any one have this??

what are your thoughts on it, did it help?

where you get it from?

thanks
Bryon

 

pics would be fantastic. If its what I am thinking it is then yes, I do have it, but I would need a pic to tell you for certain.


BC

 

 

why not just put an exhaust cut out on the down pipe, and get better power when its open, and attract less attention when its not ?

 

nope, not what I have. Sorry.


BC

 

becausethe exh i have is 3in, so even with the muff on there, its not that quiet.

 

Throttling it isn't going to make it a whole lot quieter, and is gonna make your pumping losses go up like whoa (aka goodbye horsepower). Get a cut-out or a new exhaust if its too loud for you now. Is this on a turbo?

 

Actually throttling the exhaust at low load can considerably reduce exhaust noise during idle, cruise, etc. But once it's opened for high load situations the noise is the same.

 

yes turbo, and yes for cruising

 

Keep in mind having something like that in there will cause considerable flow disturbance and depending on your setup back pressure. A better resonator or muffler or a dual system (if what you have is single) would probably get the job done better.

 

what neg effect will the flow disturbance be at cruising??

 

At crusing it will probably quiet down your exhaust quite a bit. The problem lies when you decide it's time to go. Even though when you push the pedal to the floor the flapper will be wide open and causeing as little obstruction as it can, it will still cause back pressure because it is there. Depending on how much flow your turbo needs, this could choke your turbo due to the back pressure your creating.

Quieting down your exhaust comes down to fluid dynamics and soundwave characteristics. Air is fluid, sound is not. As well, understand that the air and sound of the exhaust travells at different speeds; with sound going at, you guessed it, the speed of sound, and air going much slower.

I won't go through all of this because it would get waaaaay too complicated and I don't even understand all of it myself, but the goal of the flapper is to reflect the sound wave back on itself, which will eliminate itself, but still allow air to flow. The problem is air moves fastest through the middle of the pipe. This will interupt this flow, slowing it down and create a lot of turbulence in the later part of the system.

Logically, the only possibly approiate place on an exhaust system I would put something like this is at the end of the exhaust tip. This way any disturbance this causes will be minimal as the air is simply going to atmosphear. In my opinion I think this would look utterly stupid and I can think of mutiple better ways to quiet down an exhaust system.

 

Can you explain? It seems like it shouldn't really help alot since its not adding any muffling just changing the properties of the flow itself. Does it reflect the sound waves back?

It was my understanding that the cars that use valved exhausts use the valve to divert flow from the primary muffler under high loads, not as a throttle.

 

Sound waves are not fluid. When this is mostly closed, most of the sound wave will reflect off the flapper. Some of the sound will miss it and that is what you will hear at the end of the tailpipe. If I had time I would draw a diagram.

 

when its time to go, I OPEN IT UP, NO RESTRICION, its MANUAL operation, to close and open.

 

With it there, open or not it will cause a flow nightmare.

When it is closed it will quiet down your exhause quite a bit. When it is open your exhaust will be just as loud as it is now.

When it is closed the airflow will be horrible. When it is open the airflow will be upgraded to bad.

It sounds like you have spent money on an exhaust system, and putting something like this in it is a bad idea in my opinion. To figure out how this would effect the system exactly would take an engineer a day to go through all the variables. And almost for sure unless you are making some crazy system to incorporate this into i'd bet the answer would come back as don't do it. If you are making a crazy system then I can still think of better ways to do it.

The bottom line is for a good exhaust system to work it needs constant high speed flow. This is why you try to keep pipes stright when possible, gut cat's, and use flow-through mufflers. Curves, cat's and baffeled mufflers cause flow disturbances. This can go on the list as a cause of flow disturbance.

 

"Choke you turbo"? As in suddenly it doesn't work any more? Could you be any more overdramatic? You're massively overstating reality, this simply doesn't happen. Assuming you had a decent sized exhaust to start with you'd barely notice any difference. Practical experience has proven this. These things aren't exactly new.

Exhaust restrictions are great mufflers. Why do you think stock exhasuts are so quiet? Here's a quote from an Autospeed article where a similar valve was fitted to the 3" exhaust on a 3.0L 6-cyl turbo.

"With the complete system installed, the noise level with the car being free-revved was substantially reduced. On the road the difference wasn't hugely noticeable from inside the car - but you could pick it when driving past a wall or a building close to the road. In this situation the 'big deep tone' of a large diameter exhaust system was much less than before."

No comment was made about any effect on full-throttle performance. Given the strong performance emphasis of all the other articles regarding that particular car's mods, that says to me there was no noticeable effect.

That's a pretty common OEM approach. The JC Cosmo was one of the first production cars to use it. The less restrictive (and noisier) of the two paths through each rear muffler is closed at low load.

This is no different to the intake throttle, and I've never heard anyone call the throttle a "flow nightmare".

First, it would never be closed for obvious reasons. Second, at low load the exhaust flow (and hence velocity) is a small fraction of the flow at full load. The pressure drop caused by any restriction increases to the square of velocity, so at low load the pressure drop through the exhaust is tiny no matter what you put in the way. For example you need about 8% of peak power to cruise at 60mph, so the pressure drop through the exhaust at that load would be 4% of the pressure drop at peak power.

 

i think it was opel that did some work with active exhaust tuning they had a speaker deal in the muffler that would change its tone with the exhaust tone creating a vacum effect through out the rpms....i wonder if somthing could be done with this cause back presure is needed for good low end toque and free flow for bigger numbers up high.. idk just somthing i was thinking about

 

Exhaust restriction can cause the turbo to choke. If the turbo chokes then you will watch your boost guage drop when you get into high RPM's. I could be more overdramic if you'd like... but this is realality.

This will be a hard one for you to swallow but you prised 3.0L 6-cyl turbo will be able to get away with a more restrictive exhaust than a rotary. A rotary's exhaust pulse is about 25% larger than 3.0L 6-cyl turbo. The 3.0L 6-cyl turbo's pulse will have a higher frequency, but substancially weaker. Hence why a rotary spools a turbo faster than such engine would.

The JC Cosmo application for this would be approiate... but that's not what we are talking about here. Were not talking about re-routing to other pipes were talking about putting this inline of the only system.

The intake throttle is necessary, this is not. That is the difference!!! Not to mention that due to the expansion of air right after the TB any turbulance caused by the TB is basically negligable. There are many other reasons why they are very different, but my brine already hurts so i'm not going to go through them.

I am aware that this will never be "closed." Same as a TB is never "closed." I don't know why anyone would bother bringing that up. And I never said there would be any issue at crusing load. In fact I believe earlier I said there would be very good sound canceling when crusing. What I am saying is that there will probably be signifigent performance drawbacks to this being in there.

Currently, I have a turbo that chokes. My boost is set at 8psi and when I hit 6000 RPM boost starts to drop and is down to 4psi when I hit fuel cut at 7000 RMP (that is where my megasquirt is set). It has been concluded that it is probably due to the exhaust system not being able to flow enough air. I am currently in the design/prototyping stage of building my own dual exhaust system, and I considered and option like this earlier in the design stage and scrapped the idea for the reasons listed above. All along in my design process I have been consulting my brother who is in his final year of engineering at University.

 

Would you have a link to this article?

 

All true, it's just that it doesn't happen in this case. Show me any evidence that is does. Show me an example of an adjustable exhaust valve causing a significant reduction in boost or performance. I don't care what you think might happen, only what actually does happen.

My "prised" 3.0L 6-cyl turbo? It was a web page with a proven example. I don't even like the engine in that particular car. But it's funny that you think a 3.0L piston engine, which will flow 25-30% more than a 13B under similar conditions, can "get away with" (which I take to mean make the same power with) a more restrictive exhaust. That's a truly astonishing claim. I can't wait to hear you explain how.

I know that, but he asked about it so I gave him an example.

I never said it was necessary, only that the reduction in low-load exhaust noise is proven and the effect on performance is very small.

I don't doubt that your "brine" hurts...

So why did you? You said it, not me.

You said when the valve is closed the flow would be "horrible". The valve is nearly closed at low load only, so you did in fact imply that there would be an issue when cruising.

You can say that all you like, but you'd still be wrong. Experience has proven that the performance penalty is nowhere near "significant", or even minor.

Sounds like the typical performance of a stock turbo, the turbine side in particular. This is quite common even with big exhausts.

I've been studying and working in engineering for 16 years. Does that make me brainier?

I think you need to be a member to read it...

http://www.autospeed.com/cms/A_0883/article.html

 

**** it ima just buy it

 

Do you have easy access to a dyno? Before/after install and open/closed #s would be amazing.

 

i might have found one, ill let you guys know if i buy it

 

With ANY turbo the higher th RPM, progressively, the performance will peak then start to drop off. Not because of the exhaust but, more from the turbo losing it's effiency(sp) from heat.

Side note: Hotrodders use this type of thing for running straight pipes. Not for regulating backpressure.