Tuning Calc. Load max on NA engine
06-08-2011, 07:53 PM
#27
FWIW I did some experimenting with this a few weeks back .
What I did was lower the max load to 130% then 140% and do a logs where i knew under normal circumstances the load would reach 150% .
What actually happened was that timing went above what was on my map for 150% and fuel was less so it started going lean .
I also experimented with the temp calibration table and forced the ECU to think the temp was 75C which effectively lowered the max calc. load to below what I was running. Interestingly I found the ecu seemed to pull some settings out of its **** which were in line with what i had preset in the higher load tables .
I didn't take it any further and and didn't find out enough to make any conclusion other than feeling that keeping actual load at or below max calc load was a good thing .
What I did was lower the max load to 130% then 140% and do a logs where i knew under normal circumstances the load would reach 150% .
What actually happened was that timing went above what was on my map for 150% and fuel was less so it started going lean .
I also experimented with the temp calibration table and forced the ECU to think the temp was 75C which effectively lowered the max calc. load to below what I was running. Interestingly I found the ecu seemed to pull some settings out of its **** which were in line with what i had preset in the higher load tables .
I didn't take it any further and and didn't find out enough to make any conclusion other than feeling that keeping actual load at or below max calc load was a good thing .
06-08-2011, 08:00 PM
#28
So this Rotary thing...?
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Brettus: took the words right out of my mouth. I was gonna ask why wouldn't you just measure it.
Last edited by azzuro; 06-08-2011 at 08:02 PM. Reason: brettus beat me to it
09-02-2011, 01:03 PM
#30
Been thinking about load, and the insane IATs I've gotten lately have pointed out some flaws in my approach.
First, messing with the VE table, at least if you are NA sans porting, is probably a mistake. Any corrections you apply will not be right when load changes due to baro/IAT readings. Perhaps this table can be tuned with lots of long-term logs under different conditions and some custom software (like Kane's, if it ever comes) but otherwise you'll be messing up what Mazda did on a very expensive engine dyno.
As for the load max, this is also factored in to the load calculation, not just as a ceiling. Too low is obviously bad, but too high is also problematic, I guess Einsteinian space isn't a bad analogy, maybe Hubbles law too? I think it might be simpler to think of stretching a ruler. WE
The result of setting load max too high is that small changes in airflow become big changes in load, this makes fueling (unacceptably to me) erratic during intake valve openings, etc.
If you set load max just right, you can actually use it as another way to tune, and correcting load this way will hold up with environmental variations, unlike changes to the VE table.
I'm not sure how I'd set it up with FI, but I noticed that the stock load max table follows the torque curve pretty nicely, especially beyond 5250, so maybe that would get it close.
Anyhow, I have seen some advocate setting these tables flat at 1.0, 2.0... I don't think that is really a good approach, these numbers aren't really multipliers in that respect and you can't just factor them out.
First, messing with the VE table, at least if you are NA sans porting, is probably a mistake. Any corrections you apply will not be right when load changes due to baro/IAT readings. Perhaps this table can be tuned with lots of long-term logs under different conditions and some custom software (like Kane's, if it ever comes) but otherwise you'll be messing up what Mazda did on a very expensive engine dyno.
As for the load max, this is also factored in to the load calculation, not just as a ceiling. Too low is obviously bad, but too high is also problematic, I guess Einsteinian space isn't a bad analogy, maybe Hubbles law too? I think it might be simpler to think of stretching a ruler. WE
The result of setting load max too high is that small changes in airflow become big changes in load, this makes fueling (unacceptably to me) erratic during intake valve openings, etc.
If you set load max just right, you can actually use it as another way to tune, and correcting load this way will hold up with environmental variations, unlike changes to the VE table.
I'm not sure how I'd set it up with FI, but I noticed that the stock load max table follows the torque curve pretty nicely, especially beyond 5250, so maybe that would get it close.
Anyhow, I have seen some advocate setting these tables flat at 1.0, 2.0... I don't think that is really a good approach, these numbers aren't really multipliers in that respect and you can't just factor them out.
09-03-2011, 07:59 AM
#31
As for the load max, this is also factored in to the load calculation, not just as a ceiling. Too low is obviously bad, but too high is also problematic, I guess Einsteinian space isn't a bad analogy, maybe Hubbles law too? I think it might be simpler to think of stretching a ruler...
Anyhow, I have seen some advocate setting these tables flat at 1.0, 2.0... I don't think that is really a good approach, these numbers aren't really multipliers in that respect and you can't just factor them out.
Anyhow, I have seen some advocate setting these tables flat at 1.0, 2.0... I don't think that is really a good approach, these numbers aren't really multipliers in that respect and you can't just factor them out.
10-13-2011, 02:44 PM
#32
I have run Max calc load at 2.0 right across the rev. range ever since going FI.
The tests I have done have led me believe this table works the way Cobb says it does in the help file .
So after carefully reading that - it seems important that an FI engine does NOT exceed max. calc. load.
Last edited by Brettus; 10-14-2011 at 03:36 AM.
10-14-2011, 09:04 AM
#34
What tests did you do to verify this ?
I have run Max calc load at 2.0 right across the rev. range ever since going FI.
The tests I have done have led me believe this table works the way Cobb says it does in the help file .
So after carefully reading that - it seems important that an FI engine does NOT exceed max. calc. load.
I have run Max calc load at 2.0 right across the rev. range ever since going FI.
The tests I have done have led me believe this table works the way Cobb says it does in the help file .
So after carefully reading that - it seems important that an FI engine does NOT exceed max. calc. load.
Is there anything in the setup of the Fuel Tables that would limit one tune not to read anything higher that 199% calc load while the other recorded reading over 200%?
Could this be one of those strange Cobb AP oddities like -0.16 means 0?
10-14-2011, 11:06 AM
#37
Likely it just caries forward the last value. I would expect Mazda is the only one that knows how the PCM is programmed for out of range values....we don't have access to that logic for sure. We could do a lot of logging and maybe figure it out....but in the case of the over 2.0 calc load it isn't an easy value to pull a lot of logs at 
10-14-2011, 11:52 AM
#38
So for example @ 200% load 7k with a fuel value of .68.
Then @ 230% 7k is still going to use the value of .68?
According to ATR if the calc load isnt set high enough on high power and fi cars the ecu will think its calculating to much load and switch to the default ignition timing curve that is very aggressive for fi. This can cause detination
I
Then @ 230% 7k is still going to use the value of .68?
According to ATR if the calc load isnt set high enough on high power and fi cars the ecu will think its calculating to much load and switch to the default ignition timing curve that is very aggressive for fi. This can cause detination
I
10-14-2011, 03:43 PM
#41
Some observations
If I set all values on Max. calc load table to 2.0:
Reported calc loads are in line with expected . IE 0psi boost yields 100%loads . 14psi boost would yield 200+% load. Idle sits around 25% load.
If I set the table to closely match what the engine is actually producing low in rpm range (IE as per stock NA table till the onset of boost) then up to 2.0 by 3500 and 2.0 from there on :
All loads that would normally be below 1.0 are still in that range.
All the loads approaching 2.0 are half what they should be . IE 190% load becomes 95% . When this happens afrs are actually in line with where they should be however.........weird .
If I set loads at low rpm to 1.0 then ramp up to 2.0 by 3500 :
All loads at low rpm that should be below 1.0 are double what they should be but loads approaching 2.0 are accurate . Idle becomes 50% load .
If I deliberately set max. calc load to a value that i know will be exceeded - AFRs go lean and timing reverts to some value that does not come off the main timing table.
In an NA car set to the stock table :
All loads at WOT sit close to 100% reported even though max. calc load table is way below this in some areas. Idle sits around 30%
If I set all values on Max. calc load table to 2.0:
Reported calc loads are in line with expected . IE 0psi boost yields 100%loads . 14psi boost would yield 200+% load. Idle sits around 25% load.
If I set the table to closely match what the engine is actually producing low in rpm range (IE as per stock NA table till the onset of boost) then up to 2.0 by 3500 and 2.0 from there on :
All loads that would normally be below 1.0 are still in that range.
All the loads approaching 2.0 are half what they should be . IE 190% load becomes 95% . When this happens afrs are actually in line with where they should be however.........weird .
If I set loads at low rpm to 1.0 then ramp up to 2.0 by 3500 :
All loads at low rpm that should be below 1.0 are double what they should be but loads approaching 2.0 are accurate . Idle becomes 50% load .
If I deliberately set max. calc load to a value that i know will be exceeded - AFRs go lean and timing reverts to some value that does not come off the main timing table.
In an NA car set to the stock table :
All loads at WOT sit close to 100% reported even though max. calc load table is way below this in some areas. Idle sits around 30%
10-15-2011, 01:44 AM
#45
Not a limiter but it does put a cap on the fuel that can be metered properly in an FI situation. It was designed to keep an NA engine safe within it's expected limits , but does not work well with FI when boost can be raised with the flick of a switch .
Best to keep your highest loads below it IMO.
Best to keep your highest loads below it IMO.
10-15-2011, 02:33 AM
#46
Nope. Doesn't work that way.
Once again, you are confusing causality by drawing a conclusion on coincidence.
The CalcLOAD "limit" table does not place a limit on anything. It simply shapes the response curve of the tables that are based on it.
What appears to be a limit is actually just a misallocation of granularity.
Once again, you are confusing causality by drawing a conclusion on coincidence.
The CalcLOAD "limit" table does not place a limit on anything. It simply shapes the response curve of the tables that are based on it.
What appears to be a limit is actually just a misallocation of granularity.
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10-15-2011, 08:26 AM
#47
Release the twins.
Nope. Doesn't work that way.
Once again, you are confusing causality by drawing a conclusion on coincidence.
The CalcLOAD "limit" table does not place a limit on anything. It simply shapes the response curve of the tables that are based on it.
What appears to be a limit is actually just a misallocation of granularity.
Once again, you are confusing causality by drawing a conclusion on coincidence.
The CalcLOAD "limit" table does not place a limit on anything. It simply shapes the response curve of the tables that are based on it.
What appears to be a limit is actually just a misallocation of granularity.
10-15-2011, 09:00 AM
#48
Now that reminds me of the seminar ...
However I'm still misunderstanding why a FI tune from one car using Cobb device seems to max at a 199 calculated load while another does not.
I'm sure both tunes had the Calc.Max Load table set to 2.0 where one would expect the max torque peak on the RX8.
So obviously there are other tables that impact calculated load.
I would guess (because nothing is easy) that the number and which tables are used changes between Closed Loop and Open Loop.
It must be with the setup of these tables for the reason some tunes provide values over 200% calculated load while others do not.
Unless it's a **** up with the Cobb device between models or firmware.
I'm going to go use the googles and put my reading glasses on (I do own a couple of books that aren't full of pictures of a big red dog)
10-15-2011, 11:33 AM
#49
its CALCULATED load so yes RPMs, baro, G/S, IAT, load max and perhaps more all get calculated in a magic formula to give the system load. change any of it and the calculated changes
Last edited by FazdaRX_8; 10-15-2011 at 11:51 AM.
10-15-2011, 01:50 PM
#50
Nope. Doesn't work that way.
Once again, you are confusing causality by drawing a conclusion on coincidence.
The CalcLOAD "limit" table does not place a limit on anything. It simply shapes the response curve of the tables that are based on it.
What appears to be a limit is actually just a misallocation of granularity.
Once again, you are confusing causality by drawing a conclusion on coincidence.
The CalcLOAD "limit" table does not place a limit on anything. It simply shapes the response curve of the tables that are based on it.
What appears to be a limit is actually just a misallocation of granularity.
You reach a max calc load of 200% at say 6000rpm and 12psi of boost .
The number in the AFR lookup table is say 11.3 and the actual AFR recorded is say 11.2 .
Now you increase the boost at that rpm to 16psi - the number in the table at 200% and 6000 rpm is still 11.3 because that is the AFR you want to see . So you now have an extra 50ish g/s of air going into the engine , the actual load is more like 230% , and the cel we are using to give us the fuel we want is the same cel as before.
What is the ACTUAL AFR you will see now?
Last edited by Brettus; 10-15-2011 at 02:06 PM.