Clarification on Fuel tables and the MAP tables

[MattACK]

I'm still learning, so any advice would be appreciated.

How do the 3 MAP based Load Calc tables factor into the fuel ratios. I've been messing with the High Octane Fuel tables and keep finding spikes and dips that cannot be accounted for with the High Octane Fuel table.

Does the MAP Based Load Calc table tell what load & RPM cells to reference in the High Octane Fuel Map?

How do I know when it shifts between the 3 MAP based Load maps?

Finally, what is the difference is the Fuel Compensation MAT vs MAP tables? I know one is in PSI and the other KPA... is that two maps for two different types of MAP sensors that can be installed?

Thanks,

--Matt

[MattACK]

This needs to be moved to the ECUflash section. Sorry.

[candymanjl]

PSI and KPA are just different ways to display load. You just need to learn how they relate to each other.

0 PSI on a gauge, or sea level pressure (which is really 14.7 PSI not 0 PSI), is the same as 100 KPA. Positive 14.7 PSI on a boost gauge is about 200 KPA.

Some (mostly engineers) prefer KPA because 100 KPA is always 100 KPA. It doesn't depend on sea level pressure as a reference like boost gauges do. But most people like PSI since it references boost, aka the extra air we're forcing in. I prefer PSI just because I'm used to it and it's quicker to reference.

All that said there's online unit converters you could use to start to get a handle on what equals what. You may even be able to change how things display in the software but to me it's not worth the hassle.

[MattACK]

Yeah I understand the relationship between units of measure, just wondering why the two different tables with the exact same values and how the ECU uses them.

[chetrickerman]

One thing that may help is the way you look at the MAP table. A lot of people look at it as a load setting table, meaning that at this boost pressure and rpm, load should be _____.

But if you look at the table as a VE (Volumetric Efficiency) table, which is what it really is. So for example, if you look at your MAP tables Imdrax, at 2000 rpm, and 2.19 psi you are saying that the engine is 107.4% efficient (think of efficiency as an engines ability to pull in air) so the ECU is going to add the amount of fuel it thinks is needed for 107.4% efficiency. BUT, maybe your engine really isnt 107.4% efficient at that rpm/boost, so you are adding too much fuel.

If you lower the value to what is actually the engines efficiency at that rpm/boost, then the correct amount of fuel will be injected.

Doing it this way has helped me dial in MAP tables quickly and make the car run as good as it possibly can.

make sense?

[candymanjl]

So do you try tuning that table first then the regular high octane fuel map? Seems like they would both be effecting fuel simultaneously right?

[sstevojr]

We don't have VE tables in this car, unfortunately. That is more of an engine dyno for NA GM type fo thing.
But, we can treat the MAP tables as such, since they are the first step in deteriming fuel. There is an order of operations for how the ecu works, HOF occurs after MAP (and Fuel Cal occurs after HOF).

[sstevojr]

Also, you can use the basic assumption a free flowing FI engine is operating in the 95% efficiency range up to a certain psi.

[MattACK]

So if I'm understanding things correctly, MAP Calc Table 3 is used to determine load, which is referenced in the HOF and a percentage based value from the Fuel Calibration map is applied, correct. Steps 1,2, and 3?

I understand there are MAT tables that adjust things as well, but those listed above are the main 3 that make significant changes?

[prowakeskater]

do this-

log rpm, boost, and load.

set up a pivot table from lots of data. Like half an hour of driving to start, more thereafter.

Have your data plotted on the table in the same fashion as it is in the MAP tables. Here is what I do different-

since the tables have set psi intervals of 1.9347 and start from -11 or something, I split the 1.9347 in half, add it to the -11.whatever, then continue to add 1.937 in the data plot. I have found this is a much more accurate way of interpolating the data on a graph. You can then take that info and paste it right in, and repeat a few times. It helped me get a super flat (as can be) fuel curve

That may sound very confusing, so let us know if you know how to make a pivot table. you need to know how to group columns too. I can walk you through it