Convenient lean-burn for all?

[theunchosen]

In light of something Tasdrouille said on a thread about diesels, wouldn't it be possible(maybe even easy) to insert a potentiometer(more accurately a variable resistance box) between the MAF and the ECU?

Leave the potentiometer with 0 resistance if you want the engine to perform as normal and increase the resistance slightly to induce leaner burning. The further you turn it the wider open you'll be able to run the throttle(and hence the more air you can get into the engine) without dropping any extra fuel.

The advantage would be you could install turbos and ram air intakes with the intent of jacking up your lean burn mode. Also it would allow the option to engage lean burn whenever. . .not just when some engineer decided most people would use it without damage.

Problems? opinions?

[SVOboy]

This is what the EFIE does. I don't recommend it. It will throw your engine way out of tune, and if it doesn't reduce your fuel economy from inefficient combustion, you'll be spewing all sort of pollution. The Honda lean-burn system is incredibly complex for a few good reasons.

[Daox]

I completely agree with SVOboy for said reasons. You'll be spewing out a fair amount of NOx which has the lovely side effect of creating acid rain.

[theunchosen]

Originally Posted by Daox

I completely agree with SVOboy for said reasons. You'll be spewing out a fair amount of NOx which has the lovely side effect of creating acid rain.

Yep, if I just lean burn a little. The instant you go above the stoich you start doing that, so you could just set the initial setting for the potentiometer to be greater ratio than that.

So you have the option of running normal or running pretty heavily lean-burn(26:1+). At 26 you're on the asymptotic downcurve of NOx so you'll be producing some but not a mountain or as much as diesels produce in their driving range.

That said I'm really considering it for a couple of reasons.

1.) Its hard to convert heat in the exhaust to useful FE work.
2.) If I am going to have to suffer high pressure drag on the nose of my car shouldn't I put that to work for me?
3.) It could entirely replace cruise control with a DWL cruise control(Throttle open all the way all the time and just push the resistance down as you want more power).

Besides you could incorporate it in a hand throttle unit. And you could have the pleasure of explaining that no it is not turbine powered.

[tasdrouille]

Usually the O2 sensor has the last word. It'll say your MAF is out of wack, throw a CEL and just ignore it.

You'd need to take care of both the O2 sensor and the MAF.

[theunchosen]

I think they are both operating on 0-5 volts as the relay. I am pretty sure 5 for both means that throttle is wide open and there is no O2. I could be wrong in that the O2 could be 0 for no O2 and 5 for way too lean.

Either way I am prety sure I can connect them to the same switch and have it run in reverse on one and forward on the other(with two dials/rods connected together and just switch the direction of resistance if they are opposite or leave the same if they are the same).

I don't forsee it causing extra knock or pre-ignition, but I could be wrong. Christ, aerohead anyone?

[Concrete]

tasdrouille is right - at least for my vehicle - O2 sensor rules
because it is there to protect your Cat

but you could tweak the O2 output

I have exactly the issue you describe
cleaned up the intake - now I get too much air at mid throttle
but the O2 over rides the tables and adds fuel

[theunchosen]

The only reason I could think this might damage the cat is in fluxing between lean and regular burn(the cat will have something to burn up and then it will cool, fatigue thermal wear).

But as long as I . . .modulate the boltage from the MAF and the O2 I don't think there are any other sneaky sensors to trip me up.(?)

[Daox]

You're right, at very high AFRs NOx does go back down. However, most engines can't handle AFRs of much more than mid to high teens. Honda in their lean burn engines specifically use high swirl/tumble heads in order to achieve their 20+ AFRs. Without modification, a normal engine will have major problems with misfiring.

Conventional zirconia narrowband O2 sensor outputs are 0-1V, not 0-5V. I'm not sure about the titania sensors. They are different, but are rarely used. Also, the EFIE will not be accurate at the high AFRs you are wanting to run since zirconia O2 sensors only have high resolution near 14.7 AFR. Once you get outside that, they have horrible resolution. You'd have to go with a wideband system that simulates a narroband signal.

I haven't played with things enough to know if other sensors will trip you up or not. But, I have read to the effect that they may.

[theunchosen]

I've got access to some engines that are destined for the scrap heap so I'll be testing it on those over the summer. If they survive the initial WOT, low injection for thirty minutes without spitting out any negative data I'll move to in car trials.

I suspect the misfire might be a problem so I'm thinking of setting up a supercharger(already have it) with intercooler at say 10 Gauge PSI and then releasing the pressure down to 3 psi. IF the intercooler works enough the intake air would be substantially cooler than air temps(only a problem in the summer) and would need enough BTUs to warm it back up to keep it under conditions of spontaneous ignition.