Scangauge Suggestions

[MetroMPG]

jjf - thanks for the oil info. Seems to me that if one is going to extended change intervals with synth, regularly scheduled filter changes might address the issue, no?

Originally Posted by puddleglum

this thread was about what guages to use in winter. Most new cars with heated O2 sensors will drop into closed loop very quickly, long before the engine is warm

Originally Posted by jfitzpat

My point was that it is better to directly monitor the ECU's decision, rather than inferring it

I can confirm that the SG reports loop status directly from the ECU; it's not inferred from other sensor readings.

And I agree, puddleglum: some cars go to closed loop really quickly, even in sub-sub-zero conditions. My Firefly does; but others have reported longer transition times.

(FYI, I don't generally watch the LP (loop) indicator in winter. I do sometimes monitor it when pulsing at high load to prevent going into fuel enrichment).

[jfitzpat]

Originally Posted by puddleglum

But, my intent was not to suggest that we should wait till the coolant is warm before driving, just that we should use whatever means available to get the engine/drivetrain up to temp. and use the SG to monitor it.

I don't disagree, I am just noting that, in this case, OBD-II is not particularly helpful. For example, we have ECT, which is a very crude indicator of actual head temp, and IAT, which is generally beyond our control.

Originally Posted by puddleglum

Most new cars with heated O2 sensors will drop into closed loop very quickly, long before the engine is warm, so the Cl Lp guage doesn't seem of much value to me.

I have to disagree, I think it is a very good indicator of what the ECU thinks is going on in the actual cyls. Remember, a heated O2 sensor is basically heating a small bit of zirconia, essentially a ceramic thimble or waffer, to, say, 750 degC.

The ECU won't even start heating the sensor until it is reasonably certain that moisture is cleared from the exhaust, because a droplet of water will shock cool the ceramic and dramatically shorten sensor life.

The same is true with unburnt fuel. When the engine is cold and intake air is cold, the points are generally out of temp range, which is surprisingly narrow, so there tend to be misfires. Also, when the intake air is very cold, you tend to get partial condensation from the charge. So the ECU waits until all indications are for flame front temps within range and normal valve action - ie, an engine top end that has achieved a suitable operating temp.

Another reason I am a big fan of knowing when you are OL is it is a spectacularly dirty, environmental wise, condition. Cat efficiency is narrow anyway, but when you dump rich, the cat floods with CO and efficiency basically drops to 0, sending out huge spikes of NOx, etc.

Something we are working on is a much more durable O2 sensor. The idea is that you don't have to wait to heat it up, but could start it heating when the door opens or the key goes in the ignition. This doesn't solve the air charge issue, but it helps solve the pig-rich-zero-cat-efficiency intervals.

-jjf

[jfitzpat]

Originally Posted by MetroMPG

jjf - thanks for the oil info. Seems to me that if one is going to extended change intervals with synth, regularly scheduled filter changes might address the issue, no?

Partially. It removes particulates, but not any leaching contaminates. Most the newer synthetics actually address this chemically, but some of the older ones do not.

I guess the science would be, synthetic oil + regular filter changes is very reasonable. On the far more subjective front, I'm a regular oil change guy. I don't have controlled data to back it up, but I know I got 100K out of vehicles when it was rare, consistently get 250K-300K now, and have taken a number of light aircraft engines far beyond recommended TBO.

Interestedly, the only time I didn't get great engine life between rebuilds was my first experience with synthetic oil in aircraft usage, but everyone had that problem, so it was a rebuild I didn't have to pay for!

Originally Posted by MetroMPG

I can confirm that the SG reports loop status directly from the ECU; it's not inferred from other sensor readings.

I didn't think it did, though if it has just has one indicator, I presume it combines the multiple indicator bits from the PID.

Originally Posted by MetroMPG

And I agree, puddleglum: some cars go to closed loop really quickly, even in sub-sub-zero conditions. My Firefly does; but others have reported longer transition times.

See my post above, it is still a good indicator of when the ECU thinks that head temps and the flame front are in normal operating range.

Originally Posted by MetroMPG

I do sometimes monitor it when pulsing at high load to prevent going into fuel enrichment).

A good idea.

-jjf

[gone-ot]

Originally Posted by MetroMPG

For most people, winter is less of a "how do I improve fuel economy" situation than a "how do I keep the MPG decrease as small as possible!"

...+100 on that!

[moonmonkey]

living in fl my mileage will be lower in summer,, 100% humidity and 90+ temps,, i might look into a cold vest.

[puddleglum]

Originally Posted by jfitzpat

The ECU won't even start heating the sensor until it is reasonably certain that moisture is cleared from the exhaust, because a droplet of water will shock cool the ceramic and dramatically shorten sensor life.

The same is true with unburnt fuel. When the engine is cold and intake air is cold, the points are generally out of temp range, which is surprisingly narrow, so there tend to be misfires. Also, when the intake air is very cold, you tend to get partial condensation from the charge. So the ECU waits until all indications are for flame front temps within range and normal valve action - ie, an engine top end that has achieved a suitable operating temp.


Something we are working on is a much more durable O2 sensor. The idea is that you don't have to wait to heat it up, but could start it heating when the door opens or the key goes in the ignition. This doesn't solve the air charge issue, but it helps solve the pig-rich-zero-cat-efficiency intervals.

-jjf

I won't begin to debate this with you because you obviously know far more about it than I do and I've been wrong before. But, for the sake of curiosity, I will check how long it takes my car to get to CL from cold and see what the temp reads when it does. I was under the impression that the O2 sensor in my car did start to heat as soon as the key was turned on or at least as soon as the engine started. Maybe I'm wrong. Now you've got me curious.

[puddleglum]

Originally Posted by MetroMPG

jjf - thanks for the oil info. Seems to me that if one is going to extended change intervals with synth, regularly scheduled filter changes might address the issue, no?

I wouldn't recomend this. I was told I could do that the first time I used Synthetic in a previous car. The oil couldn't hold all the condesation in suspension and caused a lot of rust.

[jfitzpat]

Originally Posted by puddleglum

I won't begin to debate this with you because you obviously know far more about it than I do and I've been wrong before. But, for the sake of curiosity, I will check how long it takes my car to get to CL from cold and see what the temp reads when it does. I was under the impression that the O2 sensor in my car did start to heat as soon as the key was turned on or at least as soon as the engine started. Maybe I'm wrong. Now you've got me curious.

No, not heated until condensation is cleared. And not CL until all the indications are for in range combustion and the O2 sensors are at temp.

As far as first, you should generally be CL long before you see much in terms of ECT change on most newer vehicles. In older vehicles, ECT was a thermal switch. On, normal, off, timing retarded and richer for cold operation. Then it advanced to a thermister, with multiple steps of enrichment, etc.

But think about what "Closed Loop" means. It means that the ECU is targeting lambda 1.0 for emissions purposes, so no extra fuel is involved. So, if the system reports "closed loop", the ECU has made the decision for normal, not cold engine, operation. On some vehicles, you can pretty much count on this being a specific ECT. But on many new vehicles, this is not the case. They are making the decision on a combination of other sensors instead of just accumulated radiant heat.

The problem with relying just on ECT is that energy goes three places, work, CHT, and EGT. EGT is put to use in driving emissions systems, and work moves the car. But CHT is, beyond a certain, fairly low, threshold, wasted energy, and destructive, since high CHTs lead to things like abnormal combustion.

So, modern engines try to minimize CHT with lots of techniques, including sophisticated timing systems, which move peak pressure. So, in cold weather operation, you've got ambient temp (and many modern ECU's have AAT even if there is no outside air temp in the cabin), which impacts how much air cooling is occuring, and ignition system trying to hold CHT down, and a cooling system which is meant to carry excess heat away, but whose efficiency is also impacted by AAT and air mass... (and so on)

If the decision was just a simple case of 'heat X has found its way into the coolant', there would be cases where vehicles stayed open loop for no valid reason, which would be bad for emissions.

-jjf

[jfitzpat]

Originally Posted by puddleglum

I wouldn't recomend this. I was told I could do that the first time I used Synthetic in a previous car. The oil couldn't hold all the condesation in suspension and caused a lot of rust.

This is what I meant by "leaching contaminates" above. Some synthetics supposedly do a better job at this than others, but I'm an 'oil is cheap compared to engines' guy.

-jjf

[gone-ot]

...an ounce of prevention versus a pound of cure here too.