Electronic Throttle Control

Hey Andre,

Do you have any input on how Torque Based-ETC Systems are tuned. What is the relationship between Requested Torque, Accelerator Position and RPM and what does this mean to you as a tuner? I understand that Requested Torque is used as an input in the Target Throttle Angles Table and is used to determine Target Throttle Position, i.e. engine acceleration response. Does this type of system allow the user to define the "nature" or "personality" of the Engine Response as a whole? If so, what parameters are most important to you as a tuner to modify or adjust to achieve a desirable result? Thanks for any input!

For the most part a torque based throttle request is a technique a manufacturer uses to control the throttle opening in response to the driver's torque demand rather than directly via driver throttle position. You can affect the feel and throttle response of the engine by altering the requested torque table and raising the requested torque vs driver throttle position value will result in more throttle opening and a crisper, more aggressive throttle response. Particularly if you are modifying the engine and achieving more power/torque, it's usually essential to raise the requested torque values to match the engine's actual power torque delivery otherwise you may not reach full throttle in certain areas of operation.

When you're making changes to these tables I suggest making changes of 10% at a time before testing. This should be large enough for you to feel the effect without being too large. It's also worthwhile to log the actual throttle opening to confirm what is really happening.

Since you have to adjust the values to match the engines actual output capabilities, it's safe to assume that this is a table left for the end of the tune? Would you just use your dyno output values to fill in this table directly? Thanks for the info!

The answer is that it depends (not useful I know, but read on).

In most cases the requested torque table can simply be used to adjust the 'feel' of the throttle. in this case you can leave this until the end of the tune. If the ECU is smart enough though and you're increasing the power significantly, not raising the requested torque values at WOT will result in the ECU closing the throttle slightly and obviously messing with the tune. That's why it's important to watch what is happening on a logger.

Andre, So how does the 'requested torque ' on the table correlate to the output of the engine?

If the range of torque demand values range from 0 to 400 within the existing table and I then requested 5 or 600, what will the end result be?

Hello Ricardo, if you requested 600 where it was 400 then the dbw throttle will open fully and give full torque and by shifting the lower from 0-6 will mean it will be less sensitive than if it was set to 0 00

My thoughts - consider as discussion points.

If I understand the crux of your question correctly, you need to consider the torque curve of the engine.

At fully open throttle, or partially open throttle, the torque output can vary substantially. This is even more noticeable with turbo-charged engines as they come on boost.

Normally a SKILLED driver can largely control this by careful throttle control, but it is difficult - especially with 'peaky' engines.

However, by using the engine's ECU to control the throttle opening it is possible to alter the opening to achieve the desired torque output. There are three basic ways of doing this and they may be used with each other if the control strategy allows - the first is simply mapping a pedal position to the throttle opening the engine mapping should give a consistent maximum torque value for, if a strain gauge is incorporated into the transmission it is possible to measure the actual torque output and modulate the throttle opening to suit, and the last is to incorporate traction control to control wheel slip by altering the torque applied to the tyres.

The concept has been around for a couple of decades, at least, in top tier motorsport - to the point where the throttle pedal is usually referred to a torque control pedal.

There is another advantage, though, as some applications, such as IR setups, may have more torque at lower rpm when the throttle butterflies are partially closed. You may have noticed this yourself, if the engine is more responsive on part throttle than when you put your foot right down - is some cases it feels like it's almost stalling.