Electronic cutouts questions

[cheesy9]

I'm interested in electronic exhaust cutouts, e.x. http://www.m3post.com/forums/showthread.php?t=196007

A couple questions:

• What is the loss/gain in power like in both positions? Someone mentioned it may add turbulence to the stock exhaust. Someone else mentioned a potential loss in back pressure when open.
• Following up on that, someone mention the ECU needs time to adjust to the different exhaust configurations. Is this true? How much time?
• Presumably this isn't a bolt on, and requires cutting into the stock exhaust? Does this void the whole cars' warranty, or just the exhaust's warranty? What's the warranty situation with aftermarket exhausts in general?
• Who here has cutouts? Do you like them?

Thanks!

[jml]

Originally Posted by cheesy9

I'm interested in electronic exhaust cutouts, e.x. http://www.m3post.com/forums/showthread.php?t=196007

A couple questions:

• What is the loss/gain in power like in both positions? Someone mentioned it may add turbulence to the stock exhaust. Someone else mentioned a potential loss in back pressure when open.
• Following up on that, someone mention the ECU needs time to adjust to the different exhaust configurations. Is this true? How much time?
• Presumably this isn't a bolt on, and requires cutting into the stock exhaust? Does this void the whole cars' warranty, or just the exhaust's warranty? What's the warranty situation with aftermarket exhausts in general?
• Who here has cutouts? Do you like them?

Thanks!

>I doubt that enough turbulence is introduced to reduce flow rate/increase backpressure - but that said, the M3's exhaust system is highly tuned to optimize scavenging effects across the whole RPM spectrum, and any flow rate change has the potential to throw things off a little. Most of the wizardry is in the header design, but I can imagine small flow rate changes downstream having an impact. With the valves closed, assuming the Y-pipe design caused enough turbulence to reduce flow rates, you might expect to get a breath of more torque at low-mid rpm where you are helping scavenging, and a loss of top end power. With the valves open, there is clearly a higher flow rate because you've taken a flow resistive component (about 3 feet) out of the system, so you might expect a small loss in low-mid range torque where the scavenging effects are most sensitive to higher flow rates, and higher power output at high RPM.

I *edit* "perceive" a difference at high RPM, but since I don't have a baseline, I am not sure if it's because the the flow rate is reduced with the valves closed relative to stock, or if it's the increase with them open.

>It's possible that with ECU tuning I could get more power out of more exhaust flow rate. The same statement can be said for any exhaust change. I am not motivate to. The car drives fine and it's not worth the warranty headache.

>Yes, you will need to hack up the tubing between the muffler and midpipe connection. Since the OEM tubing is hydro formed (with an irregular cross section), you are probably best off cutting out a large length between two round cross-sections and replacing with standard round SS tubing.

Warranty-wise, sure the muffler is now likely no longer under warranty. Rest of the car is fine. If you ECU tune, and they can detect it, your motor is voided.

>I've had cutouts since Feb 2009. Aside from the shitty mechanical design of the Raceready units, I like them a lot. The jekyll/hyde tunability adds a ton of character to the car without changing the livability. W/r to drone, yes, there is low-mid range drone with the valves completely open, and as the car gets older and the interior loosens up, that turns into buzzes and rattles that sing to you at different times as the car sweeps through 2K - 4K rpm. The simple design of the cut-outs also lets you control how far they are open, so you can crack them open a bit to change the character of the exhaust without introducing any major drone issues.

No regrets except the raceready units. I would try another brand next time around, something with a better coupling between the "servo" (if you can call a motor on a transmission without position control a servo) and the valve. I've seen/heard a few different systems at the track, and the unanimous feedback I get is that my car sounds the best from the stands/infield - though this is redneck country down here.

[cheesy9]

Thanks for the detailed response.

Regarding the ECU question, I didn't mean I wanted to tune the ECU, rather someone mentioned that it will automatically adjust to changes in the exhaust system, however switching back and forth using cutouts might not give the ECU time to adjust, thus you'll always be running more inefficiently than with fixed exhaust systems (at least in one of the two positions). I don't know if that's true though.

[swamp2]

Originally Posted by jml

I can feel the difference at high RPM, but since I don't have a baseline, I am not sure if it's because the the flow rate is reduced with the valves closed relative to stock, or if it's the increase with them open.

Nice write up on valves. I considered them heavily for some time but decided against them. Even with my Vorsteiner system I'd still like something louder but only louder on occasion. For road trips and longer drives the V. is at the limit for me for noise.

I've heard that there is no really solidly designed and durable valve on the market for this applicaiton. You could probably buy a nice aerospace certified valve buy maybe not in quantities of 2 and the price would probably be astronomical. Do let us know about any leads on a truly solid brand.

Also, are you saying you can feed the power effects from this valve? I kind of doubt that. I'd guess you can get 5hp max from this which is only about 1%. If you can feel 1% hats off .

[jml]

Originally Posted by swamp2

Also, are you saying you can feed the power effects from this valve? I kind of doubt that. I'd guess you can get 5hp max from this which is only about 1%. If you can feel 1% hats off .

It's probably just the noise that makes it feel faster

[cheesy9]

To be honest in fine with having to replace the valves every couple years. The valves aren't welded directly to the pipes, right? They're bolted onto the flanges, so they should be easy to replace on your own?

[jml]

Originally Posted by cheesy9

To be honest in fine with having to replace the valves every couple years. The valves aren't welded directly to the pipes, right? They're bolted onto the flanges, so they should be easy to replace on your own?

Yes, plug and play.