Kickdown: Boost Performance Explained

Hello,

I just had an idea for a "tuning <-> series" foot switch.

Basic principle:
After a chip tuning, for example, the original torque curve is written into the driver preference module (KF) when the accelerator pedal is pressed 80% of the way.
If the driver uses (a maximum of) 80% throttle, the engine's power characteristics will be the same as those of the standard engine at every RPM. Only when the throttle is opened beyond 80% does the engine enter the tuning range.
To make the 80% pedal pressure clearly noticeable, a pedal mechanism with a higher spring force above 80% would be needed, similar to what I've seen in automatic cars with a kickdown function.

The 80% pedal pressure at the beginning of the kickdown range is just an example: if the pedal mechanism only becomes difficult to operate at 92%, the standard torque curve is simply programmed into the driver preference settings at 92%.

The question is whether the mechanical kickdown threshold is actually below 100% pedal pressure, or whether the kickdown only activates a switch while the pedal pressure has already reached 100% - in that case, the whole thing wouldn't work like this, and one would have to, for example, use an additional spring element under the pedal to make the kickdown range noticeable.

Does anyone here know what the PWG (pressure wave generator) characteristic curves are like in automatic cars, perhaps specifically in the Polo/Ibiza 6L/Fabia?

Information about specific accelerator pedal adjustment regulations for the 9N automatic transmission might also be helpful...

Basic principle:
After a chip tuning, for example, the original torque curve is written into the driver preference module (KF) when the accelerator pedal is pressed 80% of the way.
If the driver uses (a maximum of) 80% throttle, the engine's power characteristics will be the same as the stock engine at every RPM. Only when the throttle is opened beyond 80% does the engine enter the tuning range.


Hello Ulf,

I don't want to commit to anything right now, but if I remember correctly, my tuner works exactly according to this principle.

It only releases the extra capacity when a full load is requested.
However, even for him, 80% pedal equates to maximum power output.


Therefore, he also believes that the fuel consumption will not change with comparable driving behavior.
Since I usually use this feature even when tuning is enabled, I unfortunately can't provide any information about it.
However, I believe that a tuning setup built as described above is more suitable for passing the emissions test.
If I don't use the increased power output in the emission cycle, I will have 'the same emission values' as the standard engine.

Best regards, Jochen.

Jochen_145 wrote:

I don't want to get bogged down in details right now, but if I remember correctly, my tuner works exactly according to this principle: It only releases the extra capacity when a full load is requested. However, even for him, 80% pedal equates to maximum power output...

Hi Jochen,

You're probably confusing something.

In a tuning process based on my idea, there should be, somewhere within the driver profile settings, a kind of copy of the torque limit, so that when you reach that pedal position (which is noticeably at the threshold of the kickdown range), you only get the standard power output – but I haven't seen anything like that in any tuning file yet.

In a tuning process based on my idea, a copy of the torque limitation should somehow appear within the driver preference settings (KF).

Okay, this one might be difficult to find, but I understand that at 70% pedal travel, the maximum driver-desired values for the standard performance curve are being used.

The torque limit is set at 51 mg/h, depending on the engine speed. Therefore, the difference will only be the difference between the standard torque limit and the maximum injection amount of the standard driving mode.

Okay, it's a bit more than the standard performance, but it's quite close to your idea, isn't it?

Best regards, Jochen.

Jochen_145 wrote:

ulf wrote: In a tuning process based on my idea, a copy of the torque limit should somehow appear within the driver preference settings (KF) Okay, this one might be difficult to find, but I understand that at 70% pedal, the maximum driver-desired values of the standard characteristic curve are entered.

No: For example, at 70% the values of the standard torque curve would be entered.

Result: At 70% throttle, the driver would experience the original torque curve.
"The challenge is to find a way to indicate to the driver that they've reached the point where the standard engine is operating at full capacity, so they know that even with 100% throttle, they won't get any more power."
And what I imagine this marking to be is the kickdown threshold, which can be felt through the accelerator pedal.

Above 70%, the driver's preferred engine map would return to normal, possibly with a tuning surcharge to ensure the increased tuning torque is achieved (or, as is common with TDI engines, to allow for a bit more power than indicated by the torque curve).

What will the transition be like when exiting partial load operation? Shouldn't the load be increased at least to the kickdown threshold beforehand, so that there is no further soot buildup or delayed throttle response? It would be really useful in the lower gears, until it then runs with the full tuning level and exits the soot reduction mode, but you might already be hitting the rev limiter.

When running at full load immediately after a gear change, the vehicle behaves like a normally tuned vehicle. However, I'm a bit concerned about the transition from partial load. Can you really control the increased load torque properly if there isn't a smooth transition?

Herr Antje wrote:

How will the transition/change be when exiting partial load operation? Shouldn't the load be increased at least before the kickdown threshold, so that there is no further soot formation or delayed throttle response?

No, that is normally prevented by the blurring filter.

Quote:

It wouldn't really be worthwhile to go into the lower gears until it's running with the full tuning, because then you'll hit the rev limiter before you reach the soot limit.

I don't see those problems. It's likely that you have certain assumptions that don't align with the software's actual functionality, and that's making you unnecessarily skeptical.

Quote:

Can the increased LD still be properly controlled if there is no smooth transition?

Yes, that's possible. It's just like when you use normal tuning and give it so little gas that, by chance, only the standard amount of fuel is injected.
If you go all the way through with it: where would problems suddenly come from if the tuning software is okay?

Quote:

No, that is normally prevented by the blurring filter.

Well, no matter how much my turbidity map wants it to, it won't work below 2000 rpm. In the range you described, there's also significantly too little LD (likely referring to light intensity or similar) initially, in the extreme case.

Quote:

I don't see those problems. It's likely that you have certain assumptions that don't align with the software's actual functionality, and that's making you unnecessarily skeptical.

Probably, I don't really know much about it. LD regulation, input tax credit chart, your project should be something that a good tuner can assess (maybe someone will chime in).

However, I assume that the customer (me) wants exactly what everyone else wants, which is why the accelerator pedal map is shaped the way it is.

Quote:

Yes, that's possible. It's just like when you use normal tuning and give it so little gas that it accidentally injects only the standard amount. If you then fully commit to it: where would problems suddenly come from if the tuning software is okay?

Isn't the lambda value slightly increased when the same amount of fuel is injected during tuning, so that the vehicle runs richer and performs better on gasoline, in case full load is expected?

I expect a delay between the stock settings and the tuned settings once a certain threshold is exceeded, a delay that wouldn't be present with a normal tune. So, a too large jump between, for example, 70% and 71%. However, if full throttle is applied from the moment the clutch is engaged, the maps are the same.

I don't think this idea is groundbreaking. It seems too simple, and it probably won't deliver what customers generally expect. However, if he's really as enthusiastic about it as you anticipate, I actually see more of a risk...

Herr Antje wrote:

Is it possible that the LD (lambda value) is slightly increased during tuning, even with the same injection amount, to ensure the vehicle runs better on gasoline, in case of full load?

You can choose to do it yourself, but you don't have to.

Quote:

I don't think this idea is that groundbreaking. It's probably too simple, and it likely won't deliver what customers generally expect.

That's right, it's only intended as information for interested drivers (see above: "without tuning, there would be no more acceleration"). Those who aren't interested might find it confusing.

Quote:

But if he's really pushing the gas pedal as much as you expect, I actually see more of a danger...

My goal wouldn't be to suddenly unlock the full tuning potential with a single adjustment of 1 mm of pedal travel.
But rather, for example, with my Polo, to put it simply:
20% gas = 32 horsepower.
40% gas = 65 horsepower.
60% gas = 98 horsepower.
80% throttle = 130 horsepower = standard power; from this point on, the accelerator pedal requires more force to achieve higher power.
90% gas = 145 horsepower.
100% Gas = 160 horsepower = full power.

Hello Ulf,

I tested your idea of integrating torque limitation into the driver demand map, using an ASV as an example. However, it only works to a limited extent.

It is correct that you must actually enter the torque limit values here, because these can differ by up to 15% from the driver's desired setting in higher RPM ranges.
Looking at the areas below 2000 rpm, the fuel injection map (KF) appears somewhat unusual, as it specifies injecting more fuel at levels below 80% than at 80%.

Now, the question is whether it fundamentally makes a difference if I limit the amount based on the torque limit, for example, to 42 mg/h, while the driver's desired value in the driver profile is, for example, 48 mg/h, or if I directly enter the 42 mg/h into the driver profile.

Could we reconfigure the entire driver-selectable performance mode system so that modes below 80% utilize torque limiting, and modes above that utilize the tuning range?
The actual torque limitation could then be optimized for tuning.

@Rudi or Rainer, maybe Ulf knows this too:

Why do I specify up to 54mg/h in the driver request profile for low speeds, when I simultaneously limit the amount via a torque limitation to, for example, 38mg/h?

However, one would need to somehow mark these 70% for the driver, so that he knows 'now the standard engine is at full load, and more would not be achieved even with 100% full throttle.' And I imagine this marking as the kickdown threshold, which is felt by the accelerator pedal.

Here's the translation:

'Use a simple, relatively strong spring to create a sudden increase in resistance as you approach full throttle. The size of the spring should be chosen so that you experience a significantly greater resistance in the last 20% of the pedal travel. This will give you an indicator of the optimal tuning range.'

In summary:
Basically, from my point of view, this tuning should be feasible.

Best regards, Jochen.

[edit]

Something like this could be the appearance of a driver-defined characteristic map based on an ASV (Adaptive Stability Vector).
The range up to 693 rpm will continue to be limited by the (modified) torque curve.
Clearly (or at least, I hope so), the drop in fuel injection volume is visible in the range between 50% and 80% pedal travel.
At full load, I would personally limit it solely based on smoke reduction (personal preference ).

Jochen_145 wrote:

Looking at the areas below 2000 rpm, the driving request "KF" appears somewhat strange, as it aims to inject more fuel at levels below 80% than at 80%.

Sure.
To make the range of our engine's performance more understandable, we could, for example, limit all driver-requested torque settings below 80% pedal travel to the standard torque output at 1900 rpm, within the range of 1000 to 1900 rpm.
The 100% line will then follow a normal trajectory (with an optional tuning surcharge if needed), and between 80% and 100%, the EDC automatically interpolates the requested quantities.

Quote:

@Rudi or Rainer, maybe Ulf knows this too: Why do I specify up to 54mg/h in the driver request profile for low RPMs, when I simultaneously limit the amount via a torque limitation to, for example, 38mg/h?

I can't find an explanation for this within my current understanding... perhaps it's trying to mimic the behavior of a mechanical pump, which also delivers the maximum amount of fluid even at low speeds with minimal throttle.