Great option to keep the valves always open with valved controlled exhaust systems.

[dturn37]

Hey guys, I recently upgraded my exhaust from a Tubi to a Capristo solely because I wanted to go back to a valved system I could control. I wanted a controller that bypassed the Audis ecu valve controller and kept the valves open without actually unplugging the hoses. I was looking into the controller Capristo sold but really didn't want to spend $1200. I found a few mods that required splicing into the ecu and didn't really want to go that route either. I finally found a company that made valve controllers for ferraris and inquired about them making one for Audis. Steve, the owner, was super helpful and made me one to test on my RS4 and the thing is great. It is controlled either by a remote similar to the Capristo system or you can wire it to a switch. The nice thing is its plug and play without any splicing and took me 15 min to install. So if anyone is looking to have 3 modes (stock, S button, Valves always open) for a really good price hit him up [email protected] and here's the website http://www.forzacomponenti.com/index.html

[Seattle squash]

I like that. Do you have any pictures of install?

[bshanna]

i'm currently ordering one and have my trunk torn apart. I can take pictures with it installed but it's not something that you will see once it's installed as it's basically a control module that you install between the stock valve controller and the wire harness it plugs into. All of clips are universal and completely reversible and the control module sits in the same area where the XM radio box sits. Once installed you shouldn't be able to see anything :)

FWIW i think it also supports "always closed" mode.

[azforza]

Hi guys. I'm the owner of Forza Componenti. I am not a sponsor here, so cannot advertise here. But, if you have specific questions about the exhaust controller for Audi, I can answer them. Of course you can also send me a PM.

I see that bshanno says he thinks it supports "always closed". That is correct. The controller has three modes of operation

1. Normal Mode. The car's ECU controls the valves
2. Always Open
3. Always Closed

Regards,

Steve

[forbiddenbeat]

That's awesome! A fellow AZ'er made me a custom controller that wires into my S dash button (S mode is controlled by my Euro FBSW), but I had to splice into the ECU wires.

What does this module plug into?

[DOCEVG]

Sounds like a nice add-on!
What is the point of having the "always closed" option?

[bshanna]

Plugs into the stock valve control mechanism in the trunk. It interrupts the signal that controls the valves and either passes through (support stock setup Sport/not sport) or blocks (to support always closed or always open). Uses a key fob to change that setting.

always closed = love thy neighbour/don't get pulled over? :)

[azforza]

That's awesome! A fellow AZ'er made me a custom controller that wires into my S dash button (S mode is controlled by my Euro FBSW), but I had to splice into the ECU wires.

What does this module plug into?

As bshanna stated, you unplug the existing vacuum solenoid valve in the luggage compartment and plug that connector into the controller wiring harness. A return cable from the controller module plugs back into the vacuum solenoid. The controller module will either pass the electrical signal through with no change (Normal or Stock operation) or it will interrupt the circuit to the valve. When interrupted, the valve will be forced open or force closed at all times ... depending on your choice. Also, when the circuit is interrupted, the signal is shunted to a special circuit in the controller module that simulates the solenoid valve. In this way, the ECU does not see that the circuit has been interrupted. If it does, it could throw an error code which could result in a check engine light. So in this way, there is no error codes generated. Also, there is no wire cutting or splicing so everything is 100% reversible.

Steve

[azforza]

Sounds like a nice add-on!
What is the point of having the "always closed" option?

The Always Closed option is not for everyone. Generally, just keeping the car in Normal mode will close the exhaust bypass valve when at low engine RPM and/or low speeds. But, there may be times when in the Normal mode, the car's ECU will "decide" to open the exhaust bypass valve with the result of louder exhaust. If you do not want this to happen, you can force the exhaust bypass valves closed.

One place where people like this feature is when tracking the vehicle. Many tracks are implementing maximum sound levels. For example, Laguna Seca in California has something like a 94db sound limit. I know many cars ... even with stock exhaust systems ... that fail new track max sound level restrictions. For example, the Camaro Z/28 will fail at Laguna Seca's maximum limit with the stock exhaust. With the "Always Closed" option, the Z/28 passes Laguna Seca.

Regards,

Steve

[DOCEVG]

Thanks, Steve. Appreciate the explanation. Have driven with bshanna; thats a lot of dBs combined from two cars!

[forbiddenbeat]

As bshanna stated, you unplug the existing vacuum solenoid valve in the luggage compartment and plug that connector into the controller wiring harness. A return cable from the controller module plugs back into the vacuum solenoid. The controller module will either pass the electrical signal through with no change (Normal or Stock operation) or it will interrupt the circuit to the valve. When interrupted, the valve will be forced open or force closed at all times ... depending on your choice. Also, when the circuit is interrupted, the signal is shunted to a special circuit in the controller module that simulates the solenoid valve. In this way, the ECU does not see that the circuit has been interrupted. If it does, it could throw an error code which could result in a check engine light. So in this way, there is no error codes generated. Also, there is no wire cutting or splicing so everything is 100% reversible.

Steve

Sounds great! My install is not reversible (spliced wires in the ECU), but the controller works with the S button in the dash (required a flip-flop circuit), which is nice.

For anyone considering something like this, it's pretty nice to have. I love having the valves open all the time, which adds a nice extra level of grunt to the exhaust, with the ability to close it when the wife is in the car. :)

[mpdbrown]

This is something I would probably purchase if available.

Does it remember settings after cycling the ignition? Or do you have to choose each time you start the car?

[azforza]

[LIST=1]

This is something I would probably purchase if available.

Does it remember settings after cycling the ignition? Or do you have to choose each time you start the car?

There are two ways to use the controller:

1. Remote transmitter
2. Manual switch

The remote transmitter, uses a simple RF signal on the 433MHz band. When there is no power, the controller module will default to the Normal operation mode ... i.e., the car's ECU manages the exhaust bypass valves. When there is power, the receiver inside the controller module will be "listening" for a signal from the transmitter to select either the Always Open or Always Closed mode. If the power is lost (e.g., turn the engine off), the controller will reset to fail safe mode and it will return to the Normal mode. When power is lost, the controller will not "remember" what position it was in at the time of power interruption. When you start the engine again, you would have to select either Always Open or Always Closed again.

If you use a manual switch, you would install a three way, double pole switch. The three positions would be On-Off-On. When Off, the controller would be in Normal mode. The two On positions would be Always Open and Always Closed respectively. Because the manual switch is mechanical device, there is no dependence on power being available to "remember" the switch position. When you turn off the engine and power is interrupted to the controller module, and controller will reset to fail safe, or Normal mode, but the switch would remain in position. Next time you start the car, the controller would immediately assume the operation mode the switch is set for.

Regards,

Steve

[AussieDan]

Very cool, electrically it's the same thing as the controllers I made for my car and forbiddenbeat, just interrupting the same circuit in the trunk instead of under the dash.

With the wireless controller it makes more sense to do it that way since you don't have to worry about getting a wire back up to the front of the car for the switch. If you're just going to use a 3-way toggle switch then you can do the mod for under $20 with just the switch and a resistor, you don't need any kind of controller.

Here's a switch I made, and the circuit diagram.



My complete write-up on how this works, and how to make your own cable.

The more interesting part for me was integrating with an OEM Audi momentary switch, and using the switch backlight for mode feedback. That took some figuring out and a lot of soldering, and right now forbiddenbeat has the only example in existence. The RS4 button shown in the article (in my car) is using an off-the-shelf latching relay which works but doesn't give any visual feedback. At some point I'll get around to making another controller for myself, but so far I've had too many other things on my plate to get around to it.

Here's a video showing the backlight feedback

[azforza]

Very cool, electrically it's the same thing as the controllers I made for my car and forbiddenbeat, just interrupting the same circuit in the trunk instead of under the dash.

With the wireless controller it makes more sense to do it that way since you don't have to worry about getting a wire back up to the front of the car for the switch. If you're just going to use a 3-way toggle switch then you can do the mod for under $20 with just the switch and a resistor, you don't need any kind of controller.

Here's a switch I made, and the circuit diagram.

Very good work. I like the fact that you use a load resistor to prevent the ECU from detecting an open circuit. Without the resistor, the ECU could indeed log an error code which could result in a check engine light. In my controllers, I used similar logic to prevent that very thing.

The only modification I would recommend is to use a switching relay. Although there is very low load, as you stated, the risk of running +12V to the switch is that a short circuit will draw significant current (as much as it can) which could melt the wire, blow a fuse, damage the ECU or all three. The risk might low, but the consequences can be severe. And running a single wire that length increases the risk of something happening down the road that might cause a short. Friction points, body movement, etc can all be potential causes of wire becoming frayed and shorting out. Placing a relay in the circuit and then running the wire from ground side of the relay coil to the control switch will mitigate any risk of short circuit as the wire to the switch would only be a ground wire. The switch would only be completing the circuit to ground and a short circuit in that wire would not have any damaging consequences. Otherwise, your circuit will work just fine and someone could save some money if they are handy with doing the electricals.

The only thing your circuit will not accomplish is to provide an Always Closed option to force the exhaust bypass valves closed at all times. Not a big deal, but could be handy for anyone who might be thinking of tracking the car at a location with noise restrictions.

I am bit biased, but on newer cars that are in warranty, making these wiring changes could likely give cause for an Audi dealer to void the warranty on the vehicle. Whereas, the Forza controller does not require any wiring mods on the car and is easily removed ... erasing any evidence of it ever being installed.

Regards,

Steve

[forbiddenbeat]

Hey Dan! Figured you might chime in. The controller is working perfectly, by the way. :)

Cutting ECU wires definitely made me nervous, but Dan provided perfect instructions, and made it easy with the posi-tap connectors. Agree that not cutting wires is better. :)

[azforza]

Very cool, electrically it's the same thing as the controllers I made for my car and forbiddenbeat, just interrupting the same circuit in the trunk instead of under the dash.

Here's a switch I made, and the circuit diagram ....

Hi Dan,

One thing I noticed in your write-up. You recommended a 1000 ohm resistor with a 0.5watt rating. That is much too small a power rating. At 12 volts, that resistor will be drawing 0.144 watt which is 23% of the power rating of the resistor. The temperature rise for a simple resistor running 23% of power rating could be as much 200 deg F. It will very likely be very hot to the touch ... and will increase the likelihood the resistor will have failure.

If you want to use a 1000 ohm resistor (I would have chosen a lower value), then you should be specifying a resistor with a power rating high enough so the temperature rise will not be so alarming. With your 1000 ohm resistor, I would recommend a 5 watt resistor. Using that value, the temperature rise should not be more than 20 deg F. If you were to choose a 2 watt resistor (easier to find) it would be drawing 6% of the rating which will equate to a temperature rise of about 35 to 40 deg F. which is acceptable.

I recommend a 5 watt resistor. A 2 watt resistor would be acceptable, but only just. But in any case, your selection of 0.5 watt resistor is way off base and would be dangerous in the way you have stated to use.

Regards,

Steve

[AussieDan]

Thanks for the feedback Steve, it certainly wouldn't hurt to throw a small fuse in the circuit in case of a short, though I would note that the OEM circuit running the full length of the car back to the solenoid doesn't have any additional fuses other than the 15A fuse feeding the green/yellow 12v wire being tapped for power (the same wire present in the solenoid connector).

For the resistor I'm not sure I understand why you'd want to increase the rating so drastically, I just tested one of the 0.5w 1000ohm resistors connected across a 12.5v supply for 15 minutes and the maximum delta from ambient I could measure was 4 degrees Fahrenheit. For larger resistors the temperature rise at ~29% of rated load can get pretty extreme but at this end of the scale the 0.5w resistors don't seem to have an issue dissipating 0.144w. There is certainly no reason you couldn't step up to a higher wattage rating, but it doesn't seem to be necessary.

The 'always closed' position isn't really needed in the RS4 since that is effectively what you get with the switch off and s-mode off, but if you did want to be able to run in s-mode with the exhaust flaps closed (not sure why you'd want that) it is also possible with a DPDT switch. I know the R32 guys have done that since those cars don't have a factory mode where the flaps are closed all the time like the RS4 does (they also commonly use 1k 1/2watt resistors).

Your product definitely seems to be well thought out, and using factory-style connectors to plug in to the solenoid is a nice touch.

[bshanna]

I think he mentioned that he developed the functionality specifically to run on the track where there are sound restrictions ( and since these were originally not developed for the RS it is just an option we get for free:) ). For some reason i thought even with sport mode off the flaps opened up past 5k or something?

just got mine today, packaged exceptionally well and looks like great quality! I will complete the install this weekend.

[azforza]

Thanks for the feedback Steve, it certainly wouldn't hurt to throw a small fuse in the circuit in case of a short, though I would note that the OEM circuit running the full length of the car back to the solenoid doesn't have any additional fuses other than the 15A fuse feeding the green/yellow 12v wire being tapped for power (the same wire present in the solenoid connector).

For the resistor I'm not sure I understand why you'd want to increase the rating so drastically, I just tested one of the 0.5w 1000ohm resistors connected across a 12.5v supply for 15 minutes and the maximum delta from ambient I could measure was 4 degrees Fahrenheit. For larger resistors the temperature rise at ~29% of rated load can get pretty extreme but at this end of the scale the 0.5w resistors don't seem to have an issue dissipating 0.144w. There is certainly no reason you couldn't step up to a higher wattage rating, but it doesn't seem to be necessary.

The 'always closed' position isn't really needed in the RS4 since that is effectively what you get with the switch off and s-mode off, but if you did want to be able to run in s-mode with the exhaust flaps closed (not sure why you'd want that) it is also possible with a DPDT switch. I know the R32 guys have done that since those cars don't have a factory mode where the flaps are closed all the time like the RS4 does (they also commonly use 1k 1/2watt resistors).

Your product definitely seems to be well thought out, and using factory-style connectors to plug in to the solenoid is a nice touch.

Hi Dan,

The recommendation for resistor rating comes from tables that describe the temperature rise for various classes of resistors. The amount of temperature rise varies. Variables include type of resistor, the surface area, how it is installed, etc. In the application that we are using where we include the resistor as a means to keep the ECU from sensing an open circuit, most designers would term that a power resistor application ... i.e., be there to burn off power when asked to do so. It is important that the resistor be sized so that the max power is not exceeded, but is well within limits. The reason is that the resistor will go up in smoke in very short order if the power exceeds capacity. At 23% of power capacity, you are getting too close for comfort. The difference in cost between a 0.5 w resistor and 5 w resistor is very small.

It is quite difficult to accurately predict what the temperature rise is likely to be. Obviously, performing an experiment such as yours is a very good way. But, when you are recommending a circuit design, unless you are very specific with regard to resistor type, manufacturer, surface area, etc. ... it would be better to over specify. What I tend to use is manufacturer ratings for temperature rise for various resistor values. One company, Ohmite, has a paper, Resistor Selection. They show a graph that depicts temperature rise vs. percent of rating. Here is a link to that paper ... http://www.ohmite.com/techdata/res_select.pdf

I like to err on the side of caution ... so I would recommend that you specify at least a 2 watt resistor for that application ... that way you have a pretty good assurance that someone following your design will not be foiled by a blown resistor because it approached the maximum temperature rise. In the Forza controllers, I use a 5 watt resistor to make sure that the temperature rise is kept very low.

You comment about Always Closed ... in my opinion, the main use of that for an Audi and most cars is when tracking the vehicle and you want to make sure the car's ECU does not open the valves under high speed / open throttle conditions. For example, at some tracks in US and Europe, it is becoming more common that noise restrictions are becoming common place. For example, Laguna Seca in California has a 94 db noise limit and there are many examples of cars with stock exhausts (with bypass valves) where the car is keeping the valves open under wide open throttle ... the cars are failing noise requirements. To keep under the maximum noise limit, cars have to have the means to force the valves closed. You are right though, for vast majority of time, simply going back to normal mode accomplishes this. The Always Closed is only for extreme cases. One exception ... the Chevrolet Camaro. The designers at Chevy, have set up the bypass valves so they are open at engine idle up to about 1500 rpm. So some guys, who are trying to gently sneak out of the garage in the morning (or sneak in at night) are finding that the car makes too much noise at low engine RPM. They want to close those valves. This is not a problem with Audi.

In order to force the valves Always Closed, one has to apply +12V continuously to the solenoid valve(s), while simultaneously interrupting the normal circuit and shunting through the power resistor. This is not trivial to do and just putting a DPDT switch in the circuit might work out OK, but I then get back to the relay thing. Why? When you pushing +12V to the solenoid valve(s), you have higher current than you would experience through the 1000 ohm resistor. I would expect the resistance of the solenoid valve is closer to 20 ohms which would pull about 0.63 amp. I might be overstating the current .. but then again, better to err on the side of caution.

I recommended a relay and then the control wire for the relay would only be a ground wire. Yes, the risk is low running +12 v through the control wire. But if a short circuit were to occur you might cause damage. But, the risk is zero to cause damage if you use a relay and then the control wire is merely a path to ground. Then if a short circuit should occur, the worse that would happen is that the you would enable an always open condition. But you would not have sparks and smoke. For someone who has good practice of wiring, good quality connectors and work practice ... maybe not a big deal. But there are lots of people with lesser skills who might not take the care in running wires carrying load to make sure they use caution when making connection. Again, the cost of a good relay is under $5 and it mitigates a potential risk. Best practice for any control circuit in automotive and aviation is have the control wire only be a path to ground and not carry a load voltage if it can be avoided. If you look at a typical car's schematic diagrams, in nearly all cases loads are managed by relays and control of those relays is performed by managing the ground wire of the solenoid coil. Obviously there are exceptions and then fuses are placed inline.

Best regards,

Steve

[lucidmatt]

Awesome to see all this info flowing, thanks for the lesson! Great read, definitely putting the best foot forward Forza!

[bshanna]

A couple of install pics

The trunk lining taken up and the box removed ready for install:


The ground wire i used in my install:


Where i mounted the control unit:


Almost installed and bolted in:


Finished install lol:


yeah. that's just a stock trunk :P

i took video of the FOB working but it didn't really come out.

bret