can anyone tell me what this is for.

 

RPM threshold the Baro is updated (or maybe not updated)at? Do you have specific Baro update needs?

 

The barometer in the LT1 is also the MAP sensor, GM's way of saving money on another sensor, I believe alot of people use it. Baro modifies the base fuel calculation.

The trick to getting an accurate Barometer reading from the MAP sensor which is plumbed to the intake manifold, there's certain conditions which the Intake manifold is very close to Ambient pressure, and that's low RPM and high TPS.

So, when your driving in the Mountains and climbing elevation there's two ways the PCM gets a baro update to keep fueling accurate, than that's during crank or something and the other is when parameters in the "Baro Update RPM Threshold" is met.

NA (no turbo or Supercharger) you wont need to change it, if you run boost, a problem arises where the BARO is resetting (updating) when boost is building since the stock RPM for the resets (or updates) is high enough in the RPM range. Since it starts at ambient pressure and only builds/resets with boost, it alters the fuel calculation somewhat inconsistently since if you rev over the update limit then enter boost the Baro will not update, so you end up with two possible fuel calculations.

To make this work for boosted applications, simply lowering the RPM threshhold to something like 1200-1500rpm is usually all that's needed, that way it can still reset/update, but not when it's sensing boost.

 

thanks for reply, I like learning a little more about tuning, who knows when I may need it.

 

Question:
Does the MAP sensor have a separate port (open to atmosphere) used for the reset? If not, then, wouldn't it be better to raise the "Baro Update RPM" value above your red-line? Unless you're in the mountains, the initial, pre engine start value should be more accurate than a guess at what RPM and TB opening would have the intake manifold at atmospheric pressure.

 

[QUOTE=NJ-LE;6172184]Question:
Does the MAP sensor have a separate port (open to atmosphere) used for the reset? If not, then, wouldn't it be better to raise the "Baro Update RPM" value above your red-line? Unless you're in the mountains, the initial, pre engine start value should be more accurate than a guess at what RPM and TB opening would have the intake manifold at atmospheric pressure.[/QUOTE

The MAP uses the Manifold Air Pressure as what it's sensing.

If you raised it to redline then it would be resetting all the way to redline.

 

Dookie454:
Thanks for the info ... I mistakenly thought the Baro reset meant it would try to get a fresh baseline reading at that rpm. If I understand correctly what you're saying then the "baro reset threshold" is where it STOPS taking new readings. (I still use the stock MAP sensor. I've been reading the 2 bar tuning stickie but don't feel I understand it enough to try ... I only got a baby puffer anyway!)

 

Mines set at 3600, does that sound about right?

 

onefastmx5:
3600 rpm is what my factory stock value was.

 

Yes, the value is where it stops taking updates.

The stock value (3600) is fine unless you have a 2bar MAP and a 2bar sensor and a supercharger/turbo.