[stevo12886]

Hi all,
I am looking into doing some modifications to my corolla to make it a milage machine, and as a proof of concept for automakers that very efficient cars can be practical and a cheap upgrade. Anyway, one of my plans is to upgrade the ECU to allow for a lean burn window. I am wondering if any of ya'll know the dangers of a normal engine getting into lean burn mode. I know that NOx is produced and I wouldnt pass smog, but i would add a NOx cat onto the exhaust package, so unless NOx would have adverse effects to the machinery, please dont quote that as a concern.
Cheers,
Steven

 

[b1shmu63]

My understanding is that there are a lot of subtle changes required to make an engine run in lean burn mode. Honda pioneered the idea with CVCC (controlled vortex combustion chamber) engines. Personally I think you would have more success turning it into a quasi Rankine cycle engine by adjusting the valve timing as Toyota does on the Prius. Just a thought. I don't want to sound negative as there is far too much of that around.

Personally if I was rich I'd like to build a solar powered hydroplane just to prove that it is possible. Others have already done solar cars and airplanes.

 

[Holicow]

Generally, lean is bad. I don't claim to be an expert on the Honda VTEC-E engines, but I understand they are specifically designed to operate at high air-fuel ratios. "Charge stratification" is one method they use, which I believe is adjusting the fuel injection timing to make a lean mixture usable.

Like I said, just leaning out the mixture is bad. The temps in the combustion chamber will be too high, and you burn up your spark plugs, for one thing. Will probably cause other heat damage, and results in major power loss.

So, unless an engine is designed from the beginning (valves, injectors, computer management, etc) to permit a lean mixture, I don't think it will be feasible. I don't know of any other engines that can do this, but hey, you can give it a shot and see what happens.

 

[stevo12886]

I was just thinking about the tempurature issue while doing yardwork today. I think water injection could be a possibility to keep the temperature down...but then again, there is another variable on the effectiveness of running lean. I will research the Rankine engine and get back. I am also going to run some calculations to see if running lean, or making the engine autostop would give better efficiency.
Cheers,
Steven

 

[Tim Maddux]

Take a look at the encylopedia on the main part of this site, esp. the engine-related parts. There are a number of things you won't get in your software-modified Corolla, like the swirl of fuel-air mixture in the cylinder, oxygen sensors that can handle a lean mix (this will affect your ability to make a workable add-on NOx cat), the rich/lean purging of the Insight NOx cat... and so on.

I think you'd be better off hunting down a lean-burning CRX or Civic from the 90's.

 

[jtmco]

Steven,

I think the Prius runs on a modified Atkinson Cycle - not a Rankine Cycle. The Rankine Cycle is the one used to model a steam power plant. The Atkinson has different compression ratios on different engine strokes.

Jim

 

[stevo12886]

Jim,
You are correct, i was thinking the same and went to make sure. Changing the corolla to an Atkinson cycle would be posible, but i need to do some further reasearch into the control mechanisms of the VVT-i.
Cheers,
Steven

 

[b1shmu63]

Too many cycles, too little sleep. :lol: