Question regarding fuel ve tables

[Moody]

On an ITB turbo application, would it be advised to setup the fuel ve 2 table axis to kpa and register from 100 kpa - 200 kpa versus 30 kpa - 200 kpa? When I allow the TS to generate the table it sets the axis up form 30 -200 kpa. It would seem to me that even in off boost driving and idling it would be adding fuel. I seem to think that it would be best to use the fuel ve 2 table for adding fuel during boosted situations....any thoughts?

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[Matt Cramer]

Most engines are very linear in the boosted range. We typically use about four rows for boost.

[Moody]

Thanks matt...
I have another question regarding the fuel tables, I may be adding more needless complexity to my tune by even running more than on fuel table. Do you advise just running one fuel table to even control fuel above 100 kpa? I have been trying to use 2 tables, the second to control above 100 kpa. It just crossed my mind to simplify it and only run one fuel table in the itb mode for 30 to 200 kpa....

Any thoughts for going that direction?

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[dontz125]

You could use a secondary fuel load set to "Speed Density" and "additive"; the top row of VE1 would be all '0.0' at 100.1kPa, with the second-last row being 100.0kPa. VE2 would start at 100.0kPa with a row of '0.0'; the second row would start at 100.1kPa.


Edit: Corrected "VE3" to "VE2", which is the correct table.

[Moody]

You could use a secondary fuel load set to "Speed Density" and "additive"; the top row of VE1 would be all '0.0' at 100.1kPa, with the second-last row being 100.0kPa. VE3 would start at 100.0kPa with a row of '0.0'; the second row would start at 100.1kPa.

Do you mean ve2? I know that the ve2 can be set as "speed density" and "additive"....I wasn't aware that the ve3 could be setup that way

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[dontz125]

Do you mean ve2? I know that the ve2 can be set as "speed density" and "additive"....I wasn't aware that the ve3 could be setup that way

You are of course entirely correct; VE2 is for Secondary, VE3 is for Switching. My apologies for any confusion.

[Matt Cramer]

It's very rare to require table switching between vacuum and boost. There are some people who do this but usually it's way overkill.

[Moody]

just going back and researching some more and I found this thread I started awhile back....I think Im going to run in ITB mode and tune that with the charge tube off the best that I can, then I will set up a secondary fueling in SD from 100 kpa to 200 kpa for fueling will boosting.

My question now is, would it best to set the secondary fueling table to "additive" or "multiply"?

I think it might be simplest to "multiply" the secondary fueling because as matt said the boost fueling should be fairly linear...any thoughts?

[whittlebeast]

Start with plain old speed density with about 4 rows for boost. Once you start collecting data, and the motor starts developing a fueling pattern, we can look at the data and figure out if we need to make it more complicated. Most likely your turbo motor will dial right in with speed density.

[Moody]

Start with plain old speed density with about 4 rows for boost. Once you start collecting data, and the motor starts developing a fueling pattern, we can look at the data and figure out if we need to make it more complicated. Most likely your turbo motor will dial right in with speed density.

This is a 4 cylinder 1052 cc short stroke motorcycle engine, the vacuum signal is very weak at 10" HG at the highest vacuum and that vacuum goes away quickly with little throttle input. I think that's kinda the reason they developed the ITB mode, and the way I understand it that's the way modern oem sport bikes are tuned as well. I have read all of your posts regarding ITB tuning and I do understand your reasoning, but on my engine it would be easier to setup a decent AN tune then add the SD later as secondary.

I already have the ITB mode with the switching points laid out and it seems to be happy, but tuning with boost I was thinking it might be more consistent to have a secondary table for pressures above ambient pressure, because when boost comes on can vary with rpm and load...

It seems to me that the ITB mode is the exact same thing that you did on your ITB tuning tread, it's just you did it on your own starting with SD

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