rb25 with R32 ECU load going off the map

[gonz12345]

specs
S2 rb25DET r33 gtst manual
r32 ecu
Stock injectors
Q45 maf
garret ar50/ar63
15psi
walbro pump
blitz intercooler etc etc

new to nistune my problem is i have set my AFR's to match the fuel map at at idle and during transition and even up on WOT on the end of the scale it almost matches up to the estimated afr's on the map , done this with 02 feedback off as your meant to (set it to q45 afm and changed injection multiplier to suit) .I didn't touch the load scales as matt said you did not need to? (also knocked back 2 degree of timing up top for now as safety measure until i get some dyno time ) . The highest load index reached on a 3rd gear pull is around 131-132 , what do i need to do to keep it inside the factory load scales as right now ?

can i change/ increase scales to increase resolution up top end? or will that mess something up , like the closed loop area


Also how do i set deceleration trims? as while im cruising and let off the gas im reading 10 afr on the wideband for a second or two then slowly transitioning back to the 14.7

Thanks guys

[gonz12345]

apologies realized this topics been covered a few times, however since i dont want to mess up my fuel tables too much do i adjust the k constant up or down if my tracer is going off the map(hitting load of about 130) ? cant figure that part out . Whats the consequences of changing the load scales? say bring my transition load of 44 down a bit to increase resolution up the top end and increase max to around 130? . I thought that by configuring the afm function it would put the k constant at a rough average for my afm.

thanks guys

[Matt]

Do you have Feature Pack with Total injection multiplier parameter on the board? Part # ECU ID: 23710-11U0F

If so then lower K constant, and increase TIM
If not then adjust the TP on fuel and timing scales

[gonz12345]

yep i do, cheers didn't know which way to change k constant and what effect it would have on my tracer positioning on the map.

[gonz12345]

last question, is there any formula or anything i can do to know roughly exactly how much to pull out of my k constant or is it basically trial and error

[Matt]

Work out the maximum TP (load) is is reaching (use the log player to record). Have a look at the second last TP column value. Divide one by the other and this is your amount to reduce K by

Increase your TIM by a similar amount to put the fuel back to normal

Dropping K will reduce TP and move the cursor further to the left

[gonz12345]

perfect exactly the info i needed , thank you

[Shaker]

Hi.

I'm facing a similar problem after changing the MAF sensor. It's a CA18DET and I swapped the stock MAF sensor to the one taken from a VQ35DE (350Z). Performing the change in nistune, the K-CONST went from 183 to 504, causing my load to go off the map.

I understand to reduce the Load Multiplier and increase the Total Ignition Multiplier by the same factor as stated above, but my question is: What's the use increasing the Load Multiplier at all, when this will in almost any cast result in the max load going off the map? Why don't we in general only play with the Total Injection Multiplier also when swapping the MAF sensor?
I'm thinking ... the ECU is working in the wrong areas of the map, when the same airflow, after the swap, causes higher load values and it's using columns too far on the right? Or is the way of adjusting the Load Multiplier and Total Injection Multiplier as described above the method to exactly deal with this problem? Is it never ONLY the change of the MAF sensor (and a re-mapping)?

Is it somehow better to adjust the scales of the fuel and ignition map and keep each value (Load Multiplier and Total Injection Multiplier) as it "should be"? Should be is like Stock ROM -> Change MAF -> Resize Injectors. I am aware that when rescaling some values of the affected columns must be copied or interpolated...

[Matt]

When you adjust the MAF to one of a larger capacity, you are telling the ECU by using the 350Z MAF for example you are going from stock CA18 MAF HP to that of the 350Z HP (444HP for example). To keep the vehicle running the same with the larger MAF, the K constant is adjusted to compensate for this load change

However TIM is only recent addition, and the MAF rescaling code has not been modified to take TIM into account.

The software does not know know how much of the MAF capacity your engine will actually use (for example your turbo may only allow the engine to reach 350rwhp out of the 440rwhp capacity of the MAF max measurement for example). The vehicle may not necessarily use the entire load range, hence further adjustment to K may be required regardless

[Shaker]

Thanks for the quick reply!
I'm not sure if this answeres all of my questions, but... I would think, that scaling the MAF sensor / K-CONST would lead to this:
Stock: e.g. 1kg air / min --> 3V MAF sensor --> Load index 90.
Larger MAF: 1kg air / min --> 2.5V MAF sensor --> Load index 90 (due to a scaled Load Multiplier) to ensure, that the same amount of air meets the same fields in my map...
I guess, that's not the case? Which is why we have to adjust the multiplier?

[Matt]

If you did not change the K constant, the mixtures would run leaner, since the 3V to 2.5V reading using the different MAF sensors. This is why K is increased by MAF capacity to have engine running same after MAF resize. However that increase in K that instead of load index 90 it may not be on load index 120

Perhaps I would try adjusting TIM instead during the MAF resize and see if it stays on the same load point... would be easier to tune

[Shaker]

Thanks. I managed to tune the map to match my new specs. (devide K, multiply TIM)

But the questions I had are more related to how nistune works in theory than to simply get a proper result in the end. Maybe the reason is that I'm a software developer myself It helps me understand how the different tables and values affect each other and to estimate the expected result when modifying one or the other and more important - whether it is better to keep the one value and modify the other or modify both ...

[mtnickel]

Thanks. I managed to tune the map to match my new specs. (devide K, multiply TIM)

But the questions I had are more related to how nistune works in theory than to simply get a proper result in the end. Maybe the reason is that I'm a software developer myself It helps me understand how the different tables and values affect each other and to estimate the expected result when modifying one or the other and more important - whether it is better to keep the one value and modify the other or modify both ...

Thanks for the quick reply!
I'm not sure if this answeres all of my questions, but... I would think, that scaling the MAF sensor / K-CONST would lead to this:
Stock: e.g. 1kg air / min --> 3V MAF sensor --> Load index 90.
Larger MAF: 1kg air / min --> 2.5V MAF sensor --> Load index 90 (due to a scaled Load Multiplier) to ensure, that the same amount of air meets the same fields in my map...
I guess, that's not the case? Which is why we have to adjust the multiplier?

This is a thread revival, but Shaker was channeling my thoughts exactly. The change between injectors or Mafs, and how they interact with the factory maps has always been a very very confusing aspect for me.
K Constant, Load, TIM, scalars? which are changed? Then there's the point that if you change K constant and load it can make other values now incorrect (for instance the TP Load min for VTS, or max TP Load).

It would be nice to start from a factory ECU map/definition. Change injectors, change MAF, and still have the engine log the exact same way and use the same tuned cells it did on the stock hardware. I realize that you are then limited on low load maps, but perhaps a function could then be added to Rescale the maps; Condense existing 10 cells down into 6 and have 4 more higher load cells available for higher boost.
If I understand it correctly, the current methodolgy doesn't do this. The problem being, lets say they used Timing table 2nd last column = 12psi boost and 25 degrees...well if they put a new MAF, now that column/load may be 25psi of boost yet still be requesting 25 degrees timing (even if the fuel is corrected).

Thoughts?

[mtnickel]

Ok...after more theorizing, what I'm asking is partially possible with the new TIM.

Would it be correct that, when you add a different MAF and adjust the K-constant only, then nothing really changes regarding all the loads and such.
Because the calculation of K doesn't change.

Formula for calculating load:
TP (load) = VQMap [MAF voltage] / RPM * K Constant
So for a given load, if the MAF voltage drops by the same proportionate amount that K constant increases. It evens out.
IE. TP (load) = 100 = stock voltage 1v / RPM (1000rpm) * 1 (K) = New maf voltage .5 / RPM * 2 (k).

This combined with the use of TIM, would allow both the MAF to be changed and the Injectors, while still using the factory maps.

Now the only thing needed would be a tool that Rescales the stock map down and approximates what the new Load columns might be. Would even be nice if you could request your new RPM scalers as well (for when more tuning is done in higher RPMS). New load areas could use some generic rule like 5% more fuel per 10 load increase, and perhaps 2* timing decrease per 10 load increase. Something that's conservative and ready for the dyno. Then you would ideally have the entire vacuum part of your map and low boost areas running completely stock fuel and timing without the need to readjust anything. Only boost/load higher than stock would have to be tuned.

Wouldnt' that be the best way to create a new map? Or am I missing some details?

[Matt]

With the default Nissan ECU, we could only ever change K constant for fuel (and load) adjustments. As a result anything load related (fuel and ignition scales) needed to be adjusted to compensate for those changes

This is because injection is calculated from TP (load) but TP is also used to index all the tables in the ECU

With the feature pack updates, I've added the Total Injection Multiplier to adjust fueling AFTER the TP parameter is calculated. This allows injector rescaling without affecting load (good!)

When the MAFs are changed, the amount of load measured by the ECU is altered, and K constant needs adjusting for the load normally for the vehicle to run fine afterwards. However if the full load capacity of the MAF is not used then that K constant needs to be tweaked further (until the ECU operates within the range of the factory load scales)

Any adjustment to K to change where the load is referenced in the fuel/timing maps will affect resulting injection, so that needs to be trimmed to normal using TIM parameter

Yes I agree it would be nice to have the same tuned cells as before. However, the software does not know the power output of your vehicle. It does not know if you will use the full 500hp of the Z32 MAF you just fitted, because that is dependent on the turbo you fitted, the amount of boost, the type of fuel, mods to the engine etc

It might be possible with the MAF resize to change TIM instead of K but even doing that, there will still be manual rescaling required

One option I have considered is Nistune taking note of the maximum TP during the run, then automatically scaling K constant to adjust the load accordingly, and then offset TIM (which is a slightly different percentage). That will require some dyno time to get right but something I want to implement in the future... after the many other things on my plate are done)

My thoughts here, are do it manually on the dyno. We are able to resize MAFs quickly and bang those two parameters (K and TIM) into place after several dyno pulls once we have established the maximum load for the vehicle. No automatic calculation will ever get it right

It is possible to therorise the above but have a play on the dyno, and then you might realise it cannot all be done with maths given the power of each vehicle is different