Keeping Load Multiplier (KConst) close to stock

[adamky]

I'm just looking for confirmation of a tune I'm working on. Before FP1 release, we all used K-value to adjust base fueling. Of course, the bad part about this is that adjusting K can affect all of the other maps such as cranking, warm start, cold start, etc, etc.

The new Throttle Injection Multiplier is supposed to help to minimize this issue. So, if I can adjust the tune for my injectors without messing with K much, it should be a better tune, correct?

My new setup is a KA24DE-T with a blow-through Z32 MAF (VG20DETT) in an aluminum MAF housing, and 2000cc Bosch injectors. (I'm planning to set the car up as a flex fuel vehicle using Zeitronix ECA-2). Stock K-value for S13 KA24DE is 39720. If I just use TIM to adjust the fueling, it won't work because the Z32 MAF swap roughly doubles the K, which is higher than it can go. So I have to do an injector swap first. Also, if I refrain from using TIM and just start out by upgrading to the 2000cc injectors and then do the Z32 MAF, my K is nowhere close to stock: 10265.

So, I played around and did it in stages which got me back to a K that is very close to stock.
1. First, I did an injector change from the stock 275cc to 520cc and I unchecked TIM so it would adjust K-value. This got K to: 21005
2. Next, I did a MAF change to Z32 which got the K-value back to within a few hundred of the stock K-value: 39483
3. Finally, I did another injector swap from 520 to 2000, this time leaving TIM checked. So, I ended up with the above K-value (very close to stock) and a TIM of 133.

Am I correct in my thinking that this will be a better place to start from?

Also, I realize that I will max out my MAF way before I ever get close to maxing out the injectors. I'm going to slowly work my way up in power and when I get to that point I will either upgrade the MAF or I'll have to switch to something MAP-based.

[Matt]

It doesnt necessarily affect cranking or warm start (NEO engines it will affect cold starts). Moving K around will affect the resulting Theoretical Pulsewidth (TP) or load. This has side effects to do with throttle enrichment, O2 learning areas, knock feedback areas and anything else which is TP (load) related

The main aim is to keep TP operating within the factory TP scale range rather than changing the scales when TP is affected (due to adjusting K constant)

So the extra total injection multiplier (TIM) parameter was added to let you adjust only this parameter for fueling changes (eg injector resize) and to fine tune K/TIM constants after MAF upgrades to have the vehicle operate within the factory TP range

2000CC injectors are massive, and I don't recommend using them on the majority of Nissans. Why do you have such large injectors on a vehicle where there is no possibility of even using half this potential with that setup (you will max out the MAF before 1000CC injectors even on E85... as you wrote above)

It makes controlling them around idle more difficult and complicates the tuning process

Yes you are correct in that you will need to adjust K and TIM for the injectors.

If your car is running okay after step 3, now to a power run on a dyno and see how far (with factory TP scales) you go across the map. If not far enough, reduce K (and offset TIM) or if too far then increase K (and once again offset TIM)

You want K adjusted so you have full use of the factory load range, and TIM to get fueling spot on. Yes you will will get a very low TIM value as a result of large injectors

[adamky]

I'm eventually shooting for 500-600 whp. On E85, I would need 1600cc injectors to reach this goal. I got a great deal on 2000cc injectors and after seeing some posts on here from this fella and his success getting 2000cc Bosch injectors to run and idle great (viewtopic.php?f=12&t=2420&p=17764#p17764, viewtopic.php?f=12&t=964&p=18117#p18117) that's the direction I ended up going. I know the limit on the Z32 MAF is ~500hp but I imagine it would be a little higher on a blow-through setup, wouldn't it? From what I remember, most people report a lower MAF voltage after switching to blow-through.

[adamky]

Just to update, I switched to 1600cc Bosch injectors. I have had no problem controlling them. Latency is around 830. K is 39xxx-something.

Now I need to decide between upgrading my MAF to one of the HPF's, or possibly switching to speed density.

[adamky]

If your car is running okay after step 3, now to a power run on a dyno and see how far (with factory TP scales) you go across the map. If not far enough, reduce K (and offset TIM) or if too far then increase K (and once again offset TIM)

Hmm, this actually differs from what you wrote in an e-mail to me:

5. If the TP goes too high then lower K constant (TP multiplier) or too low then increase K constant until you get full use of the map

I played around with the tune today and it seems what you wrote in the e-mail is actually correct. Increasing K just seemed to make me hit the last load column even sooner.

[Matt]

Yeah... email was correct. I've got the forum post backwards

[adamky]

That's understandable considering how hard you work!

I played around with K and TIM today and already see major improvements.