Lean burn-thoughts, theorys, and discussion

[ConnClark]

Just get a diesel and you can run it as lean as you want by taking your foot of the accelerator

[euromodder]

Originally Posted by ConnClark

Just get a diesel and you can run it as lean as you want by taking your foot of the accelerator

It's actually one of the first things I started doing around mid 2008.

I had seen that reducing the throttle a bit after overshooting the target speed by a few kph gave better FE than accelerating to the target speed and staying there.
So I made it into a habit to lightly and slightly lift my right foot to increase fuel economy while the speed remained constant - but overdoing it made the speed drop considerably.

Very tiring, as I had to keep my foot in the exact same position - a bit of a bump was enough to ruin the effect.

Even now with the CC, I hit the "-" button after setting the speed.
It hardly changes the speed, but it improves the (indicated) FE instantly.

[cmj]

I wish I would have taken pictures of the sparkplugs I pulled out of my car. I melted a good 1/16th inch off the trode! I'm interested in this technology as well.

[frank316]

cmj did that setup have a wideband? a vac gauge? what rpms were you turning and what af's and all that... I'm thinking about buying an egt and documenting some hard data to really get a better handle on how af's and timing affect cruise egts.... I have personally ran my car lean everywhere on the map, full throttle included(28* of timing at wot 17-1 afr's) power sucked but no noticeable ill effects what so ever on the plugs. they were white, but thats too be expected no hot spots or indications of melting..

Ben

[bestclimb]

To get the Exhaust gas temp you can do a couple different methods. One is to just put one probe, close to the exhaust port on the manifold this lets you know what one cylinder is doing. Another is to put one probe just after the header goes down to one pipe, this will get an average of what all cylinders are doing. or you can put one on each cylinder so you can see what they are all doing.

Falcon EGT Gauges from Aircraft Spruce

[cmj]

Originally Posted by frank316

cmj did that setup have a wideband? a vac gauge? what rpms were you turning and what af's and all that... I'm thinking about buying an egt and documenting some hard data to really get a better handle on how af's and timing affect cruise egts.... I have personally ran my car lean everywhere on the map, full throttle included(28* of timing at wot 17-1 afr's) power sucked but no noticeable ill effects what so ever on the plugs. they were white, but thats too be expected no hot spots or indications of melting..

Ben

I removed the factory o2 sensor to put the car into open loop and to use my wideband, but I was tuning beyond it's capabilities. Timing was stock. Map voltage was reduced by 30% last wideband reading was 19:1 before reducing a bit more fuel and maxing out the o2 sensor. Average RPMs were 2200-2600. Average MAP pressure was -19.7inHG and maximum was -11inHG.

Took it for a test run and car started smoking, and stumbling. Wouldn't hold idle. I got it home, checked the plugs and found my problem. This being my daily, I decided to forgo any extreme tuning as such until I can find a wideband that is capable of accurate readings at > 18:1

[Ptero]

Those who understand what we actually burn in our engines will find some value here:

Title: Predicting the behavior of a lean-burn hydrogen-enhanced engine concept
Author: Ivanic, Åziga, 1978-
Other Contributors: Massachusetts Institute of Technology. Dept. of Mechanical Engineering.
Advisor: John B. Heywood.
Department: Massachusetts Institute of Technology. Dept. of Mechanical Engineering.
Publisher: Massachusetts Institute of Technology
Issue Date: 2004
Abstract:
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(cont.) Lean operation of a spark ignition (SI) internal combustion engine (ICE) offers attractive performance incentives. Lowered combustion temperatures inhibit formation of nitrogen oxides (NOx), while reduced intake manifold throttling minimizes pumping losses leading to higher efficiency. These benefits are offset by the reduced combustion speed of lean mixtures, which can lead to high cycle-to-cycle variation and unacceptable engine behavior characteristics. Hydrogen-enhancement can suppress the undesirable consequences of lean operation by accelerating the combustion process, thereby extending the "lean limit." Hydrogen would be produced on-board the vehicle with a fuel reforming device. Since operating an engine in the lean regime requires a significant amount of air, boosting is required. Hydrogen is also an octane enhancer, enabling operation at higher compression ratios, which results in a further improvement in engine efficiency. The focus of this thesis is on the modeling aspect of the lean boosted engine concept. Modeling provides a useful tool for investigating different lean boosted concepts and comparing them based on their emissions and fuel economy. An existing architectural concept has been tailored for boosted, hydrogen-enhanced, lean-bum SI engine. The simulation consists of a set of Matlab models, part physical and part empirical, that have been developed to simulate performance of a real ICE. The model was calibrated with experimental data for combustion and emissions in regards to changes in air/fuel ratio, load and speed, and different reformate fractions. The outputs of the model are NOx emissions and brake specific fuel consumption (BSFC) maps along with the cumulative NOx emissions and fuel economy for the urban
and highway drive cycles.
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Description: Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
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Includes bibliographical references (p. 90-91).
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http://dspace.mit.edu/bitstream/hand...pdf?sequence=1
6.314Mb PDF

[pgfpro]

I don't post to much on here anymore. I found this thread by doing my typical once a month routine of googling "Lean Burn"

Anyway keep up the great thread!!!

Here's some post's from the past of my radical lean burn engine that's been a work in progress for the last 11 years.


http://ecomodder.com/forum/showthrea...ign-11500.html

Good Luck with all your lean-burn adventures!!!

[amcpacer]

I tried running lean with my 85 Chrysler Laser turbo by programming the computer to ignore O2 feedback and run lean under light cruising conditions. I have a LC-1 wideband readout. It would only function as low as 17:1 and anything leaner would cause misfire. I did however get best fuel economy running 16:1 at idle at hot idle and light cruise until +2 psi manifold pressure where it descends to 11.5:1 all the way to 19psi of boost.

I always wonder why this engine won't run lean like the rest of your guys engines.

[Phantom]

Going from some info I have picked up along the way and some reading of "Engine Management: Advanced Tuning by: Greg Banish" I would say the AFR you are looking for is around 17.64:1 (lambda 1.2) for close to the same emissions as running at 14.7:1.

For cars that have a issues when going to/from lean burn aim for 15.43:1 (lambda 1.05) according to above book. I have not finished looking over the book but just to let you know there is not much of anything on lean burn in it.