Nissan GT-R Forum banner
1 - 15 of 15 Posts

·
Registered
Joined
·
100 Posts
Discussion Starter · #1 ·
What are the air fuel ratio targets for tuned GTR? At which air fuel ratio is the car running to lean? If i dont see any knock on the car it means that the fuel ratio is ok ? Just want to make sure what to look out for when i do a data log?
 

·
Premium Member
Joined
·
737 Posts
one more thing to mention. i also realized that stock o2 sensor readings are not that accurate. I suggest you to use an additional o2 sensor to check if its inline with your stock ones.
 

·
Registered
Joined
·
2,844 Posts
The right air fuel ratio is the one that delivers peak torque with the correct Exhaust Gas Temperature.
Put an EGT gauge in an E85 burning VR38DETT and you will some interesting results!
 

·
Registered
Joined
·
734 Posts
The right air fuel ratio is the one that delivers peak torque with the correct Exhaust Gas Temperature.
Put an EGT gauge in an E85 burning VR38DETT and you will some interesting results!
I would think the stock manifolds probably heat up the EGT's a bit. Wonder how much that changes with new tubular manifolds.
 

·
Registered
Joined
·
2,380 Posts
Most times I see 12.0-12.2 as measured on the car's O2 sensors on e85. A conservative tune will have them at 11.8.
You definitely don't want to run too rich on E85.

For 93 octane 11.5:1 is what I target on both my EVO (34psi) and my GTR (19psi) using an actual wideband. However, in the software 'AFR (Old)' is offset from the actual AFR so I command 12.22 in the Fuel Low Det table, which gives me ~11.5:1 on the actual dyno wideband. In the EVO community most people target 12:1 using a gasoline lamda meter when tuning E85 so I would think you would want to see ~12.72:1 using 'AFR (Old)'. If you look at Jeff's map in the link below he commands ~12.22 in his Fuel Low Det table for E85.

http://www.gtrlife.c...l-lots-of-data/
 

·
Registered
Joined
·
2,978 Posts
Fwiw Cobb has done away with AFR "old" in newer versions of the software and now "Air/Fuel Ratio" more closely mimics the tailpipe AFR. Accordingly it's not a good idea to target 12.2 in the tables on the newest revisions of AccessTuner.

EcuTek's AFR is similar to this.
 

·
Registered
Joined
·
2,380 Posts
Fwiw Cobb has done away with AFR "old" in newer versions of the software and now "Air/Fuel Ratio" more closely mimics the tailpipe AFR. Accordingly it's not a good idea to target 12.2 in the tables on the newest revisions of AccessTuner.

EcuTek's AFR is similar to this.
I read that as well so I decided to call Cobb to get the scoop. From what they told me, if you are an ATR user this will not affect your 'Fuel Low Det' tables so if you were commanding 12.22 before that number will stay the same. As you stated, the only change should be that 'AFR Old' is no longer used and "Air/Fuel Ratio" is now used and should better approximate the actual AFR value. I would personally want to verify this using an aftermarket wideband to understand the offset for my vehicle. I think Cobb is going to post something about his in the Cobb forum.
 
1 - 15 of 15 Posts
Top