Lean Burn all the way!

[brucepick]

Thanks guys.
I previously gave it a seafoam treatment, twice. A couple months ago. Instead of sucking it in via a vacuum hose I poured it in slowly, into the big corrugated rubber air intake hose - right after the air cleaner which I temporarily disconnected. I've used the vacuum-hose method before on my Volvo 240, this method seemed to work the same - made lots of smoke and needed extra rpms to keep the idle going. And, lots of smoke and junk when restarting afterwards. I'm sure I cleaned out lots of junk that way, myself.

The shop used a cleaner they sucked into the engine via a vacuum line. Also supposedly produced lots of smoke/junk when restarting afterwards - but I wasn't there for that. Seems to run better now though.

[RobertSmalls]

The first video at http://ecomodder.com/forum/showthrea...ions-8629.html mentions that the computer will enrich the mixture now and then to regenerate the catalytic converter. This behavior would obviously involve exiting lean burn. I'm not sure if your cat is of the same type, but if so, you'll want to decide whether the occasional fuel dump is required to keep your cat alive. Find out, because IIRC, your cat costs buckets of ducats.

I'll watch this thread with interest, since I hope to join the lean burn club soon.

[brucepick]

Originally Posted by RobertSmalls

The first video at http://ecomodder.com/forum/showthrea...ions-8629.html mentions that the computer will enrich the mixture now and then to regenerate the catalytic converter. This behavior would obviously involve exiting lean burn. I'm not sure if your cat is of the same type, but if so, you'll want to decide whether the occasional fuel dump is required to keep your cat alive. Find out, because IIRC, your cat costs buckets of ducats.

I'll watch this thread with interest, since I hope to join the lean burn club soon.

Robert,
That's probably happening. I sure wish there were a screen to tell you what's going on, or a manual. Anyway, as long as I can keep it from happening often, I'm pleased.

Here's hoping you do join the Lean Burn club soon!

There's a thread currently on honda-tech.com that you should look at.
better gas mileage out of an eg - Honda-Tech
Near the bottom of the first page there's a post by member HXor. The thread is now up to 4 pages and includes a lively discussion of lean burn and FE driving. IMHO the information here at EcoModder is better, but it's an interesting discussion nonetheless.

[theunchosen]

It wouldn't keep the at alive in terms of the cat being destroyed. . .it keeps the cat active.

I think I made a note of this, but maybe it was on another thread. To get by EPA you can't have any arguments like "well the car is really not producing any HCs in this mode so it doesn't need a cat during this. . ."

They slap you with a fail and send you packing. So Honda had to ensure that the cat stays up at operating temps. During LB EGTs are higher but the cat is going to be acting like a huge exhaust radiator. Its a big metal box with lots of wind exposure and no HCs are getting burnt inside so its surviving in the operating range only by the higher EGTs. To ensure to the EPA's satisfaction that the cat stays hot enough to burn the one in a million HC that slips through the engine unburnt it has to kick out of lean burn to reheat the cat.

It won't damage the cat to run at low temperature(assuming there are no HCs in the exhaust flow, otherwise its going to get covered in soot).

[rkcarguy]

I've heard(can anyone verify) that the base problem with much of this technology is that our EPA is corrupt and emissions limits here are based on emissions per X amount of fuel used, not per mile. So a big guzzling SUV getting 10mpg can emit pollutants at the same percentage per unit of fuel consumed, but if the 35mpg car emits 1.01 times the pollutants of the SUV, but overall it's less than a 1/3rd of the total emissions per mile of the SUV, it still fails.
Regarding the lean burn, the OBD-2 system uses the knock sensor to keep lean burn at the edge of detonation, instead of the wideband o2 sensor like the OBD-1 VX. Fuel is pulled back to the brink of detonation, not the timing.
The perimeters of this computers tuning were worked around emissions, not efficiency. I don't doubt that the system exit's lean burn and dumps fuel to heat the cat to keep it operating. I've heard that the new diesels are doing the same thing and have lower mpg ratings as a result.

[greasemonkee]

Originally Posted by rkcarguy

Regarding the lean burn, the OBD-2 system uses the knock sensor to keep lean burn at the edge of detonation, instead of the wideband o2 sensor like the OBD-1 VX. Fuel is pulled back to the brink of detonation, not the timing.

Are you sure about this? Haven't studied too much into the D15Z3 operation, but both engines have the wideband. An ecu must hear knock before it can retard timing and honda's knock boards (at least the OBD 1 versions) were the equivalent of silicon excrement. I find it difficult to believe any manufacturer would intentionally set a system up ignition and timing wise to operate at the mercy of the knock sensor which would need to hear detonation in order to maintain efficient fueling. Once detonation does occur, air/fuel readings (via the O2) will go lean and skew the fuel trim. If this were the operating principal, it is often difficult to achieve detonation at low manifold pressures. It would be likely that in the instance of leaner than stoich operation, if continued to be leaned out, flame speed would become increasingly slower until misfire would ultimately set in without a whisper of a knock. Besides that, all detonation isn't audible nor detectable by a piezoelectric device, there are levels of detonation - detectable or not, it still is a hindrance to power and economy.

This is theory, but stranger things have been known to happen in the real world with engineers.

[stevey_frac]

Originally Posted by greasemonkee

Are you sure about this? Haven't studied too much into the D15Z3 operation, but both engines have the wideband. An ecu must hear knock before it can retard timing and honda's knock boards (at least the OBD 1 versions) were the equivalent of silicon excrement. I find it difficult to believe any manufacturer would intentionally set a system up ignition and timing wise to operate at the mercy of the knock sensor which would need to hear detonation in order to maintain efficient fueling. Once detonation does occur, air/fuel readings (via the O2) will go lean and skew the fuel trim. If this were the operating principal, it is often difficult to achieve detonation at low manifold pressures. It would be likely that in the instance of leaner than stoich operation, if continued to be leaned out, flame speed would become increasingly slower until misfire would ultimately set in without a whisper of a knock. Besides that, all detonation isn't audible nor detectable by a piezoelectric device, there are levels of detonation - detectable or not, it still is a hindrance to power and economy.

This is theory, but stranger things have been known to happen in the real world with engineers.

I could be wrong, and i haven't studied them either, but don't these lean burn engines all have LAF (Linear Air Fuel) Sensor systems? They can detect how lean the burn is, and then run at 16.0 AFR? If they ran much leaner then that the EPA would refuse to license it on account of the amount of NOx they would produce.

[greasemonkee]

According to Recardo's studies, peak thermal efficiencies generally occurred at about 15% lean which would put the AFR at roughly 16.9, that is to my knowledge, a typical number and is due solely to the fact that combustion temps are colder. Any leaner and flame speed drops off drastically.

According to Stone, highest flame temps occur just rich of stoichiometry, however, sufficient oxygen must be present for NOx to form so it occurs just lean of stoich.

Low ratios of EGR dilution significantly reduce NOx emissions. The catalyst is the booger, it must receive a burst of rich followed by oxygen; a continuous cycle.

Credits to Toyota Motor Sales

[Superturnier]

Originally Posted by greasemonkee

According to Recardo's studies, peak thermal efficiencies generally occurred at about 15% lean which would put the AFR at roughly 16.9, that is to my knowledge, a typical number and is due solely to the fact that combustion temps are colder. Any leaner and flame speed drops off drastically.

According to Stone, highest flame temps occur just rich of stoichiometry, however, sufficient oxygen must be present for NOx to form so it occurs just lean of stoich.

Low ratios of EGR dilution significantly reduce NOx emissions. The catalyst is the booger, it must receive a burst of rich followed by oxygen; a continuous cycle.

Credits to Toyota Motor Sales

I've been wondering why an (older) EFI system switches between lean and rich fuel mixture instead of keeping very close to 14.7:1 ratio. (the 14.7:1 is said to be best for killing emissions) Is it because the control system is not capable doing it or is it for the catalytic converter that actually needs to have different poison after another poison to work properly? Not just steady mixture all the time?

[stevey_frac]

Originally Posted by Superturnier

I've been wondering why an (older) EFI system switches between lean and rich fuel mixture instead of keeping very close to 14.7:1 ratio. (the 14.7:1 is said to be best for killing emissions) Is it because the control system is not capable doing it or is it for the catalytic converter that actually needs to have different poison after another poison to work properly? Not just steady mixture all the time?

The original closed loop systems used a O2 sensor that really only detected two states: Lean, and Rich. If the sensor said rich, it would get leaned out. If the sensor said lean, it would richen the mix. The cross over point for these sensors was 14.7:1.

Is this what you meant by switching between lean and rich? These systems were fairly good at holding close to 14.7:1.