Improving lean burn
 

I was thinking today about the VX lean burn engine, and I have read that only one of the intake valves opens all the way, the other partially opens to create the swirl to mix up the fuel/air.

I've also read that lean burn engines get awesome fuel economy when in lean burn, but only okay gas mileage when not in lean burn.

Is this mediocre gas mileage a result of the 2nd intake valve only opening slightly? Would you get better gas mileage if the valve opened all the way like a normal D15 engine?

If this is the case, couldn't honda have just activated the Vtec solenoid whenever the car wasn't in lean burn? Thus giving you better mileage? And then when conditions were right to put it into lean burn, the vtec solenoid would just be turned off, thus causing the 2nd intake valve to only open a little bit to make the swirl?

Actually my thread should have been called, improving non lean burn operation of lean burn engines. lol

The additional swirl effect will always help combustion in the VX engine no matter if its in lean burn or regular mode. A well mixed air/fuel ratio will burn at the same speed, and won't have pockets that don't burn next to pockets that are fuel rich. This all leads to a stable burn and allows ignition timing to be advanced further which can also increase efficiency.

Maybe you could do some mods that would cause you to spend more time in lean burn mode like aerodynamic stuff, weight reduction, LLR tires, slowing down.

True, but I want to focus this thread on just the engine.

Does the engine drop out of lean burn when the tps is too high due to emissions, or because too much lean mixture can melt engine internals?

Can you trick the ecu into thinking you only have the tps open 20%, when its really 50%? Like some kind of voltage divider circuit. I think the tps gets a 5volt signal from the ecu and as the throttle opens it changes from 5 to 0 or maybe its 0 to 5 at WOT.

I know the main fuel/ignition maps are rpm and MAP based, so maybe playing with the tps wouldn't screw with cruising much. I know there is TPS tip in, when you go from no throttle to "some throttle" the ecu tip in shoots more fuel into the engine briefly. Something about smoothing out the transition and probably flow through the intake tract.

Ah crap, just read this thread, http://ecomodder.com/forum/showthrea...o-18050-2.html

Looks like that the TPS probably only affects lean burn in open loop, and as I recall the engine is only in open loop when its cold. Might be worth checking on.

Sounds like you need a vac. gauge.

Yeah i think you're right. Gotta check autometer, see if they have a nice one that shows a lot of resolution between 0-10inches.

Only the 49 state civic vx has lean burn, the CA sold VX does not and thus gets slightly worse gas mileage, the CA and the 49 state have the same Vtec and the same head, the valve timing and the number of valves that open are in relation to engine speed, I don't think it has as much to do with lean burn other then that lean burn I think is also a slower burn so to get it to be complete the engine needs to be spinning slower.

Oh, well that's good info to know the cali VX also has the same head. I totally forgot you can just convert a cali to fed with an ecu and wideband. Do the cali ones also have EGR? Not that that really matters for my tricking leanburn to happen more quagmire.