Why no more lean burn??
 

If the Honda VX and HX were so good at achieving fuel mileage with lean burn, why is it not in all current Hondas and other economy cars?

May seem like a simple question or stupid question, but those are the sought after cars....why not keep using the "lean burn"? What did they find wrong with it?

Too much nox generation. :eek:

Q: Why no more lean burn??

A: EPA regulations.

Notice how "Best Economy" (blue line, ie: Lean Burn) coincides with NOx peak in below graph...and, remember, it's NOx which creates LA's brown-smog.

http://www.endtuning.com/images/airfuel.jpg

• source: EndTuning - Air Fuel Ratios

Big Oil hates lean-burn.

NOX isn't the problem
 

NOx emissions were actually NOT a problem for the gen. 1 Insight. 2 catalytic converters, one specifically designed to store/process NOX meant the lean-burn car was rated ULEV (Ultra-Low Emissions Vehicle) by CARB, with 50% lower emissions than an average new car (ie. non-lean burn). Independent dyno testing supposedly found no NOx in the Insight's exhaust. (Source)

(This *was* a problem for the older, lean-burn Civic VX, which didn't have a NOx catalyst, so wasn't sold in Cali.)

So if it's not NOx itself, maybe the additional cost of emissions control to deal with the issue is one reason. The NOx cat was a ~$1200 (retail) part.

Another major reason it may be gone could be driveability issues/consumer acceptance. In my Insight, there was a noticeable change in engine character when lean burn engaged: throttle response deadened, power output as a function of throttle position changed noticeably.

My car also had a very slight (but noticeable if you're attuned to the car) "stumble" when transitioning into lean burn. And then again when going in & out of periodic NOx purge events (about every minute or 2 cruising at 80 km/h / 50 mph).

The Insight's EGR system (which also helped regulate NOx, and was possibly active much more than on non-lean burn cars) tended to gum up over time, causing even more driveability issues.

I could see these things bothering lots of drivers.

Also, it required an a lot of care/attention to take advantage of lean burn to truly maximize its benefit, something most drivers wouldn't bother with. (IE. finessing the throttle to hold lean burn as much as possible as power demands change.)

The cost/benefit balance for the average driver probably doesn't work out.

Perfect Darin.

One thing I was thinking about is what if car buyers were better educated about lean burn operation when purchasing these cars new. I was just a wee lad when the vx and hx were in the showroom so I'm not sure how knowledgable the salesmen were about the cars and if they used that knowledge to educate the buyers and potential buyers.

Heck some "Honda enthusiasts" put these vxs for sale and they don't even know what they are about. Some ads feature the stock vx drivetrain with aftermarket intake/ header. Then the seller says "this car is fast vtec kicks in hard" When in fact the car is slow as balls and they are used to driving an 86 escort.

There will be new developments to be sure.
 

Lean Burning engines is under much scrutiny. Along with improved controls, there will be applications with larger drive cycle regimes and much more seamless transitions. Of course, if a driver still insists on heavy footed driving, no technology is going to help them.

Yep, no amount of 'technology' can "...idiot-proof idiots..."

Idiocy will find a way!

In the future I think we will see Stratified 'Ultra Lean Burn Engines" at 65:1 A/F ratios running "Gasoline Direct Injection" and "Spray Guided Piston Injection" in conjunction with new Turbo Charger technology in the forms of "Turbo Compounding Motor Generation Units Heat" and dual stage high-pressure/low pressure turbos systems.:thumbup:

People want power, lean burn doesnt offer that.

With direct injection coming out the afr is really a moot point.

Not really, as the Air Fuel Ratio (AFR) is still the ratio of AIR-to-GASOLINE, except with Direct Injection (DI) it occurs *instantly* within the cylinder when the injector pintle opens and injects a specfically-metered amount of GASOLINE into the compressed AIR inside the cylinder...it's still a ratio.

With DI, AFR can become more dynamic, but only *IF* the Engine Control Module (ECM) "brain" is smart enough to make "right" changes rather than just "some" changes...which boils down to intelligent algorithms and software/firmware inside the ECM. Thus, some manufacturers will have it, some won't.

The *problem* comes back to what's coming OUT of the exhaust pipe, and DI (as currently implemented) has been shown to INCREASE exhaust particle pollutants...and, particles "plug" catalytic converters.

And, NOx scrubbing isn't currently *up* to meeting current EPA emission requirements, much less, the anticipated FUTURE requirements coming down the pike. So, *lean-burn* (AFR ~ 16-18:1 or more) is not likely to come-back soon, without new break throughs in both DI and catalytic converters...ie: probably something like urea purge injection, etc.

Two converters is unusual, no? Maybe unique? i went looking to confirm and see what the costs are. Seems the second converter is quite cheap. Here is a parts diagram and list:
http://www.partswebsite.com/honda-pa...00&catid=30152

The way manufacturers are currently going is kind of disappointing. I think there will be a larger increase in cam phasing before lean burn is brought back. It's hard to find a car now that doesn't have cam phasing. Personally it seems like band aid after band aid after band aid. While the technology increases the cost of operation goes up. Some of these timing belts and chains take an intricate installation process due to the phasers. If a phaser goes bad it may cost from 600-1000+ to get it fixed. How much gasoline will 600 bux buy you?

I find current engine tech exciting!
 

You make the assumption that hi-Tech engines mean high failure rates. This is far from the truth. On the whole, most car engines survive to 100K miles with ease. 200K is quite common and 300K+ is not unthinkable. The biggest cost for most new car owners is not the repair costs, simply because most modern cars are very reliable in comparison to cars just a few decades ago. And they have more power as well as being much cleaner emissions wise.

As Old Tele Man pointed out, the technology is pretty much in place to re-introduce lean burn into the market. No, it is not used when power is needed or wanted so it does not effect wide open throttle settings. It will be transitioned in when light load and cruising regimes are detected.

Cam phasing is becoming common and reliable and allows internal EGR to occur dispensing with external EGR valves and passages that can be problematical as Metro pointed out.

As Old Tele also pointed out Gasoline Direct Injection (GDI) causes increased sub micron particulates to occur but technology such as Transonic's critically heated fuel injectors can minimize or eliminate that.

And as pgfpro pointed out, high turbulence will allow even leaner AF ratios, resulting in minimal NOx being produced. If you look at the chart posted on the first page, you will see that NOx as well as CO taper off drastically when you go past 20:1 AFR. Honda lean burn systems could operate as lean as 22:1 AFR. The HC output does climb as miss-fires increase as well as partial burns. However, implementing high turbulence combustion chambers can cut HC emissions.

One area of continuing research is in effective catalytic converters and NOx traps which can operate at reduced temperatures as constant lean running can reduce the exhaust temperatures to the point that the CATs and TRAPs are unable to work for a period of time when the engine transitions back to stoichiometric AFR (14.7:1).

To make a lean burning engine even more effective would be to couple it to a light weight and aerodynamically efficient body as Honda did with the first Insight so as to allow the system to run in lean burn mode a greater percentage of the time the vehicle is operated.

Hey more power to ya but my 20 year old technology currently outperforms current technology in the fuel mileage region. My fiances car has cam phasers and can only return 32mpg. 35 if im driving. You are def correct in the longevity. I'm seein cars at my shop that have 150-200k miles on them and the valve covers never been off. Nothing wrong with that. But on the other hand I'm starting to see variable valve timing codes come up.

Probably the earliest cam phaser used is the 2.0 zetec. That is used just for egr imitation. Ive been to classes on cam phasing and variable valve timing so I know how it works. I'm just saying I'm not impressed In the least. When they start getting in the 28:1 and higher afr range I'll be sure to edit my post. I'm more impressed by pgfpros work with his work on his talon. 9 second in the quarter mile and 50+ mpg capability. THAT'S impressive.

FWIW -- EPA requires Heavy Duty Diesel Emissions equipment have a 10-year/435,000-miles warranty life...yes, that's NOT a typo!

I highly doubt it. With all due respect.
 

You must compare apples to apples.

Most of the "econo - cars" I have seen are much bigger and heavier than the Metro's and Civics of 20 years ago. The Dodge Dart II's, the Chevy Cruz and the Ford Focus all seem to be around 3000 pounds and still they get 40+ MPG. Their aero is marginally better than the econo cars of the 90s but the real thrust of the package is still buyer bling. Cut out the fat on a Dart II and I have no doubt it will hit 50 MPG. I've owned several llittle Hondas and Metros and I can assure you, I'll never own one again. I'm too old to be beat up like that. Noisy, rough and cramped for my six foot frame.

If you look at the situation in Ton*MPG, you can see that late model cars are actually quite efficient as a package. The only issue is that they weigh a ton! Not all the added weight is useless bling as the structural design as well as the added safety of side airbags are worth a few hundred pounds of mass. And remember, this current crop of econo cars doesn't use lean burn in EPA
trim. But, in a few years they will. Some may have HCCI or PCCI combustion technology. Some may have advanced clean diesel Tech or hybrid diesel injection. They may have a combustion engine not discussed yet. And they may become lighter as aluminum and composite structural assemblies become advanced enough to be used in mass production situations.

My point is, if you took today's production car technology and applied it to yesterday's light-weight econo cars, 50 +MPG would only be the starting point.

And pgfpros work is impressive. He, along with several others, have added much to this forum's knowledge base in the difficult area of engine mods. It is simply beyond the capability of most people for many reasons. But, his research is simply that - research. You are comparing a research vehicle to a production vehicle that has a ton of restrictions applied to it's design parameters.

The best way to compare engine efficiency across time and space is still BSFC ( brake-specific fuel consumption ). Can you produce power with as little fuel as possible, and can you adjust your gearing and chassis load to maximize the time you spend in your BSFC sweet spot? That is the essence of constant velocity ecomodding.

For the record, this 6'2" economodder loves his HX! :)

But were you around for the Kennedy administration?
 

And the coming of the Beetles?

Seriously, I do drive a 40 MPG car from 1985. But it is a Mercedes that is quiet and smooth and cushy! And it runs on used veggie oil. And it has 600,000 + miles (estimated - ODO broke at 549,000 - like 10 years ago ).

My back loves the old Mercedes seats. Not so much the Honda seats. And certainly NOT the Metro seats! And the NOISE! I'm partially deaf from working in machine shops as a young boy and I still hear too much background noise in those early cars.

But, those Honda Civics and Geo Metros were fun and easy to work on. My wife drove them into the ground as she was the spokes model at the time, for a large Telcom and she covered the California , Nevada and Arizona areas. 3 cars in 6 years she destroyed. Her fourth car, a little Daihatsu, survived and I am in the process of rebuilding the little 1 liter engine.

But I will be putting in aftermarket seats!

This is very true for many fuel/weight saving technologies. Six+ speed transmissions, direct injection engines, removal of overun clutches in auto transmissions, neural idle, ect, all make measurable improvements in economy. The fact of the matter is, fuel is still considered cheap to the average new car buyer. Until fuel economy becomes a real concern for most people, they will not accept anything that feels any different than what they are used to.

Agree to disagree i guess. It all about tradeoffs and personal preferences. It's a question of where I put my money and what's the best probability of a good ROI.

Even if I was excited about this technology it still wouldn't influence me to go buy a new car. Is the cool factor enough to go buy a new car and LOSE money on increased fuel costs alone? (comparing a 1993 no hybrid vs a 2014 non hybrid) its a large gamble in my opinion. Everyone keeps saying this technology is coming but I have yet to see it. Until that changes my thought process will not.

Like you said about the comfortability factor. It's all about where an individual is willing to make compromises. I hope when I'm old I'm driving my 28 model a around. My crappy 20 year old civic will feel like a Cadillac compared to that haha.

You just changed the thrust of your argument.
 

Sure, it doesn't mean that there is reason to run out and buy a new econo car. But, my contention that advances in technology trump what was available 20 years ago still stands. And that we are on the verge of even more breakthroughs. And my 85 Mercedes trumps your Honda in ROI by a large margin - and I drive with free fuel.

I didn't know there was an argument haha

Yes true the mileage to weight ratio has increased. Does it impress me ? Not in the least. You win I surrender. Whether the technology is superior or not does not change the fact that my 1993 vx gets better mileage than a comparable class new vehicle non hybrid.

Gettin back on topic, if they do achieve extremely lean afrs above 50:1 what effect will that have on performance? My car has significant power loss at just 20-22:1 afrs. What kind of driving characteristics can we expect out of ultra lean burn engines?

Most likely, only during constant load applications such as powering generator for EV...sorta like the Mazda Wankel is being resurrected to do.

Assertion and argument.
 

It is the classic flow of any discussion. But never mind, I had too much college.

It was your assertion that current tech was inferior. Impressing YOU was not the goal of the manufacturers.

Your "high tech" lean burn engine flames out at 22:1 AFR. A similar engine was used in an Xprize endeavor with heated fuel resulting in the ability to run 24:1 AFR. A small change in the the combustion enthalpy is the reason for this. They set the ratio at 20:1 to provide acceptably snappy response which still resulted in excellent fuel economy from their lightweight aero tri-wheeler.

The Ale'

There is little need to go leaner than this as the gasoline combustion becomes so lazy that even with complete combustion, you would have to gear the vehicle to accommodate very low engine revolutions.

This is where hydrogen augmented combustion becomes viable. Even the small amounts produced by a HHO electrolysis generator can extend the effective lean limit significantly. Much faster flame speeds mean I can run my Daihatsu engine at 28:1 AFR ( the limit of my wide band O2 sensor )at freeway cruise speeds. This engine has a very lazy, low turbulence combustion chamber, so it is far from ideal.

I do not see much point in running 50:1 AFR even if we could get there except at idle and very low load situations. And believe me, in lab tests combustion can be sustained at 100:1 AFR with enough hydrogen augmentation and turbulence. A paper by College of the Desert, has them running an engine with pure hydrogen as a fuel at 180:1 AFR. But, power production is minimal.

Lean burn is not coming back. The only way to pass NOx emissions is to rely on the cat to remove most of it, and cats can't do that above stoichiometric without a dedicated NOx treatment device. Direct injection can allow high AFR because it concentrates the fuel in a smaller area, but that fuel will burn hot and produce NOx.

Cam phasing is alright, but isn't SUPER effective with the small duration cams you usually find on cars. With a longer duration cam, in retarded position you can get extremely late intake valve closures which really allows efficient operation. My guess is that the internal combustion engine's final evolution will be to direct injected, phased cams + variable lift as standard, perhaps a novel multipoint ignition like the Mazda experimental laser plugs, or little to no improvements to the engine and just relying on hybridization to improve the performance.

And if we can use the pricing at Majestic Honda as a guide, that Nox device (a second cat) is really cheap, about $40.

IMHO I think we will see Lean Burn technology for the next 10 years. The reason is because gasoline engines are developing very rapidly to meet the tight European 2020 CO2 regulation and LEVIII LD regulation from the California Air Resources Board (CARB). At this time Lean Burn and down sizing are being used to get us into the future.

A good example is the BlueDIRECT petrol engines from Mercedes-Benz

The BlueDIRECT petrol engines from Mercedes-Benz, which to date have comprised the familiar V6 and V8 engines, boast the very latest technology. A new addition is a six-cylinder engine which is being offered for the first time in the E-Class Coupé and Cabriolet not only as a naturally aspirated engine, but also as the E 400 with a displacement reduced to three litres but with a biturbo drive to compensate. With its power potential and formidable torque at low engine speeds, this six-cylinder model sets new standards in its segment. It produces 20 kW more power compared with the E 350. Its torque has increased by 110 Nm and is on tap between 1400 and 4000 rpm. On top of this, the new, efficient six-cylinder engine also fulfils the EU6 emissions standard. The E 500, meanwhile, not only promises sports-car-like performance – it is also making a name for itself as the most economical model in the V8 segment.

Another new addition to the BlueDIRECT petrol engine family is the four-cylinder petrol unit. With a combined fuel consumption in the E 250 Coupé of 5.7 litres and CO2 emissions of 132 grams per kilometre (Cabriolet 6.2 litres and 144 g CO2 per km) and producing 155 kW (211 hp) from a displacement of just two litres, plus 350 Nm of torque across a wide range from 1200 to 4000 rpm, it redefines standards in the four-cylinder segment. Producing a 0 to 100 km/h acceleration time of 7.1 s (Cabriolet 7.5 s), it really underlines the sporty temperament of the Mercedes-Benz E-Class Coupé and Cabriolet.

Lean-burn process with stratified charge operation

Depending on the operating conditions, the new four-cylinder engine operates in stratified charge or homogenous mode. With stratified charge operation, the high-compression engine runs with significant excess air. To achieve this, the fuel is only sprayed into the air, which has already been compressed by the pistons, during the compression phase. A precisely controlled electronic multiple injection system helps to ensure that a fuel/air cloud builds up in a limited area around the spark plug, precisely at the time of ignition. The spark plug lights the ignitable fuel/air mixture around it, while only a very lean mixture with a high proportion of excess air is to be found in the remainder of the combustion chamber. This enables extremely efficient combustion.

A prerequisite for stratified charge operation is fast piezo injectors. They spray the fuel into the combustion chambers several times in succession per power stroke, and as such enable specific control of the mixture formation and thus the flammability.

The new four-cylinder petrol engine from Mercedes-Benz also sees the world’s first use of this stratified lean-burn process in combination with exhaust-gas turbocharging and external high-pressure exhaust gas recirculation. As a result, the E 250 Coupé is the only vehicle in this segment to achieve efficiency class A. In addition, the new BlueDIRECT four-cylinder petrol engines already meet the EU6 emissions standard which will apply from 2015. The new four-cylinder unit also meets the EU6 emissions standard in the guise of the homogenous variant for countries with different fuel qualities.

Source 2014 Mercedes-Benz E Class Cabriolet | Sense The Car

With Lean burn engines they will have lean NOx control (lean deNOx) technologies.

My bad -- I referred to the expensive conventional 3-way cat. Thanks for the correction.

Rusty- so let me get this straight. If weight was taken out of the equation on a new gasoline non-hybrid to equal the weight of my 2000 lb vx then the return would be the same or superior to the lean burn technology? They are making new cars that are lighter and more aerodynamic and they still don't touch the vx. Speculation or educated guesses about a certain drivetrain in a lighter car is not enough to sway my opinion.

I have tested my vx with 650 lbs and mileage dropped 3-4 mpg from my average. (to 49mpg from an average of 51-53) That's about 2750lb curb weight. If I increased the weight to 3000 lbs I highly doubt it would drop below 45. This makes me want to try it. I'll drop a small book Chevy in the backseat haha.

No sweat. You taught me something. Why shouldn't I experiment with this "second cat" at prices like these (~$40)? Would be good for the planet if it worked and might save my butt at my August 2014 Cali smog test.

GM has lead the field with DI, and guess what, they have done EXACTLY the opposite, trying to get as homogenious a mix as possible, again due to "emissions concerns" read don't want to mess with having better emissions equipment or fuel economy, just cheaper emissions and less hassle.

Honda claims the two valve ISDI engine can match the VX lean burn engine in efficiency.
Valves are offset with two plugs per cylinder. Personally I am a fan of transonic combustion technology, which highly preheats the fuel which ignites without spark when injected at ultra high pressures directly into the combustion chamber. You may see a combination of the ISDI configuration with transonic injectors, which could possibly pass the 50% efficiency threshold, maybe even 60% after considerable refinement.
Better mixture distribution will eliminate NOX emissions as far as regulated amounts, possibly altogether.

regards
Mech

That's not the right part... it's the $660 or $1300 one. I think the $40 part is the converter cover like on this other parts site.

Honda still does lean burn when it can get away with emissions, like all their 40+ hp outboard motors.

I'm not sure of that... the diagram you link only quotes one price for one CAT, instead of two as it should. It's true the pic points to what looks like a second downstream cat, but it does not list the price for the first. The site I linked offers both prices, one high and about what the page you linked lists, and also another price for a separate item that's about 40 bucks, and it labels that the price for the second cat. I don't know which is right, but I'm certain neither offers a completely clear answer. Lots of cats. But my apologies for distracting the thread from strictly lean burn stuff... cheers.

I had a cat efficiency code on my Insight, and eventually ended up buying an aftermarket cat… it seems like you can get the rear catalyst from Honda, but the front is only in a front/rear kit (at about $1k). This is a 2000 so it doesn't monitor the second cat.

The two prices were for different years: parts 18160-PHM-A00 vs 18160-PHM-A20. There's a third O2 sensor port on the later part, but maybe other hidden changes. My link only shows one year but your link shows both under diagram #5.

NOx absorber catalysts are pretty unusual, but they're basically the same as a normal catalyst. I think even the scrap value is more than $40. Although the parts place did label it "converter" the too-good-to-be-true rule of thumb applies here. :)

Folks on the market for a new car are not willing to pay more just for the "eco" factor, or to deal with some complexity-enhancer stuff such as SCR/DEF, unless they feel entitled to brag about it like the stereotypical hybrid owners.

Good thread going here.

I am also in the "not impressed" camp. My 84 SVO Mustang can cruise out nice fuel mileage in the low 30's, when I'm not spooling the turbo for fun. It will haul ass or sip gas, but not both, lol.

I cannot seeing paying the high price of the "eco" car until it bangs out impressive numbers. What I see on here from some of the older cars getting decent mileage makes me want to pay used prices to save money, then save at the pump. The other thing is the longevity of the new tech. Until it is proven, let others pay to be guinea pigs.

Power? I ran a low 10-sec 86 Mustang GT for years. Nothing will impress me now in that department, so I'm ok with slower and drive-able. My current car is a 92 Volvo Turbo wagon which gets 20-ish. I want 35+ out of the box and then search for more.

Mazda says:

So says Mazda's chief exec for powertrain development, Mitsuo Hitomi.

Though he's talking about HCCI petrol engine development, not a "lean burn mode" in an otherwise standard engine.

http://www.autonews.com/article/2014...on-skyactive-2