airworks-fc3s

the cops in CH are not very keen on loud cars! so i thought this would be a nice idea... like the valve apexi sells!
it will be operated by a cable linked to the throttle. and if fully closed, i'll fab some bypass that has very narrow piping for silent operation when only part throttle. do you think that could work? my only concerns are closing of the throttle after WOT, then the vlave is also immediately closed and the exhaust is pressed through the bypass...

Landon303

iTrader: (25)

dang dude that is cool. ya i'd be concerned too about that big increase in backpressure... maybe drill a few holes in it for relief? let us know how it goes

RotaryEvolution

iTrader: (30)

nice idea but in all honesty, i don't think it will last all that long before it turns into a projectile from your exhaust. the material used looks too flimsy and weak to stand up against the rotary exhaust temps.

That Rx-7 kid

Take some time to work on it and it should come out right- sounds like an awsome idea and I have heard of somone doing this before and being successful.

SSRx7

I too have heard of this being done, in fact it was on a muscle car in a magazine. Guy an AMX with some serious power, with true dual 3" exhaust. about 12 inches before the end of the tailpipes, he had little 1 3/4" pipes welded to them that came out at about a 45* angle and then angled back along side the regular 3"tips. With the valve closed, it was pretty quiet, but when they opened, the world could hear. Of course that was with big v8, I don't know how well it would work with rotary and it's temps. Keep at it though and let us know how it goes.

Later,
Bill

spot_skater

Lots of people use those.

Srt-4 guys use em, lots of muscle car guys use em. A buddy of mine with a highly modded STi used one off his downpipe.

Some are electronic now, that use a solenoid to open/close.

Nice work though. Make sure it's strong enough to hold up, though.

James

Black91n/a

Don't hook it up to the throttle, give it a seperate control.

Tmato

Could've just bought a electronic ebay cut-out and used it in your exhaust system rather than making a y-pipe out. Basically exact same as the Apexi one, just make sure you never close it all the way haha.

88turbotime

SureShot on the forum has one (or did, i think his car might have been wrecked though )

I remember driving in front of him at deals gap at night and i could see flames shooting out under his car.. it was awesome.

anewconvert

iTrader: (1)

Dont get the electronic one. They hysterisis is too long.


Take wastegate actuator from an internally wastegated turbo and rig it on a bracket to open the valve. If you have an NA you can rig the airpump to open it with an RPM switch much like the electronic control of the 6PI and VDI. If it is a turbo you can rig it to open off of boost pressure. It will open and close with pressure.

similar to this. http://www.atpturbo.com/root/releases/release091004.htm

BC

coldfire

iTrader: (1)

this is an interesting idea that i would like to see someone try.
they are starting to do this on quite a few high-end sports cars. Jaguar and Lamborghini are two i know of. i was watching the show Top Gear and they tested those cars, and it's pretty cool because the car goes from quiet to very loud.
it shouldn't be too hard to make something that will be durable, but the control aspect might be more complicated.

Tmato

Actually, I got a electronic DMH one which opens and closes fast =). But the one posted with the wastegate seems interesting. But mines just lieing around since it's made with a 3 bolt exhaust flange and I didnt' feel like changing things up to make it fit yet.

pengarufoo

A few of the posts in here seem to be mixing up what the OP is making and an electronic cutout / dump valve.

The DIY job above is just a restriction when closed and won't cause much restriction when open, it's not a bypass/cutout/dump.

These are used often on exotics with ex-race engines that have too much overlap to run well / clean at low rpms without significant exhaust restriction.

You can find these also on a number of sportbikes, yamaha calls it "EXUP", ducatis new 1098 has one also, I'd expect most naturally aspirated others with very high HP per liter to also have something similar.

It's not a bad idea, especially if you are planning on some really agressive porting, it can help keep the car streetable while letting it become a monster when flogging it @ the flip of a switch.

Tmato

Correction, I am refering as the same thing as the OP. I meant use the cutout valve inline to the exhaust system between flanges or wherever as an internal silencer. I refered to the Apexi ECV as an example, which is basically what I'm trying to explain.

airworks-fc3s

thanks for the comments guys!

first of all: i used only high grade stainless steel components (including the shaft and the flapper). i know our rotaries produce quite high temps

i didn't want to drill any wholes in the flapper, because then the effect of absorbing noise is weaker.

some of you don't recommend hooking it up to the throttle. to me it has some strong advantages. first it only comes out loud when i give sufficient amount of throttle and it comes out loud linearly, as throttle angle rises. the idea with the wastegate actutator is nice, but imagine you are slightly accelerating with 1/3 throttle but let her go up to 5000, you will have some serious heat restriction due to the valve being closed because of no boost. also on the highway i would very much appreciate being able to "talk" to my passenger. with my system, i'll have the valve almost closed, exhaust gases going through the small silencer, 'cause i only have a very small throttle angle.

i think there is much misconception around now, so i made a little scheme (don't flame me on the childish finish)
the small silencer you can see on the left will be some perforated piping, that forces the gases to move back and forth to make them quieter!

pengarufoo

If you look for something already made (not DIY) don't bother wasting money on something marketed to the high performance world, you will pay through the nose.

Look at stock exhausts on ebay from modern sport bikes, the ZX-10R for example. Or even a used exhaust butterfly valve from the International Scout II which had it stock... I'm sure you can find other vehicles that came with them from the factory if you look.

The nice thing about the bike valves is they are usually done in exotic materials like cast titanium, and you pay little because it's "stock junk" someone replaced with an expensive full system. If you want to blow money there is a fully developed system for this, article here: http://autospeed.drive.com.au/cms/article.html?&A=2291

Considering the subject of the thread though, I doubt the OP is interested in fancy overpriced options...



edit:

I see the OP has responded before I submitted this, regarding the bypass you don't need one. You will need a decent amount of clearance around the butterfly valve to prevent it fro binding becuase of carbon (among other pollutants) depositing all over the place... so the fluid will just leak around it and the engine will work fine, just with more back pressure.

airworks-fc3s

yeah that australian one would be delicious... but the price...

the ones off sport bikes are too small in diameter for my application!

do you think the bypass is useless? don't you think it would be more efficient to completely close the valve and let the gases go through a narrow restrictive muffler as on the scheme.
'cause on thing i'm not sure about: i think what makes noise is a large diameter piping... so after the gases have passed the narrow valve (2-5degrees open) they could develop some noise too... i'm confused

Mankdrake 2661

iTrader: (8)

I'm thinking that with it connected to the throttle it might kill you turbo spool between shifts.

airworks-fc3s

had that thought too... may installing some sort of damper would help! after WOT, there would be some delay of closing... but now we have the heat problem again

Alex6969

it sounds like a sound idea, i would love to see the final project.

splatterbass

why bother with all the complicated stuff.
why not a setup like a double disk check valve?
http://www.weirvalve.com/weir/valves...atmordualplate
disk split down the middle, spring loaded?
opens with pressure. this designe is meant for keeping water ( or whatever material ) flowing in one direction.
i have seen a few variations on the same idea from other companies.
the spring dosn`t have to be on the inside, on the outside would make it easier to tweak.
and would work on pressure alone.
http://www.watts.com/prod_images/hi-res/ICV-125.jpg
better picture of how it works, should be pretty clear on how it works.
http://www.watts.com/pdf/ES-ICV-125-2-2-T.pdf
some spec drawings.
making somthing dual shaft with external spring would be a good way to go.
just some ideas.

airworks-fc3s

interesting, but seems to be too much of a restriction to me!

i'd like to take up the turbo spool issue: there could be some problems between shifts, when going from WOT to closed throttle while the engine is running at full rpm and therefore needs some time to "breath out" - but at the time i close throttle, the valve will also be shut!

turbo-111

yeah i got a buddy of mine that just bought a 2005 GTO and he couldent afford an exhuast system so he bought two cut out valve's from ebay and rigged them up to his car right before the cats and gaind a few good ponies and an awesome sound

airworks-fc3s

you misunderstood! please read the entire thread: it's not about a cut out valve, i'm developping some quitening valve, to give the exhaust flow a restriction at low throttle angles!

RxFC3S-13B

I have a very high doubt that this will keep your exhaust quiet. If you have to accelerate onto a highway or from a stop light with a cop behind you or even around you, and you then start opening up the throttle which will open the valve and especially going on the highway, when this starts to open up a lot. Its going to be noisy.

The RIGHT way to do it, is to have the cutout as a seporate path. When its closed, the exhaust passes through your muffler of choice, when open, most of the exhaust gets routed out through the valve.

I see bad things doing it the way you are picturing.