ElmScan + Customized Scantool Software = data logging!

[lyd]

I can't comment usefully on the above, but there seems to be a number of links to information and code in this thread on gassavers.org: OBDII CarPC MPG Calculator - GasSavers.org - Helping You Save at the Pump

[lyd]

DOH! I just noticed that thread is all about you! Sorry. ;-)

[mtgeekman]

Do you know if your version will work with the ELM327 1.3 chip? I just sent my scantool in for an update (was free aside from shipping) they threw in a new chip and upped the data rate to 38000bps.

I might get a chance to test is this weekend. though I think they released the 1.14 to be compatible with it, even that one didn't work.

also some thing I noticed in the OBD2007 pdf that was posted:

Late model vehicles which use Oxygen sensors known as wide range linear Oxygen sensors, can also introduce another Pid 0x44, Commanded Equivalence Ratio. This pid allows fine adjustment of air fuel ratio from the constant 14.64 by modifying the air fuel ratio by a value between 0 and 1.999 which permits air fuel ratios to be measured to greater precision. If a vehicle supports Pid 0x44, OBD 2007 fuel consumption figure is modified by the effect of Commanded Equivalence Ratio.

[cfg83]

mtgeekman -

Originally Posted by mtgeekman

Do you know if your version will work with the ELM327 1.3 chip? I just sent my scantool in for an update (was free aside from shipping) they threw in a new chip and upped the data rate to 38000bps.

I might get a chance to test is this weekend. though I think they released the 1.14 to be compatible with it, even that one didn't work.

also some thing I noticed in the OBD2007 pdf that was posted:

I am 85% sure that mine is based on the 1.14 version. If you can't get that version to "talk" to your ELM327, you'd probably have the same problem with mine.

Originally, I had lots of problems making it work. I found out that I needed a "vanilla clean" XP OS install to make it work. It didn't work with my XP off the bat because it was encrusted with all sorts of "barnacle-programs" that interfered with the COM1 port connection. Here's an experiment to emulate a "vanilla clean" OS that might work for you :

1 - Assuming you have Windows XP
2 - Assuming you are using COM1 or COM# port connection.
3 - Assuming COM# ports work in Safe Mode.
4 - Boot into Safe Mode
5 - Run Scantool 1.14 and see if it works.

I am also assuming that the Alegro SW graphics package won't get too upset with Safe Mode.

I will also try this experiment this weekend if I have the time (messy weekend coming up to say the least).

EDIT: No comment on the wide range linear oxygen sensor because I am narrow band. This may be a BIG help to wide band owners. Good catch!!!

CarloSW2

[cfg83]

Hello -

(edited multiple times to get info correct)

I have a question. If you know the following about your car :

1 - Engine displacement in Liters. For example, my engine is 1.9 liters (1901 cc).

2 - Manifold Absolute Pressure (MAP) in inHg (inches Mercury). For example, the value that my engine returns in the OBD II protocol.

3 - Compression Ratio (Optional?) . For example, my car has a compression ratio of 9.5:1.

Question : Can you *calculate* the Manifold Absolute Flow (MAF) in grams per second?

Reason : I ask because I am trying to emulate the published OBD 2007 algorithm

Thank You,

CarloSW2

[lyd]

Do you have a link to that alg, Carlo? I was looking for it the other day and couldn't track it down.

[cfg83]

lyd -

The "alg"(orithm?) is from post #10 above :

OBD 2007 - Installation Guide
http://www.glmsoftware.com/Documenta...de20080822.pdf - Page 15 of PDF

fuel consumption can be calculated, if a vehicle supports Pid 0x0D Vehicle Speed and Pid 0x10 Mass Air Flow. All vehicles support vehicle speed and nearly all vehicles support MAF.

MAF, the mass of air moving into the engine is measured in grams per second. A petrol/gasoline engine burns the air/fuel mixture at the stoichiometric air fuel ratio of 14.64:1. The oxygen sensors in a modern vehicle are designed in conjunction with both the short and long term fuel trims to maintain this ratio. Under ideal conditions for every 14.64 grams of air an engine will consume 1 gram of petrol. We can therefore calculate FuelFlowGramsPersSec = MAF/Air Fuel ratio. We can convert the previous figure to FuelFlowLitresPerSecond by dividing FuelFlowGramsPerSec by the density of petrol/gasoline.

We can then readily convert that figure to FuelFlowLitresPerHour -- i.e. litres/hour. Fuel consumption is then simply SpeedKmsPerHour/FuelFlowLitresPerHours -- i.e. litres/kms.

CarloSW2

[lyd]

Oooohh. Right, sorry. ;-) I misunderstood what you were referring to there.