Overboosting on a s2 3b - problems

[larsaskogstad]

Hello hello

Just got my car back from exhaust building and four wheel alignment etc.

Ran it for a test drive (first drive after a year) and I'm having some problems.
I bought the car in shabby condition, havent tried it after i've been building at all so this is kind of the first real test drive.

Car is running a k24 hybrid turbo, except from that it's pretty much stock.
Boost hoses are new etc.
Rotor/dizzy is the Bosch small tip and with new magnecor cables, new F5DP0R plugs etc.
I've changed diverter valve, n75 etc.
Lambda was changed to correct part number from Bosch earlier.

I've installed a turbopressure gauge but I dont have a wideband lambda installed in the car yet.

Anyway, it looks like the car is trying to run boost into oblivion.

On partial throttle it seems normal. with slow gearshifts and partial throttle I hear the wastegate going off like normal.
On maybe 70% throttle it pulls and pulls and seems okay.

On 80-100% throttle it goes to 3000rpm then just boosts and boosts until its cut off and car "stalls" complete, like a emergency shutdown.
It does not seem like a misfire happening its pulling evenly, not "stuttering", it just seems like it boosts way too much for my setup.

I am pretty sure that vacuum lines etc should be correct fitted, went through it several times before re-fitting everything according to schematics

I was thinking maybe:

- pressure hose to MAP sensor
- WGFV
- ECU with custom chips (Not sure what they are, Ill add a picture).
- MAF?


I havent connected up VCDS to see if there is any codes yet since I just got it back.
going to try a MTM 280 ECU from a friend tomorrow also. Just to see..

Any help would be appreciated

- Lars

[Tractor Dave]

I had this issue. I went through the normal checks like boost leak and maf pins. Eventually found that my fuel pump couldn't keep up with demand (it was new Bosch pump). Replaced with RS2 pump and all fixed.

[larsaskogstad]

I had this issue. I went through the normal checks like boost leak and maf pins. Eventually found that my fuel pump couldn't keep up with demand (it was new Bosch pump). Replaced with RS2 pump and all fixed.

Oh, hmm might just change that also then
Did it have a particular sound or?

[newsh]

“ it boosts and boosts” more than 1.5 Bar? 2Bar?

The wastegate is not opening and controlling boost for some reason.

If you unplug the N75 it should boost to about 0.4 Bar max (spring pressure). If it still overboosts then either N75 is plumbed wrong, WG is jammed or you have a hole in diaphragm or the pipes from face of turbo to N75 to WG are not connected or split.

Have you had the wastegate top off? Does it have the stock spring? Take a pic of the spring and we’ll tell you. Make sure the diaphragm doesn’t have a hole in it.

Do a proper boost leak test, just from the MAF hose, it should hold 1Bar.

[larsaskogstad]

Hello mr newsh

Yup seems so, accoring to the boost gauge it goes to 2.0bar ++.
If I pull it to over 1 bar - 1.5bar no problems if I change gears before etc.

Have not had the wastegate top off, not sure if it has the stock spring I will check later today or tomorrow. Was thinking about that aswell.
Think I will trying to do a boost leak test but I need something to plug it with.

Too tight for me too reach the contact housing on the N75, is it possible to disconnect somewhere else or does it goes straight to ecu?

[newsh]

Straight to ECU

It’s tight in there
Maybe take the headlight out?

[newsh]

Is the hex bolt visible on top of the WG?

[larsaskogstad]

Its almost rounded by previous owner.
Havent had the time today to check it out yet.

:/

[larsaskogstad]

IMG_20210626_194957.jpg IMG_20210626_194945.jpg IMG_20210626_194953.jpg IMG_20210626_194948.jpg

[newsh]

Someone has drilled a hole in the blanking plug but not actually removed it to get to the Allen bolt? Looks like maybe there’s still threadlock in there, it’s red stuff and needs heat and or thinners to release.

Anyway, push down hard on the grey cover and undo the 6 x 8mm nuts, the spring will push the cover up at you. If it’s a stock spring it’s easy to hold down, if it’s a 2 bar spring it’ll be really strong! Slip your fingers under and catch the spring and the upper spring perch to avoid dropping it in the engine bay.

[larsaskogstad]

I feel like chaning it to a refurbished one lol.
But Ill take it off tomorrow

[larsaskogstad]

Someone has drilled a hole in the blanking plug but not actually removed it to get to the Allen bolt? Looks like maybe there’s still threadlock in there, it’s red stuff and needs heat and or thinners to release.

Anyway, push down hard on the grey cover and undo the 6 x 8mm nuts, the spring will push the cover up at you. If it’s a stock spring it’s easy to hold down, if it’s a 2 bar spring it’ll be really strong! Slip your fingers under and catch the spring and the upper spring perch to avoid dropping it in the engine bay.

Think i find the fault..
A new kind of wg spring.
Let me introduce socket spring

[newsh]

Hahahahaha

A Bahco 32mm too, a good quality socket in a useful size, bonus!

[newsh]

That’ll do it!

So now you need a spring and perch

[larsaskogstad]

Its a bit broken. Wobder about getting a used one and change the "diaphraphphm"..