Mercedes Power Unit Hardware & Software

[saviour stivala]

“Such as a stuck VLIM on one side?”. It is not like fueling and ignition adjustment to match the needs of not only one cylinder bank side but also of individual cylinder cannot be made.

[saviour stivala]

VLIM causing excessive EGT that can compromise the engine?. The ECU has built-in-intelligence capability to prevent such things. The level of EGT is the end result of combustion. The ECU controls the EGT level by controlling combustion by managing fueling and ignition. But the ECU is as good as the signals it receives from numerous senders. An example of readings that can result in engine catastrophe is a quote from an F1 engine authority “One knock and a 2800 Euro built-in-cylinder sensor is broken and the result is then there is no knock sensor any more”.

[henry]

“Such as a stuck VLIM on one side?”. It is not like fueling and ignition adjustment to match the needs of not only one cylinder bank side but also of individual cylinder cannot be made.

This has already been discussed, as have the automatic mechanisms for doing so. Assuming the VLIM failure mode it is possible that some of the changes that engineering instructed Hamilton to make involved recalibration of parameters that affect that functionality. We can’t know but we can make an educated guess.

[saviour stivala]

“Such as a stuck VLIM on one side?”. It is not like fueling and ignition adjustment to match the needs of not only one cylinder bank side but also of individual cylinder cannot be made.

This has already been discussed, as have the automatic mechanisms for doing so. Assuming the VLIM failure mode it is possible that some of the changes that engineering instructed Hamilton to make involved recalibration of parameters that affect that functionality. We can’t know but we can make an educated guess.

Agree that the instructions from pit-wall to driver was because the "automatic mechanisms (built-in the ECU) to compensate could not compensate. as to why the ECU could not compensate I just posted my opinion right before you posted.

[Dr. Acula]

"Well our exhaust is just about to fail, and we're overshooting all temperature limits".

Right so high EGT causing the exhaust to fail. What is causing the high EGT?
That's what was being discussed but again you can't be bothered to read previous posts.

I think you both misunderstood what they meant.
As far as i know the inital problem was a cracked exhaust manifold. The "and we're overshooting all temperature limits" part in my opinion doesn't refer to the EGT temperature at all. It refers to the temperature around the engine. With a cracked exhaust the exhaust gases start to go to places where they shouldn't and to heat things up excessively which don't like to be heated up.
That's actually nothing new. Michael Schumacher nearly lost his certain victory in Spain in 2004 because of a cracked exhaust. The exhaust gases started to boil his rear suspension.
Now if you look at how temperature resistent for instance the resin in carbonfibre composits are, you realize quite quickly that this could get problematic. Even the more temperature resistent resins generally start to fail at temperatures between 200-250°C.
That doesn't mean a part will simply fall apart if it's hit with 1000°C exhaust gases, but i recon Mercedes has to deal with some serious delamination of some parts. I mean we know for a fact that the intake plenum is made of carbon fibre.

[Webber2011]

For dumbos like me, could someone explain how the VLIM works, or point me to the proper thread please ?

I have a basic understanding, but always like to learn more.

Thanks

Not a thread, but here’s a basic video from YouTube:
https://youtu.be/FaYIHQGU00k

Thanks mate, much appreciated

[saviour stivala]

"Well our exhaust is just about to fail, and we're overshooting all temperature limits".

Right so high EGT causing the exhaust to fail. What is causing the high EGT?
That's what was being discussed but again you can't be bothered to read previous posts.

I think you both misunderstood what they meant.
As far as i know the inital problem was a cracked exhaust manifold. The "and we're overshooting all temperature limits" part in my opinion doesn't refer to the EGT temperature at all. It refers to the temperature around the engine. With a cracked exhaust the exhaust gases start to go to places where they shouldn't and to heat things up excessively which don't like to be heated up.
That's actually nothing new. Michael Schumacher nearly lost his certain victory in Spain in 2004 because of a cracked exhaust. The exhaust gases started to boil his rear suspension.
Now if you look at how temperature resistent for instance the resin in carbonfibre composits are, you realize quite quickly that this could get problematic. Even the more temperature resistent resins generally start to fail at temperatures between 200-250°C.
That doesn't mean a part will simply fall apart if it's hit with 1000°C exhaust gases, but i recon Mercedes has to deal with some serious delamination of some parts. I mean we know for a fact that the intake plenum is made of carbon fibre.

"imminent" engine failure due to an exhaust issue (high temperature). a cracked exhaust will not in my opinion lead to "imminent" engine failure.

[aral]

It could lead to various issues leading to engine failure ! Escaping heat can have a detrimental effect to a tightly packed engine by overheating exterior oil coolers, burning wires, overheating ecu etc etc. Note that the team specified "all temperature limits", so it was getting info from many sensors. And overheating is putting a lot of stress on components not designed for such temperatures.
And in the past, many cars have had to be retired due to broken exhausts. It happens.
But it is over and done with now. Lets move on.

[ian_s]

something as simple as a lambda sensor giving the wrong result could really mess up the fuelling and spark maps, in this already very complex and delicate combustion process.
could a failed VLIM on one side cause odd behaviour in combustion? definitely.
could a failing turbine cause odd boost behaviour? possibly
could a failing wastegate (failing open) stop the compressor making boost? yes
could a failing wastegate (failing closed) cause boost peaks? yes

so many other possibilities for a tiny failing causing huge PU issues that could *possibly* mean its about to die. Mercedes telemetry would have been telling them the worst, so they did all they could to secure the championship.
next race is going to be all out banzai!

[gruntguru]

“VLIM?”. On lap 28 Mercedes PU engineers both at pit garage and back at base in UK monitoring telemetry reported that a failure was imminent due to an exhaust issue that had led to high temperatures.

And what exhaust issues would cause high EGT ?

A serious leak from the exhaust upstream of the turbine eg header pipe or leaky wastegate valve. Such a leak would reduce boost pressure, increase FAR and increase all cycle temperatures.

[saviour stivala]

And I thought "it is over and done with, lets move on".

[turbof1]

something as simple as a lambda sensor giving the wrong result could really mess up the fuelling and spark maps, in this already very complex and delicate combustion process.
could a failed VLIM on one side cause odd behaviour in combustion? definitely.
could a failing turbine cause odd boost behaviour? possibly
could a failing wastegate (failing open) stop the compressor making boost? yes
could a failing wastegate (failing closed) cause boost peaks? yes

so many other possibilities for a tiny failing causing huge PU issues that could *possibly* mean its about to die. Mercedes telemetry would have been telling them the worst, so they did all they could to secure the championship.
next race is going to be all out banzai!

Funny you mentioned that. Totally not comparable, but I did have lambda sensor issues with my own roadcar a few years ago. It did cause the combustion to be more toxic (as I was told). Just to underline that indeed a simple sensor issue can have a massive effect.

To all: Save to say we all can only speculate on what the issue exactly is. It is important to give eachother the room to make argumentatively-based speculation and counter-speculation. Just make sure the conjecture does make sense. It is also important to think about how a single sensor giving a faulty reading, can cause a knock on effect in the system trying to compensate for said faulty reading. It is not necessarily something in the exhaust that was the culprit. Anything really that goes wrong can cascade into a full PU meltdown. The issue was probably first picked up at the exhaust, or the exhaust was getting to the critical point first.

[henry]

“VLIM?”. On lap 28 Mercedes PU engineers both at pit garage and back at base in UK monitoring telemetry reported that a failure was imminent due to an exhaust issue that had led to high temperatures.

And what exhaust issues would cause high EGT ?

A serious leak from the exhaust upstream of the turbine eg header pipe or leaky wastegate valve. Such a leak would reduce boost pressure, increase FAR and increase all cycle temperatures.

There’s a trade off between boost pressure and MGU-H energy recovery. Again the automated tuning systems may not have been able to cope with a large change from the norm, but reduced output from the race might be a price worth paying to get to the end of the race.

[saviour stivala]

something as simple as a lambda sensor giving the wrong result could really mess up the fuelling and spark maps, in this already very complex and delicate combustion process.
could a failed VLIM on one side cause odd behaviour in combustion? definitely.
could a failing turbine cause odd boost behaviour? possibly
could a failing wastegate (failing open) stop the compressor making boost? yes
could a failing wastegate (failing closed) cause boost peaks? yes

so many other possibilities for a tiny failing causing huge PU issues that could *possibly* mean its about to die. Mercedes telemetry would have been telling them the worst, so they did all they could to secure the championship.
next race is going to be all out banzai!

Funny you mentioned that. Totally not comparable, but I did have lambda sensor issues with my own roadcar a few years ago. It did cause the combustion to be more toxic (as I was told). Just to underline that indeed a simple sensor issue can have a massive effect.

To all: Save to say we all can only speculate on what the issue exactly is. It is important to give eachother the room to make argumentatively-based speculation and counter-speculation. Just make sure the conjecture does make sense. It is also important to think about how a single sensor giving a faulty reading, can cause a knock on effect in the system trying to compensate for said faulty reading. It is not necessarily something in the exhaust that was the culprit. Anything really that goes wrong can cascade into a full PU meltdown. The issue was probably first picked up at the exhaust, or the exhaust was getting to the critical point first.

Good so we can go on after all. Your own car lambda sensor gone wrong case gets us back to the ECU role. The lambda sensor sends signal to ECU to adjust the amount of fuel entering the engine and ECU will compensate as per lambda sensor. If lambda sensor is broken there will not be signals to ECU and ECU cannot correct/compensate, in that case the ECU will either shut down engine or goes into limp-home mode. In any which case the ECU holds all in memory for later download diagnoses. The system used in F1 have added real time telemetry traffic to the pit capability. Having touched on the role of the ECU capability to compensate, this discussion reinforced my opinion that in F1 the ECU limp-home and shut-down modes to avoid catastrophic engine failure is not used.

[saviour stivala]

And what exhaust issues would cause high EGT ?

A serious leak from the exhaust upstream of the turbine eg header pipe or leaky wastegate valve. Such a leak would reduce boost pressure, increase FAR and increase all cycle temperatures.

There’s a trade off between boost pressure and MGU-H energy recovery. Again the automated tuning systems may not have been able to cope with a large change from the norm, but reduced output from the race might be a price worth paying to get to the end of the race.

And that is what Mercedes did.