Adjustable UK mod?
Thread Starter
Joined: Oct 2019
Posts: 30
Likes: 0
Adjustable UK mod?
Has anyone seen info on an adjustable UK mod? My idea is to put a valve in the cut off, either a butterfly valve or a block-off plate, so that you can switch between stock sound and UK mod sound. Ideally it would be a butter fly; just reach under the bumper, turn it open for a weekend drive, then flip it back when you want the stock sound. I doubt I'm the first to think of this, but I can't find post about it. Would a butterfly valve be strong enough to effectively block the cutoff?
Joined: Aug 2012
Posts: 8,753
Likes: 1,858
I have thought a lot about this. Not so much for on/off, but for variable sound level.
Like a dial 'volume' switch that would open the valve to match the dial setting. Been thinking about this since before that became a popular feature on many performance cars.
For such a diy variable volume control you'd need a rugged stepper motor, and circuitry to control it. I was thinking a repurposed cruise control stepper motor could work. Could take the heat and vibes. I found a cable controlled butterfly valve meant for manually controlling an exhaust cutout that could be used. Could then control with an Arduino. It was the cost of it all that held me back.
That and some research I did led me to understand a butterfly valve isn't very good at partial sound control in such an application. Apparently it sounds quiet until it sounds almost as loud as fully open.
It should be noted the cable operated valve I found had a handle to manually control it, so could have accomplished my basic desire without the electronics, just would have needed a way to lock handles partially open. But again not sure how effective given noted volume limitations of partially opening a butterfly. It would also have required dealing with two handles, or fabbing something like how an ebrake cable works so one cable pulls two.
A whole different approach I considered was using a small uk mod pipe on one muffler, and a large pipe on the other, with an on/off valve on only the large one. That would give two sound levels to choose from. Plus its way easier to find these valves in larger sizes. Plus its only one valve to buy and control.
You could obviously do variations like no uk on one muffler, and large valved uk on the other, to choose from stock sound to decently loud uk. Or a valve on each uk pipe, and choose between stock, mild uk sound, medium uk sound and loud uk, depending if you have them both closed, both open, or just one open, or just the other open.
I also looked for gate valves, assuming it might be better at progressive volume control, but couldn't find any suitable. I considered fabbing one.
To answer your basic questions, there is no reason to think a butterfly would have any difficulty holding the exhaust pressure. They make so called dump valves for almost this exact application in muscle car world (except there its to route exhaust to either muffler or open pipe). A gate valve would equally be robust enough. A butterfly might be easier to seal from leaking exhaust under car, which could lead to dangerous co2 poisoning. Plus they make exhaust butterfly valves so wouldn't need to fab from scratch.
They make manual cable handle versions as well as electric motor controlled versions (way more expensive). They were never suitable for my needs since they are fully on or off,no in between (but could work for my 4 levels of volume idea mentioned above but for the cost)
Like a dial 'volume' switch that would open the valve to match the dial setting. Been thinking about this since before that became a popular feature on many performance cars.
For such a diy variable volume control you'd need a rugged stepper motor, and circuitry to control it. I was thinking a repurposed cruise control stepper motor could work. Could take the heat and vibes. I found a cable controlled butterfly valve meant for manually controlling an exhaust cutout that could be used. Could then control with an Arduino. It was the cost of it all that held me back.
That and some research I did led me to understand a butterfly valve isn't very good at partial sound control in such an application. Apparently it sounds quiet until it sounds almost as loud as fully open.
It should be noted the cable operated valve I found had a handle to manually control it, so could have accomplished my basic desire without the electronics, just would have needed a way to lock handles partially open. But again not sure how effective given noted volume limitations of partially opening a butterfly. It would also have required dealing with two handles, or fabbing something like how an ebrake cable works so one cable pulls two.
A whole different approach I considered was using a small uk mod pipe on one muffler, and a large pipe on the other, with an on/off valve on only the large one. That would give two sound levels to choose from. Plus its way easier to find these valves in larger sizes. Plus its only one valve to buy and control.
You could obviously do variations like no uk on one muffler, and large valved uk on the other, to choose from stock sound to decently loud uk. Or a valve on each uk pipe, and choose between stock, mild uk sound, medium uk sound and loud uk, depending if you have them both closed, both open, or just one open, or just the other open.
I also looked for gate valves, assuming it might be better at progressive volume control, but couldn't find any suitable. I considered fabbing one.
To answer your basic questions, there is no reason to think a butterfly would have any difficulty holding the exhaust pressure. They make so called dump valves for almost this exact application in muscle car world (except there its to route exhaust to either muffler or open pipe). A gate valve would equally be robust enough. A butterfly might be easier to seal from leaking exhaust under car, which could lead to dangerous co2 poisoning. Plus they make exhaust butterfly valves so wouldn't need to fab from scratch.
They make manual cable handle versions as well as electric motor controlled versions (way more expensive). They were never suitable for my needs since they are fully on or off,no in between (but could work for my 4 levels of volume idea mentioned above but for the cost)
Joined: Jul 2014
Posts: 13,827
Likes: 1,549
From: Chesterfield VA
If I recall correctly, those Ford flat head V8s just purred like a kitten 'till the lake pipes roared.
We put "snuff or nots" in the TT pipes of our motorcycles. No mufflers whatsoever. I called them "snuffer-knots" or "snuffer-knobs" until this morning
when I googled them to see if they'd work in the bypass pipe in the UK-mod exhaust. Simple 90° twist of the knob to put the "snuffer" across the exhaust and cut the noise level. Still seems a viable solution although I'm not sure there is a problem. Too many nice aftermarket exhausts to fool with retaining the heavy OEM system and altering it for more noise.
-- Chuck
We put "snuff or nots" in the TT pipes of our motorcycles. No mufflers whatsoever. I called them "snuffer-knots" or "snuffer-knobs" until this morning
when I googled them to see if they'd work in the bypass pipe in the UK-mod exhaust. Simple 90° twist of the knob to put the "snuffer" across the exhaust and cut the noise level. Still seems a viable solution although I'm not sure there is a problem. Too many nice aftermarket exhausts to fool with retaining the heavy OEM system and altering it for more noise.-- Chuck
Thread Starter
Joined: Oct 2019
Posts: 30
Likes: 0
I have thought a lot about this. Not so much for on/off, but for variable sound level.
Like a dial 'volume' switch that would open the valve to match the dial setting. Been thinking about this since before that became a popular feature on many performance cars.
For such a diy variable volume control you'd need a rugged stepper motor, and circuitry to control it. I was thinking a repurposed cruise control stepper motor could work. Could take the heat and vibes. I found a cable controlled butterfly valve meant for manually controlling an exhaust cutout that could be used. Could then control with an Arduino. It was the cost of it all that held me back.
That and some research I did led me to understand a butterfly valve isn't very good at partial sound control in such an application. Apparently it sounds quiet until it sounds almost as loud as fully open.
It should be noted the cable operated valve I found had a handle to manually control it, so could have accomplished my basic desire without the electronics, just would have needed a way to lock handles partially open. But again not sure how effective given noted volume limitations of partially opening a butterfly. It would also have required dealing with two handles, or fabbing something like how an ebrake cable works so one cable pulls two.
A whole different approach I considered was using a small uk mod pipe on one muffler, and a large pipe on the other, with an on/off valve on only the large one. That would give two sound levels to choose from. Plus its way easier to find these valves in larger sizes. Plus its only one valve to buy and control.
You could obviously do variations like no uk on one muffler, and large valved uk on the other, to choose from stock sound to decently loud uk. Or a valve on each uk pipe, and choose between stock, mild uk sound, medium uk sound and loud uk, depending if you have them both closed, both open, or just one open, or just the other open.
I also looked for gate valves, assuming it might be better at progressive volume control, but couldn't find any suitable. I considered fabbing one.
To answer your basic questions, there is no reason to think a butterfly would have any difficulty holding the exhaust pressure. They make so called dump valves for almost this exact application in muscle car world (except there its to route exhaust to either muffler or open pipe). A gate valve would equally be robust enough. A butterfly might be easier to seal from leaking exhaust under car, which could lead to dangerous co2 poisoning. Plus they make exhaust butterfly valves so wouldn't need to fab from scratch.
They make manual cable handle versions as well as electric motor controlled versions (way more expensive). They were never suitable for my needs since they are fully on or off,no in between (but could work for my 4 levels of volume idea mentioned above but for the cost)
Like a dial 'volume' switch that would open the valve to match the dial setting. Been thinking about this since before that became a popular feature on many performance cars.
For such a diy variable volume control you'd need a rugged stepper motor, and circuitry to control it. I was thinking a repurposed cruise control stepper motor could work. Could take the heat and vibes. I found a cable controlled butterfly valve meant for manually controlling an exhaust cutout that could be used. Could then control with an Arduino. It was the cost of it all that held me back.
That and some research I did led me to understand a butterfly valve isn't very good at partial sound control in such an application. Apparently it sounds quiet until it sounds almost as loud as fully open.
It should be noted the cable operated valve I found had a handle to manually control it, so could have accomplished my basic desire without the electronics, just would have needed a way to lock handles partially open. But again not sure how effective given noted volume limitations of partially opening a butterfly. It would also have required dealing with two handles, or fabbing something like how an ebrake cable works so one cable pulls two.
A whole different approach I considered was using a small uk mod pipe on one muffler, and a large pipe on the other, with an on/off valve on only the large one. That would give two sound levels to choose from. Plus its way easier to find these valves in larger sizes. Plus its only one valve to buy and control.
You could obviously do variations like no uk on one muffler, and large valved uk on the other, to choose from stock sound to decently loud uk. Or a valve on each uk pipe, and choose between stock, mild uk sound, medium uk sound and loud uk, depending if you have them both closed, both open, or just one open, or just the other open.
I also looked for gate valves, assuming it might be better at progressive volume control, but couldn't find any suitable. I considered fabbing one.
To answer your basic questions, there is no reason to think a butterfly would have any difficulty holding the exhaust pressure. They make so called dump valves for almost this exact application in muscle car world (except there its to route exhaust to either muffler or open pipe). A gate valve would equally be robust enough. A butterfly might be easier to seal from leaking exhaust under car, which could lead to dangerous co2 poisoning. Plus they make exhaust butterfly valves so wouldn't need to fab from scratch.
They make manual cable handle versions as well as electric motor controlled versions (way more expensive). They were never suitable for my needs since they are fully on or off,no in between (but could work for my 4 levels of volume idea mentioned above but for the cost)
