LNF 3 bar map sensor not reading over 20 psi

[street253]

I recently installed a 3 bar map sensor and maf relocate. The scanner is not showing my boost over 20 psi?
Info below

[JimmyS]

Do you have the same settings (65.89kpa and -6.35kpa) in the SC/TC Boost Sensor tab as well?

Are you boosting more than 20psi? You definitely should be but your post could also lead one to believe that the scanner stops showing pressure above 20psi. I would also recommend lowering your boost numbers in your scanner. You'll never hit 105psi and lowering it to say 35 will make an easier to view graph. Just a thought.

[street253]

Do you have the same settings (65.89kpa and -6.35kpa) in the SC/TC Boost Sensor tab as well?

Are you boosting more than 20psi? You definitely should be but your post could also lead one to believe that the scanner stops showing pressure above 20psi. I would also recommend lowering your boost numbers in your scanner. You'll never hit 105psi and lowering it to say 35 will make an easier to view graph. Just a thought.

Yes, i have the same settings under sc/tc boost sensor tab. When i had first install them i had turbo flutter when i didnt change the value under the sc/tc boost sensor tab. Is it possible that my map sensor on the lower is not working?

Here is a log i recently did it show that i'm boosting 32 psi? I know the boost low res is the lower map sensor. By being able to read that value the 3 bar map sensors are working?


I also lowered the boost numbers in the scanner. Thanks for that helpful tip

[JimmyS]

Looks like it is working correctly as it is subtracting Barometric Pressure from Boost Low Res.

[cobaltssoverbooster]

barometric is not the correct value to subtract. that only works if your at sea level because the value you need to remove is 101 kpa which is what the baro reads at sea level. jimmys objective of course still remains in tact, boost_lo_res kpa - 101 kpa = true boost output in kpa. convert after that to psi and your good.
the goal is to not subtract barometric pressure because it wavers with elevation. what you do by subtracting 101 kpa is remove the coded portion of the map sensor range that is initially responding to vacuum. since this sensor doesnt see vacuum due to its location pre-throttle body, the vacuum portion must be removed in order to offset the output values back into the correct range of data.

[street253]

barometric is not the correct value to subtract. that only works if your at sea level because the value you need to remove is 101 kpa which is what the baro reads at sea level. jimmys objective of course still remains in tact, boost_lo_res kpa - 101 kpa = true boost output in kpa. convert after that to psi and your good.
the goal is to not subtract barometric pressure because it wavers with elevation. what you do by subtracting 101 kpa is remove the coded portion of the map sensor range that is initially responding to vacuum. since this sensor doesnt see vacuum due to its location pre-throttle body, the vacuum portion must be removed in order to offset the output values back into the correct range of data.

Thanks for a detail explanation on finding boost.

I change the pressure limit and my boost gague is now saying i'm pushing 25 psi..Yikes...Stayed out of boost until i got home and lower the values. Even after that initial change the scanner still did not show the correct values.. I was reading it to KPA then converted it to psi. Is their a different pid setup for finding boost than the one you show in your lnf scanner setup? wg vs duty cycle?

[cobaltssoverbooster]

is you read straight kpa off the boost lo res, with a factory turbocharger your max limit will be 255kpa which is 23.5 psi

[street253]

Yes, i'm on the factory turbo charger.

Error was on my part i was reading the graph in average kpa instead of max.. In addition the math i had for the baro sensor was not the correct sensor id ...if i'm reading my scanner right and doing the conversion correctly.. i'm pushing 22.30 pounds of boost?

I attach a copy of my log.

Thanks for all the info and help its greatly appreciated.

[cobaltssoverbooster]

can you post a config file. all of mine are for LSX so i cant see what your seeing

[street253]

can you post a config file. all of mine are for LSX so i cant see what your seeing

my config file is a bit all over the place lol pre-warning

[cobaltssoverbooster]

so i made a custom math function inside your file.
i can see where you did hit roughly 30 Psi for a split second but that is because you throttled it and then let off abruptly in second gear.
if you want to adjust boost you must make a pull in order to keep it consistent. after you let off, most people have a small pressure spike as the system waits a split second for the BPV or ABOV to vent the system pressure off.

i can see in another section of your tune that the boost is roughly 22-23 psi. My suggestion would be to use 3rd since its the closest to 1:1 and tune boost. once its set make a pull in second and use available traction aids to lower the boost and prevent spiking.

math function:
boost_lo_res: [2338.98]-14.6488
units: psi Decimal: 2 (user preference)

[street253]

so i made a custom math function inside your file.
i can see where you did hit roughly 30 Psi for a split second but that is because you throttled it and then let off abruptly in second gear.
if you want to adjust boost you must make a pull in order to keep it consistent. after you let off, most people have a small pressure spike as the system waits a split second for the BPV or ABOV to vent the system pressure off.

i can see in another section of your tune that the boost is roughly 22-23 psi. My suggestion would be to use 3rd since its the closest to 1:1 and tune boost. once its set make a pull in second and use available traction aids to lower the boost and prevent spiking.

math function:
boost_lo_res: [2338.98]-14.6488
units: psi Decimal: 2 (user preference)

thanks for the feedback! Really appreciate it. I have started to do pulls in third and tune boost.