Currently I am running the latest Tephra 96530706 V7 Rom on my car, using Load based boost control with a 3 port solenoid and everything is working great.

I recently purchased the Universal Omni 3Bar map sensor http://www.omnipowerusa.com/product.asp?P_ID=158 and first checked with MrFred that it would work with direct boost control.

I know have it installed in the car, but I am still using the Load based boost control.
My first step it o make sure that I can get the map sensor to log the correct boost in Evoscan.

A few questions.... more to follow

1.) In Evoscan, do we use the same formula for the 4 Bar Map sensor? as posted over here. in MrFreds post "Omni 4 bar MAP sensor ROM compatibility settings for USDM Evo 8/9"
I had to change the formula to make allowance for my local elevation which is 5500 feet, This is my current formula Evoscan.

0.2369*x-12.0

When I log boost in Evoscan, while doing a WOT 3rd gear log, and then comapre it to my reading on my boost gauge I get strange results.
My boost gauge peaks at 1.6 Bar (23 PSI) but I am logging just over 30PSI at peak boost in Evoscan.

Am I using the correct formula for the Universal Omni 3Bar sensor?

Thx for looking.

 

You can't use the 4bar scaling for the 3bar sensor. According to the omnipower manual, for the 3 bar sensor:

P_kpa = 1.233*x + 1.110

If you want it in psi:

P_psi = 0.1789 * x + 0.1610

That's absolute pressure. If you want "boost", subtract your atmospheric pressure.

d

 

Thx , strange that mine never came with a manual.

 

I don't think there is a pack-in manual that comes with any of the senors. Omnipower USA provides a calibration document here:

http://www.omnipowerusa.com/calibrations.doc

The information for the 3 bar sensor is on page 2.

d

 

how come many of the people are going with the 4bar map sensor instead of the 3bar? all of you guys are boosting over 30psi??

PEACE
NAB

 

Just in case you decide to turn up the boost

Its just like running 1400cc injectors when you can probably get away with 1000cc. I'd go with the 4bar.

 

Exactly, im kicking myself now for not buying a 4 bar over the 3 bar im currently using. Limited to 27psi

 

Its never too late. LOL. sell me yours for cheap. LOL.

 

if I am not planning to run over 27psi then the 3bar should provide a better resolution than a 4bar no??

PEACE
NAB

 

The 3 bar sensor will provide 85 samples per bar, which is about 30% better resolution than the 4 bar sensor.

In the end though you're talking about 0.17 psi increments rather than 0.23 psi. I'm not sure anybody actually tunes down to the 0.2 psi range.

d

 

The format of how the ECU is interpreting the MAP sensor data is actually 16 bit in the ECU and only 8 bit in the datalogging. So the ECU is dviding relative pressure with 1024 as the ultimate value not 256. This would mean on the absolute scale (since it is reading vacuum) that a 4 bar would be 1024/4 or 256 samples per bar for actual calculations. The 255/4 would be 63.75 samples per bar.

On the 3 bar this would be 255/3 85 for logging only. For calc purposes we'd be around 341.3 per bar.

Since there are quite a few of us running 28-29psi on pumpgas on larger turbos and many running over 29psi on racegas and E85 the 4 bar makes sense. Really if you arent going to go over 33, the JDM "3" bar (actually 3.25 or so) makes the most sense. But when you factor price and availability the 4 bar is equivalent in price, as available, and still allows for more in the long run.

 

Good point, but it's a 10 bit ADC, not 16 -- which is where the 1024 comes from.

d

EDIT: Two-byte boost anybody? J/K.

 

Der... yeah 16 bit would be like 65,335 or something...my bad.