recompile

iTrader: (38)

I'm not sure if anyone did a write up for this yet. I'm sure it's been done before, but I didn't come up with any search results, so just in case...

You can log estimated boost by converting 2ByteLoad (kPa) to psi. This is a pretty simple, process...

1. Make sure you're logging 2ByteLoad
2. Add this to your EvoScan Data.xml:

<DataListItem DataLog="Y" Color="" Display="EstBoost" LogReference="EstBoost" RequestID="00" RequestID2="01" Eval="(0.3125x-100)*.145" Unit="psig" MetricEval="" MetricUnit="" ResponseBytes="1" GaugeMin="-10" GaugeMax="30" ChartMin="-10" ChartMax="30" ScalingFactor="1" Notes=""/>

It's not perfect, of course, but it's close. Here's a comparison from a log of mine:

recompile

iTrader: (38)

Also, I'm not sure if this calculation needs correction for different atmospheric pressures... I'm pretty much at sea level so I can't really test this.

If someone else wants to test, you can put your local atmospheric pressure in and see if that's more accurate than the formula in the OP.

Go to www.weather.com, enter your zip code, and get the Pressure in inches, multiply this by 3.376

So for me it's:

29.75 in x 3.376 = 100.4 (round to 100)

<DataListItem DataLog="Y" Color="" Display="EstBoost" LogReference="EstBoost" RequestID="00" RequestID2="01" Eval="(0.3125x-100)*.145" Unit="psig" MetricEval="" MetricUnit="" ResponseBytes="1" GaugeMin="-10" GaugeMax="30" ChartMin="-10" ChartMax="30" ScalingFactor="1" Notes=""/>

l2r99gst

iTrader: (2)

Unfortunately, load isn't kpa like some people believe. Load is a mass airflow per rev, so the load number can very dramatically from car to car, conditions to conditions, for the same psi.

I made a thread on a way to approximate boost a while back here.

In post #4 I showed how much boost can vary with the same load.

Here is the equation that I came up with...test it out with your data to see how well it matches, as I didn't really get any response to that thread:

BoostEst=[(load*T)/(P*VE*280)]-14.7
T = actual intake air temp (not MAF temp) in degrees Rankin (degrees F +460)
P = atmospheric pressure in psi at the MAF(baro)
VE = VE of engine at the RPM being measured


The only problem is that you need to know your actual intake temp, not the temp at the MAF and your VE. VE of the 4G63 is about 1 at 5500 or so, so I used that RPM point for most of my calculations. For intake temps, depending on the IC, I used ambient plus 20* or 40* or 60*...all depending on what IC/boost etc.

Actually, this equation is a good way to find your VE curve or your intake temps, if you are actually logging boost and know one of the other variables.


Eric

recompile

iTrader: (38)

Interesting read... I might have been too optimistic thinking we could estimate boost that easily.

Can some people who have JDM map test this equation in Excel against some of their logs and post the comparison of EstBoost vs. JDM MAP ?

If you're not sure of your local atmospheric, you can go to www.weather.com, enter your zip code, and get the Pressure in inches, multiply this by 3.376

So for me it's:

29.75 in x 3.376 = 100.4 (round to 100)

kreionic

iTrader: (14)

I will gladly try give this a try for you tomorrow morning . I am basically at sea level as well so I will just use your same equation

inco9nito99

iTrader: (90)

updates?

kstpeter33

iTrader: (10)

subscribed

kstpeter33

iTrader: (10)

i added the coding to my data.xml file but it doesnt show up as an option to log when i open evoscan?

Shadowpriest

iTrader: (3)

Here is an example of log not correlating to boost as expected

Evo IX
3rd gear pull
2-byte load, 2-byte rpm, JDM MAP sensor adjusted for local atmospheric

Log point: 3218.75 RPM
2-byte load: 230
JDM MAP: 18.02psi

Log Point: 3433.594 RPM
2-byte load:218.438
JDM MAP: 18.396

Log Point: 3582.031RPM
2-byte load:210.313
JDM MAP: 18.59