VEP TDI: Technical Background & Troubleshooting

Hi

The topic of "free driving" for diesel vehicles is certainly familiar to most people.
Nowadays, this term is mainly used in reference to particulate filters.
But what about older diesel engines?
What exactly happens during the "free driving" phase?

I've been driving a Sharan with an AFN engine for 60,000 km, it has a red sticker (indicating higher emissions), and it already has 270,000 km on the odometer.

I often tow cars on a trailer for distances of several hundred kilometers, which is mostly a grueling experience for the small AFN engine, and I always have the same experience:

The engine already runs very well and reliably, but in the first few days after being towed, it performs significantly better. It has noticeably more torque and power.

Unfortunately, this effect really only lasts for a few days, even though I don't drive the car on short trips and I try to use all its features as much as possible.
After that, the engine returns to its "normal level," which I find quite disappointing.

What exactly is happening that makes him perform so much better in the days following the "hang time" sessions?

Hi Flo

Quote:

What exactly is happening there, and why does he feel so much better in the days following the hang time sessions?

Your brain stores the rides with the trailer attached to the vehicle as the "normal" state, which is why it feels better afterwards...

It always depends on what you're used to driving. For example, if you're coming from an SQ5, you'll probably feel like you're driving a lawnmower.

In my opinion: purely a subjective feeling... I sometimes feel exactly the same way.

Or can the performance increase be measured and verified?

Autoservice wrote:

Quote: What exactly is happening there, and why does he feel so much better in the days following the "hang time" sessions? Your brain stores the rides with the trailer attached to the vehicle as the "normal" state, which is why it feels better afterward... It always depends on what you're used to driving. For example, if you're coming from an SQ5, you'll probably feel like you're driving a lawnmower. In my opinion: purely a subjective feeling... I sometimes feel exactly the same way. Or can the performance increase be measured and verified?

I know what you mean, as I often drive different cars.
However, in the case of the Sharan, it's definitely not just a matter of personal opinion.

It's not about acceleration or speed, but rather about the turning ability.

You can really notice the difference, especially when you accelerate properly in second gear. I've already noticed it after just the first longer highway drive, even with the trailer still attached.

Hi,

You're already writing it correctly, "you can tell." However, unfortunately, you're only noticing it subjectively.
It's possible that it might perform close to its factory specifications after such a trip, simply because a lot of deposits that build up due to high loads and temperatures are removed. However, you probably won't notice any difference.

If you bring actual measurement data from a test bench, things get interesting here .

At 270,000 km on the odometer, the variable pump timing adjustment of the VP37 is likely no longer functioning correctly.

It is possible that, due to the increased load and speed, it may become "movable" again for a short period.

Best regards, Rainer.

Hello!
I can also contribute my own experience.
that it doesn't necessarily have to be an illusion.
Until 1996, I also worked as a professional truck driver.
Back then, I drove all sorts of cars, from Wartburgs to large trucks.

I once had a VW LT 28 for a week. It had a 6-cylinder naturally aspirated diesel engine. Of course, it was a VEP (vehicle for special purposes). I think it had an engine displacement of 2.4 liters and produced around 75 or 90 horsepower.
That was a car that had only been driven within the city for years. We had 8 different driver groups, and each car was always assigned to a specific tour. And the drivers who primarily drove within the city were always the group closest to retirement.

I was given the LT for a trip, exceptionally, for the entire week, during which I had to drive a lot on highways and highway-like country roads.
Initially, the top speed, I'd say, considering the years that have passed, was...
Maybe around 90, and on Friday, I pushed it so hard that it reached 115 km/h. Don't focus too much on the exact speed.
"But it was already possible to notice a huge difference according to the speedometer. And it also felt better."

I can't come up with any reasons for that either...

Quote:

I can't really come up with any reasons for that either....

Probably, you have regenerated the entire exhaust system .

Steffen G wrote:

that he scored 115.

There was more potential there; we had one like that in the civil service, with a raised roof, that could easily reach 130 km/h on the speedometer.
But it was always done at full speed.

Greetings,
Dieter.

Hello!
"So, 130 seems a bit risky for a wardrobe system with only 75 horsepower."
At work, we sometimes had a daily exchange system.
Okay, so I also drove a car from around 1992 at some point.
"It wasn't a high-roof model, but it had a turbocharger, and it probably went around 130 or 140 km/h. For that time, before the Mercedes Sprinter, that was an incredible speed for a van."

But somehow, I've gotten off track here, because the question was about TDI engines. And that doesn't apply to the first generation LT vans.

My own Golf TDI is also somehow "done for" due to constant short trips; the exhaust is probably clogged, and the VTG (variable turbine geometry) sometimes gets stuck.
But that's not really relevant to the topic here.

What might be contributing to this now?
Deposits on the nozzles that burn off under full load?

Or, does the control unit have any kind of learning function?
It was claimed many years ago at informal gatherings, but I never really believed it. Can anyone definitively deny this?

Oh. Is motor-talk now here?!

When running at full throttle, exhaust pipes and mufflers get hotter, and therefore expand more - resulting in a larger cross-section and less flow resistance for the exhaust gases - which means more power for propulsion (duck, run away).
Sure, here's the translation:

"Best regards," or "Sincerely,".
H.

I can understand that towing with a trailer requires more torque, and the VTG (torque vectoring) system responds accordingly by engaging more frequently and becoming more active, which creates a subjective feeling of increased power.

If my girlfriend has been driving my V6 TDI gently for a longer period (shifting early, like she does in her AFN Galaxy), then it might feel a bit restricted at first. But then, if I drive it more aggressively, it will feel freer. The AKN engine needs to rev up to really get going.

Ockham's razor is applied throughout science, but it seems not to be used here in this forum. Something cannot be true if it cannot be explained in a straightforward way. And if it can be explained, then it must have been copied from Motor-Talk; there's no other way.

I understand what you're describing, a similar situation: a 2000 km vacation trip, 4 people in a Toledo 1L with an AFN engine, a trailer attached, and 4 bicycles on the roof, so a high load and high air resistance. No problem for the car itself, just a high load leading to higher fuel consumption. Back home, I didn't change my driving habits on my usual routes. However, the car changed: it suddenly felt much faster (which, according to the opinions here, can only be interpreted as a "feeling" or "imagination," as who among us can provide a dynamometer test to prove it?). And: it suddenly started consuming a lot more fuel, 2 liters more per trip, despite unchanged driving conditions compared to before the vacation. Same driving profile, same load, same speed, same route... Yet, there was a 2-liter increase in fuel consumption (not an imagination or feeling), which returned to normal levels after 2,500-3,000 km once the (actual) high load was removed, just like the performance.

Here's the translation:

"Second example: Opel Sintra 3.0 V6 gasoline engine, with a gasoline consumption of approximately 10.5 liters. It experienced a cold start issue and an immediate switch to E85. E85 has approximately 30% less volumetric energy content than gasoline, so a consumption of around 14-14.5 liters would have been expected. The consumption suddenly increased to 17-18 liters one day, and then settled within the next approximately 3,000 kilometers to the initially expected, but not achieved, level of 14-14.5 liters."

According to Occam's Razor, the most plausible explanation is that both control units have certain adaptive capabilities (although this is not proof, but only a hypothesis). It is the simplest and most plausible explanation because it involves the fewest variables. Until proven otherwise.

Best regards, B.

Hi,

It's always interesting to see what specific characteristics certain control units are supposed to have, 99.9% of the time stated by people who have absolutely no idea about the respective control unit.

Nochmals: Alles älter und gleich EDC15 (MSA15, MSA12 und noch älterer Kram) hat definitiv NICHTS adaptives! KAFN has it!
In 2018, one could be happy that an AFN engine was still running reasonably well, as due to its age and resulting mileage, extreme wear and tear is to be expected, meaning that the majority of engines are essentially scrap.

Quote:

AFN, purchased at 4 years old with 20,000 km on the odometer, sold with 390,000 km:

If that ancient, clunky piece of equipment happens to function correctly, well, someone might call it "adaptive," but that just proves they don't understand what an adaptive control unit actually does.
Normally, an ESP from an AFN engine is typically finished after an average of ~250,000 km. And I'm saying that not because I'm a baseless know-it-all, but because I have driven, tested, and tuned many AFN engines.

Regarding EDC16 and DPF systems, there is ongoing debate about whether the maps that are activated depending on whether or not regeneration is occurring should be considered "adaptive."

If "Freifahren" (presumably a process to verschandeln or clear something) changes anything, it's the already mentioned issues that I and others have observed, such as awkward initial injection timing on VP37, clogged injectors, and VTG (Variable Turbine Geometry) problems, etc. But NOTHING changes in the engine control unit (ECU). Even a razor blade won't help with that; it's better used for shaving.

Best regards, Rainer.

Hello!

I can tell you about what happened to me today with my company car:
Okay, so it's a VW T6, with a 4-cylinder diesel engine, a small engine, but it uses AdBlue.
23,000 km, 1.5 years old.

Normally, I only drive in city traffic and on country roads. The A 72 is usually congested with trucks, so I rarely exceed 120 km/h on it.

Today, I was completely fed up with all the construction sites and city traffic.
and then, in order to get off work on time, I took a completely different route than I usually do (a huge detour, but it was faster).
50 km of highway, with unlimited speed, and at that time, it was unrestricted.
Initially, the car reached 140 km/h, then it increased to 150 km/h. Later, it went slightly uphill, and it reached 160 km/h there, which it then maintained on the flat highway.

I don't want to start calculating, but that car was definitely missing around 20 horsepower, somewhere between 140 and 160.
In normal driving conditions, I haven't noticed any difference.
Before, I didn't pay attention, and after the sudden, full-throttle ride, I didn't notice anything either.