I have a 1972 Datsun 510 with S13 KA24DE that is now running with S13 SR20DET engine management. Mods include:
Audi R8 Coilpacks
GM L9H Flexfuel injectors (~490cc/min at 3 bar)
Z33/R35 slot maf in 3" piping
SR titania narrowband O2 sensor
SR CAS disc
I'm currently working to get the car running well NA and taking this opportunity to learn how to use Nistune before I add boost. Goals with boost would be 250-275whp.
I am a little confused on how important maintaining K close to factory is.
Today, I drove the car with the SR tune modified with an injector resize (TIM) and advanced MAF swap done to R35/3" tube scaled back to 60% (266HP) to match the original MAF. Injector latency etc was messed around with a bit to try to get things running alright. K const for this was now maintained at original SR levels (K=21475).
On the drive today it was apparent that I was not reaching the second last column on pulls (4th or fifth last column were reached with 73 TP). Factory load scales were employed so the last column was TP=104. The scaling is only slightly different between SR and KA so I'm not sweating that at this point. Apart from not accessing the whole map, STFT and LTFT were low and consistent so this seems not too bad of a start so far.
I read some typoed information and tried to decrease K/increase TIM so that the load scaling would move deeper into the map but I now realize that was backwards! To pusher deeper/further right into the maps, you need to INCREASE K. This only makes sense since K and TP are proportional.
Let's say now that I wanted to figure out how to properly set the load scaling so that I place my full load values in the second last column... I think I could I take my target TP (98 to be pretty much in the last column) divided by actual TP seen (73). So 98/73 = 1.34. So I need to increase K by this 1.34 factor or increase my load scaling from 60% in the VQ box to 60*1.34 ~= 80% to bring K to 28830.
Alternatively, I assume that I could increase K (without touching VQ) by 34% and drop TIM by 34% to effectively achieve the same thing... Would that be correct?
Some questions...
1. Are the days where you need to open loop cruise at ~3000rpm to set/fine tune K behind us? Is there still some merit to doing that?
2. Am I barking up the right tree with calculating desired Kconst from TP/Load data gleaned on a pull?
3. After all this, K would be ~30,000 but the stock KA K const is 39,720. Is this OK?
4. Once I add boost, obviously TP will go up and run off the map. Will my solution then be to manually re-do the load scale or decrease K/increase TIM to keep things in check on the factory load scales?
Once the car utilizes the full extent of the factory load scales in the SR ecu, I'll patch in the NA KA tables and fine tune from there.
I read this post which helped me get on track. viewtopic.php?t=3356
Thanks in advance for help!
First Street Drive SRed KA24DE
Moderator: Matt
Re: First Street Drive SRed KA24DE
It is more of a matter of maintaining the vehicle within the existing load scales, rather than trying to leave K at factory position.
What I mean by that is where you have the factory load scales upto TP=104, there are also other tables (like the O2 closed loop, knock feedback and also accel/deceleration factors which use their own TP load ranges)
So if you keep everything running in the factory load ranges upto 104 for example, then the other things like closed loop, knock feedback etc don't get affected
What we found is that if we ended up with large MAFs and previously doubled the load range, say upto 200 then closed loop would hold longer, and acceleration might be affected (lean spots on take off for example)
So it is not specifically about keeping K near factory, its keeping the resulting load scales near factroy. All K does is adjust where TP sits in the load scale (since it is a multiplier)
So... 98/73 = 1.34 is what increase K by to get the load across the scale further right (34% increase). That will add more fuel, so then decrease TIM by similar amount (34%)
After this run in cruise and see what your mixtures and STFT/LTFT are like. If they are near 0% and 14.7:1 then all good. If too rich, then lower TIM, otherwise increase TIM if too lean
If you add more boost later, and it goes above 98, then you will need to lower K to keep the cursor within range (and then make sure you adjust TIM again to get stoich at cruise again)
What I mean by that is where you have the factory load scales upto TP=104, there are also other tables (like the O2 closed loop, knock feedback and also accel/deceleration factors which use their own TP load ranges)
So if you keep everything running in the factory load ranges upto 104 for example, then the other things like closed loop, knock feedback etc don't get affected
What we found is that if we ended up with large MAFs and previously doubled the load range, say upto 200 then closed loop would hold longer, and acceleration might be affected (lean spots on take off for example)
So it is not specifically about keeping K near factory, its keeping the resulting load scales near factroy. All K does is adjust where TP sits in the load scale (since it is a multiplier)
So... 98/73 = 1.34 is what increase K by to get the load across the scale further right (34% increase). That will add more fuel, so then decrease TIM by similar amount (34%)
After this run in cruise and see what your mixtures and STFT/LTFT are like. If they are near 0% and 14.7:1 then all good. If too rich, then lower TIM, otherwise increase TIM if too lean
If you add more boost later, and it goes above 98, then you will need to lower K to keep the cursor within range (and then make sure you adjust TIM again to get stoich at cruise again)