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#1
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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.
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Only the depth varies.............. |
#2
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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.
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www.svxfiles.com The first SuperCharged SVX, ![]() the first 4.44 gears, the first equal length headers, the first phenolic spacers, the first Class Glass fiberglass hood, the first with 4, 4.44s in his driveway ![]() Fiberglass Hood thread My locker 4.44 Swap link |
#3
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Re: Stupid exhaust idea
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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 Last edited by zagato; 01-13-2011 at 09:42 AM. Reason: mistake |
#4
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Re: Stupid exhaust idea
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Only the depth varies.............. |
#5
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Re: Stupid exhaust idea
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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. |
#6
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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 !!
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Only the depth varies.............. Last edited by Phil Hill; 01-13-2011 at 09:49 AM. Reason: mistyping damn it !! |
#7
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Re: Stupid exhaust idea
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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.
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Disclaimer: The above post is on the internet. |
#8
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Re: Stupid exhaust idea
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#9
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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. |
#10
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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
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