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Clarification on Fuel tables and the MAP tables

11K views 24 replies 7 participants last post by  MattACK 
#1 ·
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
 
#2 ·
This needs to be moved to the ECUflash section. Sorry.
 
#3 ·
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.
 
#4 ·
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.
 
#5 ·
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?
 
#7 ·
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).
 
#9 ·
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?
 
#10 · (Edited)
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
 
#11 ·
I'm not familiar with pivot tables. Please advise.
 
#12 ·
MAP/MAF are used to give a Load value (based on psi/rpm); you can choose to either drop MAF out entirely or set it as to close to MAP as possible. This Load is cross referenced w/ RPM on the HOF to give a value. That value is then multiplied against Fuel Cal.
Then the "smaller" adjustments occur, such as MATvMAP, etc. RPM is going to be your constant. PSI is going to be whatever you tell it (WDGC and Boost). MIVEC will make life difficult, until you figure it out.
As for Excel, take an on line tutorial
 
#13 ·
Gotcha.

One thing I've not been able to find yet, is how it decides to use the MAF or MAP load values. When does it use the MAF loads and when does it use the MAP loads?

When does it know to use "MAP based load calc #2 or MAP based load calc #3?
 
#14 · (Edited)
If you install RAX Fast Logging, you can watch the "MAP vs. MAF" stuff in action...

- MAFCalcs. Load input derived from MAF scaling.
- MAPCalcs. Load input derived from the 3xMAP Tables
- IMAPCalcs. A crazy load input, based on MAPCalcs, with an interpolation/scaling factor.
- ChosenCalc. The ECU chooses the middle of the above three.

Extra notes...

MAFCalcs is jagged. Not a problem - smoothing happens later.

MAPCalcs is affected in a minor way by an interpolation/scaling factor that is related to throttle back-off... either real, or "decayed". This mechanism is poor, and interferes with smooth load calcs. It shows up as "steps" down, then up, in MAPCalcs. There is a TPS-related hysteresis value that can be tweaked to eliminate these "steps".

IMAPCalcs is affected in a MAJOR way by the same interpolation/scaling factor as MAPCalcs. It shows up as huge spikes in IMAPCalcs, which can punch holes in your MAFCalcs line, if you're unlucky. Tweaking the abovementioned TPS-related hysteresis value will totally eliminate such problems, keeping IMAPCalcs to ZERO while at WOT.

ChosenCalc has velocity limits. On some ROMs (Rallairts, especially), these are set too low from factory, and load CANNOT rise fast enough to keep up with boost spool-up. You'll see it in the graphs at initial peak boost - ChosenCalc will lag behind the "middle" value of the above three inputs. Adjust "Load Ramp Rate #1" to fix.


More reading material...

http://forums.evolutionm.net/ecuflash/635617-bunch-load-calculation-related-maps.html

http://www.evoxforums.com/forums/showthread.php?p=1380801#post1380801

http://forums.evolutionm.net/09-ral...ool-up-load-calculation-problem-solution.html

Rich
 
#15 ·
Thanks alot Rich... some of these things should be stickied... way to much stuff to dig through for gems like this.
 
#16 ·
I patched my ROM (first time ever and I was worried to hell about bricking it, haha), and have been logging and tuning the past few days. This is what my Load comes out to, which probably correlates to some fluctuations I've been having with my A/F. Should I work on the TPS issue patch that you mentioned in the linked threads to keep these IMAP spikes down?

White Text Line Slope Diagram


Text Line Diagram Plot Pattern
 
#18 ·
Depends on your ROM id. Check in this thread to see if your ROM id is listed.
 
#23 ·
I'll wait as long as I need to for these gentlemen to continue to add functionality to our ROM's considering it is purely driven by the love of the community.

Now waiting for Cobb to come out with a 2012 MR map, good god, might as well be a $500 paper weight! Sorry I ever bought the AP in the beginning.
 
#24 ·
I'll wait as long as I need to for these gentlemen to continue to add functionality to our ROM's considering it is purely driven by the love of the community.

Now waiting for Cobb to come out with a 2012 MR map, good god, might as well be a $500 paper weight! Sorry I ever bought the AP in the beginning.
the day i sold mine and switched to ecu flash was as good as the day i bought my evo.
 
#25 ·
BOOM!

The next is finding someone who can take you under their wing and show you the finer points of SST and ECU tuning. A very nice community we have here.
 
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