View Full Version : Needing a better $42

03-14-2011, 12:23 PM
I know it's an oldy but is there any better versions that may include Injector Size cylinder size?

03-14-2011, 06:16 PM
I'll see if I can dig up the $42 hack, but I don't think those variables are in $42.

03-14-2011, 06:26 PM
I have found out from Robart Saar that they are not. Maybe he will duplacate his answer here.

04-04-2011, 12:54 PM
OK I started on a Super $42 and added a BLM table in the history, then I added vacuum as inches of mercury but never got the formula correct.

Then I gave it to someone? And I forget who? Thinking maybe it was Six_Shooter... who added a SWEET day and night dash. So if anyone wants to add something I will post it up.

And I know there's a guy here whos pretty good with def files who could maybe help with the vacuum inches of mercury conversion?

04-04-2011, 07:13 PM
inverted values are simple enough...

0kPa MAP is ~30" of mercury, right?

04-04-2011, 09:00 PM
0kPa MAP is ~30" of mercury, right?

04-04-2011, 09:45 PM
well, for future reference, here is how to deal with the inverted values (MAP to vacuum or in reverse, stuff like that)

take the max value of the unit you have (in this case, 104.45kPa MAP), use it as a "basis" for converting to the value you want.


X being MAP in kPa

as you can see, the closer you are to 104.45, the smaller the end result will be.

so, then you multiply that by the "constant" you need to convert it to the value you want (inHg), and since 30" is 0kPa, then:


(.2872 is derived from 104.45 divided by 30 (=3.48166), then divide 1 by that number)

do the math for max value: (104.45-104.45 = 0)*.2872 = 0"
do math for min value: (104.45-0 = 104.45)*.2872 = 29.998"
and for fun, a middle value: (104.45-55 = 49.45)*.2872 = 14.2"

make sense?

04-05-2011, 05:32 AM
Yes that all makes sense, except what is the equation needed in the conversion and argument paremeters?

04-05-2011, 06:17 AM
i stated it:


X is MAP in kPa

that equation will convert it to inHg.

04-05-2011, 07:07 AM
When I said it all made sense, I meant it all made sense to you, or it all made sense except the math! :lol:

Anyway since x is KPA I linked to it and added the equasion and guess what? It worked!

I've been working on cars for so long and a vacuum gauge is a main tool to see what an engine is doing. So now I can see the vacuum like I always have along side the Kilipascals and they will start to intergrate in my brain...

04-05-2011, 12:45 PM
Well didn't work right... I got this from Dave at TunerCode.com awhile ago

Posted: Wed Feb 09, 2011 3:52 am Post subject:


Just duplicate everything in the definition for MAP KPA and multiply the conversion and ranges by 0.2953.

For example, I have MAP kPa defined as:
title="MAP kPa"
units="MAP kPa"
range low="0.000000"

I also have the same value defined in PSIg:
title="Boost (psig)"
range low="-14.500000"


04-05-2011, 07:28 PM
i just downloaded the ADX you posted that had my suggested conversion in it:

you used X *0.2872 instead of (104.45-X)*0.2872

04-06-2011, 08:45 AM
I changed that. But something is still off. My idle is 14.49 inches of mercury which is low! I know the car is 18-19. Also at WOT the gauge goes to 0 but the numbers go negitive...

When I convert the 14.49 to KPA it come out to 49.07 ?

Now my TunerPro says vacuum at idle is 14.49 and KPA is 30.28.

30.28 comes out to 8.92 inches of mercury?

04-06-2011, 09:14 AM
i just plugged the math into the calc:

30kPa should come out to ~21.3"

got a log? luckily V5 allows you to manipulate logs, so i should be able to test in real-time.