Convenient lean-burn for all?
 

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?

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.

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.

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.

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?

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

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.(?)

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.

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.

That sounds like a lot of fun theunchosen! I wish I had the time to do that kind of stuff. I also wish I had an engine or chassis dyno at my disposal. :D

An engine dyno would be nice in this situation, but I kind of have something close. . .

My grandfather(not the one with the Porsche) has more or less a private junkyard of cars. At least a hundred. Most of them are 60s models but there are some newer and some of them are my old cars(which I will stake a claim on the engine for this project).

He also has several generators rated for different amounts of power. one is 75KW and they are all not fully assembled as you would buy them. He has them in a bank of engine-driveshaft-generator so he can use a common fuel tank(In ground and massive like you find at your local Shell). My plan is to just mate the shaft of the old Taurus to the 75 and not gas it very hard at all for the tests since the danger zone is at very lean mixtures which the engine is only going to accomplish at low-rpm-low-fuel. Oh and then just measure the power output of the generator. It won't be an even match because its converting it to AC but I don't need an absolute reading. . .I just need the relative amount of power that the lean burn gets. So I know what the Taurus v8 produces at X(big) rpm, it produces x(little) AC electricity and the lean burn produces this percent less of x(little).

He is likely going to hate me because I don't really have time to do this either but since I don't have to take tests or study over the summer I can afford to sleep only a few minutes a night ^_^

Really its not about the power curve or the relative power though. As long as I can watch the DMM and see its producing an even power supply I know its working(no check engine lights on my non-existant gauge cluster). The test is for survivability to make sure this won't kill my B series, which is important. The Taurus V8. . .not so important.

Try using a water injection system with your lean burn. I've been doing some research and found that it can replace approx 10-12% of the fuel and may also allow you to push lean burn leaner. An added bonus is that it should reduce NOx emissions as well.
If your looking a the typical honda lean burn engine math says you'll want about 16cc/min of water injection, and it will have to be triggered by lean burn engaging via a relay or something. It's my lastest brainstorm to try and get more out of the lean burn setup.

Speculation on why thats beneficial to the engine?


I'm guessing the cylinder is going to go through the saturation dome at some point before ignition and if it does this would drastically cool the cylinder charge.

I suspect the benefit is created because the cooler mix is more flammable than the hot mix(air at temperatures close to oxygen's boiling point is much more flammable)?

Any other reasons?

I'm asking because maybe it can be done more efficiently. Also any potential dangers? As long as the water does stay that long it won't have time to cause/assist in serious oxidation but I suspect it might make the pistons and cylinders more brittle?

The way I understand it, the lean burn pushes the AFR to the limit of detonation, which is caused by some part of the engine inside the combustion chamber getting too hot obviously. The water injection helps cool the internals to prevent detonation. A friend of mine was running a turbo kit on a stock 1.5L sohc civic engine at 15 psi, he got away with it because he ran water injection. For over 2 years it survived, but one day he forgot to fill the water injection and popped the head gasket. Surprisingly everything else was ok and actually very clean inside, no carbon buildup on anything. Something to do with the quenching effect doesn't let the carbon build up. The only danger is having the water inj. system improperly setup and having it hydrolock the engine.

To avoid the lock I would go low and keep the charge as cold as is possible, I'm thinking maybe CCAI.

I can see the water having the quench effect, if something gets too hot, as well as the evaporative cooling, but I had not thought of it.

I would gamble the water injection is able to absorb some of the carbon debris to reult for his cleaner engine.

For the CCAI. . .

Massive hood scoop on the left side of the hood/engine bay, jack the pressure up, run it through(The AC cooling fins are on this side and are removed now) a pre-cooler, charge it(15-20 PSI), another cooler(more aggressive) BMPC, pressure release valve down to 3-4 PSI to drop AIT to 30-40 degrees lower than ambient, inject/drip water, valve. The assembly runs from left to right with the turbo mounted lower to reduce the amount of bending to merge the pipes, the second pre-cooler would be mounted along the bottom of the car with alot more area and then up to the intake tubing(maybe with some venting to additionally cool the air as it travels towards the release valve).

Too complicated - but do it
 

umm... I think you are making this too hard

water injectors are old school - like WWII propeller war bird old
many of the real high performers had water injection

Why does it work?
a little sprits of water goes in liquid and boils in combustion
and comes out a big puff of hot steam
- the steam comes out hundreds of times the size of the liquid water that went in
it also evens out the temperature spike of combustion - gentler but stronger bang
- all because the latent heat of water is freaking hugh

why is it clean inside - because you are steaming the cylinders

Normally This works best for engines and high throttle settings
a car at cruise or idle power is not going to see much benefit

but with lean burn maybe it would help
you could probably test with a rather primitive set up (spray nozzle in intake)
Go for it:thumbup:

I researched a bunch of info on the net and also had friends making big HP with water injection, both N/A high compression setups and boosted cars.
That's what I was thinking, try running a mister setup like we use on the milling machines off of a compressed air canister and see what happens. At cruise, I agree it's pretty pointless, but in lean burn could be beneficial.

I'm thinking initial test(to make sure the gnine is surviveable) on a weed eater. That said I'll have to jury rig the carb to make sure it doesn't flow WOT fuel as well. Its a junker so I don't mind if it goes(10 bucks). If that works out smooth I'll test on the Taurus with water injection, and if that works out I'll bump to the Del Sol and see what happens. Prefer to keep my daily driver able to do just that.