RS2 No boost after 30seconds of startup

[prj]

Explaining that with out seeing the car is hard, but that could easily happend like so: Hard acceleration ->the Autocheck gives a (!) warning, let´s say about low brakefluid level and at the same time some other thing like airleak or wrong MAP reading cut´s the Boost. Has happened to me like this, just poor luck. It doesn´t even leave a code for the low fluid level... Mine was leaking from the clutch slave cylinder...

Indeed, you are correct.
Or an alternative explanation can be that there is problems with the wiring.

[UrS4boy]

Indeed, you are correct.
Or an alternative explanation can be that there is problems with the wiring.

He isn't "correct". That would assume that his explanation is exactly what happened. You don't know that for sure. That said, his explanation is "plausible", as in "Sure, that is a good possibility as to what might have happened".

My *guess* would be a reasonable safe solution. However, since I can not find any connection between the autocheck and the Motronic ECU that would make it reality, there has to be a coincidence of two or more events to trigger the red ((!)) warning and the boost cut at the exact same time.

[twoqu]

At a loss to explain no boost, but if boost is dropped to the mechanical and there is a Warning symbol perhaps it is a faulty MFTS. The symbol might be the overheat warning. Don't forget on the S2/RS2 there is this function!

[UrS4boy]

At a loss to explain no boost, but if boost is dropped to the mechanical and there is a Warning symbol perhaps it is a faulty MFTS. The symbol might be the overheat warning. Don't forget on the S2/RS2 there is this function!

Agree about the interaction between the MFTS and the S2/RS2 ECU and that potentially resulting in reduced boost. However, the red warning symbol in that situation would be a thermometer in waves of water (see pg. 2/16 of this: http://www.leesehold.dsl.pipex.com/200/pdf/ffp2.pdf) not the red ((!)) brake system warning symbol that the original poster mentions.

[twoqu]

Might be worth eliminating this as a potential cause:

http://www.s2forum.com/forum/showpost.php?p=592845&postcount=47

[RS2ZuidAfrika]

Thanks for all the feedback guys. You have been a tremendous help and I am attending to all the possibilities step by step.
Please keep them coming

[Faheemo]

I been attending to rs2zuidafrica's car.
The car is in a very stock condition.
Car still has the cats on and computer box has never been opened.
The car needed to be set an entire tooth to the left to drop the hallsender fault.
I started off with checking wgfv and all the other regular issues.
I'm going to explore the brake pressure sensor mentioned and then the MFTS.
The Brake warning signal comes on but after a long drive it goes off.
My personal experience with my s2 , i know the brake warning has no effect on performance. (but this is a rs2)
Last i will atempt the Map sensor , i just havent heard of a map sensor go south before.
I prob have my original map sensor (s2) somewher , but rs2 has a 3 bar sensor ?
Does the rs2 have a fuel pressure sensor ?

[prj]

Clear the faults, does the MAP sensor fault come back all the time?
And "attempt the MAP sensor", this lives inside the ECU and it is not user serviceable.

[veneto rs2]

My two pennies....

prj any chance that the performance issue it's due to a faulty knock sensor?
The knock sensors are in deed triggering the ignition point if I remember well ?

About the brake warning light in all my 15 years Ihad several times for different reasons the red brake light lit on the dashboard but this ha never had any influence on the boost or performance in general.

About the MFTS I had run before with the plug disconnected (bad MFTS was triggering off my A/C in august...) and again I can assure there's absolutely no affection on the car performance.


Stefano

[prj]

prj any chance that the performance issue it's due to a faulty knock sensor?

Then there would be a code for it.

About the MFTS I had run before with the plug disconnected (bad MFTS was triggering off my A/C in august...) and again I can assure there's absolutely no affection on the car performance.

If it is disconnected, there is no effect yes. If the MFTS is bad and it is shorted together, THEN there is an effect on performance.
The thermal switch is open in normal operation and closed during high temperature, and they usually fail closed.

But in this case there is a clear fault code. What's the point of coming up with imaginary reasons, if there is a MAP sensor - signal too high code in the ECU?
That code will ALWAYS and INSTANTLY trigger limp mode with no boost. So if that code is there and it is impossible to erase, you have found your problem.

[UrS4boy]

G71 Manifold Absolute Pressure (MAP) sensor information

...Last i will atempt the Map sensor , i just havent heard of a map sensor go south before. I prob have my original map sensor (s2) somewher , but rs2 has a 3 bar sensor ? Does the rs2 have a fuel pressure sensor ?

The RS2 doesn't have a fuel pressure sensor (nor does an S2 or UrS4/S6). However, the RS2 does have a 300 kPa (3 Bar) MAP sensor, compared to the ABY S2s's and UrS4/S6s 250 kPa (2.5 Bar) sensor. OE Bosch sensors don't seem to fail very often. I have been around these cars (20V Turbo I-5s) since 1998, on various UrS forums and honestly do not recall anyone posting about a failure. That said, it is common to upgrade the 2.5 Bar MAP sensors to 3.0 Bar when going to say MTM Stage 1+ chip levels (280 hp) and above. Definitely required when adding larger turbos (e.g. RS2 K24-7200) and injectors.

The G71 MAP sensor is soldered to the bottom ECU PCB. As such, it is not normally an owner serviceable part. That said, lots of people know how to properly desolder chips from the PCB. These same people could certainly remove a faulty MAP sensor and replace it with a new/know-to-be-good 3.0 Bar Bosch or a VMAP or the $80 one from EFI Express.

More G71 nfo:

http://forums.quattroworld.com/s4s6/msgs/20417.phtml

VMAP from 034 for about US$105

http://www.034motorsport.com/034efi-engine-management-engine-management-sensors-034efi-varimap-switchable-25-bar-map-sensor-p-521.html

EFI Express's US$80 offering:

http://www.efiexpress.com/catalog/product_info.php?products_id=82

[prj]

More G71 nfo:

http://forums.quattroworld.com/s4s6/msgs/20417.phtml

VMAP from 034 for about US$105

http://www.034motorsport.com/034efi-engine-management-engine-management-sensors-034efi-varimap-switchable-25-bar-map-sensor-p-521.html

EFI Express's US$80 offering:
http://www.efiexpress.com/catalog/pr...products_id=82

This part will perform exactly the same function for 10$:

http://www2.mouser.com/ProductDetail/Freescale-Semiconductor/MPXH6300AC6T1/?qs=sGAEpiMZZMt7FrWooXVB13CCYzmk53xJ

No need for big ugly VMAP things which do not match the bosch specs of voltage output and give signal too low and signal too high codes in some cases.
At least that was the case with the older one, I have not tried Marc's or 034's solutions.

[UrS4boy]

This part will perform exactly the same function for 10$:
http://www2.mouser.com/ProductDetail...VB13CCYzmk53xJ

Manufacturer: Freescale Semiconductor

But it still needs a PCB for installation.

[UrS4boy]

No need for big ugly VMAP things which do not match the bosch specs of voltage output and give signal too low and signal too high codes in some cases. At least that was the case with the older one, I have not tried Marc's or 034's solutions.

Ugly? What does that matter? Who sees it?

One of the advantages of the VMAP was that it could be adjusted. Some versions required changing jumper positions to do this. The version that I got was the one that I could adjust it from 3.0 Bar down to 2.7 Bar and up to 3.1 Bar in 0.1 Bar steps by turning the ignition to on and toe tapping the throttle. Very clever in my opinion. That said I only had to do that once when I could only get an inferior octane fuel. Nice to have. Only cost $40 more at the time.

[prj]

Ugly? What does that matter? Who sees it?

One of the advantages of the VMAP was that it could be adjusted. Some versions required changing jumper positions to do this. The version that I got was the one that I could adjust it from 3.0 Bar down to 2.7 Bar and up to 3.1 Bar in 0.1 Bar steps by turning the ignition to on and toe tapping the throttle. Very clever in my opinion. That said I only had to do that once when I could only get an inferior octane fuel. Nice to have. Only cost $40 more at the time.

Yeah, really good to fool the ECU by giving it wrong signals without altering the map.
Maybe you think putting a potentiometer on the MAF signal is a great idea too???

Manufacturer: Freescale Semiconductor

But it still needs a PCB for installation.

And your point is? The voltage curve has below 1% deviation from Bosch curve in the usable range.
I also don't see what you mean by "needs a PCB for installation". I have installed about 120 of these without any PCB.

You just need this sensor, a soldering iron, some wires, a single cable tie and some skill.