PDE Tuning: NW Adjustment, Performance Boost

Hello,

Last weekend, while browsing for vacation ideas, I stumbled upon a thread where someone was discussing exploding pressure discharge valves (PDVs) in tuned engines. The explanation given (as a tangential topic) was that the PDVs were failing because their closing time was too short, with a burst pressure limit of 2500 bar.

Today, I can't find this topic either through the search function or by browsing the forum .

I don't remember the author either...

Actually, I wanted to quote this passage here, but that's not possible now.


I have not yet read any concrete and understandable explanation why the pressure in PDEs can increase without an increase in speed, i.e., only by increasing the opening duration.

The only explanation I can think of is an increasingly steep angle of the injection cam throughout the entire stroke.

At low engine speeds, the injection occurs relatively late, specifically towards the end of the piston's stroke -> at this point, a large displacement per degree of crankshaft rotation does not yet generate an excessively high pressure.

At high speeds, the injection timing is advanced (i.e., shifted to the beginning of the injection cam).
Since the pressure increases with the speed, the cam profile could be made flatter in the front area to prevent excessively high pressures.

If the opening duration is extended into the steeper cam lobe area for low speeds at high engine speeds, this would result in excessively high pressures during the injection of the tuning fuel additive.

In any case, the transition from the flat beginning to the steep end of the cam profile must be smooth, as the speed-dependent shift of the injection timing also occurs smoothly.
This would result in a relatively low injection pressure at the beginning of each injection process, which would then increase towards the end (excluding the pre-injection and main injection phases).

That's my theory, as far as it goes.
Can anyone confirm or refute this?

If that is the case, why can a short closing duration of the PDEs lead to excessively high pressures?

Hello Ulf,

After reading your report about your adjusted NRR (Noise Reduction Ratio), I also checked my own NRR.

Mine was exactly in the middle, within the tolerance range of the long hole!

Okay, so I thought I'd try something out and set the NR (noise reduction) to the extreme limit of the adjustable range, towards the "early" setting. This actually works perfectly with a small hand mirror.
Translation: "Following: the improved high-RPM performance in the upper rev range that you described."

Okay, so I adjusted it a little more towards the early position – so much so that half of the hole for the bolt disappeared – and the result was: the car wouldn't even start!

So, the golden mean: 1/3 of the hole was already covered, and the car started!

Result: 5 km/h faster than the factory setting on my usual uphill route on the highway (195 km/h uphill instead of the usual 190 km/h).
BUT: Fuel consumption at idle is 1.3 liters instead of the usual 0.6-0.7 liters without the air conditioning running.
and a motor running or a noise coming from the PDE units, as if they were about to explode right next to you.
That's why I'm now driving again right at the limit, heading towards the early hours!

What's the point of all this?
I thought this might help you understand the pressure conditions in the PD a little better, as the pressure seems to have increased here as well, but without any software adjustments!

And before I get yelled at again:
My car is a Golf IV with an ASZ engine, manufactured in 2003, and it's not modified.

loveme wrote:

Then I thought I would try something out and set the NR (noise reduction) to the extreme limit of the adjustable range, towards the "early" setting, which, by the way, works perfectly with a small hand mirror.

What specific setting do you consider to be the "absolute limit of what's possible," and how do you measure that value?
It couldn't have been a fluke, since you were still able to follow up with another shot.

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Okay, now a little more: so, I adjusted it a little further towards the early position - so that half of the hole for the bolt disappeared - consequence: the car didn't even start!

This is, of course, very interesting.

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So, the golden mean: 1/3 of the hole was already covered, and the car started! Result: 5 km/h faster than the factory setting on my usual route up the hill on the highway (195 km/h uphill instead of the usual 190 km/h). BUT: Fuel consumption at idle is 1.3 liters instead of the usual 0.6-0.7 liters without the air conditioning

.
It only shows the converted operating time. If it were actually injecting that much more fuel, the "idle" speed would be incredibly high.
This suggests that you've taken some of the normal fuel delivery for the idle speed, as the rising fuel delivery curve likely flattens out significantly while fuel is still being injected – which, in turn, is compensated for by a longer injection duration.

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and the sound of the engine running, or a noise from the PDE's, as if it were about to hit you in the head. I thought this might help you understand the pressure conditions in the PD a little better, as the pressure seems to have increased here as well, but without any software tuning!

Your report seems to confirm my initial suspicion about the "increasing rate of change" of the injection camshaft.
Thank you for your attempts and your post!
Do you also have DZR times for before and after?

As a potential future addition, it would be interesting to see if the overnight charging consumption, as measured by the MFA (Multi-Function Analyzer), permanently changes due to the adjusted NW (nominal voltage) setting.

So, as the absolute limit, I would define the position where the NR (Neutral Reference) is set, where the hole is still fully visible, meaning not partially covered, but the hole and the outer long slot are aligned.
(This is, of course, on the side facing the early part of the process). So, still within the manufacturing tolerance!
I used a small mirror as a reference.

Als das Auto nicht mehr ansprang, war ich warscheinlich außerhalb der Winkeltoleranz des Gebers zur 1. Zylinder-Erkennung an der Nockenwelle. D.H. die Abweichung KW zu NW war zu groß! Ma guess!
"The 1/3 hole cover was probably just within the acceptable angular tolerance!"

I drove approximately 100 km with the settings, mostly at full throttle on the highway.
Then, out of fear of engine damage, I postponed it again.
That was probably too short a period to detect any discrepancies in the MFA's consumption.

Was mir aber noch aufgefallen ist: der Maximalverbrauch > 3500 U/min 6. Gang was 13.0 liters.
Under load, including when going uphill.
With the usual settings, it was always around 13.7 liters, plus or minus 0.2!
But still, I was faster than usual! (+5 km/h uphill and +5 km/h downhill).

I can rule out factors like tailwind, as I conducted numerous test drives on that day with various possible settings, and I tested the routes twice in both directions.

Unfortunately, I didn't take the DZR test back then!
Subjectively, the peak torque at 1900 rpm felt a bit weaker, but it had more power at higher RPMs.

Something else!

If you adjust the NR (Neutral Range) towards "late" (i.e., increase the tolerance for being late),
Then, the instantaneous fuel consumption while idling drops to 0.5 liters.
So, the pressure must have increased in this case, assuming...
that the same amount of fuel is needed to reach the idle speed.

Or could it be due to a reduced air mass?
What is the reason for the delayed opening of the intake valves?

loveme wrote:

So, as the absolute limit, I would define the position where the NR is set, where the hole is still fully visible, meaning not partially covered, but the hole and the outer long slot are aligned. (This is, of course, on the side facing the early part of the process). So, still within the manufacturing tolerance! As a control, I used a small mirror!

However, that is not an "official" indicator.
It seems that the NW gear on my engine is mounted approximately one tooth later than it should be, meaning that even when the crankshaft is at its top dead center (TDC) position, I'm already about 3/4 of the way along the elongated hole.

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I drove approximately 100 km with this setting, mostly full throttle on the highway. Then, out of fear of engine damage, I postponed it again. That was probably too short to detect any consumption discrepancies of the MFA.

Hmm... Is your "final new" setting different from the previous one (and if so, by approximately how many degrees Kelvin), so that after a few tankfuls, a change might actually be noticeable?

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Was mir aber noch aufgefallen ist: der Maximalverbrauch > 3500 U/min 6. Gang was 13.0 liters. Under load, including when going uphill. With normal settings, it was usually around 13.7 liters +/- 0.2!

I have also seen similar apparent differences at my location, even without changing any settings (!). Once, I even saw a reading of 13.9 liters on the display.
It's likely due to the fact that the maximum value is only achieved within a very narrow speed range around 1900-2000 RPM, and that the instantaneous consumption is also averaged over a certain distance. Usually, the car is accelerating during the measurement, so lower "instantaneous consumption" values are also recorded within the measurement interval.

The actual maximum value would likely only be achieved on a slope where it takes at least 20 seconds to reach, or by applying the handbrake accordingly.

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Subjectively, the torque peak at 1900 rpm felt a bit weaker, but it had more power at higher RPMs!

It's funny - I had the same feeling after adjusting my ignition timing from about 3° BTDC to the exact target value.

What we can hardly estimate is the effect of the also altered valve timing .
It's possible that the altered engine noise is due to a shift in the timing of the intake air swirl, which also "wraps" around the fuel injection jet... ?

Hello Ulf!

Okay, based on my current understanding, here's how I calculated overtime:

Rotate the engine forward until the notch on the flywheel aligns with the indicator hole on the transmission.
Then, rotate it forward another 2mm.

This is the setting where my car was out of time, specifically with the dowel pin inserted at the bottom of the crankshaft.
It's a good thing to remember for all future adjustments, after you've checked it once.

Okay, and now set the NWR to the specified "maximum setting within tolerance," and proceed early!

If the notch on the flywheel were currently perfectly aligned with the mark in the viewing hole, then everything would be off by those 2mm.

I have no idea how much 2mm on the flywheel translates to in degrees of KW, but I think it's probably less than 3 degrees, like in your car!

This is now the best setting for my needs.

The excessive idle speed has been relatively eliminated, at least for a diesel engine!

According to the MFA, the fuel consumption when idling is also acceptable (0.7-0.8 liters)!
Since I have to commute approximately 100 km to work every day, I can't afford high fuel consumption (whether the MFA is displaying the correct information is another matter).
After refueling and checking the mileage, it was found that the fuel consumption displayed by the MFA (Multifunction Display) was always about 0.1-0.2 liters less than the actual consumption.

The maximum speed is quite impressive compared to other options!

According to the official specifications, it has 148 horsepower and 350 Nm of torque.

loveme wrote:

I have no idea how much 2mm on the flywheel translates to in degrees KW, but I think it's probably less than 3 degrees, like in your car!

Probably not... 1 degree at the flywheel is approximately 2.5 mm, if I recall correctly.

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This is now the best setting for my needs, because - The lack of responsiveness at higher RPMs has been relatively eliminated, at least for a diesel engine!

That's probably about 5° KW too advanced. How does the engine sound now, compared to before?

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After refueling and checking the fuel consumption, it turned out that the MFA (Multi-Function Display) always showed approximately 0.1-0.2 liters less than the actual consumption!

Are these values reflecting data after the new hire was onboarded, or before?

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According to the DZR, it has 148 horsepower and 350 Nm of torque!

"Nisch" sends a message for an untuned ASZ.

I'm a little confused right now!

So, 2 mm on the flywheel corresponds to approximately 1.5 degrees, okay.

Why should it then be 5 degrees too early?
Basically, everything is within the tolerance limits: the KW (rear axle) is within the specified range according to the bolt on the KWR (rear axle carrier), and the NW (front wheel alignment) is within the adjustable range of the elongated hole in the NWR (front wheel alignment rod).

After the reinstallation, the power consumption calculation is not the same as it was with the previous extreme settings, and it wasn't different even with the factory settings at the very beginning.

It doesn't sound any different compared to before!
Definitely much quieter than a 74kW D4 of the same year!

Ah, yes, AGR used to be...

loveme wrote:

2 mm on the balance wheel therefore correspond to approximately 1.5 degrees, OK. Why should it then be 5 degrees too early?

Um. . . if 2.5 mm equals 1°, then 2 mm is closer to 0.8°.

The 5-degree angle was a rough estimate based on your descriptions of the elongated holes near the northwest wheel.

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Basically, everything is within the tolerance - the KW is aligned with the OT according to the bolt on the KWR, and the NW is within the possible adjustment range of the long hole in the NWR.

Hmm... To get a definitive answer, it would be interesting to hear about your "final" new position.
To do this, you would need to rotate the engine forward again to the Northwest (NW) timing mark and then tell me the position of the crankshaft relative to the Top Dead Center (TDC) mark – if it's possible and not too complicated for you.

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After the new installation, the power consumption calculation is not the same as it was with the previous extreme setting, and it wasn't different even with the factory settings at the very beginning. It doesn't sound any different compared to before!

Ah, so no (significant) changes in terms of power consumption or noise.

Do you still have any DZR values from the old settings?

Has the final new setting maintained the impression of "better performance at the top end with a less pronounced torque surge around 2000 rpm" compared to the old setting?

Hello,
Regarding 'Exploding PDs'.
When you delve into the workings of engines, you'll notice that in tuning, the injection times are always extended, and in the direction of later timing.
The duration of the injection time determines the pressure within the element.
Simply put, the longer the valve is open, the higher the pressure becomes, because in the same amount of time, less fuel can escape through the nozzle relative to the compression.
One could theoretically influence the compression by adjusting the valve lift on the intake side, but to my knowledge, this is not done. It wouldn't make sense anyway, because changing or adjusting the valve timing would also shift the pressure buildup in the pump-injector system.
Concise and to the point: Extremely long nozzle opening times result in extremely high pressures.

Greetings, btreyer.

Hello Ulf!

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Do you still have any DZR values with the old settings?

Unfortunately, I don't have any old DZR documents, as I only started dealing with them later.
I will be testing various settings today and documenting them using a detailed record.
I will report the results here.

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With the final new setting, has the impression of "better performance at the top end with a less pronounced torque bump around 2000 rpm" remained compared to the old setting?

It's hard to say, as it's been over half a year since I last used the factory settings.
What I can say is that the handling is better in the higher RPM range (above 3500).
As I said, this is always just my subjective impression!

Perhaps my new DZR measurements will provide more insight.

btreyer wrote:

The length of the injection time determines the pressure in the element. Simply put, the longer the valve is activated, the higher the pressure, because in the same time unit, less fuel can escape through the nozzle in relation to the compression.

Hmm, that sounds logical at first glance.

But as the internal pressure increases, so does...
1. The flow rate through the nozzle holes = Injection rate (mg / °KW)
2. the outflow due to leakage losses within the PDE (Positive Displacement Element).
"Therefore, in my opinion, a balance would have to be established between higher pressure and higher outflow."

However, if the PDE is designed in such a way that it takes "some time" (on the order of milliseconds) for this equilibrium to be established , and the injection is terminated in the series state before this equilibrium is reached , then your argument would be correct.

The diagrams in the yellow Bosch PD manual seem to confirm this.
After that , the injection pressure not only increases with the engine speed, but also with the injection quantity , i.e., during the nozzle opening time.

-> Thank you for your answer - I think it provides the explanation .

It would also be interesting to know, from what engine speed and injection quantity (for the various PDE sizes), the critical pressure limit of 2500 bar is reached.

I just did some test drives with the DZR (direct injection) system, experimenting with different camshaft settings.

The result of the DZR is astonishing!

Okay, let's start with the values:

Golf 1J ASZ (completely stock!!!)
Weight including driver: 1377 kg (tare weight determined using a calibrated scale!).

Trip 1: Settings as usual, i.e., NW set to OT + KW set to OT!
The reading on the graduated disc is 2mm before the marking in the direction of rotation , which exactly corresponds to the precise timing setting with the timing pin on the crankshaft pulley!
So, you would need to rotate it another 2mm so that both markings on the disc align. I hope that makes sense.

Temperature: 22° C
Fuel consumption while idling without air conditioning: 0.7 liters.
DZR Time: average 6.19 s. According to DZR, this corresponds to an increase in power of 13.8% and 148 PS and 352 NM.

Trip 2: Setting 1/3 hole at the NW side, early, which corresponds to approximately 11 mm before TDC (Top Dead Center) on the flywheel (~4.5° crank angle earlier)
Temperature: 24°C
Fuel consumption at idle without air conditioning: fluctuating between 1.0 liters and 1.1 liters.
DZR Time: average 6.02 s.
According to the DZR, this corresponds to an increase in power of 17.06%, resulting in 151.8 horsepower and 360 Nm of torque.

Someone should try to tell me that this is useless!

Setting 2 is probably a bit gentler than the extremes I mentioned in a few previous responses, as it only uses 1.1 to 1.3 liters of water.

Regarding the noise levels of the PDEs, I couldn't detect any deviation with this setting.

The torque peak now has less of a "peak" characteristic; it starts around 1900 RPM and subjectively decreases less sharply than before, more like a gently sloping plateau.

I really like this setting, so I'm going to keep it for now to see how much the consumption changes!

loveme wrote:

Trip 1: Settings as usual, i.e., NW set to OT + KW set to OT! The reading on the flywheel scale is 2mm before the marking in the direction of rotation , which exactly corresponds to the precise timing setting using the timing pin on the crankshaft pulley! So, you would need to rotate it another 2mm so that both

markings on the disc align, I hope that makes sense.

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Okay, I don't understand... if KW is aligned with OT, what markings would still have a 2 mm gap between them?

1. 148 HP, 352 Nm.

2. 151.8 horsepower and 360 Nm of torque.

Someone should try to tell me that it's useless!

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It seems to be roughly the same as the continuation of my adjustment experience: on average, about 2 horsepower more with a 3° KW earlier setting.

The torque peak now has less of a "peak" characteristic, but it starts around 1900 RPM and subjectively decreases less than before, so it's more like a slightly sloping plateau.

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So, it appears that the subjective characteristics of the engine can be varied. "It has a significant power surge around 2000 rpm, but then it loses power at higher RPMs." Early ignition = less low-end torque, but better high-end power and slightly more power in the mid-range. The question is, what proportion of that is due to the change in valve timing... unfortunately, you can't just adjust the injection camshaft.

Regarding the noise levels of the PDEs, I couldn't detect any deviation whatsoever with this setting!
I like this setting very much, so I will keep it for now to see to what extent the consumption changes! }
OK, I will occasionally write the result.

And thank you for your "basic research." If you don't mind, I will incorporate the results into the technical article on PD-NW alignment.

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loveme wrote the following:: Trip 1: Settings as usual, i.e., NW set to OT and KW set to OT! The reading on the graduated disc is 2mm ahead of the mark in the direction of rotation, which exactly corresponds to the precise timing setting achieved with the timing pin on the crankshaft pulley! So, you would need to rotate it another 2mm so that both markings on the disc align. I hope that makes sense. Okay, I don't understand... if KW is on top of OT, then what other distance of 2 mm exists between which markers?

It's actually quite simple:
I noticed that the timing mark on the crankshaft pulley, with the lower timing cover removed, is not aligned with the mark visible through the inspection hole on the transmission housing and the notch on the flywheel; it's offset by 2mm.

The discrepancy is between the marking on the flywheel and the marking on the inspection window in the gearbox, where the rubber stopper is located.

I believe that the setting value using the dowel pin on the crankshaft is more accurate than this notch on the flywheel!

That's why, when doing adjustments where the timing cover isn't completely removed, I simply use this specific adjustment position (2mm before the marking) visible through the inspection hole in the crankshaft pulley.
It's actually simpler.
The most important thing is to be 100% on time!

P.S.: Feel free to continue using my test results!