ODBWiz, anybody using it?

[gone-ot]

...received my OBDWhiz & CD the other day, but haven't (yet) been able to "try it" because wife is busy using her laptop.

...ironically, it was shipped from ScanTool.net, LLC, in Phoenix, AZ...just up the freeway from me, hence I got mine one day after ordering it.

...as for "cable routing" (for SGII™, now), I use three of these (they're white, so I colored them black using a marker-pen) to "hold" the cable out of the way:

[Diesel_Dave]

I'm going to have to get one of the right angle ones, becaude for me it's not just the cable that's in the way but the actual "box" (before it forms a cable).

Anyway, I played around with it some more. It's reading the engine okay, i.e, I can get coolant temperature, engine speed, etc. but I can't get the fuel economy to work.

I assumed for diesel, I should select the direct fuel calculation method, but that gives all zeros. I tried the MAF method just to see what happened, but it gives bogus numbers (average of 70+ mpg), and reads zero fuel flow at idle.

I sent a note to the OBDwiz support, asking what I'm doing wrong. When I get a chance I may dig through my logger to, to see if I can make out anything.

[Diesel_Dave]

Okay, so OBDwis support is telling me:

Based on the log, your vehicle doesn't report the PID required for the direct fuel calculation method. You will have to use mass airflow.

Personally, I find this hard to believe (that my vehicle doesn't have a direct fueling PID). Somehow the fueling info has to get to the factory display (which only reads average fuel economy). Plus, I know that some of the diesel tuners display instant mpg. I'm going to have to do some research to find out how those devices do it.

And the suggestion of using MAF is rediculous in my opinion. Air fuel ratio is going to vary from under 20:1 to over 40:1 in a diesel--knowing air flow won't tell you hardly anything about fuel flow. I can guess my instantaeous FE better than that. Plus I tried the MAF method and it read zero fuel flow at idle.

Grrr, I'm frustrated.

[lamb.chop]

Just wanted to say a public "THANK YOU VERY MUCH" to mbrac for purchasing an ELMScan USB OBD & OBDWiz & shipping it to me in the UK.

This is the sort of community spirit that makes Ecomodder.

Mike, thanks very much again.

Cheers

Chris

[Diesel_Dave]

Thanks to cfg83 too. That right angle OBD cable woorks great! Wish I could say the same about the OBDwiz. It can't read the fuel flow and the MAF method tells me I'm getting over 50 mpg. Oh well. At least I can learn some things by watching the other PID's.

[benphyr]

Diesel_Dave,

re: "the MAF method tells me I'm getting over 50 mpg."

Is the quoted mpg above an instantaneous or average for a tank?

If the 50mpg is instantaneous: I notice that your mpg average is approximately 32mpg, not up at 50 mpg, but an instantaneous mpg could easily be much greater than the average. Also, if the calibration is only out by a factor of 2 then you are in the range (ballpark) that you can probably calibrate the machine to make it accurate.

You may be reading a zero at idle because the measurement is below the threshold that it displays and so it "rounds" to zero.

Some food for thought and hoping that you can get it to work for you.

Cheers,
Ben.

[Diesel_Dave]

Originally Posted by benphyr

Diesel_Dave,

re: "the MAF method tells me I'm getting over 50 mpg."

Is the quoted mpg above an instantaneous or average for a tank?

If the 50mpg is instantaneous: I notice that your mpg average is approximately 32mpg, not up at 50 mpg, but an instantaneous mpg could easily be much greater than the average. Also, if the calibration is only out by a factor of 2 then you are in the range (ballpark) that you can probably calibrate the machine to make it accurate.

You may be reading a zero at idle because the measurement is below the threshold that it displays and so it "rounds" to zero.

Some food for thought and hoping that you can get it to work for you.

Cheers,
Ben.

The 50+ mpg number was the average for trips (~24 miles).

Unfortunately, the basic version of OBDwiz doesn't give you the ability to calibrate things. Of course, if it's using the MAF method, then it wouldn't matter anyway--the whole principle it's based on (constant AFR) is flawed for a diesel. Sure, you can calibrate a MAF-based method and get close to your real, long-term average FE, but what's the point? By now, I can get pretty close to my real long-term average just by guessing.

What I wanted was a way to compare different shifting patterns & P&G techniques. A MAF-based method will never work for that because of the constant AFR assumption. For example, when P&G'ing the true AFR at idle is easily double or triple that of what it is under load. That means the MAF-based method will overestimate the idle fuel flow rate by 2-3 times, easily destroying any usefulness the data might have.

So far I've managed to do a pretty good job just by watching and logging what the factory-installed trip mpg meter runs. It reads 10-15% high on average, but that 10-15% has been fairly consistant. Just a loggable, instantaneous version of that would be nice. Apparently the OBDwiz software can't access the same information that's going from the ECM to the in-cab display.

Oh well, I'm still pursuing a few more options for getting the info.

[benphyr]

Diesel_Dave,
That makes sense. Thank you for the explanation and the further information on the basic OBDWiz limitation.
Cheers,
Ben.

[Diesel_Dave]

Just to clarify, the MAF based method does work fairly well for most gasoline engines (non lean burn), because AFR is fairly constant. I suspect OBDWiz would work quite well in those applications.