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      12-11-2019, 06:13 AM   #23
Thecastle
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Quote:
Originally Posted by quick View Post
I think you meant lean? My understanding is the AFR's are still above 13 at the higher RPM and need to be richer like under 12, no?
No, I mean rich especially the afrs in the 11s in his spreadsheet. I suspect the tuner just cranked up the boost (too far) and is running the turbos way outside their efficiency range. As such the turbos aren’t flowing more air, but more heat. To compensate for the heat they’re throwing in fuel. DI engines are superior at cooling down temps with fuel evaporation right in the cylinder.

I don’t think except for potential turbo surge their tuning strategy is unsafe, just not optimal. That’s why I asked for more data, such airflow, timing, etc.

So potentially this tuning strategy is leaving more power on the table. They might back off the boost aka heat, to where they achieve peak airflow, increase timing and back off the fueling. Without more data it’s hard to say for sure. Running rich is typically a way to combat too much heat from running the turbos to the point where they only add heat instead of air flow. Increasing combustion chamber temps and increasing the chance of knocking, so they dump fuel, and back off timing, which probably isn’t the way to make peak power.

The key is matching the air to fuel, minimizing heat and maximizing timing, also the rough graph looks like they maybe having turbo surging problems... or lots of noise in their test setup.

Last edited by Thecastle; 12-11-2019 at 06:57 AM..
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