guys, just looking for some advice on how to tune for better fuel economy during part throttle. its a budget b20v that i've been having fun with. never been taken to the tuner. It uses a hondata s300. i spent about 2hrs playing with the part throttle, and took it to the drag strip to play with the WOT. obviously im jus an amateur and playing with this as a hobby for myself. no need to spend money on a tuner until the build gets serious, this is jus for fun.

the setup is a b20v. 11.8:1 compression. 91oct. i get around 20mpg in the city, and 25mpg on the freeway.

on the s300, at 4000rpm, i have column 1-3 at 42 degree timing, column 4 at 40 degree, and column 5 at 36 degree.

the AFR at 4000rpm .. column 1-2 is about 14.5-14.0 .. column 3-4 about 13.8 and column 5 at about 13.5

when cruising, i couldnt get it any leaner or itll start popping slightly. during very light accel, i had it at 13.8 because any leaner felt like there wasnt any power to it. same for regular accel.

my columns 6-8 are around 13.3 and 9-10 at 13.0

any suggestions tips are appreciated

 

what brand/flow of fuel injectors do you have?

i have no problem driving around at 15.5:1afr or leaner if i wanted to. i can easily get 30mpg or more in the city..

 

i am using the ID725

what compression is your setup? u have it at 15.5:1 at cruising or at light acceleration also?

 

i have similar injectors...750cc bosch injectors and i get them to idle at 15:1 no problem. light cruise and light acceleration no richer than 14.7:1 but usually in the 15:1 range.

mine is 9.5:1cr turbo setup running ectune...

you should be able to run leaner than what you are at now...im not familiar with the s300 software but im sure there is some injector settings you could probably play around with to get the most from them.

 

I did tunes like this with 12:0 c/r with 91 octane.with RC 440's and ID 1000's on a 81.5 mm gsr block putting down 200 whp if that matters. in the 15:1-15:5 status on the freeway and super light throttle, and 14.7 with light accel, into the lower 14's with a little more pedal.

 

hmm, i get light backfires/pops any leaner than 14.5 during cruise. i also feel the lack of power/torque any leaner than 13.9 when doing light acceleration. do u guys think its because of the timing being too low in those area? once again, i have timing at 42 columns 1-3.

i also wonder if having a cam with bigger primary lobes is the cause. what cams are u both running?

 

i had pro 2's and bc stage 3's. i've also tuned big 85x89 gsr's with pro3's and AFR's are about the same. the pro3 motor was with crappy rc 440's and it still ran great at those lean conditions.

on e85 you can go about .5 leaner without it popping and gasoline i liked the AFR be between 15.5-15.8 ish 40's were the highest timing i did in those lean conditions. is your distributor sync'd up with your ECU? did you actually use a timing light to sync in your distributor to 16-18*? whatever your tune calls for, there's a window you can click on up top of the s300 program and it tells you what your base timing needs to be at, at idle.

 

yea i used the s300 and sync'd the ECU to 16 degrees. ill experiment with it a little. ill keep the AFR at a safe 14.0. and ill increase and decrease timing by 3 degrees and see how the car reacts to it. does E85 typically run more timing than pump gas on WOT as well as cruise?

 

it doesn't require more, but you can run more safely to add more power.

whenever you're tuning light loads and you lean out the mixture and it starts cutting out, this is where you'll add timing to reduce the motor cutting out.


when it's "popping" is it just making noise or does the motor also cut out?

 

when cruising, it jus makes the popping sound. the engine doesn't cut. I felt like 42 timing is pretty high already so I never tried higher.

under very light acceleration like column 3 and 4. when it pops, the engine feels very weak, like there's no power to it. even at 14 AFR. I have to run 13.7-13.8 to get the "crisp" feeling and no popping