Wow! These sound nice! I haven't installed a controller on them yet...but, there's very little drone even with my headers, etc. At around 70 some drone would make a long trip a little uncomfortable on the ears, so sometime soon I'm going to make a decision on the controller I will install. Around town, though, it sounds just like I like it. Overall, I'm very happy with the sound and my installer did a great job installing them for only $100. He made a hybrid pipe before the mufflers of 2 1/2 to 3 inch but he said it was a pain in the butt. I'm happy for the price! Oh, the bigger exhaust tips look awesome, not at all embarrassing like the C6 stockies. Now, it's time for a full on Dyno Tune and I'll be happy for a while, well, maybe after the Fast 102...lol.

 

Nice exhaust upgrade, I sure like the ZR1 exhaust I have

 

Yep...very nice. I wish I understood the method of function of the stock bi-mode system. I know it closes when there's vacuum or low throttle input, and with WOT the vacuum reduces and the butterflies open, but that all sounds like it only needs a vacuum setup. If that's so, why does the stock bi-mode need an electrical connection and on the stock Z06, what does the vacuum box do?

 

Exhaust Tail Pipe Flow Control System Description and Operation

The Exhaust Flow Control (EFC) System enhances engine performance. The system has 2 modes of operation:

Normal & Competition



Normal Mode

When the vehicle is stationary with the engine running the exhaust flow control module (EFCM) commands the vacuum solenoid On, which supplies engine vacuum to both exhaust flow control valves. This causes the valves to close, diverting exhaust flow through a baffled path inside the mufflers. As vehicle speed increases, throttle position reaches 25 percent or greater and engine speed reaches 3500 RPM, the EFCM commands the vacuum solenoid off. This causes the valves to open, diverting exhaust flow through an un-baffled path inside the mufflers, thus enhancing engine performance.

Competition Mode

When traction control is driver disabled, vehicle speed increases, throttle position reaches 25 percent or greater and engine speed reaches 3000 RPM, the EFCM commands the vacuum solenoid off. This causes the valves to open; diverting exhaust flow through an un-baffled path inside the mufflers more frequently and at lower engine speeds.

The system also delays exhaust valve activity during wide-open throttle acceleration to inhibit exhaust valve actuation when the accelerator pedal is released and reapplied while shifting gears.

The EFCM has the ability to detect electrical malfunctions within the system. Any electrical malfunction detected will cause the system to be disabled and increased exhaust audibility.

The system uses the engine control module (ECM), body control module (BCM), electronic brake control module (EBCM), EFCM, exhaust flow control valve vacuum solenoid, vacuum reservoir, vacuum lines, 2 exhaust flow control valves and the serial data circuit to perform the system functions.

 

I've got a complete ZO6 setup for my GS that I will be installing this Spring............once it warms up a bit.

It is rumored that it is the most bang for your buck mod that you can do to an LS3 car.

 

The Stock bi-mode system and our Exhaust Commander All-in-1 NPP retrofit kit uses a vacuum check valve in the main vacuum line and a vacuum solenoid to regulate the engine vacuum to the butterfly valve actuators in the mufflers.

This prevents the exhaust from opening when a High Engine Load, Low RPM condition exists. Such as in 6th gear at 1500 RPM and going up a hill.

If there was no check valve, when the engine vacuum falls below 14 inches of vacuum while the engine is under load the butterflies would open. When you go wide open throttle the butterflies would open due to no engine vacuum, but would snap shut as soon as you let off the gas, thus eliminating the exhaust "burble' if the engine decelerating with the exhaust open.

With a vacuum check valve and a vacuum solenoid and controller to control when and how the butterflies open you are able to tailor the operational characteristics of the exhaust maximizing the tones you find desirable and eliminate undesirable engine noise.

Check out our video of our Exhaust Commander Elite NPP retrofit kit:

It has everything you need to make your bi-mode exhaust functional, and controllable.

If you have any additional questions, feel free to give us a call or send us a message.

We are always happy to help!

Ben

 

I've been running the complete Z06 system for the last several years in the "dumb" mode - simply hooked up the the manifiold vacuum when I wanted it quiet, or completely disconnected when I want it loud. It's true, even in quiet mode, the butterflies will partly open when pulling a load (like a hill). Just yesterday I installed an old transmission controlled spark (TCS) vacuum switch so that I can make the change on the fly. All I need is to wire it and add the check valve. Simple stuff.

As a side note, I cut the mufflers open to seal off the perforations in the straight pipe - sounds MUCH better!

 

I have a complete Z06 exhaust on my 05 A4. I took the time to install the vacuum lines and etc from a Z06 a bit more work but it sounds great when you jump on the go pedal.

Just a suggestion try the fast 90 instead of the larger fast. The car really woke up after I installed the fast with the complete Z06 exhaust and a tune

 

These three comments have explained three different setups each of which I was curious about. It' looks like there's a lot more to the "control" in the factory Z06 setup and a "tailor it your way" with the exhaust commander system and what happens if you simply hook the intake manifold vacuum to the vacuum motors on the mufflers. I really appreciate the education you have offered and now I have to decide what I want to do. Thanks a bunch!