What would you monitor from OBDII?

[ABerns]

Hi, all --

I just got in a BAFX OBDII reader which connects over Bluetooth to my phone. I've been happy with the few uses I've done so far.

Anyway, I can display any information I want from the OBD2 computer. There are a lot of values, and I don't know which ones are the most entertaining/suggestive to watch. I thought I'd ask it here:

What readings would you monitor from an OBD2 computer?

Clarifying the question for my purposes: I'm not watching to identify any problems, I'm only watching from the 'auto nerd' standpoint. I'm watching the standards: oil, tranny, and coolant temperature. What else would you watch?

As far as vehicles, I have a 2000 Camry and a 2011 Traverse with the DI. Again, though, feel free to suggest what you would watch on your car!

Thanks in advance!
Andy

 

[danthaman1980]

Oil, tranny, cooolant, intake temp are fun to monitor. Timing advance can be fun to watch.

Sometimes fun to put engine RPM on a large RPM vs. time graph to see how smoothly your engine is idling.

O2 sensor and fuel trim values are useful when troubleshooting problems.

 

[glock19]

If you're able, I would watch the oil pressure. I'm not a big believer in warming up vehicles but it is nice to know the oil is up to pressure before driving off.

 

[Leo99]

Originally Posted By: danthaman1980
Oil, tranny, cooolant, intake temp are fun to monitor. Timing advance can be fun to watch.

Sometimes fun to put engine RPM on a large RPM vs. time graph to see how smoothly your engine is idling.

O2 sensor and fuel trim values are useful when troubleshooting problems.


I used my OBDII to troubleshoot my O2 sensor but it took a bit of learning/research to know what it is supposed to look like. It doesn't do you any good if you don't know the difference between normal and abnormal.

It's amazing how much information is in there that I never knew about.

 

[Stewie]

I only use it when there is a check engine light

 

[eljefino]

If you can get knock retard (from optimal timing) that'd be fun to know. It's "okay" under certain scenarios, as you're wringing the most from your gas, but always something to look for less of.

 

[Donald]

Originally Posted By: ABerns
Hi, all --

I just got in a BAFX OBDII reader which connects over Bluetooth to my phone. I've been happy with the few uses I've done so far.

Anyway, I can display any information I want from the OBD2 computer. There are a lot of values, and I don't know which ones are the most entertaining/suggestive to watch. I thought I'd ask it here:

What readings would you monitor from an OBD2 computer?

Clarifying the question for my purposes: I'm not watching to identify any problems, I'm only watching from the 'auto nerd' standpoint. I'm watching the standards: oil, tranny, and coolant temperature. What else would you watch?

As far as vehicles, I have a 2000 Camry and a 2011 Traverse with the DI. Again, though, feel free to suggest what you would watch on your car!

Thanks in advance!
Andy


I would look out the windshield while driving vs your engines metrics on your phone.

 

[PF52]

Originally Posted By: danthaman1980
Timing advance can be fun to watch.



LOL I was going to say spark advance. Fun to watch, not that I can do much with it.

 

[Cadenza]

I would look out the windshield while driving vs your engines metrics on your phone.



That's the reason I basically concern myself only with transmission temps when I tow a small travel trailer. Everything else, while interesting, is a distraction while I'm driving. They are fun to have, though.

 

[Klutch9]

To the OP, in my experience, most cars only support a few real-time values. Of the several cars I've tried the BAFX on (using Torque app), things like atf temp, oil pressure, oil temp, etc are NOT supported.

 

[Hokiefyd]

Originally Posted By: css9450
LOL I was going to say spark advance. Fun to watch, not that I can do much with it.


I think spark advance is quite useful, especially if you can map it over time. I can see in my Honda, for example, that the engine really can tell if I'm using premium fuel vs. regular, because the peak spark advance under certain conditions is higher. I can also tell immediately when the engine goes into fuel cut-off mode, because the spark advance immediately drops to -17 deg BTDC (basically, 17 deg ATDC). When I give it just the slightest but of throttle, I can feel power resume and spark advance jumps back up to about 5 or 10 deg BTDC or whatever is appropriate for those conditions.

I'll take a picture of my Torque screen and post it. Fuel flow and engine load are my two large displays. Engine load tells me when the engine is consuming all the air it can at that engine speed (so more throttle isn't necessarily helpful). I also monitor coolant temp, ambient temp, and manifold vacuum on smaller displays. Manifold vacuum, like engine load, is another general indicator of when the engine's giving you all that it can, and when more throttle generally just means more fuel wasted.

What's really cool about manifold vacuum is you can see just how efficient the stock intake system is, and I've even seen a "boost" of 0.1 psi sometimes under certain conditions due to the intake system producing a "supercharging" effect due to plumbing/resonators/tumblers/etc.

 

[SHOZ]

Depends on the engine. turbos have more to watch. But on my other car I look at the engine coolant temp, Intake air temp, spark advance, O2 voltage for both O2s. I find the voltage more informative as to what is going on over fuel trims.

The absolute load is a good one too.

 

[Hokiefyd]

Here's my Torque screen:

This is after my drive home from work yesterday. Comments on the gauges:

Fuel Flow: I believe fuel flow is an OBDII parameter and not calculated by Torque. The units are gal/min, and I've set the gauge to show from 0 to 0.1. You can see that my peak fuel flow during my trip home was about 0.047 gal/min. It will flash up to about 1.1 or 1.2 gal/min during WOT, but I like to see the resolution on the graph at lower flows. This graph will show the engine going into fuel cut-off mode during deceleration. In fact, you're seeing fuel cut-off in this screenshot; I was coasting as I took the picture. Normal idle fuel flow is just shy of 0.01 gal/min.

Engine Load: This graph is neater and neater the more you think about what it represents. It doesn't mean "load on the engine" in the intuitive sense. After all, this screenshot is during fuel cut-off: engine load should be ZERO, right?! No, the engine load parameter in OBDII is an estimation of the percentage of maximum torque available at that engine speed, and it estimates that by measuring actual volume of air consumed divided by maximum air volume capacity at that engine speed. For example, you can be cruising along at 1,200 rpm at 45 mph or so and see engine loads of 50-70%. This means that, at that engine speed, the engine is consuming about half of the air that it can at that speed...even though the throttle may be only cracked open. That's because the engine can't consume nearly as much air at 1,200 rpm compared with what it can at 6,000 rpm. It's neat to load it to 100% with the throttle pedal, and observe the engine "climbing out" of that torque hole...as engine speed rises, it has the capability to consume more air...but if you leave the throttle at the same opening, the engine load will decrease as the engine speed rises.

They say that it's normally best to accelerate in the 80-90% range, in terms of engine load. Once you get to 100%, the engine is giving you all it can at that engine speed, and opening the throttle more will generally consume more fuel than what you gain out of the engine...until it really gets up into its torque peak. Obviously, how all of this interplays depends highly on engine size and number of cylinders, but the OBDII concept remains consistent. This is one of the most useful parameters, in my opinion, if you're looking to get the most out of the fuel you're using.

Coolant Temp: pretty self-explanatory. The CR-V runs right at 188-190 deg F most of the time. If I sit idle with no A/C on (so no rad fans running), the temperature will climb to about 210 deg F before the fans kick on, and fall back to about 205 deg F before they turn off.

Intake Temp: the temperature yesterday was about 62 deg F at the time of my drive home. Intake temp will rise fairly quickly when stopped, and will fall again pretty quickly once moving. It always runs, however, about 10-20 deg higher than ambient, once everything's warmed up.

Vacuum: Torque displays this as a combined Vacuum/Boost gauge. During vacuum, it displays in in/Hg. If it goes to 0 vacuum (or boost), it switches to PSI. I'm not sure how it derives both units of measure from one physical sensor, unless it's an estimation of either or both. Manifold vacuum is similar to engine load: once you approach 0 vacuum, you're getting the most you can out of the engine at that speed. You can also use manifold vacuum to assess the efficiency of your intake system at WOT. At WOT, my manifold vacuum drops to less than 1 in/Hg, and actually goes to 0 or 0.1 psi sometimes. It's said that they design intake systems with odd plumbing and resonators and chambers to enhance airflow and to even produce a supercharging effect. It's cool to be able to watch that in action.

In general, one really needs EITHER engine load OR manifold vacuum, as they're essentially linear inverses of each other. Idle in my car (as you can see above) is about 24 in/Hg. 50% engine load is about 12 in/Hg. 90-100% engine load is about 0-3 in/Hg.

I don't have Torque running all the time, but when I do, these are the things I watch. Our 2008 CR-V has a very fast OBDII system, and the gauges update in nearly real-time. Our 2005 MDX must have a slower OBDII protocol, because I get updates about once a second or so on the gauges. So its usefulness for seeing detailed changes in these measurements is somewhat limited.

 

[Vikas]

So what you are saying is that load PID is an artificial entity and is derived from RPM and MAP (or MAF) only. The interesting question then becomes, does ECM use computed load to come up with fuel injection width or ignition timing as the output paramters?

 

[Jcp123]

Ony UltraGauge, my main page is set up for fuel economy. So, I have throttle position, RPM, and coolant temp as the ones I derive from my OBD II. My others are calculated values (fuel level, instantaneous fuel economy, trip and tank fuel economies, and fuel range in miles).

Second page, I have fuel trims and throttle position, along with a load calculation, rpm, coolant temp, and O2 sensor voltages. That's mostly my diagnostic page.

 

[sciphi]

My ScanGauge II is set up to monitor boost (PSI), ignition timing, average trip fuel economy, and gallons/hour. The other 18 or so things it monitors are available pretty quickly.

 

[Hokiefyd]

Originally Posted By: Vikas
So what you are saying is that load PID is an artificial entity and is derived from RPM and MAP (or MAF) only. The interesting question then becomes, does ECM use computed load to come up with fuel injection width or ignition timing as the output paramters?


Yes, load is not a directly-measured PID; it's one derived through calculation. I think one of the most use often used applications of engine load is to schedule power enrichment. 100% load is often achieved before WOT, so the engine computer can apply extra fuel, more than it'd otherwise normally provide, to enrich the mixture to help the engine to continue to accelerate (and to not ping).

But I'm not a powertrain engineer. Load could very well be used to continually influence spark and valve timing.

The math behind engine load can be found here:

http://www.epa.gov/ttnchie1/conference/ei20/session8/aalessandrini_pres.pdf

The slides are correct that it will reach 1 (100%) at WOT, but it often reaches 1 far before WOT...depending on engine speed and a variety of other factors.

 

[Hokiefyd]

It's my understanding that you can use engine load to help determine where you are on the Brake Specific Fuel Curve for your engine. BSFC is often mapped at 100% load, so you can determine on the fly where you are, vertically, on the BSFC map for any RPM.

 

[Stewie]

Originally Posted By: Hokiefyd
Here's my Torque screen:

This is after my drive home from work yesterday. Comments on the gauges:

Fuel Flow: I believe fuel flow is an OBDII parameter and not calculated by Torque. The units are gal/min, and I've set the gauge to show from 0 to 0.1. You can see that my peak fuel flow during my trip home was about 0.047 gal/min. It will flash up to about 1.1 or 1.2 gal/min during WOT, but I like to see the resolution on the graph at lower flows. This graph will show the engine going into fuel cut-off mode during deceleration. In fact, you're seeing fuel cut-off in this screenshot; I was coasting as I took the picture. Normal idle fuel flow is just shy of 0.01 gal/min.

Engine Load: This graph is neater and neater the more you think about what it represents. It doesn't mean "load on the engine" in the intuitive sense. After all, this screenshot is during fuel cut-off: engine load should be ZERO, right?! No, the engine load parameter in OBDII is an estimation of the percentage of maximum torque available at that engine speed, and it estimates that by measuring actual volume of air consumed divided by maximum air volume capacity at that engine speed. For example, you can be cruising along at 1,200 rpm at 45 mph or so and see engine loads of 50-70%. This means that, at that engine speed, the engine is consuming about half of the air that it can at that speed...even though the throttle may be only cracked open. That's because the engine can't consume nearly as much air at 1,200 rpm compared with what it can at 6,000 rpm. It's neat to load it to 100% with the throttle pedal, and observe the engine "climbing out" of that torque hole...as engine speed rises, it has the capability to consume more air...but if you leave the throttle at the same opening, the engine load will decrease as the engine speed rises.

They say that it's normally best to accelerate in the 80-90% range, in terms of engine load. Once you get to 100%, the engine is giving you all it can at that engine speed, and opening the throttle more will generally consume more fuel than what you gain out of the engine...until it really gets up into its torque peak. Obviously, how all of this interplays depends highly on engine size and number of cylinders, but the OBDII concept remains consistent. This is one of the most useful parameters, in my opinion, if you're looking to get the most out of the fuel you're using.

Coolant Temp: pretty self-explanatory. The CR-V runs right at 188-190 deg F most of the time. If I sit idle with no A/C on (so no rad fans running), the temperature will climb to about 210 deg F before the fans kick on, and fall back to about 205 deg F before they turn off.

Intake Temp: the temperature yesterday was about 62 deg F at the time of my drive home. Intake temp will rise fairly quickly when stopped, and will fall again pretty quickly once moving. It always runs, however, about 10-20 deg higher than ambient, once everything's warmed up.

Vacuum: Torque displays this as a combined Vacuum/Boost gauge. During vacuum, it displays in in/Hg. If it goes to 0 vacuum (or boost), it switches to PSI. I'm not sure how it derives both units of measure from one physical sensor, unless it's an estimation of either or both. Manifold vacuum is similar to engine load: once you approach 0 vacuum, you're getting the most you can out of the engine at that speed. You can also use manifold vacuum to assess the efficiency of your intake system at WOT. At WOT, my manifold vacuum drops to less than 1 in/Hg, and actually goes to 0 or 0.1 psi sometimes. It's said that they design intake systems with odd plumbing and resonators and chambers to enhance airflow and to even produce a supercharging effect. It's cool to be able to watch that in action.

In general, one really needs EITHER engine load OR manifold vacuum, as they're essentially linear inverses of each other. Idle in my car (as you can see above) is about 24 in/Hg. 50% engine load is about 12 in/Hg. 90-100% engine load is about 0-3 in/Hg.

I don't have Torque running all the time, but when I do, these are the things I watch. Our 2008 CR-V has a very fast OBDII system, and the gauges update in nearly real-time. Our 2005 MDX must have a slower OBDII protocol, because I get updates about once a second or so on the gauges. So its usefulness for seeing detailed changes in these measurements is somewhat limited.


You gotta pay for it though

 

[ARB1977]

I installed autometer gauges for trans, oil and volts ten years ago in my tacoma.