Lean burn on a stock Subaru Impreza engine

[serialk11r]

That chart is if you hold the airflow constant and change the fuel. However at constant power and speed, leaner requires a bigger throttle opening like Ecky said, and you'll get gains well past 16:1. Honda's lean burn engines ran 22:1 despite poor combustion, because it's more efficient to pump a lot of extra air and not have the gasoline burn completely than to restrict the engine and run stoichiometric with low MAP.

[ever_green]

Originally Posted by Ecky

Although going higher may not be the best for fuel economy with all else being equal, by leaning the burn out you can open the throttle plate more and run at a higher load, which helps too. The Insight goes as high as 25:1 or 26:1 sometimes, presumably to keep the throttle plate open.

You would probably be better off running only slightly lean and regearing to get load up, but lean burn is a more versatile and easier way of keeping load high.

I see, so I guess I will stay this lean since I haven't experienced any issues so far. Today I managed to hit 18:1 without issues either. I will have to analyze data logs to see if there is any difference in throttle opening. Stock it's about 15.5% throttle opening at 50% engine load at 2500 RPM or 65 mph. I'm not sure about lean burn at above 2700 RPM. the burn rate might be too slow for engine speed and cause problems. so lean burn will have to be restricted to 65 mph for now.

update: new throttle opening is at 18%. so about 2.5% more opening at 17:1 AFR.

[Hypermiler1995]

Bump!

Just wondering if there are any problems with the setup yet.

[rmay635703]

On this topic, long ago there was a rather simple stand alone interceptor device with an AFR dial ( you put in the cab)

The kit had a wideband which you put in place of your narrow 02 and then converted it to narrowband for your ECU to be happy, you could then adjust where the narrow band AFR thought STOICH was centered on using the dial.

Anyone remember what this plug was? I can't seem to find the thread. (it wasn't a simple efie)

Also has anyone ever noticed narrow band sensors that do not center on stoich?

Just curious.

Thanx
Ryan

[pgfpro]

Originally Posted by rmay635703

On this topic, long ago there was a rather simple stand alone interceptor device with an AFR dial ( you put in the cab)

The kit had a wideband which you put in place of your narrow 02 and then converted it to narrowband for your ECU to be happy, you could then adjust where the narrow band AFR thought STOICH was centered on using the dial.

Anyone remember what this plug was? I can't seem to find the thread. (it wasn't a simple efie)

Also has anyone ever noticed narrow band sensors that do not center on stoich?

Just curious.

Thanx
Ryan

SDS systems had one like your describing and Haltech had one also. Basically a POT meter that controlled PW by %.

[serialk11r]

Originally Posted by rmay635703

The kit had a wideband which you put in place of your narrow 02 and then converted it to narrowband for your ECU to be happy, you could then adjust where the narrow band AFR thought STOICH was centered on using the dial.

Anyone remember what this plug was? I can't seem to find the thread. (it wasn't a simple efie)

It's called a narrowband emulator. Innovate LM-1 is the first that shows up on Google. The problem with using one of these is that you can't make the engine run that lean since the idle will have problems.

[kyanox]

So i've spent a few weeks trying to track down more info on this. I have the 08 subaru impreza 2.5i AT. I'm having a hard time even getting about 16.5 but i also know i've probably not made tweaks where i should. I've asked for some help in some of the other threads, it would be much appreciated.

I'm no stranger to tuning either. I reverse engineered the chevy pcm's back in the day. Those devices were hard to run.

The good news is no emissions testing here in Montana as well, so if i don't quite hit emissions standards im fine with that for test purposes. Looks like you've put a lot of work into this, let me know if you can share what you've done. It would be very appreciated.

[bhazard]

What are you guys tuning with anyway?