Nistune Forums

I have a question about the K-constant in NIStune. Already searched in the NIStune manual, but can't find an answer.

With Nismo 740cc injectors, the multiplier has always bin 28164 for my engine. This seems to be the correct value, because when I look to the fuel map and its real AFR value they are almost the same. So far so good.

My ECU is the 71Y05 B13 with original 259cc injectors. So, when I load an original 71Y05 ROM, from the ROM-pack and resize injectors from 259 (original) to 740 (Nismo's), I must get a multiplier of 28164. Or at least something near 27500-28500. Am I right?

But when I try this, I get a wrong multiplier. Because I need to test a second engine I need to resize injectors and found this problem. Hopefully you can tell me what's wrong?

Below you can see the multiplier changes from 31206 to 10922. And not from 31206 to 28164.

Injector sizes rescale the injectors based on new/old sizes

K constant will vary between models. The number is effectively a magic number which is adjusted by altering the percentage. So halve this number will reduce the load (and resulting fueling) by that percentage

So with 259CC standard injectors to 740CC this is more than halve

In this case K=31200 will be 10922 since we went and did 31200 * 259/740

Ok, I understand how the resize work. But not how to get all the tables correct then.

By simply changing the K to 28164, won't change all the tables which will be adjusted automatically when I use the resize option.
And 28164 is the correct setting for these 740cc injectors.
I still don't understand why 10922 would be the correct setting. With that setting the engine won't run at all.

WalknBullzEye wrote:Ok, I understand how the resize work. But not how to get all the tables correct then.

By simply changing the K to 28164, won't change all the tables which will be adjusted automatically when I use the resize option.
And 28164 is the correct setting for these 740cc injectors.
I still don't understand why 10922 would be the correct setting. With that setting the engine won't run at all.

How did you arrive at 28164 previously? And what do you mean when you say 28164 is the "correct setting"? I don't see how you could have started with 31206 K and gone from 259 to 740 and yet somehow ended up at 28164. More info is needed.

My car is a 100NX GTi with SR20DE and 23710-71Y05 ECU. Original K-constant 32106. I upgraded the engine with a turbo and 740cc injectors.

In the fuel map I turned off the O2 sensor and adjusted the K-value, until the widebandsensor and the fuel map were the same. This is how I came up with 28164. I did this under load at arround 3000 RPM. The engines runs great with this setting, by the way.

Now for my second car I needed the same settings in NIStune. But this time I used the resize option and came up with much lower K-constant values. Both cars are the same, so I don't understand why they run okay with two different K-constant values.