Safe AFR
Safe AFR
What is a safe AFR to run at spool up using 93 octane? I know you should run about 11.5-11.0 at peak tq, but what about spool up (loads 120-200)? Also what is a safe AFR to run at higher rpms in loads 120-200?
Last edited by 5k6; Jul 17, 2007 at 03:51 PM.
A question of much debate, but I can tell what the factory does and what I do. Factory AFR's tend to be in the 12.5:1 to 13:1 range depending on mods. I usually shoot for 12:1 or so in spool up, and for 120 to 200 12:1 or down seems to work but thats kind of a loaded question because you can have varying boost and arrive at the same load percentage dependant on RPM. 11.5-12 is safe though, as I have experimented with some really lean tunes all the way through the powerband and havent generated any fuel related knock up to about 11.8 at full boost (YRMV).
JB
JB
Some of our fastest runs have been at 12.5-12.7. I am with JohnBradley though that depending on the turbo and spoolup speed, 12.5-13.0 can be acceptable if monitoring knocksums and EGT.
12.0:1 is safe on 92 for spool up (not sustained) so knowing how 93 behaves in comparison you could push it 12.5:1 pretty easy. Spool up goes to full boost REALLY quick so the key is fast transition between stoich and your desired full boost AFR's.
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So are you saying it's safe as long as you don't go and stay in spool up for a long time; this would not be something you would try on a gt42r lol, but for our stock turbo it is fine.
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the AFR that you need to run is directly related to how much boost/timing you're using at any given RPM.
During spoolup you're typically okay to be in the mid/low 12's as I suggested earlier simply because you're going to be at low load/boost and timing will be coming down as load increases initially.
as you near 3000 RPM and full boost you'll need to be at or very near to your target AFR which should be somewhere in the 11.0-11.5 range depending on how much timing/boost you're running.
none of what I said is a blanket statement, it's just an example to help you better understand, and keep asking questions, I'll gladly help wherever I can.
During spoolup you're typically okay to be in the mid/low 12's as I suggested earlier simply because you're going to be at low load/boost and timing will be coming down as load increases initially.
as you near 3000 RPM and full boost you'll need to be at or very near to your target AFR which should be somewhere in the 11.0-11.5 range depending on how much timing/boost you're running.
none of what I said is a blanket statement, it's just an example to help you better understand, and keep asking questions, I'll gladly help wherever I can.
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my AFR's are around 11.2-11.4 right now and im running meth so what should be good for me , btw thats just a quick tune still needs a couple changes so where should my AFR's be at?
thanx
thanx
the AFR that you need to run is directly related to how much boost/timing you're using at any given RPM.
During spoolup you're typically okay to be in the mid/low 12's as I suggested earlier simply because you're going to be at low load/boost and timing will be coming down as load increases initially.
as you near 3000 RPM and full boost you'll need to be at or very near to your target AFR which should be somewhere in the 11.0-11.5 range depending on how much timing/boost you're running.
none of what I said is a blanket statement, it's just an example to help you better understand, and keep asking questions, I'll gladly help wherever I can.
During spoolup you're typically okay to be in the mid/low 12's as I suggested earlier simply because you're going to be at low load/boost and timing will be coming down as load increases initially.
as you near 3000 RPM and full boost you'll need to be at or very near to your target AFR which should be somewhere in the 11.0-11.5 range depending on how much timing/boost you're running.
none of what I said is a blanket statement, it's just an example to help you better understand, and keep asking questions, I'll gladly help wherever I can.
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Hey Chris, I tried a test today that resembles these AFR numbers you mentioned here. Currently my spool up from 2500-3000 is 10.1 to 11.1 AFR, respectively. So I leaned the spoolup 12.7 to 12 AFR from 2500-3000rpm. The attachment shows my results. Its spoolup is significantly slower when it's leaner in my case. Is there something else I need to do?