Why no more lean burn??

[tony_2018]

Okay but this is about a catalyctic converter for a lean burn engine. Honda even has different part#'s for the HX and DX models. Take a look for yourself.

[RustyLugNut]

Originally Posted by eco_generator

Ehh, I think there are two sides to that coin. I was able to get a universal 3" I.D. cat for my track car for under $100.

But I guess that would be a small cat from a diesel truck perspective, lol.

If your car is the typical and runs at a lambda of one, the universal TWCC you find at the corner store and online will be adequate. However, we are talking about cleaning up the lean burn portion of our vehicles as this is the operating regime that disallows the inclusion of lean burn for most cars designed for current emission standards. The common TWCC is utterly inadequate for this purpose.

A specialized oxidation catalyst ahead of a NOx trap would allow us to use lean burn and meet the emission standards for cleanliness. Modified drive cycles and purge circuits may also need to be included. Look up clean diesel tech and you can begin to grasp just how involved this can be. A lean burn gasoline engine parallels the emissions output of a diesel to some degree ( as a diesel runs in lean burn pretty much all the time ).

[ANOMALY]

Good thread. Wondered this myself

Love my lil D15z6 1.5lsi vtec lean burn right up to near 80MPH
Best mileage near 450 on a tank with 2 passengers & weekend luggage.

[Bindegal]

For me the question is... Will the car pass the inspections?
Around here they measure CO and lambda @ idle and (I think) 2500 RPM @ standstill.
So unless the off-the-shelf cat is slowly killed by me doing AFR 22 they will never find out.
My stance is this: With all the crappy diesel cars around here, I will happily spew out NOX gasses all day long without feeling guilty. Makes no difference whatsoever.

If inspection standards were up, I would probably care more. Because that would mean they would also catch said crappy diesel cars and actually improve on our air quality.

/Allan

[cbaber]

Originally Posted by tony_2018

Okay but this is about a catalyctic converter for a lean burn engine. Honda even has different part#'s for the HX and DX models. Take a look for yourself.

I faced the problem of needing to replace my manifold. From Honda its $650. They make cheaper eBay replacements and box store replacements that run $200-$400. I'm not spending 1/3 of what my car is worth on an exhaust manifold. I chose to convert my exhaust setup from the stock cat-in-manifold to the traditional manifold-downpipe-cat. I sourced a used exhaust manifold and downpipe from a Del Sol, and bought the magnaflow cat.

Even if you need to pass emissions tests, they are not testing your car in lean burn mode. It's running an A/F ratio just like any regular Civic engine, and its emissions are going to be the same as well. So as long as you have a cat made before 1981 that isn't clogged up you will pass emissions.

[tony_2018]

I just don't know if the high nox will kill the converter, thats my issue. I'm running a lean burn d15b 3 stage and the lean burn is great. I'm wanting to go a chip ecu route so i can get away from this oem ecu. I have the proper ecu for both 5spd and cvt, cvt does not go into lean burn but does activate 2nd stage and 3rd stage vtec.

[Floppie]

Originally Posted by cujet

Those who have aftermarket, stand-alone engine management computers have done some interesting things with lean operation on very modern engines.

Lean operation requires more throttle opening, and the throttle by wire can compensate without driver input. Driveability issues are minimized with such setups.

My current "fun" car is a 2004 Turbo S2000 with stand-alone ECU, 8.8/1 compression, 19.5Lbs boost. It does not run lean under light loads, and does not return very good MPG's. (about 20) . My plan is to re-map the ECU for 17/1 operation under light loads. Those that have done this see overall increases to 25 to 27MPG.

Amusing that you posted that. My car (before my STi) was an 02 RSX Type-S, 171k on the clock when I bought the new hotrod. Moderately modified (still N/A and stock from the valve cover to the oil pan) and with KPro leaning out and jerking around with the cam phasing I was able to achieve 33mpg combined, driving it like I stole it most of the time and idling to warm up the coolant to 130degF before driving.

That was with a 17-18AFR cruise, 15.5-16AFR warm idle, 50deg (maximum) cam advance at cruise; 12.8AFR and optimized for power output at WOT.

My point being that the K series (and its cousin the Fs) seem to have some significant efficiency potential with some know-how and a desire for it

[cbaber]

Originally Posted by tony_2018

I just don't know if the high nox will kill the converter, thats my issue. I'm running a lean burn d15b 3 stage and the lean burn is great. I'm wanting to go a chip ecu route so i can get away from this oem ecu. I have the proper ecu for both 5spd and cvt, cvt does not go into lean burn but does activate 2nd stage and 3rd stage vtec.

Sorry I didn't answer the question the first time. Anyway, no you will not be doing any damage. Actually, running rich damages the cat because you are sending fuel out of the exhaust ports which can then ignite causing increased heat in the exhaust and cat which can burn it up.

When you are in lean burn your exhaust gases are actually cooler, the fuel is more fully burned, and the result is actually cleaner air coming out of the exhaust ports than with regular burn.

The misconception about lean burn and emissions is due to the cat itself. Modern cats are designed to filter regular 14.7:1 mixtures. Basically regular cats are really good at reacting with regular exhaust and create cleaner air. When you run lean burn exhaust through a normal cat, the reactions are not the same because the lean burn air is not as dirty (CO2, NOx levels are different). Since the reactions are not efficient anymore, less filtering is done. What you end up with is really good filtration with normal exhaust, not so good with lean burn after the cat.

The only reason it really matters for auto makers is federal emissions regulations. To correct this, special cats and emissions systems like EGR are required to meet the regulations. Without the special cats you are just not meeting emissions regulations (while in lean burn).

[tony_2018]

I'm curious as to how the egr system is ran, I mean I've seen the toyota camry's and nissan 240sx is directly connected to the exhaust manifold but honda has there's built into the intake manifold and I can't see where it gets being routed to.

[cbaber]

There is a passage that runs from the exhaust ports towards the rear (transmission) side of the head. From there it goes to the electronically controlled EGR valve (M/T HX, CVT HX is vacuum controlled). The EGR is mounted on the intake manifold by the distributor. It goes from the EGR valve through maze like passages, located under the fuel rail on the intake manifold. There is a small passage leading into each cylinders intake runner.

For the 92-00 Civics, the HX and VX are the only trims that had EGR valves (at least for the US). 01+ I think all Honda's had EGR valves.