ITB algorithm

[pkm123]

Does anyone have the ITB algorithm? How are the values for Load(map, tps) calculated? I looked at the source code, but can't find the Pulse width = REQ_Fuel * Load(map, tps) + etc. function. I loaded a log in MLV and loaded an ITB tune. Graphed Load vs TPS on scatter plot. It is a straight line, meaning Load is equal to TPS at all settings. Something isn't right with the software. ??

[kaeman]

Did you look in the Setting up manual, in section 3.4.5 tuning fuel ITB. it explains the curves and such used to determine the load in each portion of the fuel curves, the last part of the section technical stuff explains the fueling you are trying to figure out. Good luck

[pkm123]

Thanks, re-read the tech section. It now makes more sense. I was able to use my AN table and MLV scatter plots to build an ITB table. I don't know if it will give me better AFR control than my AN table. I'll have to try it both ways.
Thanks again.

[grom_e30]

I started out with alpha-n on my bike and it did work ok, but i found that it was a bit inconsistent at low throttle like if i was riding in traffic some times it would be fine and sometimes it just felt really bad bucking and surging, i switched over to itb and for me, so much smoother made a massive difference to how the bike rode im now on my second incarnation of the bike (bigger engine different itb's and so on) again using itb for load and i would't even contemplate going back to alpha-n.

[muythaibxr]

I started out with alpha-n on my bike and it did work ok, but i found that it was a bit inconsistent at low throttle like if i was riding in traffic some times it would be fine and sometimes it just felt really bad bucking and surging, i switched over to itb and for me, so much smoother made a massive difference to how the bike rode im now on my second incarnation of the bike (bigger engine different itb's and so on) again using itb for load and i would't even contemplate going back to alpha-n.

I wrote ITB mode specifically for cars (and bikes) that have this exact problem. I noticed that with alpha-n, load conditions at low throttle openings can change without the actual throttle opening amount changing causing inconsistent low-load fueling.

The other problem ITB mode solves is that with plain Speed Density, you end up with most of the "resolution" needing to be 90-100 kPa. IF you have any jitter in MAP at those points you end up with inconsistent fueling at high load.

ITB gives the best of both worlds. SD where it works best (low load) and AN where it works best (everywhere else).

I think that a lot of bikes do something similar to this as well.

Ken

[roulli]

Sorry for picking up this older thread,
But I'm struggling to understand the ITB algo,

I try to use the 2 examples, explaining "ITB Load Calculation in SD and AN Mode" in
http://77e21.info/mstuning_itbmode.htm
to understand how the Algo works (roughly).

But I can't figure out, how to achieve the ITB Loads in the examples.

If you have allocated the region between 0% ITB Load and 60% ITB Load on your VE table for use in SD tuning and your %baro is 50% then the VE value for 30% ITB load will be used. In this same example, a MAP value of 0kpa would use the 0% ITB load bin and a MAP value of just less than %Baro switchpoint would use the VE value just below the 60% ITB Load value on the VE table.

How do I get to the 30% ITB Load?
0% to 60% ITB Load on the VE Table are used for SD,
0% to "% Baro switch point" represent 90 %, as "% Baro switch point" is fixed at 90
Thus 50% Baro will represent 50* (60/90) = 33% ITB load in the VE table, not 30%


Same with the second example:

For example, if you have allocated the region between 60% ITB Load and 100% ITB Load on your VE table for use in AN tuning and also assigned a value of 10% TPS on your ITB load TPS switchpoint curve then a TPS value of 55% would yield an ITB Load value of 80% and the VE bin for 80% ITB Load would be used. In this same example, a TPS value of 10% would use the 60% ITB Load bin on the VE table and 100% TPS would use the 100% ITB Load bin.

60% to 100% ITB Load are assigned to AN
10% TPS to 100% TPS represent 90 % TPS
Then a TPS value of 55% should yield an ITB Load of: 60% + (55% * ((100%-60%)/90%) = 84,4%


Am I missing sth.

Thanks for advising.

Regards
Patrick

[jsmcortina]

Have you read the manual instead?

James

[muythaibxr]

Sorry for picking up this older thread,
But I'm struggling to understand the ITB algo,

I try to use the 2 examples, explaining "ITB Load Calculation in SD and AN Mode" in
http://77e21.info/mstuning_itbmode.htm
to understand how the Algo works (roughly).

But I can't figure out, how to achieve the ITB Loads in the examples.

If you have allocated the region between 0% ITB Load and 60% ITB Load on your VE table for use in SD tuning and your %baro is 50% then the VE value for 30% ITB load will be used. In this same example, a MAP value of 0kpa would use the 0% ITB load bin and a MAP value of just less than %Baro switchpoint would use the VE value just below the 60% ITB Load value on the VE table.

How do I get to the 30% ITB Load?
0% to 60% ITB Load on the VE Table are used for SD,
0% to "% Baro switch point" represent 90 %, as "% Baro switch point" is fixed at 90
Thus 50% Baro will represent 50* (60/90) = 33% ITB load in the VE table, not 30%


Same with the second example:

For example, if you have allocated the region between 60% ITB Load and 100% ITB Load on your VE table for use in AN tuning and also assigned a value of 10% TPS on your ITB load TPS switchpoint curve then a TPS value of 55% would yield an ITB Load value of 80% and the VE bin for 80% ITB Load would be used. In this same example, a TPS value of 10% would use the 60% ITB Load bin on the VE table and 100% TPS would use the 100% ITB Load bin.

60% to 100% ITB Load are assigned to AN
10% TPS to 100% TPS represent 90 % TPS
Then a TPS value of 55% should yield an ITB Load of: 60% + (55% * ((100%-60%)/90%) = 84,4%


Am I missing sth.

Thanks for advising.

Regards
Patrick

Honestly you really shouldn't worry about all that.

Basically you should set the TPS switchpoint curve to the value that results in ~90 %baro, leave the load at switchpoint curve alone at 50% across the board, and then just tune the VE table like you would a normal SD table.

Ken

[roulli]

@ James

the examples I quoted in bold are actually from the manual. They have been copied to that site.
So yes, I've read the manual, or at least the part that concerns my case.

I found in the French translation of the manual, that is available on the MSextra side, and there the principle is explained.
The translator has also used different load numbers to make the example work

Par exemple, si vous avez alloué la région comprise entre 60% et 100% pour la stratégie ‘Papillon / Régime’ et assigné une valeur de basculement de 10% PAP dans la courbe ‘Basculement stratégies ITB / %PAP / Régime’, alors une valeur d’ouverture de papillon de 50% générera une ‘charge ITB’ de 80% que va utiliser la table d’injection VE (50% de la zone 60-100 = 20%, donc charge ITB = 60% + 20% = 80%) De la même manière, une ouverture PAP de 10% va utiliser la cellule de charge ITB d’environ 60% et une ouverture papillon de 100% utilisera la cellule de charge ITB 100% dans la table VE.

@ Ken

I wouldn't mind to perceive the ITB load calculation as a black box, but I wanted to use the the VE values from my current SD VE table.
But if I can't interpret the ITB load bins correctly, then I can't allocate the VE values from the SD table to the ITB table, at least in the lower area.

The reason why I would like to use ITB is, that the current SD setup requires a rather strong resolution between 85 and 90 kPa and above 90 the MAP signal doesn't deliver further resolution, while the throttle plates are even not half open.

Regards
Patrick