Hello all,

I have been writting an OBDII software package for the PocketPC for the last few months with all my spare time . Well, I logged my drive in this morning in my Evo. The program creates a tab seperated text file that can be imported into an Excel spreadsheet where you can graph things.

Anyway, I had a question. It seems my Intake Manifold Pressure Sensor always read 1.5 psi . It seems to be broken or just not present. I was wondering if anyone else has hooked up an OBDII sensor read and had the same results? The car runs fine, its just weird. I was hoping it would read boost, but oh well. It reads fine on my S2000.

Check it out:
http://smanders.no-ip.com:8080/obdii...003_095214.xls
http://smanders.no-ip.com:8080/obdii...003_095214.txt

Right now, it supports the ISO ELM Electronics cable. It limits your sample rates to ISO 1941 standard of 300ms. The next cable I am working on supporting takes a lot more software to manage but can yeild much faster samples. The program also can display two sensors as gauges in realtime. It also can read and clear "Check Engine" codes.

Its fun stuff,
smanders

 

Where are you finding the info to work on this from? Is there documentation on the web detailing all of the protocols for ODBII? I have a laptop that could be carried to the car nicely. And I need a new programmign project.

 

I thought I saw somewhere that the MAP sensor is only a 1 bar MAP sensor. I don't know if 1 bar means 1 full bar of resolution or if it's capable of reading up to 1 bar of boost. If it's the former then that would explain why you can't get a readng much over atmospheric pressure.

 

For the lap top, I recommend https://sourceforge.net/projects/freediag/ along with a linux boot CD. Its open source and I learned a lot from it. There is another open source tool for the ELM cable, http://www.scantool.net/index.htm .

You have to do your homework on the cables though. There are several varieties with different software packages.

You can purchase the ISO standards fromhttp://www.iso.org .

 

Looks like you let the car cool off before shutting down....but you didnt allow the car to warm up for a minute before setting off! shame on you! huhu

Cool info though!

SC~

 

I'm reading 1.5 psi which is equal to .1034 bar or .1021 atmospheres. Remeber 1 bar is equal to 14.5 psi. So your comment would lead me to believe it could go to 14.5 psi. I would think it would at least fluxuate while I am driving but it doesn't. Its always, 1.5 psi.

 

You guys are just too technical for me........

 

Sure I did.....the coolant was 150 degrees before my MPHs increased . I had turned the car on before I started logging.

 

smanders: Is there a barometric sensor that you could be reading accidentally? I know my old Subie had one so it could compare the manifold pressure to the atmospheric pressure. That might explain the constant pressure you're reading.

Also, if the MAP has 1 bar of total range, it'd probably be set up to read vaccum -> atmospheric, not any boost. However the range could be skewed slightly to let you see just a little boost as long as you assume you can never have a true vaccum inside the manifold.

 

I am making the same request as I do on all other cars for intake manifold pressure . It would make sense that the sensor would obviously be before the turbo. I didn't really think about it... .

 

Isnt 1 bar 14.7 psi?

Anyways.....i am VERY MUCH looking forward to your PocketPC program for this. Most OBDII programs have been for PalmOS. I just got a Dell Axim and am looking forward to using your software. Great work smanders!

 

Well if it's manifold pressure then wouldn't the sensor be on the manifold somewhere? If it was pre-turbo then it would be measuring atmospheric pressure basically.

I'm guessing the Evo has a MAP so that when the throttle plate is closed the ECU still has an idea of what's going on in the engine. I'd guess with a closed throttle plate the MAF would be kind of useless? Perhaps the MAP is more for idle control in off-throttle situations?

Coolguy, yes, 1 bar is 14.7 PSI. And if I'm not mistaken normal atmospheric pressure is 1bar. So NA cars that use MAP sensors just need a 1bar MAP sensor to measure manifold pressure and that will cover all situations from vaccum up to atmospheric (closed throttle to WOT).

 

The "MAP" sensor is really an MDP sensor. It only reads vacuum. It is there to test whether or not the EGR valve is working.

 

Thanks for clearing that up guys... gotta learn a whole new engine here.