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Discussion Starter · #1 ·
Just wondering, what A/F does everybody run on race gas at the track? I usually run 12.2-12.5 depending on conditions....I see alot of people running 11.5 or so, why? IMO, you are leaving quite a bit of power on the table at that A/F, anybody with more experience with me...Woon, Larry, Paul, etc....please explain.

Jason
 

· Boost Junkie
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At higher power levels you create more heat in the combustion chamber and have a greater chance of melting pistons or ring lands. By running a richer a/f the excess fuel helps to keep things cooler. You may leave a slight amount of power on the table, but it is worth it for most people to keep it safe.

Steve K.
 

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Discussion Starter · #3 ·
Evill Supra said:
At higher power levels you create more heat in the combustion chamber and have a greater chance of melting pistons or ring lands. By running a richer a/f the excess fuel helps to keep things cooler. You may leave a slight amount of power on the table, but it is worth it for most people to keep it safe.

Steve K.
so I am good since my shit is weak, LOL :)
 

· Boost Junkie
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Nah,

You're running incredible times for your power level. Once you start making more power though you may want to richen things up a bit. I personally see a pretty big difference in EGTs from 12.5 to 11.5 and feel much better around seeing EGTs in the 750C range after a nice 40-140 pull.

Steve K.
 

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Discussion Starter · #5 ·
Evill Supra said:
Nah,

You're running incredible times for your power level. Once you start making more power though you may want to richen things up a bit. I personally see a pretty big difference in EGTs from 12.5 to 11.5 and feel much better around seeing EGTs in the 750C range after a nice 40-140 pull.

Steve K.
Thanks Steve...makes alot of sense. I guess I do need an EGT after all.


BTW, PayPal sent...thanks!

Jason
 

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you can still have a good a/f and have high egt's. Just depends on what gear you are in. For example your EGT's in 5th would be higher than your EGT's in 4th at the same boost level.
An egt gauge is a good idea.

From what I know about tuning on race gas, since its harder to ignite, you actually can lean out the car more, hence the more power people make on the race gas, since it allots more tuning room.
 

· Supra Owner Since 1996
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your 12-12.5 afr on race fuel are common. Max power made is closer to 13.0 but not easy for people to sleep on and leaves no room for error. I'd say you have your car tuned correctly.
 

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Best power is not at one AFR, it's between a range: lean best torque (LBT)and rich best torque (RBT). 11.5:1, however, is usually about as far as RBT goes or maybe richer than it, but is often used to cool the charge.

If you get on a loading dynomometer and hold one load and rpm you can change your injection pw and the torque will not move much ifat all between whatever values are RBT and LBT for your engine. Anywhere you are not peaking EGTs is a time to hit this range. If you aren't in fear of a meltdown, 13.5 is a common LBT so your Mean Best Torque would be around 12.5. Grab a tune motec file for instance and look at the ego target map, it's typically around 0,85 except in higher loads.
 

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Discussion Starter · #10 ·
SK VR4 said:
Best power is not at one AFR, it's between a range: lean best torque (LBT)and rich best torque (RBT). 11.5:1, however, is usually about as far as RBT goes or maybe richer than it, but is often used to cool the charge.

If you get on a loading dynomometer and hold one load and rpm you can change your injection pw and the torque will not move much ifat all between whatever values are RBT and LBT for your engine. Anywhere you are not peaking EGTs is a time to hit this range. If you aren't in fear of a meltdown, 13.5 is a common LBT so your Mean Best Torque would be around 12.5. Grab a tune motec file for instance and look at the ego target map, it's typically around 0,85 except in higher loads.

sweet, thanks for the info! :bigthumb:
 
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