Exhaust bypass valve on a 500?

Exhaust bypass valve on a 500?

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RobXjcoupe

Original Poster:

2,789 posts

71 months

Friday 5th August
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Was having a chat recently to an owner of a new Aston that sounded like it had a de-cat exhaust. Owner of Aston then demonstrated exhaust bypass via a switch on the dash.
So just wondering is this possible to fit to a cat exhaust Griff 500? So for mot, valve shut exhaust gas via cat and emission pass, then flick a switch to bypass cat and have that wonderful straight through v8 noise.
Has anyone any knowledge of fitting something like this?

phillpot

16,686 posts

163 months

Friday 5th August
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Given that the "cats" are in the manifolds it could be tricky scratchchin

RobXjcoupe

Original Poster:

2,789 posts

71 months

Friday 5th August
quotequote all
phillpot said:
Given that the "cats" are in the manifolds it could be tricky scratchchin
I have the act manifolds with the 2 separate cats. I suppose even if a bypass pipe could be fitted the valve would get too hot being that close to the engine?

Belle427

6,520 posts

213 months

Saturday 6th August
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Most I've seen just bypass a silencer or two.
Can't see how it can bypass cats if it's a factory option.

RobXjcoupe

Original Poster:

2,789 posts

71 months

Saturday 6th August
quotequote all
Belle427 said:
Most I've seen just bypass a silencer or two.
Can't see how it can bypass cats if it's a factory option.
I’ve had a little read up and the Aston does just bypass a silencer or two as you say. It did sound rather angry when bypassed though. When I run the cats on my 500 it is noticeable quieter. Put the straight through pipes on and it sounds angry. I do have a small silencer on the rear so maybe it’s that I should be looking to bypass? I think the rear silencer is a jp sports silencer

RobXjcoupe

Original Poster:

2,789 posts

71 months

Saturday 6th August
quotequote all
Yes these are very raw and bolt on.
I suppose I’m looking for a more factory fit. Something that still uses the original exhaust outlet but switches inside a silencer.
Looks like I’ve just given myself another project frown

Oldwolf

723 posts

173 months

Saturday 6th August
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Let us know how you get on please smile

I've got a Chim 500 and wouldn't want to have it permanently louder as it would make long distance tiring but switchable might be fun!

RobXjcoupe

Original Poster:

2,789 posts

71 months

Saturday 6th August
quotequote all
Oldwolf said:
Let us know how you get on please smile

I've got a Chim 500 and wouldn't want to have it permanently louder as it would make long distance tiring but switchable might be fun!
Early days yet. It doesn’t look like it’s a tried and tested mod on a TVR.
So picture below is of how I thought it would look like in my head. The picture is of an Aston part so prohibitively expensive new.
So if I can modify the rear silencer currently on my Griff to something similar it looks fairly straight forward. Probably not an absolute performance enhancement but would be great to simply hit a button for extra noise and again to mute it. Then the cats can stay permanently fitted and no carbon monoxide poisoning headache when driving.

Belle427

6,520 posts

213 months

Saturday 6th August
quotequote all
The Act cherry bomb system is the best sound I've heard on a RV8.
Is this not an option?

RobXjcoupe

Original Poster:

2,789 posts

71 months

Saturday 6th August
quotequote all
Belle427 said:
The Act cherry bomb system is the best sound I've heard on a RV8.
Is this not an option?
The initial idea was something to flip between a cats exhaust for mot and then straight through for a bit of extra noise. But without the hassle of unbolting and bolting up different parts.
To do that requires a bit more engineering than I’m willing to do as exhaust manifolds are a little expensive to chop up and weld to try out something.
Then we have the bypass valve. So the cat works as a silencer which legally needs to be fitted on a 500. I also have a small rear sports silencer fitted. It sounds nice but better without the cats. If I bypass the rear silencer via a valve I have the option of nothing after the cats and quieter when on a longer constant run.
The body is off my car having the chassis restored. Could be the ideal time to measure up and convert the rear silencer. That’s what I was thinking.

Belle427

6,520 posts

213 months

Sunday 7th August
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The valve in the front pipe somewhere would be the easiest option, the yanks do it a lot on their cars.
Exhaust fumes would be my only concern, not sure how it would sound though.

RobXjcoupe

Original Poster:

2,789 posts

71 months

Sunday 7th August
quotequote all
Belle427 said:
The valve in the front pipe somewhere would be the easiest option, the yanks do it a lot on their cars.
Exhaust fumes would be my only concern, not sure how it would sound though.
Exhaust fumes would be my concern also with just a cut out under the car. It needs to cut out within a silencer or loop around a silencer.
Since looking into this I’ve started to noticed you can see a valve throttle from the bigger engined new cars. Today a new bmw 1 series had twin exhaust pipes either side of the rear bumper. Left hand exhaust I could see a valve. Right hand exhaust was open. So I would imagine the valve opens as the revs rise to give more of a performance growl sound.
I think I can modify a rear silencer similar to the Aston db9 one. So my TVR silencer has two inputs. I need to remove the top of the silencer, create a loop with a straight through part and silenced part. Then manually open the straight through loop when more sound is desired. Sounds relatively simple. I think the space constraint is where the engineering is required.