Afr's

[Boostn]

Hey guy's....

With all this talk about people running Lean mixtures and pinging. A lot people been bagging certain tuners about how lean they run there tune to produce more power.

What are safe AFR's???

At wot and during cruise???

Would love to hear opinions of our sponsors and public...

Paulie..

[coach3062]

I also would like some answers to these questions too, plus what effect altitude (say 1300metres above sea level) has on the AFR's?

[rboksic]

I also would like some answers to these questions too, plus what effect altitude (say 1300metres above sea level) has on the AFR's?

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leaner due to thinner air less O2

having said that 1300 mt is on that high so it may only be slight change in AFR's

at WOT

[Romulus]

11.5-12.0:1 AFR at full boost. I'm not a fan of lean mixtures and high boost.

Edited 19/09/06 10:23 AM by M6 XR6T

[MYWPN]

11.5-12.0:1 AFR at full boost. Anything higher than that during sustained load is dangerous, in my opinion.

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if you have a CAT yeah, if not I would be happy running at 13.2

[Fat-Tony]

11.5-12.0:1 AFR at full boost. Anything higher than that during sustained load is dangerous, in my opinion.

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if you have a CAT yeah, if not I would be happy running at 13.2

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Even if you do have a cat you can still quite safely and realiably see mixtures of 12.5

[jetute]

I dont know... everyone has different versions... hpf tuned a car that peaked at about 13.2 or thereabouts and they said on this forum that the tune is fully safe... so go figure.

I consider 11.5 rich... and bloody expensive to run

[RAP1D]

Dont forget that timing/detonation has a massive effect on how safe the AFRs are...

High 12s with timing advance to the edge and high boost can be very risky, where as 13s on lowish boost and not so overly advanced timing can be happy sailing...

[tupperware]

Stoichiometric AFR is 14.7:1 which is controlled in closed loop by the factory narrow band O2 sensor. AFR control is in closed loop mode for realistically all normal driving. This is to maintain an economic drive.

Max power is made at 12.8:1, but blown & turbo'ed motors often run richer mixtures to help cool the air charge. Same principle as water injection. The extra fuel doesn't burn so it's similar to adding water to the charge, but with a lower latent heat of vapourisation.

It is also prudent for tuning shops to add a little fat to the tune to allow for fouling injectors & filters & the pump performance decreasing. If you don't monitor your AFR with your own reliable meter I'd run a bit rich, otherwise keep the intake charge cool, use sensible timing & run the AFRs at mid 12:1

[RAP1D]

Totally, but richening it up to lower combustion temps is a little old school these days