TP Scales

[vincentav8]

Hi all,
I've been looking at TP scales for my RB25DET (z32 AFM/ECU 550cc),
the base bin file with RB25 AFM/370cc has a fairly linear scale going up 4 units at a time until the last 2 columns which jump 8 units:
12,16,20,24,28,32,36,40,44,48,52,56,60,64 ... then 72,80

I have resized my injectors 370 - 550, and changed MAF to z32 using the Nistune operations menu, and have selected the option to change the load scalers each time ... however the new load scales have quite an uneven scale:
8,10,13,16,21,24,28,29,32,36,42,50,60,72,80,88

So my question is ... is this uneven TP scale deliberate?
Would it be detrimental to re-gap the scale to something more linear? such as:
8,14,20,26,32,38,44,50,56,62,68,74,80,86,92,98

thanks, Andy

[PL]

I'd certainly make it more linear unless you have a good reason to do otherwise.

Sometimes people keep the off-boost portion relatively stock and then ramp up the on-boost portion to stop running into the last load column too early.

These days I tend to do the opposite. Ramp it up steeper in the first half and then make the on-boost portion flatter. This gives better resolution for different boost levels. I was finding that I was tracing similar paths at 14 psi to those at 16psi. No good. Flatten the load scales out and you get better control of IGN at different boost levels. I can live with less resolution under vacuum if it gives me better resolution in the important bit!

I'm finding that I'm speding a lot more time getting the load scales right for each tune. It can make a big difference. Not so much for fuel, but worth the effort for IGN.

Just my 2c worth.
PL

[Matt]

The resize as pictured below uses a simple multiplication over the scales. The ratio of injector size and MAF is applied to each value on the resize.

There is no straightening or linear calculation applied as such. The intention is to provide modifications to the base scaling to work from (from the base RB25 scales in this case)

Furthering straightening out is the left to the tuner

[Adrian]

I'd certainly make it more linear unless you have a good reason to do otherwise.

Sometimes people keep the off-boost portion relatively stock and then ramp up the on-boost portion to stop running into the last load column too early.

These days I tend to do the opposite. Ramp it up steeper in the first half and then make the on-boost portion flatter. This gives better resolution for different boost levels. I was finding that I was tracing similar paths at 14 psi to those at 16psi. No good. Flatten the load scales out and you get better control of IGN at different boost levels. I can live with less resolution under vacuum if it gives me better resolution in the important bit!

I'm finding that I'm speding a lot more time getting the load scales right for each tune. It can make a big difference. Not so much for fuel, but worth the effort for IGN.

Just my 2c worth.
PL

Made the same experience, but never tried to adjust the curve degressive. Do you have no problems with part throttle, cause of the lower resolution ? Afr's are less a problem on different boost, so maybe the best way is to adjust only the timing scale degresiv. What do you think about?

[PL]

I tend to make load scales for fuel and IGN the same. But what you say makes good sense. I usually don't have too much trouble leaving them both the same but on some engines I've had to lower the values in the first half of the fuel scale and increase the gradient on the second half. This helped get it into the meaty part of the fuel map earlier. In fact I have a big horsepower S14 engine that I think I may have to use this technique on. It has a lean patch as it's coming on boost (it's an SR20 with HKS 3037 Pro S on it, so the area where it's trying to come on boost is quite large!!). I'm having trouble getting it to respond, so changing the load scales on the fuel map only (engine is already tuned) might be a good thing to try!

But there's really no reason to do this for the IGN scale. IGN you want to flatten in the on-boost portion.

I've never had any part throttle problems from ramping the scales up in the first half and then flattening them in the second half. Works a treat.

So we could conceiveably end up with load scales for fuel and IGN that look completely opposite!

PL

[Adrian]

Stay the ECU maybe in the closed loop on the lean spot? Had similary issues on a big power SR20. Look into this tread viewtopic.php?f=11&t=2239
If that is not the case, it could be really a better decision and less work to change the fuel scale. Nissan made on the most engines strange scalings and nobody knows why they have done that way...

[PL]

Yeah, it could possibly be that. Might try to re-scale the fuel load scale and see if I can cure it...

PL