Boost Controllers ...

[viperbl]

I have the following boost controller from when I had the S4 engine conversion, I remember last year trying to fit it again to the RS4 but had problems, if I remember correctly the lowest boost setting was only 1 bar (as opposed to what it used to be, which was 0.4 bar)

Its a neat little device when working correctly, there is a knob which you can turn to gradually reduce the boost down to very low, or back up to normal.

Does anyone know this boost controller and wither it is bust or not?

[yorkie]

Looks fooked to me but what do I know???

[MarkB]

The black goo is just potting compound to stop you getting at the electronics and build your own version. I would say from the photo's there is no way to tell if it's trashed or not.

[viperbl]

Yer, the pictures are more in case anyone recognises it and wither there is an option to rotate the little items in it (whatever they are called?!?!) to reduce the lowest boost level it will go to ...

[Nige_RS4]

IMHO you are unlikely to be able to drop below the std boost level of the RS4 which is 1.0bar. These boost gadgets are meant for winding the boost up above std, not reducing it!

[viperbl]

It should be able to.

I was able to reduce it to 0.4 bar in the S4 engine with this device, and I can reduce the boost in the RS4 to 0.4 bar (seems to be the min) with VAG COM.

[Nige_RS4]

Do you have any info on how this actually works? Looks like it plugs into the OEM harness somewhere? How about a manufacturer / part number?

[viperbl]

Do you have any info on how this actually works? Looks like it plugs into the OEM harness somewhere? How about a manufacturer / part number?

No info at all on it, just what you see.

It plugs into the N75, so breaks the connection to the N75 as such, it now all goes through this device first.

Nothing at all on it! Plus the company that sold it to me have gone bust now, but it was SKN in germany that fitted it.

[david7m]

Quick question - why do you want the boost lower than standard??!?!?

Dave

[viperbl]

It is quite handy when driving ...

My current map is quite on/off, if for example you coming out of a junction and need to get a little bit of a wriggle on, its hard to get x amount of power down, more so you either crawl out or put down all the torque and loose traction or power is cut if you have the ESP on.

Plus its handy to just run less boost, makes me drive a little more sensibly...

Oh, who am I trying to kid, its just another toy to play with

[david7m]

Oh, who am I trying to kid, its just another toy to play with

That's what I thought

Dave

[viperbl]

Just for the archive...

The "power" cable goes to the negative of the battery.

The Centre "dial", if turned all the way to the right will lower the boost (on the low setting of the controller knob) to the lowest setting for the car, which will be around 0.4 bar.

So, this sits in between the N75 valve and controls it.

On the lowest setting I am getting 0.4 bar on full boost, then I can gradually turn it up to get anything in between until eventually it will deliver the maximum "normal" boost level.

[Dippy]

From what I remember, the ECU controls the N75 with a PWM signal. Max boost is increased with longer duty cycle and reduced with a shorter one. Loss of signal is the same as zero duty cycle hence a limp mode failure mode. Having a device like this interposed between the ECU and the N75 can easily reduce the effective duty cycle by filtering the signal, whereas to increase it is more difficult (and potentially dangerous). Hence the description of being able to reduce max boost only makes sense.

Although the RS4 has a higher boost that the S4, I initially assumed that the basic operation of the N75 and wastegates is the same. If this is the case then I'd suggest that the unit is indeed broken. However in the event that there is a difference, maybe because the RS4 uses a different type of solenoid valve with different operating parameters, then indeed it could be simply that the controller is no longer appropriate. I'm actually inclined to think this might be so, because the unit has a couple of pots inside. These would control the filtering. It is quite possible that it could be adjusted for the RS4, but personally I wouldn't do that without using a scope to monitor the signal.

[viperbl]

Dippy, I was just updating because I got it working!!

Its now working perfectly, when I turn the user knob that goes in the cab all the way to the right it gives me full boost (ie, no more than before, so its not increasing it) and when turned to the right will give me 0.4 bar boost.

I can also run this anywhere in between, so I can run it at 1.4 bar for example, which will allow lots of fun, but not "Stress" the turbo's as much...

But yeah, ok, it may as well just be low or full for me!! haha

[MarkB]

I had switchable boost on a car once. You can guess which setting it went on most of the time.

Be handy for a balls out amount for short times like events then back it off a little for everyday use.