no agressive turbo, surging power

[Avantus]

Hi,

did a big roadtrip one week ago with my RS2, and the car performed perfect. Yesterday one week later I took it out again for a trip, and had some power loss. More specific:

- turbo seems to spool up later and slower
- no more typical rs2 turborush, comes in quite soft
- it still goes pretty good, but not as before and at high revs it seems to weaken off.
- oh the higher gears I notice some surging. No perfect constant power-emission. Nothing brutal, but something like a "wave".

Had it checked this afternoon and it had one fault: Lambda. Lambdasensor and CO were tested and both ok. (lambda was 0.938 at 750rpm and the sensor itself worked ok) I was at altitudes up till 3000m last week, so the chance that the managment had a little hickup is plausible. Cleared the code, went for a testdrive, came back, and it didn't come back.

Final information: when holding it at 2-3000rpm stationary, you can hear muted farts in the exhaust (exhaust was really hot however). Also last night when slowing down after some sprints it did the same on low rpm. Quiet though being at night and with the radio off. Maybe normal with an RS2?

done recently by previous owner: wgfv and dv were changed, new coilpacks, sparkplugs, WG checked, ...

Boost leak?

oh yes and car is bone stock.

Thanks!

[prj]

Check for boost leaks.
If that doesn't help, try a different MAF.

The lambda error is excess fuel, meaning it is running too rich, which is precisely what happens due to a boost leak. A faulty MAF can cause that as well though.

[EspenW]

Yep, check for boost leak. Plug the boost pipe right before the throttle body and apply pressure after the turbo

[Avantus]

Ok thanks guys! Will search for boost leaks.

[Rusty]

Might be worth checking what altitude the car thinks it's at, fairly certain that it will reduce boost if it still thinkgs it's at 3000m! Sensor could have got 'stuck' for want of a better word.

[Avantus]

On the inside I can only see some very thin cracked lines... doesn't seem to be trough yet. But mabye at full boost it looses some?

[Rusty]

That's not very healthy for sure!

[Avantus]

did about 1000km back from the mountains, and it performed perfect. So would be strange if it got stuck after that. And faultcode was reset, and went for a 10km blast and it didn't come back, but still missed that agressive turbo kick.

[Avantus]

Saw this afternoon that it already has the 710N diverter valve, but it wasn't changed that recently. Was done at 126.000km, and it now has 216.500km. So the valve has 90.000km/almost 60.000 miles .... good idea to change or do those 710N's never fail? WGFV was done 10.000km ago.

Ordered a full silicone hose kit to start, since my ECU is going to Paul I can't afford to still have any faulty parts.

thanks for the help, appreciate it!!

[Rusty]

710Ns don't last too long IME. Worth changing it.

[prj]

Just do a leak test... takes all of 10 minutes.
Why people start swapping random parts instead of just testing and /knowing/ is beyond me.

If you have a boost leak and are pushing it, you are overspinning the turbo and ruining your cats (if you have them).

[Avantus]

took them all of this afternoon, and only the throttle body hose is damaged and a plausible leak. Oh yes and the DV hose was very loose. IC o-ring didn't seem to be leaking. Had some greyish paste around it (?)

Will change the DV also then, thanks

[prj]

Visual inspection is not how you do this.
Take the hose off the IM, block it off, also block the breather lines.
Next take the hose off the MAF, and you will need a small adapter (easy to DIY), which you can use to block off the end and pump air in through.

It's really not hard to do it yourself. You need a 6mm allen (iirc), a couple screwdrivers and a pump + the "boost leak test device" which you can make from sewer pipe...

If "they" took all afternoon to do this, then I don't think they know what they are doing.

[Avantus]

I did it this afternoon (together with the ECU) because i'm changing them to silicone ones Had too much issues with hoses popping of and ripping on previous 10VT's, not for me anymore now!

I know pressure testing is the way to go, but since I'm changing it all to silicone and sunday is my only day off, I did that part already

[prj]

Ok, but after you connect everything, you should pressure test it as well.
The hoses might not be the issue, there are a few other things that can leak, such as the N75 connector and a T piece.