Where are you guys cruising at??? (AFR)
 

Okay, i am all about best economy too, not in boost but while cruizing. I was reading on PGMFI that some dude tuned his car getting 40+ miles per gallon and running mid 15 afrs crusing with part throttle. Right now i am in the 13.5 range cruizing part throttle, level road, 70 miles and hour, 3800-4000 rpms, 16-19 hgs, with base timeing that b16s have, 450 dsms. I ran one tank never hitting boost once, driving grandma style and i am getting around 27mpgs. How lean is good, can i take it to 14.7 or even a little higher as long as i listen for det??? What do you guys suggest. Also what is ideally the best afr under a load in vaccuum, espescially right before getting into boost??

its a 2000 civic si.

Re: Where are you guys cruising at??? (AFR)
 

14.7 is what the stock o2 sensor *tries* to get the afr at, so why wouldn't it be ok?

I've run low 15's with no problems. This was on an 8.8:1 compression ratio engine tho.

I tuned an h22 that would start to hear detonation at anything above 15 with 93 octane.

Re: Where are you guys cruising at??? (AFR)
 

DUH! i don't know what i am thinking :1 . I do read that alot of people keep it at 13.5 in vaccuum, i guess its cause they dont want to mess anything up. SO then under a load in the vaccuum side but almost wot, would 13.5 be a good area or little richer or leaner???

Re: Where are you guys cruising at??? (AFR)
 

Bone runs his super lean, on his d15.

Re: Where are you guys cruising at??? (AFR)
 

at 70 at about 4k 15 vac i run 15.0 at high load about 13.8 with 9.0 cpr

Re: Where are you guys cruising at??? (AFR)
 

vac afr's like stock, once you get to 0 you better start adding some fuel or something. why throw your mileage away?

Re: Where are you guys cruising at??? (AFR)
 

Run it as lean as possible without misfiring...

Nothing is going to detonate, part throttle cruising...there just isnt enough cylinder pressure to make that happen.

Re: Where are you guys cruising at??? (AFR)
 

yea, i ran my d15b super lean cruising. i had a super small turbo that boosted in every gear no matter what. i dont remember what the afr's were but i was getting 35mpg's with a 50/50 mix of city and highway driving. one i start driving again in march i will be shotting for 40mpg's highway. if there is no load on it, then it will be hard to hurt it

Re: Where are you guys cruising at??? (AFR)
 

i usually cruise mid 15s until about 7hng, then its about 13.5-ish until i hot boost

Re: Where are you guys cruising at??? (AFR)
 

Remember when you want to run leaner the burn takes longer so advancing your timing will be advisable.

Re: Where are you guys cruising at??? (AFR)
 

turboed d16a6, 70mph, 3500 rpms, 15.5 - 15.8 afrs, and about 18-15 in vac. I also advaced my timing just in cruse areas though. = around 42 to 43 mpg. I can even hit around 16 to 16.5 in my afrs before I start to get a lean misfire.

Re: Where are you guys cruising at??? (AFR)
 

22:1 ;)

Re: Where are you guys cruising at??? (AFR)
 

you got a diesel?

Re: Where are you guys cruising at??? (AFR)
 

My DD is 95 civic VX, when cruising along it goes into a lean burn mode ;)

Re: Where are you guys cruising at??? (AFR)
 

Highway cruising for me is around 15.3-15.7AFR's. Once I start hitting closed loop I drop to 13.5 right before hitting boost, and then 12.3-12.5 for the first 5psi. After that I run to the tune of 11.3AFR all the way to 25psi.

Re: Where are you guys cruising at??? (AFR)
 

I used to run my D15b7 at around 16:1 while cruising, got nearly 50mpg.

Re: Where are you guys cruising at??? (AFR)
 

ok, I have two good questions.

if you make the most power at 12.1 wouldn't running leaner like then 14.7 start lowering power and actually cause you use more throttle and not get better mileage? The question really is if jumping from mid 14's to 15's noticeable increased mileage?

and to tune your car with a rom editor, with the o2 enabled, to tune to mid 15's would you just lean out the maps enough to get out of the range that the o2 can correct?? cause I've gotten the a/f to be really steady at 12's or 11's in vac. when I first started tuning and the o2 was still enabled. but the o2 is supposed to regulate it to 14.
if that makes any sense.

Re: Where are you guys cruising at??? (AFR)
 

highway, city, mixed? did you mess with the timing at all?
I'm pulling 35 mixed, moring traffic. 44 easy only highway with slightly modded timing maps.

Re: Where are you guys cruising at??? (AFR)
 

I could get in the high 40's on the highway, thats where I do most my driving anyway. basically stock timing map, I didnt really want to mess with the timing maps to much leaning it out prolly got those exhaust valves toasty enough.


Are you using a wideband?

Re: Where are you guys cruising at??? (AFR)
 

^yes, I'm using a wideband, PLXM300.

I did a bunch of tuning yesterday. I ended up just turning off the o2 sensor to lean out the mixture.

Re: Where are you guys cruising at??? (AFR)
 

Thanks Alot, i am working on vacuum side right now, got the boosted side still real rich. I don't hit much boost and if i do, it kills the bugs. :y

Re: Where are you guys cruising at??? (AFR)
 

Set it to the low 16's. Say around 16.2 or 16.3. Beware of misfiring when you get into actual lean burns around 19-22:1 under light engine loads.
Keep in mind that you're not going to gain much, if at all on these small over-worked engines by going leaner than the low 16s. At that point, the leaner you go the less the power output. Eventually you run out of power output needed to maintain speed.
I've shown this before to JD's chargin. But I've seen this Toyota chart in several non toyota and general refferance automotive txt books. (aside from being in all the T-Ten literature)
http://www.g33.co.uk/images/fic-af-emissions.gif

See if that helps you any.

Re: Where are you guys cruising at??? (AFR)
 

I've found that different vehicles tolerate a wider range of mixtures than others.
I tune to 14.9 AFR for cruise. If you can tune leaner than that without power loss or EGT impact, go for it.

The issue that i've seen is that somewhere leaner than 14.9:1 you start to feel the power drop off. The ECU will dither - cross back and forth over your desired AFR and you'll feel the power come on and taper off.. It's annoying - so either go richer than that point or adjust your 02 correction so that it does slow more slowly.

Re: Where are you guys cruising at??? (AFR)
 

or disable the o2.

power doesnt really drop off until like 17.5 18 if that... it just idles rough.

Re: Where are you guys cruising at??? (AFR)
 

i've noticed this too since my car's vac afr is between 16s and mid 14s. Crusing afrs arfe pretty easy to deal with since the car isnt working too hard and theres little consequence for not having it perfect. Its the high load, low rpm portions of the map that needs to be perfect, and it can be easily overlooked.

Re: Where are you guys cruising at??? (AFR)
 

I get about 14.4:1 but i'm on a stock P30 basemap with low compression pistons, so it's just a tad bit rich.. not going to bother tuning now it since i'll be boosting in a few weeks.

Re: Where are you guys cruising at??? (AFR)
 

on who's dyno...

Re: Where are you guys cruising at??? (AFR)
 

On gasoline, best power is made between approximately 12 and 13:1 AFR. Any richer or leaner kills power. Pick up Jeff Hartman's EFI tuning book. Read it. Then post.

Re: Where are you guys cruising at??? (AFR)
 

^ I meant that's the way if it feels on my car. I thought someone said something about drivabilty with leaner a/f ratios.
my cars tune is messed up right now and I'm running lean when its cold and it runs maybe a little rough where it hits certain rpms. then gets past it. which is probably my tune and no cold start enrichment. but when its warm, leaner mixtures, I dont feel a power loss driving normally.