Butterfly Exhaust valves

[XY GTHO Ph III]

Does anyone have Exhaust Butterfly Valves on there Cobra. I ask as I want to drive my Cobra to work but I leave around 5:30am so with the Cobra being so loud I will become know to my neighbours as that prick that starts his car at 5:30am in the morning guy. I saw a product that Harley's have on there bikes where a butterfly valve is placed in the exhaust and when closed 90% off it quietens the exhaust sound dramatically and when you get out on the freeway you can open it up 100% and you have the sound and performance like it was not there. Anyway I want to put those on my Cobra to lessen the noise when I start up and get around the neighbourhood, Thanks

[Paintwerks]

Originally Posted by XY GTHO Ph III

Does anyone have Exhaust Butterfly Valves on there Cobra. I ask as I want to drive my Cobra to work but I leave around 5:30am so with the Cobra being so loud I will become know to my neighbours as that prick that starts his car at 5:30am in the morning guy. I saw a product that Harley's have on there bikes where a butterfly valve is placed in the exhaust and when closed 90% off it quietens the exhaust sound dramatically and when you get out on the freeway you can open it up 100% and you have the sound and performance like it was not there. Anyway I want to put those on my Cobra to lessen the noise when I start up and get around the neighbourhood, Thanks

The system is referred to as 'Bimodal'. The Xforce 'Varex' servo-adjustable bimodal mufflers are what you want. That said, with the Cobra's limited undercar space, I am not sure which of their units would fit?

Varex Mufflers

There is also the issue of legality. Despite HSV and Aston Martin (that I know of) having factory fitted, ADR approved bimodal exhaust systems, apparently to add a bimodal muffler to a vehicle that never had it from new is illegal. I guess you could get the car engineered with it after fitting and that would comply?

[gjkrv8]

Originally Posted by Paintwerks

The system is referred to as 'Bimodal'. The Xforce 'Varex' servo-adjustable bimodal mufflers are what you want. That said, with the Cobra's limited undercar space, I am not sure which of their units would fit?

Varex Mufflers

There is also the issue of legality. Despite HSV and Aston Martin (that I know of) having factory fitted, ADR approved bimodal exhaust systems, apparently to add a bimodal muffler to a vehicle that never had it from new is illegal. I guess you could get the car engineered with it after fitting and that would comply?

I had a look at the Varex a while ago too. The problem is their servo mechanism protrudes out the top a fair bit and where I wanted to put them under the Cobra floor, there just wasn't enough room.

I've seen a cobra at the Nationals that has the valve only option and diverts between a "loud" side non-mufflered exit and a "not so loud" rear mufflered exit.

cheers Gregg

[XY GTHO Ph III]

Thanks for the input guys

[Paintwerks]

You're welcome.

You may want to have a read of this (Post #26 made by a lawyer with experience in this area):

Is Gforce Varex Exhaust A Defect? - BoostCruising

[XY GTHO Ph III]

Thanks but I will be okay as i now live in southern California, moved from Perth back in 1991, Thanks

[Paintwerks]

All good. Is this what you are after? Looks like this would fit.

APEXi EXHAUST CONTROL VALVE 67mm FOR Skyline ER34 (RB25DET) 155-A015 | eBay

[Rob. Smith]

Summit racing has several "exhaust cut out valves" available. You could drill a few holes in the butterfly and tune the noise....performance would be compromised though...but I imagine Varex do the same.

[Cobrakiller]

I have two VF Commodore Bi Modal mufflers as used on HSV's etc. If you prefer a more or less straight through system there are mods that can be done to these mufflers. As they are original equipment from an OEM there shouldn't be any worries with ADR's etc.
Similar to the Corvette NPP mufflers.

[XY GTHO Ph III]

Thanks guys for your response. The APEX valve is exactly what I am looking for except I want to get it with a electric operated actuator. Thanks

[Tonus72]

Originally Posted by XY GTHO Ph III

Thanks guys for your response. The APEX valve is exactly what I am looking for except I want to get it with a electric operated actuator. Thanks

Hi

I have no idea if you could adapt it, but there are various bike systems that have an electronic butterfly valve in the exhaust system.

Many open up over about 7000 revs to free up the exhaust (as below this is probably when the db's are tested??)

Cheers

Tony

[Legless]

I had these fitted a couple of years ago, there are numerous models.

https://www.summitracing.com/int/par...ec66/overview/

They are ok but I have lost a couple of butterfly valves and they didn't sell the butterfly valve separately, I'm not sure whether that's changed. The electronic controller supplied is a bit 'flaky', that's probably why they've changed the model and gone to a wireless system.

Mine's not exactly the sort of thing you're after as I have a y junction in each branch of the exhaust system and it can be opened behind fake side pipes.

cheers

[XY GTHO Ph III]

Originally Posted by Tonus72

Hi

I have no idea if you could adapt it, but there are various bike systems that have an electronic butterfly valve in the exhaust system.

Many open up over about 7000 revs to free up the exhaust (as below this is probably when the db's are tested??)

Cheers

Tony

yes i saw that some bikes have these especially Harleys specifically to quieten them down in built up areas

[XY GTHO Ph III]

Originally Posted by Legless

I had these fitted a couple of years ago, there are numerous models.

https://www.summitracing.com/int/par...ec66/overview/

They are ok but I have lost a couple of butterfly valves and they didn't sell the butterfly valve separately, I'm not sure whether that's changed. The electronic controller supplied is a bit 'flaky', that's probably why they've changed the model and gone to a wireless system.

Mine's not exactly the sort of thing you're after as I have a y junction in each branch of the exhaust system and it can be opened behind fake side pipes.

cheers

Thanks Legless this is prety much what I have been looking for I will check it out to see if they have 2.5" or 3" dia valve, wireless would be great

[Tonus72]

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