# RS Exhaust Flap Mod, Switched.



## brittan (May 18, 2007)

Originally I did the exhaust flapper mod by simply disconnecting and blanking the vacuum hose to the flap actuator. That leaves the flap permanently open for (IMO) a better sound but of course you no longer have control from inside the car via the Sport button.
For some time I've been wanting to get round to rectifying that and finally today I did.

I'd looked up the wiring diagram some weeks ago and it has loafed on my desk while I've been busy with other things. 
There's only two wires to the solenoid and which is tucked up above the LH exhaust outlet together with a spherical vacuum reservoir. Access to the solenoid itself is quite restricted but the wires go through into the boot where access is good.

N321 is the solenoid in question served by brown/purple and black/green wires.


Eventually I decided to fit the switch on the side of the centre console. This was my third choice of switch location choices 1 and 2 having proved a little too awkward.

The lower side trim of the console is easy to remove via one bolt under the arrowed cover and then pulling gently to disengage the clips.


A careful check dictated that the switch be fitted so that the rear of it ended up within the area marked with a red oval to give suitable clearance.


I used a simple sub-miniature slide switch, £2 from Maplins. To fit it I cut an oblong hole in the console trim and after soldering on a suitable length of cable - I used speaker cable which matched the size of the OEM cable to the valve - secured the switch in place with 2 off 2mm machine screws. At this stage I checked at the far end of the new cable that the switch worked OK. The exposed terminals were covered with self amalgamating tape. 



After that the cable was slipped up under the rest of the console working past the inner side of the seat so that the cable exited from the rear of the console with the rear seat squab removed. There's an OEM loom here that if followed leads straight to the LH side of the boot where I made the final connections. I just poked the new cable in with the rest of them under every other bit of loom tape. 


The wires to the solenoid run along the LH side of the boot and are easy to see once all the polystyrene stuff is removed. There's no need to remove any trim panels. 


I cut the brown/purple wire which is in the smaller of the two bundles and then soldered to the new cable insulated them individually and bound it all with more self amalgamating tape.



Finally a quick test before putting everything back together and bingo, all working as expected. 


That's separated out one function of the Sport button. Next I'm going to look at how I might take separate control of the Sport (kangaroo) throttle map which will leave the Sport button controlling only the MagRide.


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## igotone (Mar 10, 2010)

That looks do-able! About time someone addressed this problem. [smiley=thumbsup.gif]


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## brittan (May 18, 2007)

I had the emission warning (MIL) come up today and a quick scan with VCDS showed the cause was an implausible signal from Exhaust Gas Temp Bank 1, so I've just deleted the DTC and I'll see if it happens again.

In the same scan was another DTC for open circuit for N321 the exhaust Flap solenoid valve. 
It's not a DTC that will flag up a warning light but it's annoying all the same.
Looks like I need to investigate a different switch to put a resistor in circuit to convince the ECU that it's still connected to the solenoid.


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## TootRS (Apr 21, 2009)

Nice write up Brian. Interesting about the emissions warning light. When I had my switch done the only error I had was in vcds showing an error for the exhaust flap, presumably as the flap was open without the sport button being pressed, which the ecu didn't expect, I've since has this mapped out, however, and no problems since.


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## brittan (May 18, 2007)

I think the emissions light is just a coincidence Harrison hence I'll see if it comes up again.

The flap position isn't monitored but continuity between the ECU and solenoid is hence the switch gives an error while disconnecting and blanking the vacuum pipe does not.

Some quick thoughts on possible solutions:
a) Fit an alternative switch to put a resistor in line with the ECU when the solenoid is disconnected from the ECU. Needs a smart or multi contact switch so that no momentary disconnection of the ECU from either resistor or solenoid occurs.

b) Devise a solution using an addition N321 valve with separate electrical supply and switching.

c) Keep the current arrangement and delete the fault codes every so often. I'm not sure if the fault frequency can generate some other problem when it reaches some (unknown) count.

d) Abandon the switches flap and go back to the 5mm bolt solution. It was simple.


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## SuperRS (Mar 7, 2012)

brittan said:


> I had the emission warning (MIL) come up today and a quick scan with VCDS showed the cause was an implausible signal from Exhaust Gas Temp Bank 1, so I've just deleted the DTC and I'll see if it happens again.
> 
> In the same scan was another DTC for open circuit for N321 the exhaust Flap solenoid valve.
> It's not a DTC that will flag up a warning light but it's annoying all the same.
> Looks like I need to investigate a different switch to put a resistor in circuit to convince the ECU that it's still connected to the solenoid.


That's exhaust temp sensor probe fault. Common RS problem.


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## brittan (May 18, 2007)

SuperRS said:


> brittan said:
> 
> 
> > I had the emission warning (MIL) come up today and a quick scan with VCDS showed the cause was an implausible signal from Exhaust Gas Temp Bank 1, so I've just deleted the DTC and I'll see if it happens again.
> ...


Yes, I'm expecting the error to appear again. 
Is replacement a DIY prospect? It doesn't look too bad in the manual but undoing high-heat affected components is often tricky!


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## SuperRS (Mar 7, 2012)

Apparently it's a pig to do.


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## TT-driver (Sep 14, 2010)

Personally I'd put the switch in the dash itself, as close as possible to the pedals. That way it's out of sight. Now you see it every time you get in.

Then electrically the issue is the open loop that is detected. While you can switch from the solenoid to a resistor that has the same resistance as the solenoid, the question arises: make before break or break before make? Make before break means temporary double the current. If the current comes from the ecu itself, I'd not take that risk. I suspect it's not through a relay as sensing an open loop is much harder to do.

So I'd think: break before make and only switch while the engine is off. Or introduce an additional solenoid, but that's a whole different ball game.

Or attempt to replace the solenoid itself by a resistor full time and use a relay parallel to that resistor to switch the solenoid. Then use your switch to interrupt the current to the actual solenoid in order to overrule it. But then it should be an on/off solenoid. Partially open can't be done. But I don't know if that is required.


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## brittan (May 18, 2007)

TT-driver said:


> Personally I'd put the switch in the dash itself, as close as possible to the pedals. That way it's out of sight. Now you see it every time you get in.
> 
> Then electrically the issue is the open loop that is detected. While you can switch from the solenoid to a resistor that has the same resistance as the solenoid, the question arises: make before break or break before make? Make before break means temporary double the current. If the current comes from the ecu itself, I'd not take that risk. I suspect it's not through a relay as sensing an open loop is much harder to do.
> 
> ...


First choice for the switch location was the recess on the bottom of the steering column shroud where the column adjuster lever sits, but removing the shroud involves removing the steering wheel and I didn't want to play with the airbag and steering angle sensor. Second choice was adjacent to the ashtray under the sliding lid, but that meant removing the RNS-E and I didn't have the keys to do it. Your choice would put it out of reach while on the move. Yes, my choice makes it visible, if you look, but routing the wiring was easy and that small part of trim is cheap to replace.

At the moment I've discounted the switched resistor solution as my bravery where the ECU is concerned is quite limited.

Fitting a resistor in place of the existing solenoid as you suggest is an option. I could then arrange an alternative supply/ground to the existing solenoid via my switch: cost = one resistor and some time.


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## brittan (May 18, 2007)

brittan said:


> SuperRS said:
> 
> 
> > brittan said:
> ...





SuperRS said:


> Apparently it's a pig to do.


A forty mile drive this morning and no repeat of the warning light so perhaps it was a one off? Yeah, probably not.
At first I thought I'd just buy a sensor to have 'in stock' for when the time came but at over £200 I'll wait and see.
I've had a look at the job though and as you say, it's one of those where paying someone else to swear at it is the better choice.


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## SuperRS (Mar 7, 2012)

Usually takes a while for the light to come back on after clearing it, usually I found a week or so.


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## TT-driver (Sep 14, 2010)

brittan said:


> Yes, my choice makes it visible, if you look, but routing the wiring was easy and that small part of trim is cheap to replace.


The non OEM look would frustrate the hell out of me. But that is personal.



brittan said:


> Fitting a resistor in place of the existing solenoid as you suggest is an option. I could then arrange an alternative supply/ground to the existing solenoid via my switch: cost = one resistor and some time.


Is the flap always open when in sport mode or does it close at city speeds/low rpm?


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## brittan (May 18, 2007)

TT-driver said:


> brittan said:
> 
> 
> > Fitting a resistor in place of the existing solenoid as you suggest is an option. I could then arrange an alternative supply/ground to the existing solenoid via my switch: cost = one resistor and some time.
> ...


I think it's always open in Sport mode but it's so long since I've driven it with the flap under ECU control that I do not remember!
Yes, the above arrangement would eliminate ECU control of the flap and give a simple open or shut at my command.


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## brittan (May 18, 2007)

I'm not one to give up easily so, from my previously posted alternative solutions I chose to install an addition solenoid valve to achieve my aim of switched operation of the exhaust flap. 
I removed the switch from the OEM wire to the OEM solenoid valve.
I fitted an extra solenoid valve in the vacuum hose between the OEM solenoid valve and the exhaust flap actuator with its own dedicated switch.

Initially I had wanted to replace the bank of switches on the centre console with one that included the TPMS switch and the switch for the moveable spoiler. It proved difficult to identify the right part number and ordering one from the local dealer would have been on the basis that it was non-returnable, so potentially an expensive mistake. Apart (pun) from that only the earlier RSs had the TPMS button, later ones had that function incorporated in the DIS so the right set of switches would be rare. 
Hence I defaulted to fitting the press button under the steering column where it is easy to reach but out of sight.

This is a diagram of the arrangement:









Both solenoids operate in the same way. 
De-energised they shut the vent connection and connect inlet to outlet allowing vacuum to be transferred to the actuator to shut the exhaust flap.
Energised they shut the inlet connection and connect outlet to vent breaking the vacuum on the downstream side and opening the exhaust flap.

The OEM solenoid remains under OEM control by the ECU and Sport button and with the additional solenoid valve de-energised I have OEM operation of the exhaust flap.
The extra solenoid valve allows me to effectively override the OEM one and open the flap any time I like. 
Overriding to shut the flap is not possible with this arrangement.

I used a press button (momentary contact) switch to mimic the operation of the OEM switches so that meant I had to incorporate a latching relay in the supply to the new solenoid valve.

It's all fitted and working exactly as expected and with no fault codes being logged.


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## TT-driver (Sep 14, 2010)

Yeah: you're going for the additional solenoid option. 8)

I do see the switch arrangement on the German ebay every now and then. I'm not sure what amount of current these switches can handle. Effectively they only signal the computer and don't power anything.

Looking forward to the results!


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## brittan (May 18, 2007)

Nope, I've gone for the solenoid option. 

The results are in and it all works as intended - I have the option of OEM control of the flap or I can open the flap any time I want to.

Oh yes, that console trim where I mounted the switch has been replaced with a new one, so back to OEM look.


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## malstt (Apr 18, 2007)

Would love to do this mod, do you have a link to the parts you bought ?


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