LLK Tuning: More Power, Less Soot?

Hello, especially to the motor experts .

Regarding LLK (liquid-to-liquid cooler) tuning, I'm still wondering to what extent improved (more effective) air cooling in "normally sooty" TDIs, without increasing the fuel injection quantity, can unlock additional power.

More fresh air is the standard solution for dealing with soot, and soot is ultimately wasted energy.

If, theoretically, a large-scale liquid cooling system (LLK) were to bring the engine's coolant temperature (almost) down to the ambient temperature (meaning about 20°C cooler than with conventional LLKs), then "a certain amount" more fresh air would enter the cylinders without having to increase the boost pressure.

Since virtually every TDI produces soot, the increased oxygen supply should reduce the soot content, meaning the diesel combustion becomes more "complete" (a silly term, like "pregnant" or "dead" ).

Can approximately estimate how much additional performance is achieved in the end?
-> for engines that have not been tuned, and therefore appear "clean" visually.
-> for engines that are "normally" tuned and produce the usual slight amount of smoke.
what could come out of it?

The loss due to incomplete combustion had already been taken into account in the statement that the efficiency does not increase significantly when the charging temperature is lowered.

Overall, incomplete combustion accounts for approximately 1% of the total efficiency. However, there are more effects than just soot formation, and these effects tend to increase losses rather than decrease them when the temperature is lowered.

Therefore, you don't need to take that loss into account. The efficiency gain from the higher lambda still provides a benefit, even though it is already very small, as discussed.

As the air-fuel ratio decreases, there is indeed a point where soot is produced instead of power, but the soot formation would already be unacceptable before that point.

Best regards, Ernst.

Ernst S. wrote:

As the air-fuel ratio decreases, there is a point where soot is produced instead of power, but the soot formation would already be unacceptable before that.

Hi Ernst,

Then I probably made a mistake in my estimate in the article.
that soot + more air (through LLK tuning) can only result in more power if the car has already been darkening entire landscapes.
roughly correct...?

Hi,

I also have a question about that.

Quote:

There are more effects than just the soot formation, and they tend to increase the losses if you lower the temperature.

What kind of effects are you referring to?

Greetings.
Thomas.

There are more effects than just the soot formation, and they tend to increase the losses if you lower the temperature.


What kind of effects are you referring to?


Combustion consists of many chemical reactions, and many of these are temperature-dependent, which alters the amount of energy released. The end products can include more than just the usual CO2, H2O, and soot.
For example, at low temperatures, it is more likely that individual fuel droplets will not burn completely and will then be oxidized as hydrocarbons in the catalytic converter.
However, changes in charging temperatures due to a larger heat pump will not lead to any significant developments in this area overall.

Therefore, it is also correct for Ulf to write in his article that the LLK (likely referring to a specific technology or system) can only achieve a significant performance increase if the soot emissions, even before any tuning, were already so high that they darkened the landscape.

Best regards, Ernst.

Hi,

Okay, I read something about how a large language model can reduce performance.
But I can live with that.

Does that also include nitrogen oxides (NOx)?

Greetings.
Thomas.

Hi.

The NOx emissions are significantly lower. This is one of the main effects of a low-temperature combustion (LTC) process. Therefore, a larger LTC system can be recommended, even if it doesn't increase performance, because it definitely reduces NOx emissions.
The reduction of NOx emissions achieved through lower intake air temperature does not have any drawbacks. Usually, to reduce NOx emissions, one has to accept poorer combustion conditions and lower efficiency (for example, when using exhaust gas recirculation or reducing the compression ratio).

Best regards, Ernst.

Hi,

That's roughly what I had in mind.

@Ulf

That should also be included in the technical article. I find it quite interesting!

Greetings.
Thomas.

Thomas wrote:

That should also be included in the technical article. I find it quite interesting!

Okay, I've added it (at the very bottom).

Regarding the various opinions about LLK tuning, I have to object.

I am referring to TDi engines, which already have an intelligent engine management system.
It has been proven (we tested this on a T4 TDi) that a 2.5L 65kW TDi engine (which originally does not have an intercooler) can achieve approximately 75kW when fitted with the intercooler from the 75kW version.
Not only through feeling, but also on the performance testing platform.

Similarly, the 75 kW engine, when fitted with the low-temperature cooling system of the 111 kW engine, which has three times the surface area and volume, also experienced a performance increase.

The issue is simple and can be traced back to the temperature sensor that measures the intake air temperature, which causes the engine control unit to deliver more fuel.
This results in increased performance.

Bye.

Leigh wrote:

The whole issue is simply and easily attributable to the temperature sensor that measures the intake air temperature, which causes the engine control unit to deliver more fuel. This results in the additional performance.

Hi,

Then your motors would be special cases.
The 2.5 model without the standard Low-Pressure Exhaust Gas Recirculation (LLR) system may be designed in a way that the soot reduction typically "engages" frequently. With the LLR system, it may activate more often, potentially even exceeding the engine speed or driver-desired speed limit.

I would attribute the significantly higher power output of the 75 kW system to a previous power loss (e.g., due to a faulty mass airflow sensor) rather than to the larger liquid cooling system itself.
Did you determine the fuel injection quantity limits and air mass values (using VAGCOM) before and after the change?
Only they can explain what "important" things happened as a result of the change in the LLK (likely referring to a specific policy or regulation).

I believe it's safe to say that the intake air temperature alone cannot be used as a simple "switch" to increase power, because the mass airflow sensor (MAF) already tells the engine control unit (ECU) exactly how much fuel can be injected at most without causing excessive soot, after taking the engine speed into account.

Or the 2.5-liter engine uses significantly different calculation strategies for determining the fuel injection amount.
I once tried an experiment with a tractor: lowering the LL temperature by about 20°(?) (?), but it resulted in no increase in performance whatsoever.

It's not that difficult, really.

I'm not the only one who has done this.
More people have converted their vehicles to use LLK (a specific type of fuel system) on the www.t4forum.de website.
Ask those who did it.

Let's start from the beginning again.
The colder the air, the more oxygen it contains.
And the higher the oxygen content, the cleaner the combustion, right?
The cleaner the combustion, the better the efficiency and the resulting performance.
I personally drive a 75kW TDI engine with a charge air cooler from the 111 model.
And every tuner will tell you that retrofitting with a Low-Pressure Catalyst definitely makes a difference.
And the LMM (likely referring to a mass airflow sensor) was definitely not broken. I'm sure of that. Or, does a T4 with 75 kW still run at approximately 170 km/h according to the speedometer with a defective LLK (likely referring to a coolant level sensor), and then just under 180 km/h with a larger LLK, all on a flat, straight road with no headwind or tailwind, and without benefiting from slipstream?
You'll have to explain that to me!
Oh, I forgot. All of this happened on a summer day with a temperature of around 28°C!
And that's a fact. I'm not upset if anyone doesn't believe it, but why did the tuners fit an intercooler to the 1.6 TDI Golf 2, and then increase its size?
Exactly because the oxygen content is higher then!
I was just looking for the right topic on t4forum.de, then you can read it there!

http://www.t4forum.de/wbboard/thread.php?threadid=300&boardid=3&styleid=2

Have fun!

P.S. This is not a joke, and I know how I feel!


PPS: I forgot something else...

The theory is good, but you usually only see the real results in practice.
And many scientists have unfortunately had to experience this firsthand!

I think we've entered a causality loop now!

Ulf, feel free to stop by sometime and use VAG-COM to do some diagnostics.
I live in the Palatinate region. District of Pirmasens!

Hello Leigh!

Now, briefly and concisely. If you give the engine a larger intercooler, it is most likely to reach its standard performance. In the summer, when it is hot, the engine control unit adjusts the power DOWN to avoid soot emissions. Everything you feel from the intercooler modification is an improvement in the current situation (high temperatures in the summer).

The engine has a maximum injection amount, so NEVER more fuel is injected than usual! All external circumstances only lead to a reduction in engine power, as a PROTECTION for the engine, of course.

I hope I have expressed myself clearly. Please correct me if I am wrong.

Best regards, Peter.

Hello,

Quote:

Let's start from the beginning again. The colder the air, the more oxygen it contains.

Unfortunately, that's completely wrong. Let's start over.
The oxygen content of the air is always the same, unless you take a trip to Mars.
The mass of the combustion air, and therefore the mass of the available oxygen in the engine, increases as the air temperature decreases.

Best regards, Rainer.

Well, I suppose I expressed myself in a rather simplistic way.

Of course, I meant the mass of air!
It's probably denser the colder it gets!
And with the large LLK (presumably a type of clothing), I don't notice any difference whether it's summer or winter!

But my offer still stands.
Therefore, I'm only achieving that the T4 maintains its performance throughout the entire year.
And that's a good thing!

Hello Leigh!

You already found the answer yourself!

"Quote Leigh!"

Of course, I meant the mass of air!
It's probably denser the colder it gets!
And with the large LLK, I don't notice any difference, whether it's summer or winter!

Your engine will therefore always operate close to its optimal factory performance. Never exceeding it. The larger intercooler simply allows you to better compensate for temperature differences in the summer; that's all there is to it, nothing else.

I can't figure out what you're trying to say.

Best regards, Peter.