Advertising with Partial Truckloads?

Hi everyone,

"Some VP-TDIs tend to exhibit jerky behavior when idling or during light acceleration in high gears, typically below 1300 rpm. According to a database entry by Michael II, the cause lies in the software of the engine control unit."

Based on my experience with the AFN, this jerking can be completely eliminated by reducing the pump's flow rate – this can be achieved by slightly shifting the pump's upper section with the adjustment mechanism towards the timing belt. In my opinion, this is less likely to be a software bug and more likely a tuning issue between the pump and the software.

Given the significant performance advantage of most TDIs compared to their official specifications, I suspect that the fuel delivery specifications provided by VAG to Bosch for the factory calibration of the pumps may be slightly too high. This could mean that some of the pumps (depending on the actual fuel delivery within the tolerance range) may, in conjunction with the otherwise flawless engine control software, exhibit the described jerky behavior.
During test drives (and of course, also as part of test reports ), the "incredible temperament" is immediately noticeable, which certainly evokes corresponding purchase interest.

"With newer engine tuning (e.g., from my experience with the 2001 ALH in the Ibiza), the surging might be eliminated in the standard configuration, but I am now certain that, regardless of the engine control unit's software, a "richer" pump setting can ultimately cause any TDI engine with a VP 37 pump to surge - and conversely, a "leaner" setting can (almost) eliminate the described surging at low speeds and partial load in almost any TDI engine.
While there is some performance loss, it usually remains significantly above the advertised specifications.

Unfortunately, drivers of TDI engines experiencing jerky performance are unlikely to find help with such issues at most workshops: "Oh God, adjusting fuel injection quantity, using a pump test bench, a lot of effort, very expensive, blah blah blah..."
Even Bosch service centers typically only adjust the pump to the (likely too high) target value, which, while resulting in a hefty bill, does not guarantee the elimination of the jerking.

If needed, I could post a relatively simple description of a mechanical DIY solution for adjusting the flow rate, or add it to the error database.
Since the response to previous posts about specific work done on the pump has been practically zero, I don't want to occupy server space with content that no one is interested in.
Therefore, my first question is to everyone here: Could this be useful to anyone, or perhaps to a specific person?
Of course, without anyone feeling obligated to shout "here" . . .

Hi Ulf,

Perhaps a completely different question: Why do many TDI engines have/should have more power than what is stated? Is there any information available about this somewhere? Or are you referring to this statement in relation to your power test?
Don't gasoline engines also sometimes have more or less significant deviations upwards?

best regards

Adrian.

Hi.

In most tests using dynamometer measurements, I've observed that the average deviation from the paper value tends to be particularly high whenever a TDI engine is being tested.
Specifically, the difference is much greater than it is for gasoline-powered vehicles, which generally stay relatively close to their official values.

It might be because TDIs can easily handle a slightly larger amount of fuel injection without requiring meticulous attention to the air-fuel mixture.
So, it will probably also be exploited, while with the conventional internal combustion engine, one has to perform complicated and delicate work (such as polishing channels, etc.).
With a turbo-Otto engine, you also need to increase the boost pressure simultaneously, which, with conventional turbochargers using a pressure sensor and wastegate, can still be easily adjusted with a screwdriver.

But what percentage of gasoline-powered cars are turbocharged? And conversely, what percentage of diesel cars are TDIs or similar?

What surprises me a little is that you can't eliminate the jerking motion even when you adjust the actual value of the control signal using the diagnostic interface.
Whether it's 1.6mg/stroke at idle or 3.2mg/stroke, the jerking during rolling remains the same. In principle, your practiced 'mechanical' adjustment should have the same effect, namely an adjustment of the actual injection amount to match the regulator's position, or

(This post was accidentally edited by me instead of being replied to - sorry Rainer . Regards, Ulf)

Quote:

What slightly surprises me is that you can't get rid of the jerking even when you adjust the actual value of the control signal generator via diagnostics. Whether it's 1.6mg/stroke at idle or 3.2mg/stroke, the jerking during rolling remains the same. In principle, your practiced 'mechanical' adjustment should have the same effect, namely an adjustment of the actual injection amount to match the regulator's position, or

Hi Rainer,

I'm sorry about your previous post. Perhaps you could try reconstructing it?

Subject:
Theoretically, it's probably the same, but in practice...?
I still think there are issues with the transition between idle and partial load.

You can get rid of "my" stutter by...
a) the upper part of the pump moves, or...
b) adjusts the movable short-circuit ring on the switchgear shaft (terrible German, ugh...).

However, solution b) may potentially bring the signaling system close to the limits of its electrical tolerance range, which, in turn, can be acknowledged by the indicator lamp for the heating control.

I haven't had the chance to try the diagnostic version yet, as I'm still lacking the necessary hardware and software.
Perhaps you only changed the standard idle speed setting, which the engine computer only partially takes into account because the target value of "900 rpm" takes precedence .

And wasn't the "jerking" more likely the problem when uncoupling and rolling, etc.? I don't have any experience with that... my method mainly involves rolling at low speeds with minimal throttle.

The power loss when adjusting the pump should not deter you, especially if you are a Powerbox user, IMO: just adjust a potentiometer, and the power is back .

Okay, I'll then submit a report to the bug database.

Hi Ulf,

"No problem, that editing thing has happened to me before too, but the meaning of what I wrote is still correct ."
So, the engine misfire only occurs when no gear is engaged, the engine speed is between 900 and 1100 RPM, and the car is rolling between 2 and 20 km/h.
Reducing the load on the engine (e.g., by turning off the air conditioning, rear window defroster, etc.) will amplify the effect.
"As soon as I'm in gear, there's no more shaking, and 1000 RPM in 5th gear is absolutely no problem."
It seems, as you say, to be a different "type" of stuttering.
I'm still not going to adjust the ESP settings, just in case, because I can't increase the power of my system any further without triggering a flashing yellow light ...it took me a lot of tedious 1/8-turn test phases. Never change a running system...

Best regards, Rainer.

PS: It's good that you added it to the error database.

Hi Rainer & Ulf,

'My car shudders when I try to drive in 5th gear at 50 or a maximum of 55 km/h. If I give it a little gas, it shudders. If I give it more gas, the shuddering stops immediately, but then it accelerates, and I have to take my foot off the gas again.'

Lösung (bis jetzt?): abwechselnd Gas+Leerlauf oder 4. Okay.

Regards,
Udo.

P.S.: I'm not brave enough to mess with my ESP, I can live with the symptoms.

Udo wrote:

My car shudders when I try to drive in 5th gear at 50 or a maximum of 55. If I give it a little gas, it shudders; if I give it more gas, the shuddering stops immediately, but then it accelerates, and I have to take my foot off the gas again.

Hi.

Your stuttering is exactly what I experienced. It should be fixable with an intervention at the pump.
Looking back, I'm glad I did it, because the jolting motion was quite annoying (although it didn't always happen).

Your avoidance tactic worked on me too, but I'm a perfectionist in some things, and I prefer to eliminate the root cause rather than just dealing with the symptoms.

Rainer K. wrote:

I'm still not going to adjust the ESP, just in case, because I can't crank up my amplifier any higher now without triggering a flashing yellow light ... it took me a lot of tedious 1/8-turn test phases. Never change a running system...

Hi Rainer,

I'm a little surprised by the "limited" adjustment range of the box...
Background question: Does the light blink immediately after the engine starts, or only when you are driving at full throttle ?

ulf wrote:

Hi Rainer, I'm a little surprised by the "limited" adjustment range of the box... Background question: Does it blink immediately after the engine starts, or only when you're driving at full throttle

?

Hello Ulf,

Both. It's possible that a faulty EGR valve is causing the box to be slightly active even at idle. Also, with full throttle, an overly aggressive setting can trigger an error in the engine control unit, resulting in a temporary "limp-home" mode for about 10 seconds. Because this could be dangerous during overtaking, the box is adjusted so that this situation doesn't occur (the flashing glow plug light appears earlier, but there is still power available).
Somewhere, there are definitely limits to how much the reference signal can be distorted.

Best regards, Rainer.

Rainer K. wrote:

A faulty EGR valve might cause the box to be slightly active even at idle. Even at full throttle, an overly aggressive setting can cause an error entry in the engine control unit, followed by a "limp-home" mode for approximately 10 seconds. Because this is dangerous during overtaking, the box is adjusted so that this situation does not occur (the flashing glow plug light appears earlier, but power is still available). Somewhere, there are definitely limits to how much the reference signal can be distorted.

Hi Rainer,

If your device is behaving in such a "temperamental" way, I understand why you don't want to mess with the ESP.

Through my attempts to optimize the fuel pump, I've learned that the AFN (air flow meter) moves its actuator from stop to stop when the ignition is turned on, and during this process, it apparently also checks the "linearity" between the actuator current and the mass airflow signal.
If the overall result is outside the tolerance range, a yellow card will be issued after 30 seconds.

"Nevertheless, I can crank up my Authal box (which doesn't activate until about 40 seconds after being turned on) to its maximum setting without it ever causing any issues with the engine computer."

Okay, under full load, a container might potentially cause implausible RWG (Railway Vehicle Monitoring) behavior, for example, if it pushes the switch mechanism to its limit.
Most likely, the autocalibration range has been reached, but this may not be the case for every device.

If your device fails the initial check depending on the settings, it seems to me that it's not properly designed... or it might be defective?

I can't imagine that the AGR (Abgasrückführung) system has anything to do with the RWG (Rollover Valve) test, because the check also runs with the engine off: turn the ignition on, and if it doesn't flash after 30 seconds, the pump is okay from the engine computer's perspective.

Hi Ulf,

"No, just turning the ignition on doesn't trigger the yellow light for me, not even after waiting for a while."
It only comes on after a few seconds when the engine is running, which is why there's a suspicion of an issue with the EGR valve. The system activates based on the mass airflow sensor (MAF) value, which is already around 460mg/stroke at idle...
The performance is already at the upper limit with this setting; at 1.0 bar of boost pressure, you feel guilty when accelerating because of the soot and the subsequent traffic.
Therefore, I can tolerate these minor weaknesses. However, driving it at 1.15 - 1.20 bar feels quite good. I'll probably borrow my girlfriend's phone again soon to use it as a stopwatch for the pull test .

Best regards, Rainer.

...
In most tests using dynamometer measurements, I've observed that the average deviation from the paper value tends to be particularly high whenever a TDI engine is being tested.
Specifically, the difference is much greater than it is for gasoline-powered vehicles, which generally stay relatively close to their official values.
...


hi, this reminds me of various discussions about test benches .

According to various tuners with reproducible test bench results on modern test benches (***), no unit has shown a variation of more than 5% above or below the specified values. If D is still B...

Rainer K. wrote:

No, just turning the ignition on doesn't trigger the yellow light for me, not even after waiting for a long time. It only comes on after the engine starts, after a few seconds, which is why there's a suspicion of an issue with the EGR system. The control unit activates based on the mass airflow sensor (MAF) value, which is already around ~460mg/stroke at idle...

Hi Rainer (now I've pressed the correct button again ).

Have you ever considered adding one or more diodes between the LMM (Lufft Mass Flow Meter) and the control box to increase the air mass flow threshold?
To compensate for the power loss, increase the airflow potentiometer setting on the air mass meter (LMM) - hoping that the engine will start working again later, but with increasing LMM values, it will "steeper" enrich the mixture and thus achieve the usual full-load power (or even more ).

Good idea, Ulf, I hadn't even thought of that! But right now, let's just say there's enough performance :mrgreen:available:P.
You can probably imagine how much that is, given a slightly smoky boost pressure of 1.15 - 1.20 bar .
Just wait for comparable conditions for the pull-up test, and for my girlfriend's phone (with its stopwatch function), and of course, for her herself (weight }).
For a DIY adjustment test, the mentioned diodes are certainly an option that I will keep in mind.

Best regards, Rainer.

You wouldn't drive in 5th gear at just over 50 km/h. It's not good for the bearings and pistons; they experience too much pressure under load, and the pistons can start to wobble. So, I don't drive in 5th gear below 75-80 km/h, or below 1500 RPM.