How is throttle-by-wire programmed?

[David]

I have this theory based on driving modern cars and on what's possible with programming modern aftermarket ECU's that the throttle body doesn't go to 100% open when you press the throttle to floor.

My 2023 Tundra seems noticeably faster on part throttle than full throttle and my 2011 Cayenne didn't seem to have a direct correlation between throttle position and acceleration.

Is anyone here an expert on how the OEM programs TBW and care to enlighten us?

[908/930]

I'm not an expert but I think part of what you are feeling is also camshaft timing and ignition timing being altered, part throttle the cams likely tuned for more torque.

[pwd72s]

Plus, the ECM "learns" the owner driving habits..

[David]

Originally Posted by pwd72s

Plus, the ECM "learns" the owner driving habits..

If that's the case mine would only have 0% and 100% settings

What I'm getting at is the ECU protecting the transmission or driver or whatever by keeping full throttle from happening in low speed situations.

I was watching some Motec videos on boost control for my 930 and was surprised at how throttle position control is so easily used.

[Zeke]

Only that you are correct in knowing that the air is allowed as needed. Cams and timing are part of it.

[aschen]

No expertise, but I suspect the relationship between throttle position sensor and and throttle body opening is complicated.

I assume it changes with temp, settings in the car (sport, econ, etc), adjusted by what the ECU has learned. There could be a time element built in, like so many modern cars have rev hang. The way I understand throttle position in modern cars is "torque demand" and how that request translates to throttle opening is translated by a bunch of factors and the whim of the calibration engineers.

[stevej37]

I put one of these on my Honda Fit....made a big difference in throttle response.
About $250 and well worth it. Just plugs in at the foot pedal.

[Arizona_928]

The Cummins come with a torque management with the g56 Bruce Jenners…I’m not sure if it’s the drive by wire in the throttle delaying fuel or the ecm, but an aftermarket “stock tune” will slip the clutch.

[1990C4S]

There is no single simple answer. The TB activation depends on a lot of factors, including the drive mode you have selected.

It seems very unlikely that you would never have WOT, it may not feel like you do, but at some point, you do have it.

[cockerpunk]

because of the nature of butterfly valves, airflow is non-linear to petal travel already.

mostly they are using DBW to do emissions controls, cruise control, and traction control.

[David]

My point in asking is could a simple change to the throttle map table make a dramatic change to performance driving without changing the fuel, ignition, cam or boost maps. Like change every cell in the throttle map table (if that's what an OEM ECU has) to a direct 1:1 relationship to the throttle pedal. I'd still leave TBW traction control as is.

[1990C4S]

If you can access the throttle map, then in theory yes. Spark, fuel, cam timing should all stay correct. You can make full throttle happen at 25% pedal movement.

To CP's point, one of the benefits of drive by wire is you could program the response to be 100% linear, to mimic a sliding valve plate.

[crustychief]

https://www.youtube.com/watch?v=BL3pKztZirA

about 1725 in describes it. The whole video is pretty good though.

[cockerpunk]

Originally Posted by David

My point in asking is could a simple change to the throttle map table make a dramatic change to performance driving without changing the fuel, ignition, cam or boost maps. Like change every cell in the throttle map table (if that's what an OEM ECU has) to a direct 1:1 relationship to the throttle pedal. I'd still leave TBW traction control as is.

my point was that 1:1 does not mean 1:1, because butterfly valves are not linear devices.

people are using DRW tuning to solve issues in classes like GLTC. they limit the throttle to limit the torque and stay under the power limits needed in the class. you can also generate an almost perfectly flat torque curve this way.