HPT Cylinder Airmass Calculations

1733 Views 16 Replies 3 Participants Last post by kittyboy, 6 mo ago

kittyboy

Discussion Starter · 6 mo ago (Edited)

I've been trying to verify HPT logged cylinder airmass data accuracy using math formulas. Would like to better understand and trust the HPT cylinder airmass numbers, they appear to skew in the high speed/rpm areas based on math formula comparisons, don't want to miss something important.

MAF[g/s] / RPM * 15 = cylinder airmass [g/cyl]

MAF[g/s] / ([RPM] / 60 * 4) = cylinder airmass

Following are HPT data observations:
•Appears heat has an overall effect
•Targeted fuel (EQ) accuracy has an effect
•Injector duty cycle appears to have an effect at higher speed/rpm

It's my understanding cylinder airmass calculations rely heavily on metered MAF and theoretical VE data for calculated final airflow and dynamic airflow. Does VE also play a role in the dynamic equation at WOT effecting cylinder airmass calculations that exceed the stock 4000rpm set limit, when 'Air Calc Mode' is in 'High Speed'

Example:
When I bury the pedal 100% and quickly accelerate logging into the 2.0g cylinder airmass range as shown, I sometimes find I'm having to retard timing incrementally to mitigate knock that creeps-in, losing power.

I'm considering (once again) to test incremental timing advancements in the higher cylinder mass range at WOT. However, I'm a bit hesitant based on past issues I've experienced running high octane power enabling fuel in this same area. I now have ARP head bolts installed and an improved crankcase ventilation setup, so maybe no longer an issue.

Following are examples of what appear to be HPT software limits when tuning for Dynamic Airflow:
655.4 g/s MAF
512.0 g/s Volumetric Efficiency

What's a typical 2.0g cylinder airmass spark advance on a 9.0:1 compression ratio, 3.6 ratio pulley combo, running high octane gasoline?

Thanks for any help...

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07GTS

· #2 · 6 mo ago

accuracy of the data all starts with the injectors data if that is correct and fueling is correct and fuel pressure is compensated for then it will be as close as it can be, if any of those are out then it goes out down the line with fueling tables n such but small amounts will just be absorbed and not noticed as most if not all would be 100% accurate, log dynamic airflow and maf airflow and VE airflow all in g/s and put them together in the chart v time with same min/max settings and see where they all follow, the dynamic airflow is the final product thats used, when i was on 14psi i was about the 1.8g - 1.9g if i can remember and airflow was in the 750 g/s range i think but i was revving to 6700rpm on ethanol

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kittyboy

Discussion Starter · #3 · 6 mo ago (Edited)

07GTS said:
accuracy of the data all starts with the injectors data if that is correct and fueling is correct and fuel pressure is compensated for then it will be as close as it can be, if any of those are out then it goes out down the line with fueling tables n such but small amounts will just be absorbed and not noticed as most if not all would be 100% accurate, log dynamic airflow and maf airflow and VE airflow all in g/s and put them together in the chart v time with same min/max settings and see where they all follow, the dynamic airflow is the final product thats used, when i was on 14psi i was about the 1.8g - 1.9g if i can remember and airflow was in the 750 g/s range i think but i was revving to 6700rpm on ethanol

Agree, here's a screen shot of everything in good order, let me find a comparison example with skewed.

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In the following image check out Mass Airflow/Volumetric/Dynamic, notice the max values for Mass and Volumetric? And for sure check the air cylinder mass value and timing. I have my target fuel too rich I know, I'm at 11.2 now. All my ID1050x injector data is properly characterized also. I was tuned running 92. I may not have had my VE completely dialed-in also. It seems to happen more when at high rpm and rapid acceleration.

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07GTS

· #4 · 6 mo ago

try a different volumetric airflow pid, if that one limits to the 512g/s then there should be another that will keep going to properly show whats going on

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kittyboy

Discussion Starter · #5 · 6 mo ago (Edited)

07GTS said:
try a different volumetric airflow pid, if that one limits to the 512g/s then there should be another that will keep going to properly show whats going on

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Appears there is a PID limit of 655.4 g/s MAF and 512 g/s Volumetric. Not sure if it is related to the 2 bar OS. Tried the generic and non-generic, same. What do you think about possibly scaling? Also, does VE actually have any effect since the Air Calc Mode is showing in "Hi Speed" Might just be MAF at this point? ty

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07GTS

· #6 · 6 mo ago

the high speed just shows up as ive got no maf at all and it still shows it so not too sure on that one, just looked at an old log and i dont use maf but it shouldnt limit to anything as the data is what the ecu is seeing so if it stops then fueling stops so there must be another pid, i dont like to use the SAE pids either they can be odd as they are to suit a wide variety of vehicles usually specific is better, maby try a repoll for pids see if any more show up ? i know there should be some that will limit and then some the same that wont even just add all the related ones and go for drive see what works and what dosnt just to rule them out

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kittyboy

Discussion Starter · #7 · 6 mo ago (Edited)

07GTS said:
the high speed just shows up as ive got no maf at all and it still shows it so not too sure on that one, just looked at an old log and i dont use maf but it shouldnt limit to anything as the data is what the ecu is seeing so if it stops then fueling stops so there must be another pid, i dont like to use the SAE pids either they can be odd as they are to suit a wide variety of vehicles usually specific is better, maby try a repoll for pids see if any more show up ? i know there should be some that will limit and then some the same that wont even just add all the related ones and go for drive see what works and what dosnt just to rule them out

Seems like I have a couple issues since HPT v.5 upgrade, registered the class too. Maybe nothing related? Do DTC changes have an effect logging? What do you have for the following set?

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mememe123

· #8 · 6 mo ago

^^^ Those are stock values for the V

Are your DTC codes still "greyed out" even if they are, your DTC check list in the tune will remain the same as it was before v5, you just won't be able to change them, untill HPT fixes your "account".

kittyboy

Discussion Starter · #9 · 6 mo ago

mememe123 said:
^^^ Those are stock values for the V
Are your DTC codes still "greyed out" even if they are, your DTC check list in the tune will remain the same as it was before v5, you just won't be able to change them, untill HPT fixes your "account".

Yeah, I realized that after installing v.5, reverted back to an earlier version, then had some issues. So I re-installed v.5 registered the class, and now there are some DTC items completely no longer visible?

As far as the stock values, I'm curious to know why they are set with those limits?

mememe123

· #10 · 6 mo ago

Mine were just "greyed out" for couple of months, and whatever update came after that, somehow fixed it, lol.
I'll have to check on my laptop to see if they are for sure "factory" values.
I would guess it has something to do with MAF freq and the way stock intake works.
You can obviously set them lower, but I would keep them on below ~2500rpm at least, since you do most of your DD in the <3k range, and VE has more points for various loads. Plus depending on the intake tube size, one might have MAF "turbolense"/issues at low rpm

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kittyboy

Discussion Starter · #11 · 6 mo ago

mememe123 said:
Mine were just "greyed out" for couple of months, and whatever update came after that, somehow fixed it, lol.
I'll have to check on my laptop to see if they are for sure "factory" values.
I would guess it has something to do with MAF freq and the way stock intake works.
You can obviously set them lower, but I would keep them on below ~2500rpm at least, since you do most of your DD in the <3k range, and VE has more points for various loads. Plus depending on the intake tube size, one might have MAF "turbolense"/issues at low rpm

Yeah, updates can sometimes cause weird things to happen. My Win11 update knocked-out my volume, finally got that issue fixed.

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07GTS

· #12 · 6 mo ago

factory has the maf set that way as they see it is the airflow rpm at which the maf is reliable and dosnt need the blending as much with vve, if ur going to 4000rpm then ur usually nor on/off the throttle like driving lower rpms around town, but the vve will still be used above there for any decent throttle events, u can set it lower and if so i usually just make it above any cruise rpm speeds so like 2-2.5k rpm

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kittyboy

Discussion Starter · #13 · 6 mo ago (Edited)

07GTS said:
factory has the maf set that way as they see it is the airflow rpm at which the maf is reliable and dosnt need the blending as much with vve, if ur going to 4000rpm then ur usually nor on/off the throttle like driving lower rpms around town, but the vve will still be used above there for any decent throttle events, u can set it lower and if so i usually just make it above any cruise rpm speeds so like 2-2.5k rpm

I transition 4000rpm during pulls, I was thinking about lowering this value for that reason. Interesting to learn VE is still active above the limit for transitions?

I've been going through some more data.

My injectors are characterized with ID data, my sensors are in excellent working condition, air flow is not obstructed or turbulent. I'm now zeroing in on fuel pressure settings? My current fuel pressure settings are slightly modified from stock. Current (lower) fuel pressure settings at higher MAP pressure (boost) and delta are capable to deliver optimal fuel with good duty cycle using DW pumps and 1050x injectors.

However, I'm beginning to believe there is ECM logic that assumes stock pump/flow and stock injector/flow capability based on stock pumps, injectors, and fuel pressure settings. So I think changing the fuel pressure values may be causing skewed cylinder airmass calculations at higher speed/rpm?

What are your thoughts, does this seem plausible?

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07GTS

· #14 · 6 mo ago

think of VE as always there when needed if MAF is used with any settings, because u have the fuel pressure sensor then the delta should always be accounted for so it wont matter the pressure it will be adjusted on the fly and calculated for as u go, ur airmass should be fine just try to get those pids to some that arnt limited in g/s u will have to add them and then drive again for the new data to see if it keeps reading higher, the ecu still sees the airflow going past those limits so airmass will be fine, MAF sensors cant read load they only read volume of airflow so as its realistically 2D u can have many variables with the one cell used by different loads which can require different fueling, the VE or VVE is 3D it sees depth (load) so its alot harder to use the same cell for multiple scenarios which is why its used for load/transients and MAP is faster to act then flow

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kittyboy

Discussion Starter · #15 · 6 mo ago

07GTS said:
think of VE as always there when needed if MAF is used with any settings, because u have the fuel pressure sensor then the delta should always be accounted for so it wont matter the pressure it will be adjusted on the fly and calculated for as u go, ur airmass should be fine just try to get those pids to some that arnt limited in g/s u will have to add them and then drive again for the new data to see if it keeps reading higher, the ecu still sees the airflow going past those limits so airmass will be fine, MAF sensors cant read load they only read volume of airflow so as its realistically 2D u can have many variables with the one cell used by different loads which can require different fueling, the VE or VVE is 3D it sees depth (load) so its alot harder to use the same cell for multiple scenarios which is why its used for load/transients and MAP is faster to act then flow

There only appears to be one PID option available for scanner, generic/non-generic, I re-polled to make sure.

I understand your response. So it is safe to assume, as a possibility, manifold temperature and calculated cylinder air temperature may be the wild card in the cylinder airmass calculation? There is definitely something going on somewhere causing what at times appears to be skewed data? Thanks for your help, much appreciated.

07GTS

· #16 · 6 mo ago

ok yea just found a log from a ctsv i was helping to tune a couple years ago and yea that VE g/s was maxing out at the same figure, dynamic was touching 1000g/s

running VVE only, we found that MAP value maxed out at the 255kpa so i had to scale the 3bar sensor in the 2.5bar reading so we could adjust fueling above 22psi, yea there are many variables with temps so could just be what u have to put up with as normal

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kittyboy

Discussion Starter · #17 · 6 mo ago

07GTS said:
ok yea just found a log from a ctsv i was helping to tune a couple years ago and yea that VE g/s was maxing out at the same figure, dynamic was touching 1000g/s running VVE only, we found that MAP value maxed out at the 255kpa so i had to scale the 3bar sensor in the 2.5bar reading so we could adjust fueling above 22psi, yea there are many variables with temps so could just be what u have to put up with as normal

Thanks again for the help, if you happen to come across more info please let me know. Thank you

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