cliffyk

^+1000 or so - Manifold vacuum is a very often overlooked diagnostic tool:

flyboy1294

Sorry for the late reply.

Thank you for the info Moonshine and Fastback! I found a few YouTube videos on people using the Torque app with New Edge cars, so I guess it must work. I looked on Auto Meter's website though and they side the ecometer only works for 2005+ Mustangs? Hmm.

So, CliffyK, if I'm understanding you right, you are saying that the gauges have to make calculations based on other information to give MPG read outs and may not always be accurate? Would the A/F ratio be the main reason the gauge would be inaccurate? I'm also wanting to do a wide-band O2 sensor on my car just so I can see for myself that things are running smoothly, so in that case I could know what the A/F ratio was better than my PCM did...

Interesting discussion on the vacuum gauges. The original application was a bit before my time, but it is cool nonetheless.

cliffyk

The operating parameters that can be requested through the OBD2 (OnBoard Diagnostic, type 2) port are called PIDs, Parameter IDs. There are generic PIDs described by SAE publication J1979, and manufacturers PIDs defined by each manufacturer.

Automakers are only required to support a small subset of the generic PIDs, mostly those related to emissions compliance, and most consumer level devices, and software like "Torque", support only the generic PIDs--here is a list of the generic PIDs supported by our cars (New-Edge V8s):



This is mostly diagnostic data (hence the name OBD2) with little performance tuning value. The RPM, ignition timing, MAF rate and load are useful, and the short term fuel trims to some extent, but the others are really just interesting information. The narrowband O² voltage is of no value to performance tuning.

Note that the two values needed to guesstimate fuel economy, MPH and MAF flow, are there and also closed-loop/open-loop indication that can be used to infer AFR--using 14.7:1 for closed loop and a reasonable value (say 12.5:1) for open-loop. This is how the OBD2 "performance" tools calculate MPG.

A very few tools/devices, not cheap ones, do support the manufacturers PIDs. Some partially with built-in tables, others by using manufacturer specific personality modules.

FWIW here is a list of all PIDs supported by our cars. Once again note that it is 99.44% diagnostic stuff unrelated to performance tuning.

So, my bottom line on OBD2 PID monitoring systems is that they are great diagnostic tools, not THE ultimate tool but on worth having in your tool box. Other than that they are cute toys that will at first amuse you and impress your friends, and then become rapidly just a bit more interesting than watching mud dry...

flyboy1294

I see. In that case I might invest in one of the more expensive monitoring systems just for diagnostic purposes. I live in a pretty rural area, and it is hard to find reputable shops to work on my vehicle when something goes wrong. So I find my tool box and knowledge base is ever expanding. Which may not be a bad thing. Thank you once again for the info!