Active Exhaust / Bypass Valve

[MPoxon]

Afternoon.

I am considering the possibility of fitting a switchable exhaust to my Griff and I was wondering if anyone else has looked into this?

My Griff currently has ACT MS03 S/S OEM replica manifolds (less precats), Clive F Y de-cat section and the ACT Cherry Bomb back box. In my personal opinion this setup is the best overall compromise giving a good roar when you are out on a blast yet not being too loud when cruising along the motorway.

The problem with this for me is that it is a compromise, there are times when I would like the system to be much quieter, for example those 5am early morning starts that make you want go to great lengths to avoid your neighbours for a few days, the same goes with getting home late..... wakey wakey neighbours!! Also on the motorway it would be nice to also turn down the noise a bit. There are also times that I would like the exhaust to be louder, for example runs out, tunnel runs etc.

After seeing a number of VXR8s with the switchable exhausts I have done some research the system and it works using an electronic cutout valve situated before the exhaust silencer. The cut outs on the VXR8s are provided by a company called DMH Performance although there are many other companies that make a similar product. The electronic cutout is controlled via a switch in the cabin.

http://www.youtube.com/watch?v=_ECVMuS37RM&fea...

This has got me thinking.....would it be possible to fit the same system to the Griff? My initial thoughts were to leave the system as it si (no cats and no precats) but to replace the cherry bombs with a very effective silencer so that it would be neighbour and motorway friendly (could also do trackdays). The cut out valves would need to be located before the silencers.

I am thinking that the cutout valves would give a hugely loud car when you wanted it but a nice and quiet when it needed to be.

[MPoxon]

dbv8 said:

This is being fitted to mine soon

What is the rest of your system derek and where abouts where you looking at locating the valve?

[MPoxon]

clive f said:

moosehunter did this a few years ago, he fitted the valve into the pipework just alongside the sump.........deafeningly sodding loud!

Thanks Clive, I have sent Andy an email.

dbv8 said:

There is enough room to 'slot' it in at the bottom of the Y-piece just ahead of the sump.
Mines fully decatted so should be fun.
I will also be adding a side exit pipe to fit at the dragstrip. It will be below the height of the chassis rail and exit just behind the front o/s wheel. Better to spit flames at the Marshals than under the car!

I will be very intersted to see how you get on with yours Derek, one of my concerns was about flames and fumes under the car. Where the silencers are located in the middle of our cars there is not much choice as to where to locate the valve. Fabricating a pipe sounds like a good plan.

At one stage I was wondering if it was possible to install 2 valves before the silencer and but were the pips split into 2 and then linking this up with a quad exit exhaust or rejoining the main exhaust after the silencer. It seems like a lot of work and it might not even be possible.

The good thing about the valves is that you can vary the noise by having the valve only partially open or closed.

[MPoxon]

gizzer said:

Mines @ a flick of a switch 128DB , NO NEIGHBOURS THOUGH ,,, MAY BE AN ASBO
ON THE WAY!!!!!

I have heard yours gizzer and it is very very very loud! You haven't got a bypass for yours though have you?.... I thought it was permanently loud? What back box have you got on yours?

[MPoxon]

gizzer said:

Griffs have no back box, i remade the whole system in A2 s/steel, removed the l/rover centre box, and fitted 2 moto gp sleaves [bike type} to stop the tractor affect

I did wonder what you setup you had on yours. Do you remember the make and model of the bike silencers you fitted to yours.

I was thinking I could possibly combine this with Derek's idea of the side pipe but perhaps squeeze in a sleeve like you have.

Edited by MPoxon on Friday 11th November 14:44

[MPoxon]

pjac67 said:

I have looked into this before on my Wedge and the heat/potential and possible fluid getting onto the tyres put me off - I just removed most of the box (122 db) which I know isn't your goal but was also a fractin of the cost.

On my Griff however, the ECU has different settings at the flick of a switch so can go from quiet to 'pops and bangs' mode although as it is just changing the fuel mixture/set up it is not massively louder....

I agree the heat, fumes, fluid and flames underneath the car are a concern which is why I am looking at either Derek's idea of the side exit pipe or possibly some way of getting an additional pipe to routed towards the rear of the car.

Are you achieving the pops and bangs using an aftermarket ECU (Omex???) or are you still using 14CUX. I know you can provoke pops and bangs by adjusting the amount of fuel that is injected on the over run or if you have mapped spark then retarding the ignition on overrun = fireworks May I ask how you have yours setup.

[MPoxon]

DonkeyApple said:

Don't firms like Miltek build the bypass into a silencer box? These are then operated by pressure or a switch.

Surely one of these firms can build their kit into a TVR box thus eliminating the external bypass onto a separate system/vent. That seems a clumsy solution.

I agree this would be a much better option. I couldn't find anything on the Milteak site, the only company I have found who make silencers with a build in bypass are a company called Varex. Varex sell back boxes with a electronically controlled butterfly valve which allows either straight through or silenced:



Looks really good:
http://youtu.be/K7jGYnhbQQU?t=29s

The only problem is that their centre box would not suit a TVR as one side is blocked with the valve is closed.



Providing it is loud enough when fully open a system like this would be my preference as it promises to give the best of both worlds at the flick of a switch without the need for an external valve, however I have not had any luck finding a product that is fit for purpose.

[MPoxon]

The Moosehunter said:

Hi Guys

Sadly I was expecting great things and have ended up with a car that appears to have lost some of the magical qualities of a V8 and inherited some Massey Fergusson

It sound better if you block the rear tailpipes as some of the exhaust gases still go down the original route. Though driving down the road with the sole of each shoe against the tailpipes is not very practical

I would definately persue the switchable silencer route as this would definalty give a better note 9 it's not all about the volume for me

You are welcome to hear what it sounds like once I have found some pistons that stop destroying themselves in my car

5 months without and getting pretty peeeved

Summary is it's a good comedy moment but for sustained "quality" volume it sucks ( or blows )

Spend a liitle more time / money and switchable silencer it ( then tell me where you got it )

Good luck

Andy

That said it you wish to borrow my complete system to try it out then you are welcome as it's currently in my shed and hanging from the roof of my garage. I'll swap you for a drive in yours, I can be trusted .... honest

I am really sorry to hear that you have still not got your car sorted yet

Thanks for the information on the bypass I had a sneeking suspicious that that may the case, hence why I was looking as possibly routing the bypass through a sleved silencer of some sorts although I am really not convinced it is practical.

I think I will take you advice and persue the switchable silencer route.

Matthew

[MPoxon]

DonkeyApple said:

I suspect that there could be quite a few TVR owners out there who would buy a 'Town & Country' box if it were available. It could even be cost effective if many of the models could fit the same unit. I would assume that Griffs and Chimps do but if the same middle box could fit nearly all Tivs then one of the TVR parts suppliers may be interested in reselling a bespoke Miltek (or similar) system?

I wonder if the simplest possible system would be a perforated sleeve within the perforated sleeve of the exhaust that can be slid half an inch to either align the perforations or block them? A solenoid system on the outside could then work the slide?

I agree I think there is definitely a market for this. The if there is a switchable middle box that fits the Griff then like you say this will also fit the Chim.

I system that changed the current style silencer from perforated to non would be ideal. The best sound for a Griff IMO is all cats out, sleeved with wadding left in which that system would achieve. Sleeved without wadding sounds a bit to agricultural IMO.

[MPoxon]

Chimpabollics said:

Love the solenoid activated sliding sleeve idea.

But could this be a simpler cheaper solution?

http://www.dynomax.com/mufflers.php?muffler=vt

I am not convinced this would be any louder as it still has a section of perforated pipe even when the valve is open:



They do not appear to have a dual inlet dual outlet version either.

I will have a chat with Tim at ACT next time I speak to him see if it is something he has looked into before.

[MPoxon]

pjac67 said:

Hi - Emerald ECU (not sure about mapped spark) - updated my profile if that helps. Went out for a run with a fellow Griff owner (think it was an old airstrip...) at w/e and had flames exiting exhausts (always wanted to do that ) when changing up to 5th at 5500 rpm ....

BTW, decided mine is too quiet (fully decatted/ Clive's Y fronts and ACT pre cat manifolds) s considering cherry bomb/motorbike exhaust route....

Holly st the spec of your Griff is immense. That is pretty much the exact spec I would like to have but will take me 20 years to save up and and achieve. IMO some people go a bit too far with modding but that is spot on

It says on your profile you have coil packs so Emerald will be controlling the spark..... you could have it mapped into one of your switchable maps to chuck flames out all the time on the over-run if you wanted.

If you want louder I wouldn't necessarily recommend the ACT Cherries, they sound epic and like I said earlier in the thread they are IMO the best compromise but I think you may be disappointed if you buy them to increase volume. Sleved OEM box with wadding left in is a good shout and is about as loud as you can go without the tractor sound. Gizzers bike silencers are also a good shout - very loud indeed.

[MPoxon]

pjac67 said:

Having looked at your profile Matthew (Matt?) I don't think you have anything to worry about with your spec. - and look at that engine bay - Wow!

Can't wait for next years GG (not been for a few years...) to see/hear all the cars although I do like the bike exhaust idea (a la 'Gizzer'..).

Paul.

Thanks Paul, definitely come along to the Growl next year, it would be great to catch up and get a proper look at the Griff. I know FFG has a few plans for a 30th Anniversary special.

I am hoping that Gizzer comes to his senses and decides to keep his Griff, it certainly wont be the same without the loudest car and loudest owner present

[MPoxon]

I would be very interested to see what you come up with Paul. Ideally I need to make mine quieter for track use but I would love the ability to be noisy at the flick of a switch.

[MPoxon]

I did see this ages ago and saved the picture.... look interesting but I don't think it will take enough noise off.

[Matthew Poxon]

Happy days! a solution.

What does it sound like Paul?

[Matthew Poxon]

That looks really good Paul, looking forward to having a closer look soon hopefully.

LMFAO at the second video, great launch and LOL at the pops and bangs when the car is completely out of sight... quality!