Low RPM WOT tuning?

[k4nnon]

Hey all, Link G4X PnP user here for USDM evo IX. I have some questions on low rpm wot tuning. I understand tuning and I have my car tuned making around 700 wheel with a garrett gt35r turbo. Turbo doesnt hit full spool untill about 5500rpms. Is there any specific way to tune the car for wot at lower rpms? or is it all the same? Example would be an autocross situation starting from a stopwithout the use of launch control or antilag, 100% throttle from the start at 2000rpms until the turbo kicks in. I guess what im trying to figure out is the difference between throttle opening at low rpms. Because if i go 100% throttle at 2k rpms the engine/car is not going faster than if i were to throttle it at say 30-50% throttle. This might just be the nature of the beast. I can kinda feel at what throttle position the car is actually trying to go faster or not but should I be trying to just feel for this spot or go 100% throttle. And is there any different way of tuning for this or is there a way to make the car a little more peppy down low or standard tuning. Let me know if anyone has any helpful information. Thanks.

[Adamw]

Airflow is roughly proportional to RPM, so at lower RPM you have less airflow, you dont need as much throttle area to achieve the maximum flow rate that the engine can acheive.  At low RPM you will typically reach full manifold pressure/full torque before the throttle is wide open, opening the throttle beyond this point does not achieve anything, often you may even lose a little torque compared to the opening that gives peak torque.  With single throttle plenums the loss/gain is usually small, probably ~<2% typically in my experience, but can be more significant with ITB's.  With e-throttle it is still usually worthwhile spending the extra 10 minutes mapping maximum throttle opening against RPM.

 

[k4nnon]

On 2/7/2024 at 3:15 PM, Adamw said:

Airflow is roughly proportional to RPM, so at lower RPM you have less airflow, you dont need as much throttle area to achieve the maximum flow rate that the engine can acheive.  At low RPM you will typically reach full manifold pressure/full torque before the throttle is wide open, opening the throttle beyond this point does not achieve anything, often you may even lose a little torque compared to the opening that gives peak torque.  With single throttle plenums the loss/gain is usually small, probably ~<2% typically in my experience, but can be more significant with ITB's.  With e-throttle it is still usually worthwhile spending the extra 10 minutes mapping maximum throttle opening against RPM.

 

Hey thanks for the reply. Thats kinda what I was figuring in some sense. Maybe ill do some dyno testing with this and see if there is a readable difference in a 1st/2nd gear pull from 2000-5000rpms at a few throttle angles below 100% versus wide open and look at the differences. Would be interesting to know if there is a loss at 100% throttle. Thanks for the input!