ze_shark

I've been fooling around with different options to get the exhaust note right.
I dislike the original system the closed/open valve transitions sound very artificial.
I had a vacuum line installed to be able to have a quiet "Laguna Seca" mode for noise-sensitive tracks, and an always open mode.
For road use, the always open mode drones like a cathedral bell at 2500-2700rpm, unbearable.
I gave serious consideration to the sharkwerks bypass, but it's too loud for road use in Switzerland, I'd get pulled over.

So I had this idea: what if I had one cylinder bank with the valve always open, and the other bank with the valve operating normally (switched by the vacuum line) ? Means that at low rev, the backpressure would be different between cylinder banks, but does it matter from a mechanical viewpoint ?
My goal is to retain most of the mid range noise, tone down the drone, and make the valve opening a lot less artificial. Thoughts ?

911rox

I think this may pose a problem for you and not be healthy 4 the engine... backpressure affects engine charge and therefore output. If you have one bank of cylinders working harder or producing a stronger stroke than the other, you no longer have a balanced stroke= rough running engine and maybe engine issues/damage due to the high rpms these engines achieve... must be a better way...

seefouress

Are you certain that Sharky's bypass would be too loud on the street? Mine only has serious db's when I get on the throttle hard. With smooth driving there's not really much volume and the sound is addictive. Might be worth a chat with Alex.

ze_shark

The backpressure offset would only be in the idle-3200 rpm range.

Certain, no, pretty sure, yes.
Had more than a chat with Alex, he was actually kind enough to take me for a spin. Nice note, no annoying drone, but too loud and too obvious. Likelihood to get pulled over would be too high.

ze_shark

I tested a quick & dirty prototype of the mod and it exceeds my expectation.
Very refined result, the exhaust note at low revs has gained volume and texture, a very nice blend of the type of harmonics heard on old BMW inline 6 or on a 3 cylinder engine. Then the transition to the other valve opening appears more seamless, less artificial. Not an ounce of drone.

Entirely reversible, very cheap, and much more socially acceptable than more radical situations if you happen to live in a place where cops and citizens are picky about noise.

The test set-up: I simply disconnected the near side valve and plugged a cork into the line. The cork is of course getting replaced by a suitable heat resistant item.

chardonet

Hmmmm..... interesting resolution. I think a DRC cork would have made the exhaust note more refined . Did you try unplugging the solenoid valve?

996FLT6

What year is the Chateau Margaux- yummy. One of my favorites : ). Mike

ze_shark

Yes, the drone at 2500-2700 rpm cost me too much in aspirin, way too boomy to my taste. This one is really worth a try, much more subtle.