What variables affect 2 byte load calculation?
Jan 26, 2010, 12:27 PM
#1
What variables affect 2 byte load calculation?
Just looking at some logs and dyno sheets from various people and notice that load doesn't seem to be a universal constant. What are the variables that affect this calculation the most. In case my question is poorly worded; Why do some people make more power/torque with less load? This is a MAF equipped disscussion. I understand that SD is a completely different set of values.
Jan 26, 2010, 12:51 PM
#3
there are different "versions" of 2ByteLoad. Temp + Baro are the other factors, in factoring load. Most ppl are probobly using 2ByteLoad "Raw", or 1ByteLoad, (which follows 2ByteLoad Raw) but when u switch to 2ByteLoad "temp + baro" (which is what our fuel and timing follows) load will be ~ 20% less.
Maybe thats what your noticing... Or we talking huge differences?
Maybe thats what your noticing... Or we talking huge differences?
Jan 26, 2010, 12:53 PM
#4
The main reason you can see load differences on MAF cars is the contruction of the intake and the filter assembly altering how air moves through the pipe.
Case in point, the JDM ARC induction box that the show kids seem to like will drop the load down into the 230s at 425whp worth of air and even less on a stock turbo. On the otherhand I have seen the Injen (maybe the fujita) run the load to 320-330 at 350whp.
2 byte load in all its 3 forms have to be specifically altered. The 2 byte load that most of us use is the full comped version as I recall. There is raw, temp, and temp+baro depending on the actual temp is what it chooses for what load the computer actually uses. However we only ever log the one value independent of which the ECU is actually using. It records all 3 and selects based on its variable subs.
Case in point, the JDM ARC induction box that the show kids seem to like will drop the load down into the 230s at 425whp worth of air and even less on a stock turbo. On the otherhand I have seen the Injen (maybe the fujita) run the load to 320-330 at 350whp.
2 byte load in all its 3 forms have to be specifically altered. The 2 byte load that most of us use is the full comped version as I recall. There is raw, temp, and temp+baro depending on the actual temp is what it chooses for what load the computer actually uses. However we only ever log the one value independent of which the ECU is actually using. It records all 3 and selects based on its variable subs.
Last edited by JohnBradley; Jan 26, 2010 at 07:56 PM.
Jan 26, 2010, 01:23 PM
#5
I'm on the same wavelength as Drifto, and this is a bit strange to me as well. Load is essentially VE (kPa), which approximates VE (and torque). It's interesting that two similar EVOs, both running mass air, can give drastically different indicated load values at a given value of torque as indicated using a dyno, VDR, etc.
Understanding the mechanics of this becomes more interesting when one finds himself faced with scaling the load axis due to large load values being generated. The key to the explanation lies in the logic that is used to calculate load, and I'd also like to know the influencing variables, some of which I suspect to be user defined.
Understanding the mechanics of this becomes more interesting when one finds himself faced with scaling the load axis due to large load values being generated. The key to the explanation lies in the logic that is used to calculate load, and I'd also like to know the influencing variables, some of which I suspect to be user defined.
Jan 26, 2010, 01:33 PM
#6
AWD car
Drifto is running E85, and showing around 460 ft/lbs on VDR at 35 psi w/HTA3076R, but is over 460 load.
And in my case, I am still casually tuning a 93 octane map at 30psi w/HTA2582R, and I'm showing mid 400s ft/lbs (so far), but around 430 load.
Could it be possible that all these load values truly are apples to apples and non-mechanical things like ignition timing and such make the difference, or, does something that is user defined (e.g. injector scaling) involved in the Mitsu ECU's load calc?
And that is the $64,000 question ...
Jan 26, 2010, 01:59 PM
#7
Evolving Member
Most people log the RAW uncompensated Load, which can give about 20% difference positive or negative at extremes from Compensated Load.
But what probably causes the most discrepancy are peoples Injector Scalings.
You can have much lower Load if you have you Injector Scaling a little rich, or higher if you have your Injector Scaling lean.
Also not all MAFs are not exactly the same, there is a calibration screw on the bottom that allows extra air to be bypassed.
But what probably causes the most discrepancy are peoples Injector Scalings.
You can have much lower Load if you have you Injector Scaling a little rich, or higher if you have your Injector Scaling lean.
Also not all MAFs are not exactly the same, there is a calibration screw on the bottom that allows extra air to be bypassed.
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Jan 26, 2010, 02:35 PM
#8
It can or it can be even more. The more extreme the temperature or pressure, the more the compensation affects the value. On a normal day, like today, in NM, my load_raw value peaks at 320, but my load_comp_temp_baro is only 240.
It's quite frustrating to have to log both, but I do. 96530706 uses raw for fuel and comp for ignition.
d
It's quite frustrating to have to log both, but I do. 96530706 uses raw for fuel and comp for ignition.
d
Jan 26, 2010, 02:43 PM
#9
Most people log the RAW uncompensated Load, which can give about 20% difference positive or negative at extremes from Compensated Load.
But what probably causes the most discrepancy are peoples Injector Scalings.
You can have much lower Load if you have you Injector Scaling a little rich, or higher if you have your Injector Scaling lean.
Also not all MAFs are not exactly the same, there is a calibration screw on the bottom that allows extra air to be bypassed.
But what probably causes the most discrepancy are peoples Injector Scalings.
You can have much lower Load if you have you Injector Scaling a little rich, or higher if you have your Injector Scaling lean.
Also not all MAFs are not exactly the same, there is a calibration screw on the bottom that allows extra air to be bypassed.
Interesting. I have 1450s scaled to 860 or 890 I don't quite remember, but maybe this is what is going on.
Also I definately agree on the MAF screw. I've compared Ted's MAF to mine and there is a discernable difference in screw height just by looking at them. His protrudes farther in than mine.
Jan 26, 2010, 02:49 PM
#10
Heres a quote and thread from MRFRED, explaining the different Load variables.
The thread
https://www.evolutionm.net/forums/ec...variables.html
I have some interesting news for all the USDM Evo 9 folks. Seems that the two-byte load we've been logging for about a year now (FFFF6B42) is definitely not the load used for ignition advance lookup, and it may not be the load used for AFR lookup either. I just spent the better part of the morning going through the spark and AFR code, and here's what I found:
1) Spark lookup uses FFFF6B46 when the IAT > 25C, and can use either FFFF6B46 or FFFF6B48 (load boost) when the IAT <= 25C (there is a flag that chooses, and I haven't figured out that flag yet). Some sort of offset is also added whichever value is choosen. Haven't tried to decipher the logic that controls this offset yet.
2) AFR lookup uses either FFFF6B42 or FFFF6B48. There are two flags used to make the decision. I don't know these flags yet.
My initial comparisons of FFFF6B46 and FFFF6B48 show them to be virtually identical, so my conclusion at this point is that we are better off using FFFF6B48 (load boost) to represent load. However, I want to do some more comparisons of FFFF6B46 and FFFF6B48 to see how much they differ.
1) Spark lookup uses FFFF6B46 when the IAT > 25C, and can use either FFFF6B46 or FFFF6B48 (load boost) when the IAT <= 25C (there is a flag that chooses, and I haven't figured out that flag yet). Some sort of offset is also added whichever value is choosen. Haven't tried to decipher the logic that controls this offset yet.
2) AFR lookup uses either FFFF6B42 or FFFF6B48. There are two flags used to make the decision. I don't know these flags yet.
My initial comparisons of FFFF6B46 and FFFF6B48 show them to be virtually identical, so my conclusion at this point is that we are better off using FFFF6B48 (load boost) to represent load. However, I want to do some more comparisons of FFFF6B46 and FFFF6B48 to see how much they differ.
https://www.evolutionm.net/forums/ec...variables.html
Jan 26, 2010, 04:16 PM
#11
Heres a quote and thread from MRFRED, explaining the different Load variables.
The thread
https://www.evolutionm.net/forums/ec...variables.html
The thread
https://www.evolutionm.net/forums/ec...variables.html
spark advance lookup: For air temp below 77F, baro+airtemp compensated load is used for spark advance. For temps above 77F, then baro compensated load is used.
afr lookup: for closed loop conditions when load is < ~20, uncompensated load is used, otherwise, baro+airtemp compensated load is used. This means that baro+airtemp compensated load is used essentially all the time for AFR lookup.
afr lookup: for closed loop conditions when load is < ~20, uncompensated load is used, otherwise, baro+airtemp compensated load is used. This means that baro+airtemp compensated load is used essentially all the time for AFR lookup.
Also, to answer the OP question. There are two main reasons:
1. The two cars in question may be logging different loads.
2. The intake system on maf based car can dramatically alter the calibration of the maf sensor, which is then used to calculate the load. It matter how many vortices are being created and measured by the Karmen MAS. If an intake allows more airflow to flow around the sensoring area and/or produce less vortices, then the resulting load will be lower, but not the true mass airflow.
So, you can have two different cars with very different load levels at the same horsepower or vice versa.
Last edited by l2r99gst; Jan 26, 2010 at 04:18 PM.
Jan 26, 2010, 06:12 PM
#12
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Does anyone have the addresses for the raw and comp loads for 96530706?
EDIT Found Answer or 96530706:
raw 2byte load - 898A, 898B
baro compensated load - 898E, 898F
temp+baro comp load - 8990, 8991
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EDIT Found Answer or 96530706:
raw 2byte load - 898A, 898B
baro compensated load - 898E, 898F
temp+baro comp load - 8990, 8991
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Last edited by chmodlf; Jan 28, 2010 at 10:51 AM.
Jan 26, 2010, 07:11 PM
#13
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As stated above, my 1byte load was peaking at 420% load. I havent touched the screw in the MAF sensor, but my injector scaling is a bit on the rich side. I was actually expecting it to be quite a bit higher, but its fine with me, i like not having to scale so far out.
Jan 26, 2010, 08:00 PM
#14
I forgot to add in my post up there about the intake screwing with the load% since it can alter how the Kv "hears" is if the MAF scaling has ever been tweaked, the screw in the MAF, the honey comb in or out, etc.
As Ted said some of it is "user defined". Almost all of it is the tube and filter setup.
As Ted said some of it is "user defined". Almost all of it is the tube and filter setup.
Jan 26, 2010, 08:51 PM
#15
Sorry for going offtopic: I've been meaning to raise issue with that. Logging LOAD_RAW, LOAD_TEMP_BARO, AFRMAP, and wideband o2 shows pretty clearly that the raw load is used for tephra's big map lookups in 96530706. EDIT: for fuel, not for ignition.
d
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Last edited by donour; Jan 27, 2010 at 09:51 AM.