Absolute pressure is what matters, but most everyone is used to thinking in psig.

 

But this means that your JDM MAP sensor boost control mod is the right way to control boost. Its looking at absolute, not gauge.

 

Load also scales roughly with absolute pressure. Both methods can work. Just depends on whether you want to set load targets or boost targets.

 

look at post 341

 

That was the post that got me thinking about all this. My point is you don't have to do that. The controller is controlling to absolute pressure. If you set your boost to 20 psi and your boost adder to 14.7 psia, the controller is controlling to 34.7 psia. If the ambient pressure is 10.7 psia, the controller will control to 24 lbs of boost, but this is fine because its the 34.7 psia that matters to the motor. In this case, 24 lbs of boost is not overboost.

I think the boost correction works to the psia value, not the psig value.

 

All correct.

 

Yeah. i just went to 5000ft elevation the other day and my boost was 2.5lbs higher. Perfect curve and correction still.

Also the car didnt knock or anything. I didnt log but I have the CEL on knock patch.

 

That sounds dead on. Pressure at 5000 ft is about 12.2 psia.

http://www.uigi.com/Atmos_pressure.html

 

Just wanted to mention that I have a few JDM MAP sensors available. See first post for details.

 

Is it possible to use the JDM MAP sensor to replace the MAF unit? Sorry if this was addressed earlier.

 

Only if you intend to switch over to speed density (MAF no longer needed).

 

Yes, I would be interested in seeing the pros vs cons with speed density on the stock ecu (and the how tos) Thanks

 

Its a complicated patch, so there is no "how-to", and there are no base ROMs with a patch pre-applied. From what I've seen, there's no obvious advantage to speed density.

 

What advantages do you see using MAP to control boost instead of load?

 

Load and boost do not track perfectly with each other on Evos. In higher gears, the car will boost higher for a set load. I prefer to control boost directly rather than load.