MK5 GTI down on power

[MartinNorhave]

Hi there. I just bought a mk5 gti. It has a full milltek exhaust with downpipe aswell as an k&n cold air intake. I therefore suspect that it is also remaped.
However the previous owner doesn't know if it is or not.

I feel like it doesn't have the power it should. It doesn't even feel like the 200hp that it came with from the factory.
It had a P0299 underboost code which made me change the diverter valve (It was in fact broken) but I can't feel much of a difference. It doesn't even wheel hop in first gear.
It doesn't have any other fault codes. Any ideas as to where my problem could be?

[MKVASMR]

I had this issue with two of mine mk5’s.
I would start with looking at the boost hoses if there is oil then you should change the orings. Clean the MAF sensor, look if your dipstick is broken. Also the pcv. You should do some logs. If the difference between the actual and specified boost is under 300mbar I would rule out the turbo. Last thing do a smoke test to find if you have some vacuum leaks. But you can hear those with the engine running (a hissing 🐍 sound). The n75 valve is also important. You can monitor if it works with vcds or obdeleven.

[MartinNorhave]

I had this issue with two of mine mk5’s.
I would start with looking at the boost hoses if there is oil then you should change the orings. Clean the MAF sensor, look if your dipstick is broken. Also the pcv. You should do some logs. If the difference between the actual and specified boost is under 300mbar I would rule out the turbo. Last thing do a smoke test to find if you have some vacuum leaks. But you can hear those with the engine running (a hissing 🐍 sound). The n75 valve is also important. You can monitor if it works with vcds or obdeleven.

I just did some quick looking around at home. When I pull the oil cap there is a lot of vacuum and the engine runs poorly. Same with the dipstick. Is this the pcv valve thats bad? And if so could it cause the loss of power?

[MKVASMR]

That usually means that it’s ok 👌. However I would change it anyway since the diaphragm can get lazy over the time.

[pudding]

Yep, removing the oil cap should cause rough running as it creates a massive air leak.  If no change, the PCV is shot.

[MartinNorhave]

That usually means that it’s ok 👌. However I would change it anyway since the diaphragm can get lazy over the time.

I can hear that it is building boost as I get the blowoff sound when I shift gears. I can also see the boost pipes expanding.

At idle i get:
Boost pressure specified 270 mbar
Boost pressure actual 1010 mbar

Does this seem right?

When I floor it in second gear i get:
Boost pressure actual 1700 mbar

[MKVASMR]

1700 is okay for a stock car. I don’t think you should hear any “blow off sounds” or at least not as often. Are you sure you plugged the DV back in?

[MartinNorhave]

1700 is okay for a stock car. I don’t think you should hear any “blow off sounds” or at least not as often. Are you sure you plugged the DV back in?

Pretty sure but now you got me questioning myself xD

Perhaps it is now a blowoff sound but I can hear the turbo when I let go of the gas. Through the air filter perhaps?

[MKVASMR]

Yeah it’s okay to hear a blow off sound if you change gears and releasing load but that doesn’t happen quite often.
Unplugged DV can cause stuff like that. Other than that your boost levels are okay if you were looking at the actual value. I think that max requested for these stock engines is 1700mbar (someone correct me if this is not correct) ✅.
However if your car is mapped and you are stuck at 1700mbar that tells me that the wastgate may have a small pinhole. As far as I know the diaphragm part is changeable and upgradable with the forge one. The flap on the other side is not.
It would be ideal if you can make some logs and export us the charts.

[MartinNorhave]

Yeah it’s okay to hear a blow off sound if you change gears and releasing load but that doesn’t happen quite often.
Unplugged DV can cause stuff like that. Other than that your boost levels are okay if you were looking at the actual value. I think that max requested for these stock engines is 1700mbar (someone correct me if this is not correct) ✅.
However if your car is mapped and you are stuck at 1700mbar that tells me that the wastgate may have a small pinhole. As far as I know the diaphragm part is changeable and upgradable with the forge one. The flap on the other side is not.
It would be ideal if you can make some logs and export us the charts.

I just checked. The DV is plugged in. I went for a drive and now I have a CEL. Unfortunately I won't be able to check the code until tomorrow.

I'm new to the vcds stuff so I will try to make some logs. But it may take a while. What values would you like to be logged?

[MKVASMR]

https://www.goapr.com/support/vcds_logging/

This is pretty detailed.

[MartinNorhave]

https://www.goapr.com/support/vcds_logging/

This is pretty detailed.

Just did the logs just like the link you sent (I hope I did it right). I started the log. Then set off in first gear. Shifted to second gear and floored it. Then shifted to third and then stopping the log.

MAF/Load https://file.io/DIsDpxNXFcim
Boost/Timing https://file.io/LWHnzH9YK3tG
Boost/Timing 2 https://file.io/nnpWCenVhXW5
Boost/Fueling https://file.io/pEdDs1YY89rz

[MartinNorhave]

https://www.goapr.com/support/vcds_logging/

This is pretty detailed.

Have you had time to look at the logs for me? 

[MKVASMR]

Looks pretty good to me 👍. Some small differences I would check if all of the boost are where they are supposed to be and make do a smoke test in case you have some vacuum leaks. The n75 works fine which means the turbo isn’t fighting to get boost. The engine is also good on knocking so maybe it’s just you haha

[MartinNorhave]

Looks pretty good to me 👍. Some small differences I would check if all of the boost are where they are supposed to be and make do a smoke test in case you have some vacuum leaks. The n75 works fine which means the turbo isn’t fighting to get boost. The engine is also good on knocking so maybe it’s just you haha

So perhaps it just hasn't been remapped? Just seems weird to spend the money on a turboback exhaust and a cold air intake and not on a remap. Can you tell from the logs if it has been mapped on not?