axis, and adjust from there.

Doesn't seem like fun to translate a MAP tuned fuel or ignition table to a MAF table at all.

The short answer is no, but it depends. For an NA engine translating the WOT bit is pretty easy- just grab the far right column (assuming you've scaled the map so the ECU is operating on the far right column at WOT). On a turbo car you just need to figure out which column is roughly equivalent to what pressure (and this is assuming your comparing two cars with the same turbo, so the same pressure is moving roughly the same volume of air).

Both the RPM and Load axis in the ECU are fully editable of course.

If your MAP system is using VE instead of just raw pressure for the load axis it would be a bit easier, but that would assume you've got a good VE map for the engine.

But its easier just to tune it from scratch.

i was trying chassing a ghost forever with the lower right untill i relized it was out of range.