I got my ELM327 adapter in the mail yesterday, so I set out with Torque on the tablet mounted on the CR-V's dash to observe. Very interesting stuff. Some thoughts.
TPS
It's widely postulated that the throttle "ramp" on DBW vehicles is not linear, and often aggressive, perhaps giving 90% throttle at 50% of pedal travel. At least with our Honda, this is very much not the case. Idle TPS is about 14-15%, and in most normal driving, even spirited driving, TPS never goes above about 40-50%. If you mat the throttle, it will go to wide open, which registers as 78.8%. 50% of pedal travel equals about 40% TPS. As engine technology marches on, with things like variable valve timing and even camshaft-less engines, the function of the throttle butterfly has changed forever from what it used to be...it has been supplanted from being the only means by which airflow into the engine is controlled.
Ignition advance
This one is interesting as well. Idle is around 4-8 deg advanced (which I assume means BTDC). Normal cruise with the torque converter unlocked gives about 20-30 deg of advance. If the torque converter is locked, I can easily push the advance down to near zero with the throttle...as the engine is more prone to knock in those conditions, it ratchets back the spark timing. What's interesting is that the advance dial also acts as my fuel cut indicator. Whenever the gas pedal goes to idle, and you feel engine braking as it cuts fuel, spark advance goes to -17 deg. Slow down from 25 mph, say, down to about 20 mph, you can feel the ECM give fuel back to the engine with a reduction in engine braking. At this exact moment, spark advance moves from -17 deg to around 0, then to the idle range in the positive single digits.
Fuel trim
It's not labeled either way, but I believe this is short term fuel trim (vs. long term trim). The ECM keeps it to a maximum of about 7-8% either pos or neg. It's most often in the 2-3% (pos or neg) range. When fuel is cut, fuel trim immediately goes to 0.00% (as it's not trimming anything at the moment). Once fuel is applied again, it takes a second or two before trim reacts, so while it's a good indicator that fuel is cut, this display alone will not indicate exactly when it's been re-applied (but the timing advance shows that). In doing some reading, it looks like fuel trim that is kept close to 0.00% is very good, and anything within 10% pos or neg indicates good ECM control of the fuel.
Engine load
This one surprised me. It acts very much like a "boost gauge" on a turbocharged engine. It's very surprising to see how often the engine is at 100% calculated engine load. It can be at 100% load at 1,800 rpm with the torque converter locked in 5th gear and not downshift. This gauge reacts immediately to throttle opening in a very non-linear way. I understand this is calculated based on current airflow vs. maximum airflow at that time. I need to research this PID more. I'm sure I can learn something from it, but I'm not sure what. The load never goes below about 20%, even under heavy engine braking.
Other misc data
Coolant temperature runs at 185-190 deg F. Intake air temperature is generally 10-20 deg F above ambient, though if I sit at idle, it will slowly rise. GPS and OBD vehicle speed are extremely close, with the speedometer pretty much displaying the OBD speed on the nose without much of an intentional error as I've seen on other vehicles I've owned. I've played with MAF (grams/sec) and it's interesting, too. It idles around 3 g/s and moderate throttle will give 30-50 g/s, even though the actual throttle butterfly has only moved from 15% to 25%. Again, there seems to be a lot more to airflow in a modern engine than throttle position alone.
Altogether, this has sparked a lot of interest in me to learn more about these values and what they mean. Will also play with the Acura this weekend.
TPS
It's widely postulated that the throttle "ramp" on DBW vehicles is not linear, and often aggressive, perhaps giving 90% throttle at 50% of pedal travel. At least with our Honda, this is very much not the case. Idle TPS is about 14-15%, and in most normal driving, even spirited driving, TPS never goes above about 40-50%. If you mat the throttle, it will go to wide open, which registers as 78.8%. 50% of pedal travel equals about 40% TPS. As engine technology marches on, with things like variable valve timing and even camshaft-less engines, the function of the throttle butterfly has changed forever from what it used to be...it has been supplanted from being the only means by which airflow into the engine is controlled.
Ignition advance
This one is interesting as well. Idle is around 4-8 deg advanced (which I assume means BTDC). Normal cruise with the torque converter unlocked gives about 20-30 deg of advance. If the torque converter is locked, I can easily push the advance down to near zero with the throttle...as the engine is more prone to knock in those conditions, it ratchets back the spark timing. What's interesting is that the advance dial also acts as my fuel cut indicator. Whenever the gas pedal goes to idle, and you feel engine braking as it cuts fuel, spark advance goes to -17 deg. Slow down from 25 mph, say, down to about 20 mph, you can feel the ECM give fuel back to the engine with a reduction in engine braking. At this exact moment, spark advance moves from -17 deg to around 0, then to the idle range in the positive single digits.
Fuel trim
It's not labeled either way, but I believe this is short term fuel trim (vs. long term trim). The ECM keeps it to a maximum of about 7-8% either pos or neg. It's most often in the 2-3% (pos or neg) range. When fuel is cut, fuel trim immediately goes to 0.00% (as it's not trimming anything at the moment). Once fuel is applied again, it takes a second or two before trim reacts, so while it's a good indicator that fuel is cut, this display alone will not indicate exactly when it's been re-applied (but the timing advance shows that). In doing some reading, it looks like fuel trim that is kept close to 0.00% is very good, and anything within 10% pos or neg indicates good ECM control of the fuel.
Engine load
This one surprised me. It acts very much like a "boost gauge" on a turbocharged engine. It's very surprising to see how often the engine is at 100% calculated engine load. It can be at 100% load at 1,800 rpm with the torque converter locked in 5th gear and not downshift. This gauge reacts immediately to throttle opening in a very non-linear way. I understand this is calculated based on current airflow vs. maximum airflow at that time. I need to research this PID more. I'm sure I can learn something from it, but I'm not sure what. The load never goes below about 20%, even under heavy engine braking.
Other misc data
Coolant temperature runs at 185-190 deg F. Intake air temperature is generally 10-20 deg F above ambient, though if I sit at idle, it will slowly rise. GPS and OBD vehicle speed are extremely close, with the speedometer pretty much displaying the OBD speed on the nose without much of an intentional error as I've seen on other vehicles I've owned. I've played with MAF (grams/sec) and it's interesting, too. It idles around 3 g/s and moderate throttle will give 30-50 g/s, even though the actual throttle butterfly has only moved from 15% to 25%. Again, there seems to be a lot more to airflow in a modern engine than throttle position alone.
Altogether, this has sparked a lot of interest in me to learn more about these values and what they mean. Will also play with the Acura this weekend.