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Variable Exhaust - Mk IV Videos

7606 Views 12 Replies 9 Participants Last post by  Skunkworx
A couple of sound bites of the latest and final version of the variable exhaust insert. The spring isn't set up right so I had to assist it closed but that's an easy fix. The sound difference between open and closed is more significant than it comes out in the videos since the mic on the camera is either noise cancelling or not sensitive to the frequencies.

The beast:

This is at a steady 3000 RPM with me adjusting the controller to move the cut-off above and below 3000 RPM. This gives the best idea of the difference in noise levels.

This is at 2500 RPM.

Just have to finish up the second insert and I can start buttoning things up!! Woohoo!!!

Cheers, Rod
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Wow. There is a difference in sound.
I want the truth, you use to do hand modeling, didn't you. When will your mind slow down so the rest of us can keep up. Just razzing you keep up the excellent work.
Great work Rod! Your Bundle of Snakes and variable exhaust valve works very well!

It would be interesting what the butt-dyno says running it both open and close.. Then off to the chassis dyno! :)
Lemme see now.. Gotta come up with a real smooth marketing name for it...

Rather than bundle of snakes - maybe something like Professor Rod's Macaroni Muffler with Knudder-Valve Augmentator!

I'll sleep on it and come back with some more... :)

In all seriousness - It's things like these that will help make these cars more tolerable on long rides yet still allow you to flog the day-lights out of it with little impact (presumably) on horsepower when opened up...
Thats pretty cool. Can you tell my how the valve is operated or post a link if you have already told us how. Is they a reason you put the valve at the end of the pipe instead of closer to the header? Really cool stuff you are working on!:punk:
How bout Wolly Mammoth Turbine Inserts?
Current control does'nt work out. Maybe go to electric servos. similar to what modern day cut outs use.
Neat prodject Rod:)
Does that thing have muffler bearings?!

R :D
Thanks guys!

J b Q, yep, works quite well but took a lot of tries to get it to this point.

bicman, may hands would only be good for a sales pitch about how sharp knives are!

BB, you would have to elaborate for me to know the context of you comment?

Randy, LOL, "Macaroni Muffler with Knudder-Valve Augmentator" I wonder how the patent office would respond? If you remember form the Exhaust shootout the 1-1/2 DNA's I'm using produced the most HP and torque with a small 1 db increase in noise over new stock pipes. With the slight restriction increase from the insert I am hoping to still be better than the stock pipes in power/torque and noise level with the insert open. With the valve close I will have significantly quieter pipes and possibly some torque gain at low RPMs with lots of HP loss at high RPMs but they won't be closed at high RPM so no issue there.

Skunkworx, I came up with the idea after the pipe was welded up and wasn't sure where this was going to go so for experimenting I wanted to be able to insert and remove it from the tail pipe opening. Glad I did because it took several iterations to get to this point. Take a look at these posts:




hind sight, the vacuum actuator word very well so far and can generate a pretty good force (20 lbs +). The return spring is not permanently installed yet because I didn't want to drill holes in the frame before I finalized the design. I had thought about using an electric actuator from the heater controls on an Integra and it would have worked fine.

LOL Randy, probably the closest thing to them, I have muffler bushings! :D

Cheers, Rod
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You could use a rpm switch ( nitros) off of an msd ignition, going to a electric servo to control when you want it to turn on and off
Mark d
Hi Mark, :wave:
I designed my own controller that reads the tach signal and can be adjusted from 1500 RPM to just over 3000 RPM. (That's most of the fun for me! :001_rolleyes:) In the videos above I am holding a constant RPM and adjusting the controller up and down past the 3000 RPM mark so you guys can hear the sound difference with it opened or closed at the same RPM. This controller could also operate and electric actuator if I wanted. Here are a of pics of the original controller (less electronics in the final version but same case):

Cheers, Rod
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Thanks for the links now I'm all up to speed. Vary Vary cool!!!!!!:yes:
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