Full Power

Spark map tuning axis : AirMass : RPM
Fuel Map ( VE Table) Manifold pressure vs RPM
What is the simplest relationship/ rationaization for the tuning parameter discrepancy between FUEL table and SPARK map ?
I guess what I am asking is WHY do we tune Fuel vs kPa, and Spark vs Grams/ second ?
Would it not be convenient to have a scaler or conversion factor that directly relates BOOST pressure with AirAmass, for a particular, specific engine combination ?
Is there an algorithm, or MATH channel I should be looking at in my HPT scanner ?

Tuner Experts, if you have time, and if possible, please explain as if to a young child, of average intelligence.

TrendSetter

In this case the ve table is not directly a fuel table it’s a volumetric efficiency table which is then applied to airflow calcs and fed into the target afr table for final calcs.
the output of that calculation is an air mass/cyl which is the axis of the spark table.
I guess in the order of operations of calculating engine ****, the spark table is probably closer to the target afr table than the ve table (which feeds into both)

NoGo

iTrader: (2)

If you aren't measuring airflow, then you need a volumetric efficiency (VE) function in order to calculate the massflow of air into the engine. The VE allows the vehicle to determine what volume of the cylinder is being filled on the intake stroke. The manifold pressure allows you to determine the density of the air that is filling that volume. Combined you can determine the massflow of the engine which is then us to determine g/cyl - the variable needed for the spark look-up.

In short, VE is a precursor variable needed (if you aren' measuring airflow) in order to determine g/cyl.

SkinnyG

I set up a histogram of RPM vs Airmass, with the data recorded being MAP. This at least helps me understand where I actually am when trying to decide on Spark Advance for each cell, since the row of airmass is NOT the same thing as the row of MAP.

gametech

iTrader: (1)

Just as a curiosity, one of my scanner configs is setup with an rpm vs airmass recording MAP values. It makes it really simple to tell what boost pressure maxes out the spark table at what rpm.

SkinnyG

Oh shoot. You're right - that's what I have - MAP. I'll edit my post. Duh.

Full Power

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..Brilliant summation, thank you.
Airmass is calculated from RPM,MAP,IAT, and essentially the VE table IS the last variable. Again pointing out the primary importance of a well developed VE table. FIX the VE before screwing with spark, idle, or pretty mych ANYTHING.
VE table is critical..
Another example of why chasing around spark, idle airflow, throttle crackers, fudged injector parameters, and every other driveabilty issue WITHOUT first assuring a 99% + accurate VE is "Tuning with Bandaids"
Thank you again.

LilJayV10

iTrader: (39)

When I first went 2bar, it threw me off that spark wasn't based off VE.

I maxed out the air mass value pretty quick even at low boost. There wasn't enough resolution, or actual usable areas of the table.

I scaled the tune by 75% and now my max boost(15 psi) is the 1.20 g row of the spark table.

One thing that helped me correlate air mass vs. boost is to create some math channels and histograms so I could actually see it.

Full Power

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So, if I understand "scaling" your 1.2g/sec now corresponds to ACTUAL cyl airmass value of 1.6 g/sec ?
If you have the time/patience: any chance you'd screen shot or show math channel, or your scanner setup ?
I flail around like a tard when trying to get HPT set up.
Adjusting spark map, smoothing VE table, and getting PE ramp-in I find pretty fun, and intuitive.... Setting up the scanner to SHOW me data is where I stall out.
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Thank you.

LilJayV10

iTrader: (39)

Hopefully these are what you wanting.
1. Make sure you are logging baro pressure
2. Make a boost math channel. Make sure they are both are logged in psi in the so the math will work correctly.
3. Make a boost v cyl air mass histo. For me, anything above .58 g/cyl is boost pressure. I added a filter in the histo to make reading it easier. If not, it will populate every cell it hits regardless of boost or vaccum.

I don't have a log on this computer, but 15psi hits the 1.20 g/cyl row

If this isn't what you were wanting let me know and I'll try to get it.

Full Power

Thank You a LOT.
Bunch of data for me to absorb, and apply to my scan fields.
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Side note/ question :
Do you or have you ever adjusted MAP offset to correct or align scanner to actual ambient atmospheric pressure ?

LilJayV10

iTrader: (39)

Not with a stock PCM. I've had to on a few cars I've tuned with Holley EFI before that I've had to offset just a little bit.

The barometric reading comes from the MAP sensor when you turn the key on.

As long as the correct MAP sensor data is in the tune, it will adjust for any elevation changes.

KOEO, Baro and MAP should be the same.