150 TDI - Intake Air Temperature sensor reading unusually high

[muddyboots]

Hi all

 

Car is a Mk3 Superb 150 TDi SE L Exec 4x4. DFEA engine code, MY2016. Mileage about 56k. Completely standard.

 

While looking at a separate fault (SCR pump pressure too low) using VCDS, I happened to notice in the freeze frame data that the intake air temperature is wayyy higher than expected - but this in itself it not flagging a fault.

 

I have two sets of freeze frame data from two different days.

On both days the ambient was between 0 and 5 degC.

Engine speed around 1500rpm, just normal steady driving (no massive acceleration or hills).

The air intake temp was been recorded at 91degC and 63degC 🤨

 

Car seems to drive just fine. Only thing we have noticed recently is that it seems to be doing more frequent regens. (I wondered if an incorrectly high intake air temp might be causing it to overfuel a little and soot the DPF faster? Or maybe that's a separate issue).

 

Has anyone else had this issue with the intake air temps ?

 

Maybe a common sensor fault or wiring fault ?

 

Thanks for any thoughts.

 

[SuperbTWM]

My gut tells me this might be normal as higher intake temperatures than expected would probably be picked up by the ECU and probably put the car in limp mode or at least store some codes????

 

Just done some more digging and i think you are looking at the intake temperature which is before the charge cooler, I think there should be 2 sensors, 1 before, 1 after, obviously if you are looking at the before temps they are going to be high

Edited 21 December, 2022 by SuperbTWM

[ApertureS]

8 hours ago, SuperbTWM said:

My gut tells me this might be normal as higher intake temperatures than expected would probably be picked up by the ECU and probably put the car in limp mode or at least store some codes????

 

Just done some more digging and i think you are looking at the intake temperature which is before the charge cooler, I think there should be 2 sensors, 1 before, 1 after, obviously if you are looking at the before temps they are going to be high

We are talking a turbocharger here, not an industrial compressor. 

not a chance that a turbocharger has the ability to compress air to 2/3 bar and bring the temperature to 91 degrees.

so it leaves 2 things - faulty sensor/wiring or vcds incorrectly reading the block data 

 

or user error and you are looking at coolant temperature?

[langers2k]

3 hours ago, ApertureS said:

not a chance that a turbocharger has the ability to compress air to 2/3 bar and bring the temperature to 91 degrees.

 

A quick google suggests that 91° C is a perfectly plausible temperature between the turbo and intercooler. For example, Valeo state: "The intercooler lowers the temperature of the inlet gas from 130° C to 60° C, removes the negative effects of the turbo and increases the power by around 20%."

 

Given there are no fault codes, I would have no concerns about it 👍

 

Might be worth looking at some more measuring blocks to see if there are a few more temps from other parts of the intake system?

[varooom]

Might be an idea to check your soot levels, and also to potentially get some readings of temps with engine off/ignition on (don't be slow as you will drain battery)

So if you have a temperature of 40°C with the engine off that won't be legit.

 

While you are there, you can check the DPF regens, as you say they are more frequent.

Read in measuring blocks for sensor pressure with engine off, should read close to zero, and when starting engine that should of course increase.

 

I would take some baseline measurements of your soot/ash levels so you have a future reference.

 

A full VCDS scan log would be appreciated also, if you have the tool, please provide the data, it's invaluable!

[Bap33]

Don’t forget EGR system which contibutes to get hot air from exhaust gaz to the air intake…

Since there is no fault code, I wouldn’t worry too much.  

[SuperbTWM]

4 hours ago, ApertureS said:

We are talking a turbocharger here, not an industrial compressor. 
 

 

So manufacturers fit devices to cool the charge air just for fun?

9 minutes ago, Bap33 said:

Don’t forget EGR system which contibutes to get hot air from exhaust gaz to the air intake…

Since there is no fault code, I wouldn’t worry too much.  

 Exactly, nothing wrong here at all

[muddyboots]

Thanks all.

 

Just did some baseline logging with a stone cold, non-running engine and all temps are where you'd expect - so no fundamental sensor issue.

 

I then went for a drive and did some logging.

One of the measuring values I was looking at, is "Charge air temperature sensor" (IDE04003).

The readings from this are of the format "B1S1/B1S2:23/35".

I presume that means "Bank 1 Sensor 1 / Bank 1 Sensor 2".

 

Does anyone know exactly where these two readings are taken ?

The first of the numbers rises quickly under higher boost (during prolonged had accel up a hill this peaked around 120degC), whereas the second has relatively little change, typically in the 40degC region.

From that I suspect they are the before/after air temps as it passes through the chargecooler. In which case - perhaps all is OK.

 

I wonder if in the freeze-frame data stored with the other fault, when it says "Intake Air Temp" it's actually reporting the air temp between turbo and chargecooler.

Edited 23 December, 2022 by muddyboots

[SuperbTWM]

6 hours ago, muddyboots said:

 

 

Does anyone know exactly where these two readings are taken ?

 

Pre-cooler is just after the butterfly valve, post cooler is right before the cylinder head.

 

Sounds like the control of the pump is working absolutely spot on.

 

On 22/12/2022 at 06:10, ApertureS said:

not a chance that a turbocharger has the ability to compress air to 2/3 bar and bring the temperature to 91 degrees.

 

Every day is a school day 😉

[ruivalente]

Hi all,

I don't think that I have a problem on any sensor but i'm experience since 2019 a issue that no dealership in Portugal can identify or find and that is related with Charge Air Temperature.

The issue is that when on hard load, highway uphills for example, my charge air cooler temperature is registering around 120º on sensor 1 (before charge air cooler) and in some cases more that 90ºC on sensor 2 (after charge air cooler). The effect is that the ECU cuts out diesel and I have a limitation of power until the sensor 2 gets back to bellow 90ºC and then the power is fully restored.

They already replace the charge air cooler pump, a non return valve on the exit of water pipe at the charge air cooler and even cleaned the charge air cooler, but the problem remains until today.

No fault code is stored in the ECU.

Do anyone experience this or have a clue on how can I fix this problem?

 

Here is a sample of the temperature sensors:

 

 

Thanks!

[J.R.]

Is this during the heatwave?

 

Is it more noticeable during hot weather?

[ruivalente]

it is more noticeable during hot weather yes. But even in the winter I can notice that bu it takes longer to reach those temperatures. I have some cases that the car won't let me go more than 100km/h where before I can easily go mutch more.

[SuperbTWM]

Maybe there is a restriction/blockage in the charge air coolant cooler/radiator?

 

I believe the charge air coolant cooler/radiator is behind the air con condenser but in front of the main radiator. Are the fins on the condenser straight and clean (IE not reducing the airflow through it and subsequently the charge air radiator)

 

What are the amibient temps when this happenning? 

 

Also, what is the speed limit in Portugal??? 😂 I'm willing to bet if you try not going over 100mph in the blistering heat everything would probably be fine

Edited 27 July, 2023 by SuperbTWM

[ruivalente]

Hi SuperbTWM.

Charge air cooler was removed and cleaned. On of my current doubts is related with the charge air cooler radiator it self and in fact the AC condenser looks like it was in a stone war, but is enough to block so much air? I don't have problems with the main radiator and coolant temperature. Nevertheless, it is an easy fix to try to get more air flow into the radiators cleaning the condenser.

Regarding temperatures, I get more "problems" when temperatures are higher than around 20ºC, but even with 4-5ºC I have problems, but less of course...

 

Speed limit in Portugal is 120km/h (around 75mph). Yes, you are right, but I cannot pass in some cases 100km/h when going uphill on highways. 😞

The speeds that you saw there was to monitor/record sensor values

 

Thanks!