Cruise too lean?
 

Okay, i have asked this question by threadjacking and not gotten a straight answer. Can a very lean (18:1) cruise cause you problems? i.e. burnt exhaust valves or pistions? I do not have an egt gauge

Once i cruise at 16:1 the car gets pretty upset...I dont see how you can manage 18:1

no bucking whatsoever. my uego often goes - - - while cruising.

great mpg though, over 30

^ downhill?

all the time.

goes back and forth from 17 to 18 to --- and back

there's a honda tuner advancing time way up and running like 19:1. Its not a gamble I'm going to take on my nice motor. I'm running at 15.3:1 now and noticed about 2mpg gain...getting me up to a whopping 25mpg now on highway.

so, what people are saying is i should get an egt gauge.

Once I hit ~16 and crusing on highway I get lean bucking...

I wonder how retarded you have the ignition to get away with that. I'd concentrate on running more timing and ~15:1 AFRs and use an egt to check things.

Mine ran off the gauge for while, no issues. Quizzed many people about it and the popular answer is when it get a lean "pop" in cruise fatten it up a bit. I'm 16 or so now.

i can run mine pretty lean at cruise too, i'm in the 15-16:1 range right now but it's been 17-18:1 before and seemed ok but i wasn't sure if it would reduce my motors longevity or not. my gut feeling is it won't hurt anything at cruise but i really don't know.

lean "pop"? My car pretty much behaves like a huge hand was pushing/pulling it back and forth once I get past 16:1.

I'm running an AFR of 17.5:1 at cruise without any problems. I have run it as high as 19:1 at cruise without having any hassles either.

interesting there's some that say they can't go past 16:1 and some say 17-18 no problem. i wonder how much has to do with timing

im running 16:1 at cruise no problem.

what kind of fuel pressures are you all running?

I dont think you're going to be EGT limited at cruise under 4500. just not enough load on the motor...

fuel pressure? stock FPR, nothing else.

stock fuel pressure here too

i ask because I wonder if the guys running >16:1 are getting better atomization from higher rail pressures.

I do ok with 15.5 or so.

heres a quick read. according to their rsx, 15.7:1 was the best
http://www.hondatuningmagazine.com/t...ing/index.html

wouldn't the best way to do this be to log duty cycle at 15:1, 16:1, and 17:1 for the same drive at the same speed?

I'm running about 17-17.5 no bucking or popping but who knows could be bad?

Is there any real argument against running cars so lean? It seems odd that maufacturers wouldn't program stock cars to run so rich if they could safely get significantly better gas mileage with a leaner tune. Just wondering what ill effects there are from doing this, aside from the bucking previously mentioned.

My car will also cruise at 19-19.5:1 without problem. Leaner than 19.6:1 can cause bucking from time to time.

Split, what you'll want to do is *advance* timing, not retard it. The super lean mix burns slow. And for the record, I've been consistently breaking 30 mpg according to my 4.08 rear and 4.30 speedo drive, in mixed traffic. Hard top on, A/C on 50-75%.

mmmmmmmmmm A/C..... i need an idler pulley.

Yeah, EGT goes up to a point that isn't good if timing is not advanced. Power goes down. Emissions goes way up; your cat is designed to work effectively at stoich A/F. The EPA will hate you.

Positives: Way less fuel consumption. Due to (literally) less fuel squirted and wider throttle angle for lower pumping losses.

Some of the newer hondas go into a "supercruise" mode on the highway, where the computer keeps the mix around 18:1 in closed loop with a wideband--other cars do as well. It was an uphill battle for them re: the EPA.

part of the reason they won the uphill battle is better NOx catalyzation than the standard catalytic converters use.

and yes, EGT goes up with a leaner mixture because of the slow speed of burn as Ben said. when it exits the exh valves, it's still burning and hence EGT goes up.

so you advance timing (ignite it sooner) and it burns in the chamber more.