New S2 Avant Nothelle N300 owner

[Error404]

Dave I haven’t forgotten about the terminals for the tank connector. Sorry I have been massively slammed. Will get them to you in the next few days

[Error404]

My (long!) process of elimination included power and continuity checks to N75 and MFTS (connected or disconnected), Swapped N75 and ECU (to an N300 vice MTM) put standard spring back in wastegate and vacuum checked for leaks, temporary replaced N75 with a turbosmart boost control (eventually ending up with it wound all the way out), removed air con belt. Car has full set of Roose boost hoses and a rebuilt turbo (last year). Throughout all of this it resolutely won’t go above 0.7 bar of boost in any combination.

Wastegate sticking

[cultcars]

Awesome project! Love the color.

[Tractor Dave]

good luck getting this sorted, might be worth looking at the walbro pump instead

I was looking at that Walbro post earlier but just bought a RS2 pump from Tango

[Greg_S]

good luck getting this sorted, might be worth looking at the walbro pump instead

[Tractor Dave]

This describes my drive home exactly
https://www.s2forum.com/forum/techni...of-a-fuel-pump

I bought the pump from KMS on ebay and have sent them a message

[Tractor Dave]

Took the S2 for a little spin to visit Newsh today.


We did some tests (two heads is better than one) and after a bit of head scratching and a small sprinkle of Newsh fairy dust, I think we are on to it. It looks like my nice new Bosch fuel pump might be a fake.


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[Tractor Dave]

I did some maf testing today following UrS4boy’s helpful guide. All the numbers are good and everything seems ok. I cleaned the connectors again for good measure.
I also replaced the last bits of old vac pipe left. These were the short lengths next to the ecu.
I will do another boost leak test again tomorrow.



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[Ian Simmonds]

Well done fixing yours. All my vac pipes are new. I'm still looking for my bug

I followed this -

https://forums.quattroworld.com/s4s6/msgs/20987.phtml

and in particular the vacuum schematics on page 6

[Tractor Dave]

Well done fixing yours. All my vac pipes are new. I'm still looking for my bug

[Ian Simmonds]

Only through N75.
ECU modulates N75, reducing pressure applied to the bottom chamber of the wastegate.
In limp mode the N75 is left open to the wastegate which will open at spring pressure.
If you were to disconnect the hose from the WG (and plug it). The WG would stay closed and the car would overboost till the fuel is cut.

Have you checked that your ECU is seeing boost pressure? It’s been known for the boost/vac line from the inlet manifold to leak or be disconnected at the moisture trap under the carpet on the uk passenger side.
The small cotton covered vac lines at the back of the inlet manifold are usually leaky if still original.

John, see this thread..

https://www.s2forum.com/forum/member-s-area/member-s-cars/60975-giving-the-s2-some-love/page13

You utter star!

[newsh]

Interesting point John and something for me to investigate further. Genuine question, (because I really don’t know) is N75 the only way the ECU controls/reduces boost or can it control load through ignition timing and fuel?

Only through N75.
ECU modulates N75, reducing pressure applied to the bottom chamber of the wastegate.
In limp mode the N75 is left open to the wastegate which will open at spring pressure.
If you were to disconnect the hose from the WG (and plug it). The WG would stay closed and the car would overboost till the fuel is cut.

Have you checked that your ECU is seeing boost pressure? It’s been known for the boost/vac line from the inlet manifold to leak or be disconnected at the moisture trap under the carpet on the uk passenger side.
The small cotton covered vac lines at the back of the inlet manifold are usually leaky if still original.

[Ian Simmonds]

This is weird.
If you remove the N75 and fit a manual boost controller you should be able to turn the boost up. So there must be something physically wrong.
WG is very worn and opening itself by leaking through the valve guide.
You have a leak which blows above 0.7bar (but I’m sure you would hear that whooshing)
DV is broken or plumbed wrong.

Interesting point John and something for me to investigate further. Genuine question, (because I really don’t know) is N75 the only way the ECU controls/reduces boost or can it control load through ignition timing and fuel?

[Tractor Dave]

These cars certainly keep us busy

[newsh]

My (long!) process of elimination included power and continuity checks to N75 and MFTS (connected or disconnected), Swapped N75 and ECU (to an N300 vice MTM) put standard spring back in wastegate and vacuum checked for leaks, temporary replaced N75 with a turbosmart boost control (eventually ending up with it wound all the way out), removed air con belt. Car has full set of Roose boost hoses and a rebuilt turbo (last year). Throughout all of this it resolutely won’t go above 0.7 bar of boost in any combination.

This is weird.
If you remove the N75 and fit a manual boost controller you should be able to turn the boost up. So there must be something physically wrong.
WG is very worn and opening itself by leaking through the valve guide.
You have a leak which blows above 0.7bar (but I’m sure you would hear that whooshing)
DV is broken or plumbed wrong.