Thread: K value

"This calculation is based on a simple ratio of old vs new for both injectors and airflow meter. For example if the
stock K value is 34,275 and injector size was changed from 370cc to 550cc then the new value will be 21,475 x
(370/550) = 14,447. Bigger injectors require a smaller K value.
Same deal with airflow meters except we use maximum horsepower figures to do the calculation. For example it is
taken that a standard SR20 airflow meter gives its maximum reading at around 290hp. If we fit a Z32 airflow meter,
which has a max HP rating of 550hp then the calculation is 21,475 (standard K value) x (550/290) = 40,728.
If you change both injectors AND airflow meter you need to do both of the above calculations: 21,475 x (370/550) x
(550/290) = 27,400. Experience has shown that changing to a larger AFM and injectors at the same time is a recipe
for success because one increases K Constant and the other decreases it. A K Constant that finishes close to the std
value will always make tuning easier.
These are only rough calculations to get things “in the ball park”."( FROM NISTUNE)

Is this right ? I get the injector calculation but not the afm calculation. Shouldn't the afm calculation be like 290/550 x 21475, = 11323.?

When upgrading to a larger MAF you will need to raise the Kvalue.. so their math is correct in that quotation.

Am I doin something wrong on my ve-t setup cause my car seems to be richer with a higher # not lower....my car at idle is at 14.5-15.5 Afr (z32 maf/Delphi 50lb or 525cc) k-value 47000 and Inj latency at 700,this is with nistune r/t

Nistune was calling for 23186, but car would barely start..then hooked up the wideband and work my way up to 45000-47000 for 14.5-15.5 Afr

Your probably right. I have to increase mine to 50k so far on 550cc setting and z32 maf to get 1 psi. If I use my 850cc setting the k val should shoot to more than 100k the way it is going.

Anybody know what is max k value for s13 sr20det ? Seeing the max maf value is 65535 maybe the same for k val.

that K is about right though. only thing I would be concerned with is the TP Values.

with a K Value of 47000, if you didnt modify your TP Scales you may want to log them to see what kind of figures youre getting.

hey Nismotronic Guy!

is there any "math" you could use to estimate what TP figure range (max-min) you will see with a particular K Value?

so far I see that they are positively related.. bigger K val, bigger TP's

it would be a smaller value because the injectors are larger.

Yes, absolutely.

You can use the MAF rescale function in the NismoTronic software to rescale the TP values also.

(You can apply the same math to the TP scale as you do the Kvalue)

I DONT KNOW WHY I DIDNT RECOGNIZE THAT! thanks dude