rednikos

hello
what air fuel ratio do u think that is the most lean that u can go?
in low engine load, for better dd economy!!

s2000Junky

At WOT under vtec I would target 13.2 for best torque. You should start enriching when vtec comes in or shortly after, to redline. 12.5afr generally really makes the most hp so that would be my redline target. More fuel helps keep cooler combustions temps as well, which is most important in the higher rpms. Honda tunes the F20/22 14.7afr at idle and partial throttle, up to about 35% throttle and begins enrichment a full point from there to 50% throttle before transitioning to open loop when your WOT tuning comes in as mentioned previously.

rednikos

i m intresting about econony in 1000-5000 rpm low load .in that area i eant to find themost lean

S2johnyK

I wouldn't go leaner than 15-15.5(max).
I' m sure that others would go even leaner (16afr ect).
For me, a good compromise between daily drive fuel consumption and motor life longevity is 15.2afr.
But that's just me

iDomN8U

x2

from a stop you don't want too lean to reduce chance of knock. but if you're cruising you can lean out into the 15's partial throttle.

s2000Junky

The stock ecu and any OEM ecu running in closed loop operation actively reads the conditions and sweeps from low 14's to low 15's with a stoich 14.7 as the center target, that’s where the most efficient afr is. Trying to set a leaner target of higher then stoitch is real finite ( I have noticed anything above 15.5 and the motor backs off) so if you can maintain 15-15.2 at all times it may offer some slight benefit in some scenarios, but could be worse in others, because the combustion temps are now hotter and less fuel is present to deliver optimum power for best efficiency in all conditions. With that, INMOP its a lost cause and your likely to suffer then gain anything. Further more, I doubt you can target a firm afr above stoich without running to lean somtimes. 14.7 should be the center target to keep the engine in its optimum working range at all times. Most tuners I find tune richer then OEM/stoich.

06Estukay

12.5 at any RPM/load is too rich for an n/a s2000. From my experience tuning these cars, 12.8-13 is the sweet spot. There is no benefit to going any richer.

Also, throttle position has nothing to do with the target lambda's. The ignition, fuel, and lambda target tables are all mapped using RPM vs MAP for all model year S2000's. Target Lambda is based on the manifold pressure, not throttle. Open vs closed loop is also based on MAP, and not throttle position. Regardless, the operation of the oem ecu is a moot point. OP's thread title is "a/f ratio ITB".

Rednikos,

What EMS are you running? I'm assuming your main fuel map is TPS based because of your itb setup? How about your target lambda table.. TPS based as well?

s2000Junky

The benefit is a cooler combustion temp/safer tune in the upper revs. 12.5 to 12.8-13afr can mean the difference between 0 to 2hp on the dyno yet a happy motor at the track running richer. As mentioned, I tune for 13-13.2afr under 6k rpm where there is more benefit and less risk and start adding a little fuel from there so that the redline target is generally 12.5afr. This is still light years leaner then what Honda tuned for back in 00-01. Their factory show room afr tune from approx 8 to 8.9k was 10.8!

And as for tuning by throttle position, it is employed by the factory 00-05 ecu as well as rpm and manifold pressure. I dont know about DBW, never worked with them. On a average static load you can see the throttle position and closed/open loop influence, and the % is just as I said, so for sake of ease of explanation its why I mentioned that way. As a successful E manage ULT tuner for FI and NA and for sake of simplicity in the NA arena specifically, I prefer to tune by throttle position as its proven to be less finicky and more precise in dialing in the specifics over tuning by manifold pressure. When I tune for FI I incorporate a manifold pressure map obviously. But application and personal preference is really what dictates. ITB's or not shouldnt matter, but what tuning device employed will to some degree.