hi .. a local shop built and tuned a b20vtec for me. The tuner was helpful and told me that the tune was very conservative since it was a daily driver. The power in vtec is great and the midrange overall is decent but it gets shitty gas mpg. Since then, ive added an AEM wideband kit to the header collector. I dont know anything about tuning except for the fact that stock cars aim for 14.7 AFR.

i would like to share the AFRs that ive collected from the motor and want your feedback on it.

COLD start .. idles at 11.5 and partial throttle is around 11.5-12
Normal operating Temp :

idles 12-12.5 (idles steady at 900rpm) but sounds a little lopey
cruise at 2500 rpm 11-11.5 AFR but changes to 12.5-13 at 3000 + rpm
partial throttle lightly 13.5-14 and a little more throttle leans it out to 14-14.5

( thought it should be the other way around .. the more throttle the richer it should be)

then at WOT .. it stays pretty steady at 12.6-12.8

are those AFR's about right for a safe tune or should i look for a better tuner ?

Info on the car.. it is a b20vtec .. 11.8 compression .. 91 oct .. ported head .. pro 2 cams

tuned on crome ... makes 227whp and 152tq

 

go back and tell him to tune part throttle and not just wot. This kind of **** pisses me off. Take some damn pride in the tunes u do people!

 

Should have tuned partial throttle as well.. shame.

Also lean it up a bit, 12.9~13.3 should produce almost 230whp.

 

lol, "get the a/f ratios good at wot & call it a day" haha.

If your tuner doesn't tune idle & idle with your post start, startup, cold start, a/c on/headlights etc, partial throttle at high & low speeds, mid throttle, throttle tip in etc... then find another tuner....

 

wow ... what afr should I be seeing on those other areas ( cold start , partial throttle , etc )

 

cold start 13's increasing to 14.5-15.5 as coolant temp rises.

 

It seems like your tuner just wanted a quick buck and tune WOT alone... Your motor is very rich at idle and part throttle... Go back for a complete tune... Hence your shitty gas mileage...
I strongly believe in street tuning for part throttle tuning... You are most likely going to get real life situations that the motor has to undergo on a daily basis on the street than on a dyno...
P.S. Nice numbers

 

i said the same thing once. Fact is i can fully tune a car 10x faster by starting on the dyno.

having a dyno with load control helps with that.

 

While that statement is true.. I've personally found, street tuning will almost provide near dyno tune numbers if done correctly , i've tested this on my own car.

I've used dyno tuning, for fine ign tuning, that wouldn't require me to read plugs.. also to see other things i wouldn't notice on the street.. but i've found that street tuning a car, then going to the dyno is always the best..

 

to the tuner's defense, i was watching him. He spent the whole time on a dynojet. He started off with the idle , and then started going through all different gears. Then he cruised in different gears. It took about an hr before he started doing third gear WOT. i paid for 2 hrs total. so it seemed that he tried to do partial throttle tuning, yet the AFR ended at what it is now for whatever reason. Is it even possible to do a full tune on a dynojet within 2hrs ? and besides fuel economy, is running this rich harmful at all ?

 

With no mechanical problems or wrenching, a full tune with idle/post/part throttle/wot will take me ~4-5hrs on a B-series.

Just as a side-note: I've found that 850rpm is a good idle RPM for Pro2's & 3's, but require a ~13:1-13.5:1 idle AFR and ~18-19* BTDC timing. Smooth and stable.

If you run your narrowband output from your Wideband kit to the factory O2 pin, you can enable closed-loop, which will allow the ECU to target lambda=1.

 

13 afr at idle ? :.. ic ... does your partial throttle lean out to 14.5-15 ? any pros and cons for open loop and closed loop ? ... thanks for your input !!