Modify O2 sensors
 

Has anyone modified their O2 sensor for more of a lean burn? If the sensor oscillates between .8 Volt(rich) and .25v(Lean) why can't you tap into it with a pot and have the voltage read a constant .3v? Will the ECU think it a fault since it's not fluctuating and trip a CEL? I guess if you have two sensors you need to modify both since the talk to each other. Thoughts?

The thing about narrowband o2 sensors is that they suck. They don't really read AFRs, they just read stoich and then everything is is lean or rich. But to do this I you'd make it think it was rich so it leans itself out, thoughhhhhh I'm not a fan because I'd rather my car be knowing what's going on, because if a problem were to occur with afrs then it wouldn't be corrected properly, oh no. Not that there's really too much risk, but I'm not a fan of running leaner than the car ought to, anyway, at least not too much.

Anyway, what happened to the accord?

I came across a DIY which addressed this issue. What it had, basically was a couple of op-aps set up so that when the sensor voltage got to 0.20, the output would toggle to deliver the .08 to the ecu.

From what I've read, a regular Oxygen sensor is functionally not linear when it is crossing over, it's almost more of a switch that toggles at "about" a stoic mix, but it's not calibrated, so instead of trying to read a actual value, they just keep adjusting the mix, so that it is constantly going up and down, criss crossing through stoic.

I don't think their is any reason not to do this. I don't know how much leaner it's going to go, than stock, because, my understanding is the switch point is like14:1 or 15:1, somewhere in that range. The 5 wire sensor, like is used on the HF and VX go up to somewhere in the range of 25:1, from what I've read, so even if you got the switching range tightened up, to the leaner side of the window, I don't know how much of a change we'd get.

On the other hand, with the mileage some of people are getting, it could make a bigger difference, in mileage, than it would for the average driver, on the highway.

The HF doesn't use a 5 wire, but the HX does.

Anyway, normal cars don't really benefit from going lean so much. I posted up an article a while back that dyno tested leaning out the ecu on an RSX and they found the best position was 15.7:1 and that, along with timing and cam timing yielded a total of 2% FE increase, :p

What does the HF use for an Oxygen sensor?

1 wire for the win!

There is a device out there for changing your o2 sensor... It is called the EFIE and you can get it at Eagle Research

https://www.eagle-research.com/products/pfuels.html

But I also think a POT would be much easier (and cheaper) to install.

The accord went away. The son who did not want it decided he did:(. But that's good because he was driving a SUV that got 12MPG so I'm glad he has it if he'll park the tank.

Do you have a link to the DIY? I don't think that it would run much leaner the 15.1 but I think with additives and heated fuel you would see a much better increase in FE with it. I don't think you would hurt anything because if you WTO it goes to open loop and if you try to get it too lean it will go to open loop.

Inspection would be interesting I guess. I did mine last month and the guy pops the hood and is like WTF and then starts quizzing me about the VG heated fuel belly pan etc.:)

Thanks. I'd need 2 and that's a little to much denero for me. Plus 4-6 week for delivery.

Acetone! I tried it out in the middle of summer, and for the first time ever had my coolant boil over, I decided I liked my head gasket and opted for a tow. I also saw a personal best RT of ~36mpg out of that car during the same time. I speculated that my engine was running leaner, but I wasn't sure. Then I saw a post about how acetone doesn't do anything special in the combustion chamber, but depending on your oxygen sensor catalyst, can make the ECU think you're running *richer than you are, with the result being a lean running condition. Of course this is all anecdotal, YMMV. :D

*I think it works by stealing atomic oxygen after the catalyst has split it, which reduces the current and the ECU thinks there's too much fuel and leans it out. Of course I'm no chemist, so who knows?

Eagle Research tries to say that you need 2 EFIE's but you only need 1. I found that out several years ago. Fran Giroux and I figured out that the only thing the rear sensor does is verify that the cat is working. Therfore, as long as the rear sensor sees a smaller voltage, the ECU is cool. The front sensor is the only one that controls the mixture so it's the only one you need an EFIE for. Plus, you save $50.:D

https://www.lubedev.com/smartgas/ultra5.htm


Cover Oxygen Sensors with Aluminum Foil: Wrap your oxygen sensors in the exhaust pipe with 7 to 10 layers of shiny foil.

Advantage: The car computer system depends on the oxygen sensors to adjust the air-fuel mixture being fed to the engine. The cooler the exhaust gases, more fuel gets sent to the engine. The hotter the exhaust gases and the oxygen sensor, less fuel will be sent to the engine.

Directions: To seal maximum warmth inside the area near the sensor, insulation in the form of Reynolds Aluminum Foil is employed to insulate the oxygen sensor. Wrap five inches in front and five inches after the sensor to keep it warmer. We double a one-foot section of foil and wrap that around the pipe and around the sensor itself. Do not remove the sensor. Then we repeat the process several more times. Finally we use .030" copper or aluminum wire to wind around the aluminum foil to keep it from blowing away and be sealed against water. The wire comes from any welding supply. The goal is to fool the car's narrow band sensor and computer into sensing too rich a mixture so it adjusts to a slightly leaner mixture and possibly a slight advance in timing. The end result is smoother engine operation and better MPG. This trick is especially important in severe winter climates. My catalytic converter went bad after 147,000 miles. A large piece inside was blocking the exhaust flow and cost me a drop of 12 MPG. I replaced both oxygen sensors and the catcon and wrapped the sensors with aluminum foil so my MPG came back. Do not wrap with ordinary gray duct tape as it will burn off. Have your mechanic CHECK that catcon on your car. Do not take it for granted because all the good changes you make for mileage could be negated by such things as a bad catcon or bad plug wires or bad oxygen sensors some such hidden defect.

I'm pretty sure that adding resistance to the O2 output makes the mix richer. I have an EFIE the V6...helps some.

Yeah, Iono what that lubedev site is trying to say now, but the oxygen sensor is not an egt sensor. That's not how it works, making it hotter won't do jack since it doesn't measure temperature.

He says finding "good" gasoline can benefit you 35%, and I say he's full of hot air.

Maybe it heats the sensor faster to go to closed loop. My exhaust already has a OEM shield aound the pipe next to the sensor.

That may be so, but that's not what it is claiming. Then is has some BS story about how he killed his emissions system, lost FE, replaced it, gained it back, then seems to act like the foil is some great savior in the whole thing.

If this is indeed insulation, as he says, it will prevent it for warming up more quickly.

True with the temperature reading, but many sensors have heaters for operation (many 4-wire models). I'm thinking that with an increase in temperature, the element reading changes. That's all I got...

RH77

The heater only gets it to run in closed loop faster. I moved my o2 sensor a foot closer to my enging (4" from the ports now) without seeing any dramatic difference.

What does lean burn really do, anyway? I keep hearing that it doesn't help a "normal" engine but I can't figure out why. Reduces power, forces driver to open throttle more, reduced pumping losses while cruising for increased efficiency? That's all I can think of since you theoretically reduce power output in step with the leaning effect.

If you really mean business, I would source wideband O2 sensor and develop a hack box that translates between that and your stock ECU. You set the target voltage range on the wideband that correlates to your desired A/F ratio, then the box monitors the wideband and generates the right high/low outputs so that the engine thinks it's around stoich but it is actually doing what you want. To do anything with the stock o2 sensor is just a rough and only semi-controlled approximation of lean burn. The best system would allow you to switch manually between stoichiometric and your desired A/F ratio in case things get too hot, or better yet monitor the ECT itself and switch over automatically if things get out of hand.

I'm not sure why "lean burn" doesn't do much for normal people, but I can tell you that the p07 ecu for the vx has a whole other chip just for it that no one has been able to figure out how to decode, :p

Anyway, we tried leaning out dan's stock ecu but it just said no. I just think most engines don't have the combustion efficiency at that range of AFRs, but I'm prolly full of it.

Lean burn improves combustion efficiency and torque, with the trade off being less hydrocarbon and more NOx pollution. Pumping losses are also reduced because more air is allowed in the combustion chamber and heat losses in the cylinder are reduced too, although I'm not sure how that works, probably has something to do with the size of a lean burn a/f charge.
Edit- Found something that says controlling swirl allows for stable combustion and better lean burn. Which makes sense, because hot spots in a cylinder could lead to pre-ignition, so controlling how the intake charge combusts (even combustion/heat distribution) is critical to being able to run lean without pre-ignition. Running an a/f ratio of 25:1 compared to 14.7:1 supposedly reduces fuel consumption by ~20% over the Japanese test cycle.

Indeed. Something the VX and HX have are vtec-e, which promotes swirling, especially in the VX with its bowled pistons that were designed to inhance the swirling created by having only one intake valve open.

Yup, reminds me of the long tuned intake runners, and heads ported for swirl in the old vw TDs. Now gasoline cars are using direction injection, and diesels are coming with ~16:1 compression ratios, I suppose they'll converge with HCCI multifuel engines.

Woot for long tuned intake runners. I wish someone would tell me what's best on the exhaust side for FE, but I can't figure it out. I suck!

I don't think exhaust tuning won't help much with FE because your limiting factor is pumping losses, which is related to rpm and gearing. Generally, manufacturers will tune an exhaust so that they can get a scavenging effect near peak hp, that way they can get the equivalent of a few extra psi of boost w/o a turbo. In order to do this you have to tune the exhaust based on each exhaust wave (acoustics, they travel at something like 800ft/s) so it will pull the exhaust gasses out of the piston near peak power, and allow even more air than normal to enter, and ultimately more fuel/power. I think this is why the drop off in torque/hp after peak isn't symmetrical compared to the increase...

Can you point me to your source of info please?