Right, so what you would say it should be? Asking because I was recently at a dyno session after a cam shaft upgrade that gave me basically s**t. Now I am analyzing all the graphs that I got and I can see that my torque drops down once the fuel goes below 12.4 AFR. At higer rpm (3600 and up) it is setup to be at ca. 11.8 going slowly down and that's where I was expecting more power I am not getting...
Technical Optimal AFR on (high) boost for our turbo engines
- Thread starter woj
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Technical Optimal AFR on (high) boost for our turbo engines
From a course that I followed they stated that 14.7 is the best.
Same for a turbo when I asked them.
11.8 is kinda rich I think.
Same for a turbo when I asked them.
11.8 is kinda rich I think.
I run 12:1.
14.7:1 is stoichiometric (under perfect condtions 100% oxygen and fuel is burnt.) turbos cant run this on boost (and n/a engines under high load)
14.7 is purely cruse afr.
14.7:1 is stoichiometric (under perfect condtions 100% oxygen and fuel is burnt.) turbos cant run this on boost (and n/a engines under high load)
14.7 is purely cruse afr.
From what I know is that the extra amount of fuel injected is for cooling purposes and preventing detonation.
Just like craig perfectly said, a perfect combustion will kill your block in most cases.
So the best AFR I think is a combination of variables such as:
Good luck!
(pls correct me if I’m wrong)
Just like craig perfectly said, a perfect combustion will kill your block in most cases.
So the best AFR I think is a combination of variables such as:
- Boost pressure
- Compression ratio
- Engine Temp (oil/water)
Good luck!
(pls correct me if I’m wrong)
Asteris
Member
Theory says 13.5:1 around torque revs and 12.5:1 at power band. Some cars go lower mainly for cooling purposes.
So Asteris, you say that even with full boost on my torque revs you would say 13.5? Sounds kind of lean to me. I have 12.4-ish there.
I did actually had a second look at my dyno logs at the shop - no power difference between 12.2-ish and 11.8-ish at 4500 RPM, see the attachment. Perhaps it is overfueled over the whole range
Oh, and yes, I know it should not be 14.7 Although I would like once to see how the engine would look like after this
I did actually had a second look at my dyno logs at the shop - no power difference between 12.2-ish and 11.8-ish at 4500 RPM, see the attachment. Perhaps it is overfueled over the whole range
Oh, and yes, I know it should not be 14.7
Although I would like once to see how the engine would look like after this Attachments
Asteris
Member
No, on full boost use 12.5 AFR, 13.5 is for 100-150kPa. Those who run at high or low 11s, are those who aren't sure of what's happening inside the cylinder and want to avoid possible detonation. If you are right on spot on your ignition map, or you have a knock sensor retarding spark on detonation, you don't need to go lower than 12.3 and get the full power.
I am right on spot with ignition, but no knock sensing, hence the safety margin. And as i said, we did not see any power differences between 12.3-ish and 11.8.
Oh, and 150kPa is almost full boost in my case, 170kPa is what I am pushing at the moment.
Anyhow, thanks, this is really useful for the next time on the dyno.
