lean burn rules~!

[coolwHip]

Hey,
So I'm in this Meteorology class and we’re talking about emissions related to cars and how the industry controls them through catalytic converters and burning of fuels. This guy says in class, I got lean burn on my car and how does it affect emissions? I was like; whoa...I haven't heard anyone talk about lean burn from anyone ever. I was like, yea I got lean burn too but we didn't mention what car we had lean burn. This guy looks like a hippie or a computer engineer of some sort (very smart guy) so I figured he put in lean burn himself which we did the same on my car. So class ends and we talk. He said his 1993 civic VX came with lean burn but was from Oregon. I told him about our lean burn which was incorporated through coding he was like, Wow! So anyways long story short, I start researching about the civic VX because California loves to raise high gas prices. I was reading but I could not find any threads that explained lean burn in terms how swappable or ease of swap from California’s ECU to a federal ECU.

So my questions are
Is lean burn only federal ECU’s?

Can I buy a California Civic VX with a D15Z motor and put a Lean Burn ECU in it?

If so which ECU’s come with Lean burn and how do I Identify it?

Is the lean burn code on a PROM style chip? Can I take the “bin” file and place it on a EEPROM and it’ll work in a California Civic VX? (Easy to make chips as I do this for my other car)

If it were able to burn a chip what else would I need to do on a California car to go into lean burn mode?

What is the easiest way for me to go about this process as I live in California but want a Civic VX with lean burn?

Cheers
Cool wHip ~ stewie griffen

[JohnnyGrey]

There's more to lean burn than just the ECU. The actual engine is able to get the most out of lean mixtures. I know that the HX is effectively a SOHC motor at low RPMs, and opens up the other four at higher RPMs. As for the VX, I have no idea. Not to say that you can't lean out any engine, you can, but you won't get the same results. I've got a mild lean-burn mod on my Cavalier, and it seems to give maximum benefit at around 16:1 AFR. Much leaner than that, and economy actually drops. Parts of the fuel mixture actually get too lean to burn.

Just like the VX/HX, I needed a wideband sensor to do this. You'll also have to install one to get a reliable lean burn. At this point, you can go for the VX/HX ECU (if all the sensors are compatible), or you can fashion a circuit that will train the stock ECU around an AFR of your liking. It's easier to pass state inspection this way. Just crank her back to 14.7:1 and she passes with flying colors.

[MetroMPG]

I laughed when I read new user: CoolwHip. Funny, funny. Ever since seeing that, it's one of those words that's etched in my head ... in somebody else's voice. Go figure.

I can't really offer any more info than JohnnyGrey has, but there are a couple other VX owners who may chime in.

[diesel_john]

that word whip , does that evolve from when we use to have to crack the whip to start the horses?

JohnnyGrey- i would like to learn how to lean out my gas engines when I am not loading them heavy. On a '91F250 302 for example the ECU is not reprogrammable is it? I did a brute force lean burn by putting a 0 to 10 ohms reostat in series with the injector pwr. And as I dial in more resistance the voltage to the injectors decreases, the ECU tries to compensate but evenually the 02 voltage starts dropping and I can get it down to 0.24 volts and the engine will still run. This is not a wide band 02. comparing your wide band to a stock sensor, if you had to quess how lean do you think I am. i am going to try it with a different mileage computer as the one I am using reads injector pulse width which of course gets wider as the ECU tries to compensate for low voltage.

[JohnnyGrey]

JohnnyGrey- i would like to learn how to lean out my gas engines when I am not loading them heavy. On a '91F250 302 for example the ECU is not reprogrammable is it? I did a brute force lean burn by put a 0 to 10 ohms reostat in series with the injector pwr. And as I dial in more resistance the voltage to the injectors decreases, the ECU tries to compensate but evenually the 02 voltage starts dropping and I can get it down to 0.24 volts and the engine will still run. This is not a wide band 02. comparing your wide band to a stock sensor, if you had to quess how lean do you think I am. i am going to try it with a different mileage computer as the one I am using reads injector pulse width which of course gets wider as the ECU tries to compensate for low voltage.

Modulating the injectors in this fashion probably won't give you consistant results. They're "on/off" devices, so by supplying low voltages, the cylinder to cylinder spray pattern and volume could vary considerably. As long as your car is in closed loop mode, there's no point in attempting mods like this since the ECU will compensate as far as it will go, then throw a CEL fit.

Your narrowband sensor is a poor indicator of AFR. Treat it like a digital signal, where >0.45v is rich and <.45v is lean. What actual voltage you get will vary with each sensor, exhaust temperature, ECU bias voltage etc, so there's no real way to know. Plus, if the voltage stayed at .24 for long, that's probably the voltage floor of the signal. It indicates a lean mixture, but there's no way to say how lean you were running.

A wideband lets you do so much more. Mine is made by Bosch and the driving unit is made by AEM. It puts out 0-5v which represents linearly ratios from 11:0.1 to 18:0.1. The driving unit also has a narrowband emulation mode that does switch back and forth over that .45v point at 14:7.1. This is fine if you want to run at that ratio, but we don't.

So we need a box that puts out either 0v or 1v depending on whether or not that 0-5v wideband signal has crossed a certain threshold. If the switch point is set at 4v, the motor will run quite lean (around 16:1), but the ECU will believe it's running at a steady 14.7:1 and will not throw a CEL. Also, it will be training itself around that ratio, and will hold it steadier than you could in open loop mode.

With a narrowband sensor, you're working blindfolded. The hot rod guys prefer to tune with widebands, but in a pinch, they can tune with a narrowband. Their only concern is running rich so nothing blows up, so as long as the O2 reads high and the engine sounds happy, everything is fine. For economy though, you need tight control over the AFR.

As to whether or not the ECU in your truck is programmable, I would say not for closed loop operation, and we're not interested in the open loop tables, they're for WOT operation. Also, I doubt Ford would implement a lean burn system since it is not emissions legal. I have no idea how Honda got away with it in the HX/VX.

It is technically possible for an ECU to run a lean burn on an engine equipped only with a narrowband sensor. In fact, that's exactly what GM does on cars it sells outside the US. That narrowband sensor is only good for switching around 14.7:1, so the ECU establishes fuel tables for that mixture. Once you get on the highway, the ECU goes into lean burn mode, which is actually open loop. Since the ECU already has a well-established fuel table that produces mixtures very close to 14.7:1, it can scale that table to produce whatever fuel mixture it needs. For example, 92% to run at 16:1. Because the narrowband sensor will read consistantly lean, the ECU occasionally wanders back to 14.7:1 to confirm that its tables are correct, then goes back into lean burn mode. On US ECUs, the mode is disabled.

[diesel_john]

I am definitely in open loop. I know the injectors should be either on or off but there must be a gray area there because it doesn't seem to be a knives edge. Maybe they open slow and part way open and I only do it when cruising at steady state. Yeah who knows about the cylinder to cylinder variation without an 02 in each exhaust header. Well i could do 8 channels of temperature, i guess.
Without being able to program the ECU maybe i would be better off reducing the fuel pump voltage and therefore the fuel pressure to force the mixture lean. The ECU can't deviate more than 10% or so from the fuel tables can it? This old truck is speed/density, bank injection. Obviously I would like to able to see and control pulse width. What is my alternative get some kind of after market programmable fuel management system. Staying in open loop and being able to the adjust the offset from theoretical 14.7 would be cool.

[LostCause]

The VX engine (d15z1) is the same anywhere in the world, as far as I know. People have swapped in JDM d15z1's and registered them successfully in CA.

The only difference is the O2 wire and ECU. The CA model uses a 4-wire narrow band O2 sensor while the Federal model uses a 5-wire wide-band (which is $$$). I believe the Federal ECU is the P07 model. Unlike most other Honda ECU's, it cannot be modded.

On GS, one member made the sensor/ECU swap on his VX and still easily passed his CA smog inspection. For those who care, NOx can be partially dealt with through a NOx adsorber as used on the Insight. The Insight entered lean-burn much less often (and less aggressively) and purged the adsorber through enrichment, but its basic operation would transfer over to a VX.

Most OEM lean-burn engines that I've seen increase charge turbulence and/or use a specially crowned piston to concentrate the gasses. Honda partially closes one intake valve per cylinder to improve what they call "swirl."

Extensively recirculating exhaust gasses accomplishes the same goal as a lean-burn engine without the emissions issues.

Originally Posted by diesel_john

On a '91F250 302 for example the ECU is not reprogrammable is it?

You can probably build a MegaSquirt (w/ sensors) for $100-200 and gain much wider control over your engine. While it would cost more, I think it would be more worthwhile than tricking your ECU into lean burn. Just a thought...

- LostCause

[JohnnyGrey]

The only difference is the O2 wire and ECU. The CA model uses a 4-wire narrow band O2 sensor while the Federal model uses a 5-wire wide-band (which is $$$). I believe the Federal ECU is the P07 model. Unlike most other Honda ECU's, it cannot be modded.

On GS, one member made the sensor/ECU swap on his VX and still easily passed his CA smog inspection. For those who care, NOx can be partially dealt with through a NOx adsorber as used on the Insight. The Insight entered lean-burn much less often (and less aggressively) and purged the adsorber through enrichment, but its basic operation would transfer over to a VX.

If you're sure the motor will work, do the Federal ECU swap. The 4-wire sensor is a dead giveaway that the CA model doesn't support lean burn.

I'd imagine this absorber "purging" process cancels any benefit from burning lean.

John, how are you certain you're in open loop, is the O2 unplugged? I tried doing this on my Cavalier, but the variation in AFR was too wild to run reliably for any length of time. I would advise against slowing down your pump. If it produces less pressure than the regulator needs to open, the fuel supply line will slow to a crawl and the return line will stop. Depending on the design of your pump, it may be cooled by the fuel that runs past it, which will not be much if you go below regulator pressure. Try finding an adjustable fuel pressure regulator instead.

Be careful if you do this, because you will have leaned out your WOT mixture as well. If you need a sudden burst of acceleration, you could cause severe detonation. My car stays in closed loop at around 16.5:1, but if I stomp it, open loop is still around 12.5:1, so I can still get full power out of my engine safely.

[diesel_john]

Originally Posted by JohnnyGrey

John, how are you certain you're in open loop, is the O2 unplugged?

No, the check light is on. The EGR is unplugged. Unpluging the 02 is an idea.

I tried doing this on my Cavalier, but the variation in AFR was too wild to run reliably for any length of time. I would advise against slowing down your pump. If it produces less pressure than the regulator needs to open, the fuel supply line will slow to a crawl and the return line will stop. Depending on the design of your pump, it may be cooled by the fuel that runs past it, which will not be much if you go below regulator pressure.

The pump in the tank is liquid cooled. The gas goes thur its motor.

Try finding an adjustable fuel pressure regulator instead.

I have a check valve in the vacuum line to the regulator to limit fuel press. to 36 PSI.
Be careful if you do this, because you will have leaned out your WOT mixture as well. If you need a sudden burst of acceleration, you could cause severe detonation. My car stays in closed loop at around 16.5:1, but if I stomp it, open loop is still around 12.5:1, so I can still get full power out of my engine safely.

JohnnyGrey, I would like to get into tuning these injected gasoline engines. What is a good direction to head so I don't have redundant equipment? What is the fifth wire on a wide band, temperature? I assume the other four are heater pwr, heater grnd, signal, signal grnd.

I'll look up this MegaSquirt.

[JohnnyGrey]

The extra wire is bias current. There is no easy way to hook up and monitor the sensor alone. You need either a gauge or a controller box to drive it. Or you can look at Bosch's data sheet for it and try to make your own.