This is one of several “fuel compensation” pages for additional trim values that affect the final fuel value delivered to the injector and ingnition timing. In this case the amount of fuel/spark that is added based on how much throttle is being given.
As far as I understand this functions a bit like an “accelleration pump” on a carburettor, in that it temporarily richens the mixture by a percentage.
On the Autotune it has a similar function which allows you one data point, in that beyond a certain threshold, the mixture is richened by a given % for a fixed number of engine rotations.
This setup looks to give more flexibility than that with letting you define several different values.
I am still unclear on whether the fuel stays enriched at that value or if it’s a short burst like on an accel-pump, but once I know I’ll update these pages.
From TB HQ:
“When the throttle is opened quickly, there is a sudden surge of incoming air into the combustion. This extra air is not considered when the base map is made i.e. base map was made with a slowly changing TPS and RPM.
The delta of additional air is bigger in lower throttle zones, as opposed to higher ones. Like, going quickly from 1% to 10% throttle will add more air as opposed to going quickly from 61% to 70%. That is why the fuel compensation value is higher at lower tps, and goes down as tps go up.
So the fuel compensation % is a percentage of the values in the user fuel table. If, for example you have a value of 20 in tps 10 in your user fuel table, putting 10 in fuel compensation % means adding 10% of 20 = 2.
And then you have a fuel multiplier at the bottom. This is to take a percentage of the whole fuel compensation % column. So in our example above, 100 means 2 and 50 means 1.
Spark acceleration is similar, but it is an addition to the absolute value in the table. So if lets sat you have -2 at tps 10 in user table, adding -2 in spark compensation for TPS acceleration will make it -2 + (-2) = -4
Think of it as having to advance the spark more on top of the fuel added to handle the delta of air.”
