Hi guys im new to nistune and ive been tuning my s14a sr20det with the help of a good friend and I currently have a K constant of 27120 and a latency of 620 but my idle afr's are 12.1
if I reduce the latency to 450 my idle afr's are around stoich but that latency is too low, most people say 720- 900 latency with 740cc nismo injectors.
my spec is
hks 264 step 2's with springs
z32 with hardpipe
2871r bb turbo
740 nismo's
has anyone else had this problem and solved it?
Also im abit un clear on how to be 100% sure you have the correct k constant figure?
k constant and latency question
Moderator: Matt
Re: k constant and latency question
Check you fuel pressure first as this obviously affects everything regarding fuelling.
After that you'll find that it's a balancing act between K Constant, Latency and the numbers in your fuel table.
After years of doing these things I've come to some figures that I've found work well for most situations. I don't have NIStune available to me right now but I'd suggest you should be seeing a maximum of around 30 in your fuel maps. Adjust you K constant to get your required AFR's with fuel maps set around 30. I've got 22 - 24,000 written down for S14 with 740's but I'll have to check that.
Then adjust your latency to trim out your idle/low load AFR's. Don't get to concerned about maintaining manufacturer specified latency numbers.
Happy to send you some of my tunes if you email me direct pl <at> plmsdevelopments.com
PL
After that you'll find that it's a balancing act between K Constant, Latency and the numbers in your fuel table.
After years of doing these things I've come to some figures that I've found work well for most situations. I don't have NIStune available to me right now but I'd suggest you should be seeing a maximum of around 30 in your fuel maps. Adjust you K constant to get your required AFR's with fuel maps set around 30. I've got 22 - 24,000 written down for S14 with 740's but I'll have to check that.
Then adjust your latency to trim out your idle/low load AFR's. Don't get to concerned about maintaining manufacturer specified latency numbers.
Happy to send you some of my tunes if you email me direct pl <at> plmsdevelopments.com
PL
Re: k constant and latency question
K is right, when your target AFR in fuel table is the same as you see in wideband.
If your K and latency are right and you still cant get good idle afr, when you can play a little bit with VQ map on idle. Its very sensible in low load area and it needs some time to get it right, but it works.
If your K and latency are right and you still cant get good idle afr, when you can play a little bit with VQ map on idle. Its very sensible in low load area and it needs some time to get it right, but it works.
Re: k constant and latency question
Try to lower your ttpmin across the table. This should allow your injectors to idle at lower pulse widths. I usually use this formula 12afr /14.7afr= .816 then multiply that times each number in the ttpmin table.