Lean Burn for non-Civics? (custom???)
 

Are there any cars out there, besides Civic Vx cars, running a lean burn mode? Has anyone on this forum attempted creating their own lean burn hack?

I was thinking about this and feel I could make a simple low-engine-load lean burn on my 3-cyl 1994 Geo Metro. I think it could be as simple as just monitoring the fuel injector pulse widths and the manifold vacuum pressure. Then, when the vacuum pressure suggests low engine load the fuel injector pulses could be shortened by some percentage. The trick, I guess, would be sending the fuel injector pulses into a an input on a micro-controller and duplicating them on an output without much delay. This way, the output pulses could be truncated when wanting to run lean. Because the Metro only uses one TBI fuel injector this would be a bit easier than other vehicles with multi-port fuel injection (though I believe it should be possible for all fuel injected vehicles).

Okay - Does the above make any sense? Please help me understand if I am completely nuts or if I might be onto something. Has another person around here attempted something of this nature?

Let me know what you think - I just bought a cheap hobby oscilloscope and I plan to play around a bit with this concept over the next few weeks. BTW - I will probably use an Arduino Mega or Uno for this since I have a few laying around.

This could very easily be done with a mega squirt standalone computer. Tuners have base curves for nearly every vehicle out there and can custom tune your computer to what you want to do. Meaning more power when you need it, along with more efficient idling and less fuel while crusing. Their site talks about the fact that most OEM's tune their cars (especially turbo cars) to run rich as a way to keep combustion temps down. Alot of DSM guys see big power gains and huge jumps in FE just gfrom a proper dyno tune.

The Megasquirt would be a nice option, but I'm pretty cheap. I'll have to look into it to see if I can get one without breaking the bank.

If you modified the injector pulses the stock ECU would still see the changes via the o2 sensor, right? It would not like you making the engine run lean when its mission is to keep it in the ideal AFR. You would for sure need a wideband o2 sensor which isnt cheap.

I would love a custom lean burn setup. Right now on the HX its very very conservative because of emissions rules. I would love to have a lean burn switch and not have to worry about intake temps or throttle position. Just flip it on when at highway speeds. You have me researching this now!

EDIT: After a quick search it appears Greddy's emanage ultimate could do what you are wanting. Its simply a piggy-back system that uses your existing ECU and sensors and then you can custom tune a variety of settings. One of which is to tune a target A/F ratio. You would need a wideband o2 and to buy this. From a quick read it sounds like you could potentially create your own lean burn mode.

A local tuner build a "lean burn" on an engine not designed for it.

He is a pretty sharp guy and was really helpful.

Go REALLY lean.
Advance timing.

engine needs lots of compression (over 10:1).

I need to do a bit more research on the tuning but if you could tune the ECU to run a lean mixture from certain loads and speeds that would be good. Running lean-burn in high load situations and at high rpm is not very effective. You need to be at low load at a steady speed at low RPM. I wish there were some tuners on here to ask if it was possible to set something like this up with emanage ultimate which seems to be the easiest option.

Since my engine already has lean burn I just want to control when it happens with my own settings, not with the stock ECU. With the stock ECU if will kick you out with intake air temp changes, TPS going over a certain amount, etc. I would love to have a more free running system for when I am driving on the highway.

With some more research I dug up some more interesting information. Bascially yes, you can create your own lean-burn operation on basically any car with modern EFI. A chipped ECU with your own fuel maps would allow you to set the A/F target at light loads at certain RPMs. It is a bit more complicated than that, however. As pointed out by a test done on the RSX, just because you run lean doesnt mean a huge improvement in fuel economy. The final result of their study found a 2% increase.

But on an engine designed for lean burn, like mine, the results are much more dramatic. The VX and HX run mixtures up to 20:1 I read somewhere. That is much more than the people tested with the RSX. So I truely believe with a custom map I would be able to optimize the original Honda lean burn map so that I could stay in lean burn more easily.

Lean burn is only useful at low loads because it increases chance of knock. Ideally you'd want compression to be at the very edge of safety at stoich at your max RPM, and then have the burn lean out gradually as load and RPM drop, but I'm not sure where ignition timing falls into this.

I wonder what's more effective, leaning the burn or advancing timing? It would be interesting to see a graph showing the FE increases of both.

We have a tuner in Utah that does incredible work he had two different tunes on my car one for E85 and one for 91 octane and can tune for each gear and load and use outputs to run boost controllers and in your case EGR valve and activate a lean bur tune and a normal tune and you can switch to each tune with a toggle switch but you will need to convert to Obd1

The tuner's name is Cortney Green you can Google his name and you can see his work

Wouldn't NOx emissions increase during lean burn ? One would have to install a special catalytic converter since the conventional 3-way cat just won't cut it anymore.