AEL Engine: Low Power, High Fuel Consumption

hello,

I've already browsed through this forum, but I haven't been able to find a real starting point to solve my problem.

Please ask for advice / help / assistance!!!!

Vehicle: Audi A6 Avant 2.5 TDI with AEL engine, manufactured in November 1995, currently with approximately 290,000 km on the odometer.
Location: Braunschweig/Goslar region.

Error description:

"Significant lack of power during acceleration, with almost no power output up to approximately 2400 RPM (boost pressure is only 0.4 to 0.6 bar above atmospheric pressure at this point). Above that, it improves (boost pressure increases to the target value of 0.95 bar above atmospheric pressure and remains almost constant, and it regulates down to 0.85 bar at maximum speed), but there's still a noticeable lack of power."
The fuel consumption is approximately 11-13 liters per 100 kilometers at speeds of 140-170 km/h (with 95% of the distance driven on the highway). The maximum speed is barely 200 km/h (=> despite the chip!).
It doesn't produce completely black smoke (except when accelerating hard from low RPM, around 1400-2400), but I do consistently see a fair amount of gray smoke. If I don't wash my car for 3 weeks, the rear hatch/bumper is almost impossible to touch without getting covered in black soot.

The vehicle has been/was at the VAG factory service center for 18 months due to the problem, but without a resolution. (The brief concluding response was: [quote]).

"We are very sorry, but we cannot identify any fault. The high fuel consumption is puzzling/unexplainable. The same goes for the weak acceleration. You will have to accept that it consumes over 10 liters. There's nothing more we can do about it."
and that's after I generated over 7500 euros in revenue for them!!!!

Parts worth over €6000 were replaced (including a used/new turbocharger, exhaust manifold, boost hoses, vacuum pump, new EGR valve, new EGR control valve, 2 new fuel injectors, new needle lift sensor, new glow plugs, 2 new engine control units, timing adjusted numerous times, new vibration dampers, 2 new electronic pressure control valves, temperature sensors, new vacuum lines, etc.).

According to the specifications, the compression pressure should be 33/33/33/31/33 bar. The current mileage is 290,000 km.


I have the ability to read error codes and values myself (using VAG-Com and a diagnostic cable), but so far, I haven't found any significant deviations or outliers in the measured values. The only thing is that two values are slightly outside the tolerance range.

According to the Audi/VAG repair manual (original repair guide), the value of G42 is always approximately 15-20 degrees Celsius higher than the outside temperature/intake temperature.
2.) The measured value of the mass airflow sensor (MAF) is approximately 50 at full load, while the target value is around 790. The expected value should be 840 (VAG-Com).

A comparison with other identical vehicles (without any defects or problems) revealed that they exhibited similar deviations.



I was also recently at a performance testing facility.

Original chip: 126 hp @ 137 km/h / 4057 rpm.
237 Nm @ 3582 rpm

With chip tuning: 139 hp @ 129 km/h / 3823 rpm.
265 Nm @ 3478 rpm


The dynamometer indicated that the engine was producing too little power at too high of an RPM.

It should produce approximately 140 horsepower at 4000 RPM and 290 Nm of torque at 1900 RPM, without any modifications (like a chip).
Alternatively, with a chip tuning, the engine can produce 170 horsepower at 4150 rpm and 340 Nm of torque at 1900 rpm.


I am very grateful for any suggestions that can help me.

I'm also willing to travel a few kilometers to perform an on-site diagnosis.

If measurement data are needed for assistance, we will gladly record them and provide them (please specify which data, and for test drives, include the speed ranges and gears).

Best regards,
Kristian

Have they made any changes on the fuel side?

I've tried plugging in a working VP-44 ESP just to see if it would work.
I could easily imagine what was going on. It wouldn't be the first time something like this has happened.

Possibly post some logs of fuel injection amounts sometime.
"And your boost pressure is far too low; a G-chip with AEL should be around 2100 mbar (1.1)."
Capable of withstanding pressures up to 2300 mbar.

Hi,

Just as a test, I once installed a working VP-44 ESP.

Does the old AEL still have the VP37?

@ Kristian
Groups 003 (exhaust gas recirculation), 008 (fuel injection quantities), and 011.
(Log) boost pressure, seal the exhaust gas recirculation system (e.g., with copper sheet).
and log it again. Then post it here (leave the metal in for now ).
When assembling the metal sheet, also take a look inside the suction manifold.

Dieselmartin recently posted something (part numbers, etc.) about replacing the mass airflow sensor (MAF sensor) with a diode.
posted. You might also want to start gathering the parts now.

Best regards, Rudi.

Rudi wrote:

Hi, Does the old AEL still have the VP37?

He has.
The exhaust manifold probably looks funny. It might not be the cause, but rather the result of the soot buildup.

I would also check the fuel system. There aren't many other things it could be.

hello,

Thank you all for your answers.

I still have a VP 37 installed. This is actually the third new injection pump I've put in, and none of them have lasted very long (the first one lasted 6 weeks => then it went into a limp mode at 1200 rpm, the second one lasted 2 weeks => complete failure). All of them were original replacement pumps from VAG.


As far as I know, there is no 5-cylinder version of the VP-44. Also, the VP-44 is a radial plunger distributor injection pump, while the VP-37 is an axial plunger distributor pump.

The intake manifold looks acceptable, with a light carbon buildup of up to one millimeter. Everything is dry and nothing is oily.


The boost pressure reaches a peak of up to 1.2 bar, but immediately regulates back to a consistent level of 0.95 to 0.9 bar.

Currently, a good, used turbocharger is installed, which, according to the display, achieved the highest boost pressure (even two brand new turbochargers only reached a maximum peak value of 0.9 or 1.0 bar => it was sold again).

I'll take the logs you requested this weekend and post them.

I checked the fuel system for leaks and proper fuel flow. Due to the high fuel consumption, I initially suspected a leak in the return line, but that wasn't the case.
I'll also be measuring the suction and flow pressure soon. The filter is changed regularly, and only diesel is used (with a fuel cleaner added to the tank every 3-4 months).


Best regards, Kristian.

Hello Krissi,

It's good to see you again! . I also sent you some VAGCOM comparison values before.

What is the starting behavior like with a warm versus a cold engine?

While I'm not yet fully familiar with AEL engines, I plan to perform a major overhaul on my car myself when it reaches 300,000 km, and I want to be well-prepared for that by then.

Best regards,

@Kristian

How about the boost pressure control valve? Has that been replaced yet? Is the charge air cooler system airtight? Do you hear any unusual hissing sounds from your car when you accelerate fully?

Best regards, WarLord.

hello,

@ Goldhuhn

Well, the world is so small! It's amazing how often you run into each other.

Currently, I can't complain about the starting behavior...
When it's warm, it starts perfectly. When it's cold, it takes 1-2 extra turns to start, but it doesn't require prolonged cranking or miserable pre-glow.

"My dad's engine starts even when you just touch the ignition key. It has over 730,000 km on the clock; it's an AAT engine (and everything is still original except for the clutch, gearbox, and alternator)."

Also, my auxiliary heater is working perfectly again, so I hardly ever start the engine with a cold start (it's usually around 50-53 degrees). You can definitely feel the difference whether it's a real cold start or with pre-warming. The thermostat is also working without any problems (it's one of the few original parts still on the vehicle ).

The VAG diagnostic data blocks helped me realize that almost all of the tested vehicles showed this large deviation, while the others were actually running well and without major problems.



@ WarLord

The entire charging system was pressure-tested for leaks at 1.5 bar (and 3.5 bar without the turbo) using a cold fog and a compressor. All hoses are new, including the control lines.
A hissing sound is not perceptible across the entire speed and load range.

The boost pressure control valve is still original, but I tested its functionality using a frequency generator (clock generator from 1/60 Hz to 50 Hz).


The only part that hasn't been specifically checked individually is the boost pressure sensor. However, it shows nearly the correct air pressure when the engine is not running, and the maximum value also corresponds to what the control unit detects. I haven't tested the values in between. I also don't know the sensor's control characteristic.

The turbocharger is venting at 1.630 bar through the wastegate, which exactly matches the manufacturer's specifications for the turbo. Under controlled conditions, I reach approximately 1.95 bar (with a peak value of 2.15 bar).


I would like to replace the remaining parts (boost control valve, boost pressure sensor, mass airflow sensor) with brand new ones, but after all the repairs, I am not financially able to afford it. Also, I can't find suitable used parts to exchange and test.


Best,
krissi

hello,

I have now recorded measurement data blocks 003, 008, and 011 using VAG-Com.

(4th gear and 6th gear, each from approximately 1300 RPM to the maximum RPM, and once in neutral with a throttle blip, once with the EGR valve active, and once with the EGR valve deactivated.)

I'm just having trouble now with how to get the data/files into this forum.

Does anyone have any ideas? I don't have a website or online presence where I can put it.


Best,
krissi

Hello Kristian,
Please send your logs as an attachment .

Did you record that with the engine control unit (ECU) that has been modified?
Injection amounts, which are the desired values (driver preference), are values up to 75mg .
That seems quite high to me (as far as I recall, the maximum is 51mg).

If you like, you can send me the CHIP dataset.

Best regards, Rudi.

hello,

@ Rudi

Yes, the values were achieved with the chip (without the chip, the car has even less power than a 50 HP Golf I naturally aspirated diesel ). The engine control unit (ECU) is the original one, and the chips (2x) are only plugged in for the AEL model.

The chip is from CSW in Wolfsburg, and it's called a "MAX-Powerchip." It's designed to deliver maximum performance when used with the other original components. The "horsepower loss" is just a slight reduction in power, but it doesn't bother me much.

I started recording the logs from the lower RPM range, then I let the engine reach its maximum RPM (redline) after fully pressing the accelerator (it took several attempts because I was often slowed down ). I will make some more recordings that start at 1000 RPM and increase linearly without any jumps.

What do you mean by "dataset from the chip"? Are you referring to, for example, performance specifications? Sorry for the silly question, I'm just having trouble understanding it right now (I'm a bit lost).

Best,
Krissi

With 'dataset,' I mean the content of the EEPROMs .

CSW professionals should generally know what they're doing, but the control unit is quite complex.
old (in terms of technology, not necessarily manufacturing date) and therefore outdated / lacking in sophistication.
could the dataset be

Best regards, Rudi.

Hello,

To me, it seems like the turbo boost isn't kicking in at all until around 2000 rpm, even though the engine computer is trying to apply full throttle based on vacuum readings.

Do all AELs do that?

If not:
Check everything, from the cables to the solenoid valve, the vacuum pneumatics, and the supercharger itself. Make sure the control hoses are tight and that there is sufficient vacuum pressure. Is the braking effect as expected?

Does the VTG rod exhibit a visible lift of approximately 1 cm when starting?

It seems there's still plenty of room to shorten the stroke, as long as the engine doesn't reach 90% of its maximum RPM (over 4000 rpm) when running at full throttle.

hello ulf,

You are absolutely correct that nothing happens up to 2000 RPM (actually, nothing happens until 2200 RPM, and then it starts to increase very, very slowly).

"Before, it wasn't like that; I had to be careful not to stay in full throttle at 1700-1900 RPM, because either both front wheels would do whatever they wanted (and I would end up going into a curve even though I was steering straight), or I wouldn't be able to move from the spot (doing a burnout)."

The AEL doesn't have a VTG turbocharger; it has a wastegate turbocharger, which means I can't adjust the linkage, nor can I see if anything is moving.

Vacuum is okay (the vacuum pump is new, as are all the other hoses throughout the car/engine).

Okay, I'm going to test the boost pressure build-up in relation to the vacuum control system (both will be equipped with pressure gauges to examine the timing). If there are no timing differences here, the problem is likely with the control unit itself, or the pressure sensors may be providing incorrect values.


Well... the never-ending story goes on <= as long as one can still laugh!!


Best,
krissi

Kristian wrote:

The AEL doesn't have a VTG turbocharger, but rather a wastegate turbocharger, so I can't adjust the linkage, nor can I see if anything is moving.

Then, in my opinion, you don't need to pay attention to the vacuum system either.

Try connecting the hose directly to the intake manifold (charger outlet). Does the pressure build up earlier then?

Have the valve timing/Nockenwellenposition (NW) setting ever been checked?

hello Ulf,

I checked the boost pressure control system earlier (using a pressure gauge), specifically the boost pressure sensor on the turbocharger and the boost pressure control valve.
The pressure increases identically with the boost pressure until it reaches the target limit of 0.95 bar. Then, the boost pressure valve opens as it should, and the temporarily installed pressure gauge starts to vibrate erratically.

In short-circuit operation, there is no change in the pressure increase (neither faster nor slower), only that the pressure now rises to a level of 1.3 to 1.4 bar. At 1.4 bar, a kind of protective function in the control unit seems to have kicked in, reducing the power output. A restart of the engine resolved the issue.

The valve timing has been properly adjusted, and the engine's base setting (kW to NW) has been re-adjusted numerous times (all by VAG themselves).

When I have some time, I'll re-align everything myself. Maybe they were careless, and when they tightened things, everything shifted a few fractions of a millimeter again.

Best,
krissi