Supra Forums banner

1 - 12 of 12 Posts

·
Search
Joined
·
3,305 Posts
Discussion Starter #1
I know the idea A/F ratio, but what are the max/mins I need to be watching out for? I'm getting a Maf/T with 550's and a ZT-2 wideband soon...

I want to know when i'm out drivin what are the maximum and minimum ratios that would alarm me
 

·
Escaped from infinite lag
Joined
·
1,103 Posts
from what ive been told from the good tuners go for 11.5 to12
 

·
when this baby hits 88mph
Joined
·
2,198 Posts
there is a huge diff in power output going from 10.5 to 11.5.
most tune on the safe side in the 11.8 range. you can run a bit leaner, my car kept making power up until 12.2:1. any leaner than that and power started to fall off. there isnt much power diff from 11.8-12.2, maybe around 15rw or so. id rather sacrifice that minimal hp increase for the extra safety.

as far as the 14.7:1 at cruise that is correct. under closed loop the ecu will try to maintain that a/f for maximum fuel effeciency. under open loop (anything greater than 75% throttle) it will start pouring in the fuel. run 14.7:1 under boost and you are in a world of hurt.

hope this helps

dave
 

·
when this baby hits 88mph
Joined
·
2,198 Posts
anytime justin. it is fun to tune, but you just have to be careful. you can wreck your motor in a hurry if you get careless. just take it all in small steps. back on the ct26 i went from 290rw to 340rw in just tuning.

mullenc525 said:
so 11.8 - 12.2 is for a street tune? or dyno tune? or does it not make a difference, such as I have heard?
there is some diff in a/f on the dyno vs the street b/c of loading. it is usually around .2-.3 meaning if you tune for 11.8 on the dyno it is closer to 12.0-12.1 on the street. i was just playing around w/ a/f on the dyno to see the results. after i made that 12.2 pass i richened it back up to 11.8 using base fuel pressure. otherwise it would have been closer to 12.4-12.5 on the street and that is running leaner than id prefer and like i said i would have actually lost power since leaner than 12.2 it started falling off.
so, if you are on the dyno id shoot for 11.8-11.9
if you are using a wideband on the street id shoot for 11.9-12.0
it all comes down to how much safety you want to sacrifice for power.
 

·
ƒ=1/2π(√k/m)
Joined
·
9,916 Posts
I drove from Greensboro NC to Baltimore MD (372.7 Miles) in less than one tank of fuel.


I cruise tuned for a 15.6*7:1 AFR and just monitored EGT and coolant temperatures.

But under load and full boost I'm at 12.1:1 AFR with cold air and 93+ octane fuel.
 

·
Registered
Joined
·
2,148 Posts
^ cool

with my techedge wideband I think I am able to reprogram the narrowband output curve - in closed loop I can make it cruise at any afr I want, the stock ecu will think its at 14.7...
 

·
Registered
Joined
·
454 Posts
87SilverSupraTurbo said:
What do you guys with widebands normally idle at or try to idle at? My wideband should be ordered soon, then I can play with it.
14.7:1. If it's a stock ecu it will adjust fuel to keep it at this unless you unplug the narrow band.
 

·
wastegate hose is pulled
Joined
·
4,586 Posts
Toyota runs them uber rich WOT for a reason, combustion cooling. There is more power leaner but, chances of detonation are increased. 10.8:1 is safe for pump gas FI applications IMO, depending on the rest of the engine of course. How far you want to push is up to you or whoever does the tuning.

14.7:1 cruise is for best emissions, not economy.
 
1 - 12 of 12 Posts
Top