Why no more lean burn?? - Fuel Economy, Hypermiling, EcoModding News and Forum

Mad Adder · 12-30-2013, 07:31 PM

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?

Cobb · 12-30-2013, 07:41 PM

Too much nox generation.

gone-ot · 12-30-2013, 07:59 PM

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.

• source: EndTuning - Air Fuel Ratios

cRiPpLe_rOoStEr · 12-30-2013, 09:07 PM

Big Oil hates lean-burn.

MetroMPG · 12-30-2013, 11:07 PM

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.

slownugly · 12-31-2013, 10:15 AM

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.

RustyLugNut · 12-31-2013, 04:38 PM

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.

gone-ot · 12-31-2013, 05:19 PM

Quote:

Originally Posted by RustyLugNut

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..."

Xist · 12-31-2013, 06:02 PM

Idiocy will find a way!

pgfpro · 12-31-2013, 06:54 PM

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.