Help Debugging the High Load OTS tune

[Steve @ VersaTune]

What peak load do you see with stock or HT?

If the RV opens, it will close as soon as pressure drops below the opening pressure. In my experience, fuel pressure won't drop to 1000 as a result of the RV.

The pressure limit tables are to limit the max requested pressure, not max actual pressure. The ECU automatically increases the duty cycle of the spill valve if actual fuel pressure exceeds the requested pressure. The fuel pressure control is somewhat coarse. It tends to fluctuate a bit. If you are seeing pressure hit the RV open pressure while under load, you should reduce the requested pressure. It will tend to spike when you lift the accelerator pedal at high rpm as the spill valve can not react fast enough to reduce pressure when the load goes from max to zero so quickly.

In my testing with a stock Mazdaspeed3, fuel pressure control was not a problem even with the elevated requested pressure of the high load tune.

[mituc]

What peak load do you see with stock or HT?

I think 1.58 or 1.63 peak with the stock tune and 193/1.96 with HT.

If the RV opens, it will close as soon as pressure drops below the opening pressure. In my experience, fuel pressure won't drop to 1000 as a result of the RV.

...unless there's a problem with the RV valve which is not the case. Well Steve, your statement answered my questions pretty much, so most probably the HPFP internals will fix my issue. It worked for Manselainen and a lot others, it should work for me. I just wanted to make sure I explore all the possibilities.

[Steve @ VersaTune]

What peak load do you see with the VersaTuner high load tune? >2?

[mituc]

Yes, it's consistently higher or around 2.0. I think I've seen even 2.2 at some point, but that was just a spike and I think I've seen it that high only between shifts, normally it won't go above 2.1 (only sometimes between like 3600 and 4800rpm I may see it a touch over 2.1), otherwise it stays around 1.99-2.06.

Btw, how come that while I have load of almost 2 the boost is around 15-16PSI in 3rd and 4th (I boost up to 18.5PSI in 5th for load of around 2)? At load 1.85-1.9 with hypertech boost is 18.5-19psi. Don't get me wrong, I'm not unhappy at all about this as it still leaves 3-4PSI more to play with when I'll have the pump internals, but after coming from a stock tune with upgraded TMIC,intake and BPV resulting in 17.5PSI straight up to like 5000rpm (but behaving weird and also getting load cut in 5th and 6th because the boost was raising above 18PSI) and then later from hypertech boosting to 19PSI (with all previous problems solved) this seems a bit awkward to me.

[Steve @ VersaTune]

Load will drop as RPMs increase while MAP stays the same. There are more losses as RPM increases. X MAP at Y RPM should yield the same load regardless of gear.

Load is based of MAF g/s so comparing loads between tunes with different MAF cals is not exactly apples and apples.

[mituc]

So that means that my MAF cal is a bit off or that hypertech is using a slightly different MAF cal to control the AFR's differently (especially in open loop)?

Anyway, I've seen that my MAF cal results in closer to 0 LTFT's and almost identical commanded and actual AFR's, while their MAF cal at least now when the temps are just a bit above freezing gives down to -8 LTFT's and the WOT desired and actual AFR's differ even by 1 sometimes (the actual AFR's are leaner), so I guess their secret may be in the OL part of the MAF cal.

[Steve @ VersaTune]

It sounds like your MAF cal is right on. Good job!

The stock hpfp struggles to deliver fuel at > 2 load. Once you upgrade the fuel pump internals, you will see more stable pressures.