Thread: Understanding IAT Density Correctioin - The Math

So I will be going to a MAP setup here pretty soon and have been going through the wiki and simulating some stuff to help prepare myself for the tuning challenges of learning MAP.

One thing I am having a little confusion about is the formula posted regarding Corrected IAT Density. The formula is listed as density corrected IAT = (IAT x factor) + ((ECT x (1 - factor)) however whenever I run the math, I get negative values in the thousands using commonly seen values.

Is the listed formula incorrect, and what is being shown is actually a bias table? and if this is a bias table, then for example, is 65% being based upon

corrected iat=(iat x .65) + (ect x .35) (values being specific to 65%)

so for example if IAT is 100, and ECT is 180, then corrected IAT if the value in the cell is 65% is 128?

sorry if this is a dumb question, just trying to understand this more fully and the formula in the wiki is being confusing

Your math is correct. The values in the table are percent.

w00t! any way to get the wiki updated? it confused the hell out of me for a while, and I kind of took a guess based upon what some of the guys were saying how 100 is actually 0.

The help documentation says:
Density Correction Table - This table, based on MAP load and RPM, contains factors that are the percentage of IAT to be used to calculate density corrected IAT. The MAP and RPM scales can be edited.

Tip: Right click in the Density Correction Table and select HELP. Takes you right to the topic in the documentation.

what is up with the formula that was posted then?

density corrected IAT = (IAT x factor) + ((ECT x (1 - factor))

I'm not sure I understand your question about the formula. You used it correctly in your example.

The doc states:
Density Correction Table - This table, based on MAP load and RPM, contains factors that are the percentage of IAT to be used to calculate density corrected IAT.

Since the table contains the factor(s) used in the formula as a percentage, "factor" in the formula is substituted by
"table value"/100.

Hope this helps.

i was using integer values when running this originally... makes sense now. sorry about the confusion.