Boost Problems When The Engines Warm

[Sharkey]

Hi Guys,

I have done a search and found similar boost problems but there all slightly different to mine so was hoping for a bit of assistance.

Generally my 04 plate stage 1 mapped Leon Cupra boosts fine. However, when starting it with engine up to its operating temperature, I have an intermittent boost fault. It feels like it isn't boosting at all, or very little (sorry I don't have a boost gauge).

What is stranger is that when the peddle is 'pumped' (depressed and released repeatedly), at moderate revs, the turbo will suddenly kick in. Also, the problem can be resolved by accelerating to around 5000rpm and then releasing, but neither of these can't be any good for the car!

Once the turbo is working, the engine behaves normally and the problem doesn't return until it is switched on and back on again. This only happens when the engine is started warm and not when it’s cold.

I have VAGCOM, but am a bit of a novice with it. I did a few logs and when this problem occurs the requested boost is significantly higher than the actual. Also, when the turbo is working the MAF can flow around 170-175 g/sec which I gather is about normal for a stage 1 Cupra? so I don't think it’s that. Finally, there are no fault codes logged in any of the systems.

With my little mechanical knowledge I am thinking possibly N75, sticking wastegate or sticking actuator?

This problem occurred when the car was standard mapped and with the standard DV, which are my only modifications.

Any suggestions as to what/how to determine the problem would be appreciated and I can provide some VAGCOM logs on specific blocks if required.

Thanks in advance for your time!

 

[Shaunyboy]

Hi Guys,

I have done a search and found similar boost problems but there all slightly different to mine so was hoping for a bit of assistance.

Generally my 04 plate stage 1 mapped Leon Cupra boosts fine. However, when starting it with engine up to its operating temperature, I have an intermittent boost fault. It feels like it isn't boosting at all, or very little (sorry I don't have a boost gauge).

What is stranger is that when the peddle is 'pumped' (depressed and released repeatedly), at moderate revs, the turbo will suddenly kick in. Also, the problem can be resolved by accelerating to around 5000rpm and then releasing, but neither of these can't be any good for the car!

Once the turbo is working, the engine behaves normally and the problem doesn't return until it is switched on and back on again. This only happens when the engine is started warm and not when it’s cold.

I have VAGCOM, but am a bit of a novice with it. I did a few logs and when this problem occurs the requested boost is significantly higher than the actual. Also, when the turbo is working the MAF can flow around 170-175 g/sec which I gather is about normal for a stage 1 Cupra? so I don't think it’s that. Finally, there are no fault codes logged in any of the systems.

With my little mechanical knowledge I am thinking possibly N75, sticking wastegate or sticking actuator?

This problem occurred when the car was standard mapped and with the standard DV, which are my only modifications.

Any suggestions as to what/how to determine the problem would be appreciated and I can provide some VAGCOM logs on specific blocks if required.

Thanks in advance for your time!

N75 would cause turbo chatter normally, have you checked all the hoses? is it holding boost? or is there non atall? if its a problem with N75 or any sensor normally it will throw it into limp mode and then it will hardly boost to protect its self. Is the turbo spooling up?

 

[Sharkey]

I've had a quick look round the hoses, but it boosts fine after performing one of the actions I listed above, and when starting it from cold.

Would limp mode log a fault code?

It is boosting a little, take at 2600rpm for example:
ECU requesting 2080mbar, actual boost 1330mbar

At 4400rpm it reads
ECU requesting 2040mbar, actual boost 1320mbar

Now on the second acceleration, when the turbo had started working properly:
ECU requesting 2080mbar, actual boost 1420mbar

At 4300rpm it then reaches the requested boost:
ECU requesting 2050mbar, actually boost 2220mbar

Thanks for your time!