Stupid exhaust idea
 

Hi everyone and happy new year to you all.

Right straight to the point, I attended a lecture a couple of years ago about the Aston Martin V12 Vantage. In the presentation the guy presented the fact that the exhaust silencer at the back of the car (which was very similar in general arrangement to the SVX) has a by-pass valve system.

This means at idle and low RPM the valve opens to allow exhaust gases to by-pass the silencer via a straight through pipe incorporated into the silencer box so the nice burble of the V12 idle can be heard with minimal silencing, the valve closes again off idle RPM for noise control, then at high to full engine revs the valve opens to the by-pass pipe again for the full aural pleasure of the V12 at high RPM to be enjoyed.

With the advent of people "Cracking the code" in engine ecu's and such, or the advent of RPM activated switches, the fact that all the SVX's exhausts are getting to the end of life, and that various perhaps misguided efforts at re-engineering the exhaust system on the SVX (like removing the resonator which isn't actually there for silencing but to enhance torque) I wondered if anyone had thought of a similar system for the SVX.

I can't find a diagram of the Aston Martin system, obviously, but I'll see if I can draw one.

Treat this as the misguided ramblings of an engineering idiot if you will, or perhaps it will stimulate some thought !!

Phil.

Re: Stupid exhaust idea
 

With an open or mostly open system behind our engines they, IMHO, sound bad, like an unmuffled garbage truck.:(

I have made many free flowing SVX exhaust systems, singles, true duals, ones with an electric cutout and a dump pipe, with cats, without cats, systems with no muffler but five resonators.

There are mufflers now with a built in bypass valve to be mostly open at high flow.
I have not tried that one yet.

Re: Stupid exhaust idea
 

My company sells high end exhaust systems for Porsche, Aston Martin, Ferrari etc. Most of them the owners request an exhaust with a Bypass system. So they can cruze and race with the same exhaust setup.

We made a deal with the German company www.capristo.de to sell exclusive these `dual` exhaust in the netherlands. The nice thing is, that they developed an electronic control box which controls the open or closing of the valve by the amount of backpressure that is generated. This can be programmed by the owner.

So in comfortmode, it goes open at for example 4.500 rpm. In sport at 2.500 rpm and in race mode....always open.

Normally these valve are controlled in Porsche or Ferrari by the engine ECU, and you cannot decide yourself when it is opened.

Because I own an SVX I have asked the owner of Capristo to make one for me. However they are in the middle of developing a new exhaust for the Ferrari F458. So it will take some time.

Have a look at 997 GT2 exhaust on my webpage: www.custom-concepts.nl

Re: Stupid exhaust idea
 

Yeah I agree that completely unsilenced systems are not desireable from either the sound or performance point of view.

In the case of the Aston the system retains the pre-cats, secondary cats, resonators and pre-silencers, this bypass system is only in the very last silencer which is oriented similarly to the SVX system, being a large single box mounted across the back of the car with twin inlets and twin outlets.

I was thinking from the liberation of a more pleasing noise point of view that bypassing the very last silencer might give that enhancement, and with the increasing knowledge of the electronic controls on the car that this could be done by modification to the existing control system, or at least a robust "home-brew" system.

Like I said in the original post it's perhaps the ramblings of a mad-person with too much on his mind !!

Re: Stupid exhaust idea
 

Sounds (sic) like you are idealy placed to comment on this then !! It may be that the SVX just doesn't produce a nice tone by design at any RPM, which would explain the overly silenced OEM system, but hearing Porsche flat 6's at full bore would seem to contradict that !!

Re: Stupid exhaust idea
 

If wanted, I could supply the valves incl. the electronics seperate of Capristo.
So people can make the piping themselves as a "cheaper" alternative.
Give me a few months, so I can make a better judgement.
If people are interested, send me a PM.

I have a global deal with UPS, so transport is not expensive to the USA.

Re: Stupid exhaust idea
 

The <Z06 Corvette> had this some time ago. Neat stuff.

Would there be any merit to installing a remotely actuated butterfly inside an SVX muffler? Sure enough, it's a hostile environment, and it would be some surgery to do (but not that much more than replacing the muffler itself) but you'd get mild and wild out of it.

Re: Stupid exhaust idea
 

The butterfly valves are a very special item build for harsch environments.

Re: Stupid exhaust idea
 

On modern bikes some have a butterfly valve which survives in such a hostile environment. They are usually in the silencer that many discard and replace. I'm led to believe their purpose in life is to pass the ride by euro noise test. If someone wants to have a play I'm sure I could sort one for next to nothing. They are bowden cable actuated and have a servo motor.
Just yell if you want one.

Re: Stupid exhaust idea
 

That sounds [zonks!] like a good plan Steve.

I was thinking of a similar idea, different source.

I've known that Ferrari cars have these muffler flaps that actuate to relieve restriction at high RPM. It is interesting that Aston Martin has the same thing, though they refine the idea with the straight through burble at tick-over, which is not measured for regs. Cleverrrr..

Twin turbo Legacies have these actuated bypass flaps for the opposite reason. On tickover they close, because they cut down the normal wide open unrestricted turbo exhaust passage to provide some back pressure that allows the engine to tick over in a less "lumpy" fashion than it would otherwise.

A lot of Legacy owners discard them, they don't like the idea of having an even tickover.

As they are designed for a similar system to ours, they would or should be an easy fit or mod.

I'm not sure if Phil intends to use it to relieve pressure at high revs, or just to make noise. I'm inclined to agree with Tom, the SVX sounds crap when you alter the standard flow. Letting off pressure though at high revs would be positive, however bad it sounded.

The Legacy bypass could work, though it would need to be rewired to open rather than shut. Tomato. Tomato.

Too much bother I'm thinking for an engine whose revs are limited by what suits an automatic gearbox.

Joe

Re: Stupid exhaust idea
 

Joe, you are one clever bloke. I would prefer to hear just a V8 with an auto box - only configuration which seems to suit it, perhaps through indoctrination/ US tv?.
If any of you guys get a chance, listen to/ride a Yamaha R1 with cross plane crank, 'long bang' motor. For me, it's a truly unique experience. Still to try on my list though is a Puch 'split single', a straight eight, a V16, a sleeve valve motor or most recently a Blayden/Jag jet.
Can't elaborate guys, off to see the Samaritans....

Re: Stupid exhaust idea
 

Well, if the Samaritans see you coming.........


:lol:

Re: Stupid exhaust idea
 

I'm now off to lie in a darkened room to see if I can follow that one. Maybe if they 'heard me?' it might strike a chord....
This all happened after listening to the Rubber Bandits 'Horse Outside' on You Tube, some lyrics offended Joe more than I thought perhaps. Can't get the damn song out of my head though. I think it's the sound, combined with the absolute 'edibility' of the bridesmaid thats done it. Have a listen and see what you think.

Re: Stupid exhaust idea
 

Edibility of the bridesmaid?

OK, I'll have to get past the Subaru bit and listen to the full lyrics then. U toob doesn't work on this computer, so I'll have to power up the laptop and see what the fuss is about.

Rubber bandits indeed.

;)

Re: Stupid exhaust idea
 

My new exhaust sounds pretty good I thought; slightly on the loud side but not overly-so... and possibly quieter overall than the original OEM system. Mind you, mine had had the Cats cutout from the top (to hide it from inspectors) and hollowed out; something I didn't discover until the system came out.

The new system starts at the O2 sensors, thru two resonators, then joins into a single pipe and two resonators as seen here:

http://farm5.static.flickr.com/4060/...2cb90990b8.jpg
SSVVXX-Exhaust-05543 by **Ewie**, on Flickr
http://farm5.static.flickr.com/4056/...350bcece1d.jpg
SSVVXX-Exhaust-05542 by **Ewie**, on Flickr

and then splits into two mufflers at the back followed by dual tips.

http://farm1.static.flickr.com/200/4...dcef07a650.jpg
SSVVXX-Exhaust-05544 by **Ewie**, on Flickr

Comprises 2 1/2" pipe right through.