Exhaust Butterfly Valve

[Keeper]

Hi guys,

I'm writing a bit to give people a heads up on a noise reducing device I recently installed on my R32 GTR.

Its called a butterfly valve! My mate brought it in a 3 inch size from Autobahn (I hate that f**king store so much) for around $200 and never fitted it too his car, so I bolted it into mine. It is a circular plate which can rotate to restrict airflow in the exhaust system, I found a photo of one for sale on here, and have added a link too it below but a lot of exhaust stores can get them in, but 3" is the largest size i think.

http://www.skylinesaustralia.com/forums/Wo...alve++butterfly

Anyway this is his pink fluffy velvet background picture, from his add but you can see the butterfly, the section of exhaust you bolt into your exhaust and the cable and lever to control it all.

I have a 4 inch exhaust after the gutted cat (it came that way) and I simply put the valve in line with the cat just after it then ran the cable up through the gearstick boot, but you could use the eyelet for the CAT exhaust sensor, then put the control lever on the right kick panel on the drivers side, just under the bonnet release, this keeps it out of view of the police if I get pulled over as they apparently can ask you to open it up for noise testing.

The valve when fully shut its diameter is slightly smaller than the pipe it sits inside so it doesn't completely restrict the airflow but does create a lot of back pressure. Now at idle you wont notice this much, ever revving the engine stationary wont make a huge difference, but under load when most open exhausts are noisiest it really does make it a lot quieter, great if you want to pass a cop in a 50 zone on the side of the road, or you live at the top of a steep hill.

You have to be quite mindful that with the increased back pressure your turbos will not spool up anywhere as fast or easy, and infact if you try kick the arse on the car when it is shut you could potentially blow a gasket as the pressure finds other ways out of the exhaust system, not a problem for me because I had a not standard cat converter on my car and had to trim the flanges on it to fit the cat with an angle grinder and successfully cut a couple of holes in the cat (yes I'm getting them welded next week).

The added bonus of this seams that the engine seams to be running smoother on long cruises;

I think this is relative to valve overlap which is basically how part way during the combustion cycle the intake and exhaust valve are both open, without back pressure to hold the mixture in the cylinder I seamed to be running a little rich at low to mid RPM when the turbos weren't boost like when I'm driving on the highway, something closing the butterfly once I'm at cruising speed has almost completely fixed!

Anyway I can boast enough about this device and the hassles it has already averted for me and hope this helps some of you guys, if anyone needs some help and you post a question and I dont reply please PM me.

Dave

Edited April 9, 2008 by Keeper

[paulr33]

not bad - apexi have it in a kit called the DECS

[sky30]

be interested to know if this would cause much exhaust restriction, or disrupted flow when fully open.

Anyone done any testing on the dyno??

[abu]

I have an Apexi ECV welded inline with my exhaust, so not the flange style

The difference in noise is heaps, if you pull it up and drive with it on it sounds like a stock car with a standard exhaust

Problem is the power restriction - it restricts the power heaps, I could barely make 5psi with the ECV activated where as when it was open it would make an easy 13psi

The idea of it is to restrict the exhaust making it quieter but its not to be driven hard with it activated, so don't boost it or try and push the car hard as it won't go and could cause damage

I'm sure Apexi advertise that it quietens down to 10db - I think that’s what it says on the box if I remember correctly

[WazR32GTSt]

these kind of systems are becomign standard on many cars

don't some ferrari's offer it?

i know for the V35 sedan when purchasing the sport exhaust in japan you had the option of this kind of valve..

[Basti]

if epa find it you are screwed. unless as mentioned b4, it came from factory. however, the whole point of it is to make sure you done get picked up in the first place. good bit of kit. i'll be getting one down the track sometime

[Keeper]

these kind of systems are becomign standard on many cars

don't some ferrari's offer it?

i know for the V35 sedan when purchasing the sport exhaust in japan you had the option of this kind of valve..

yeah my old mans XKR supercharged jag has something, keeps it quiet and backpressure when its needed down low

also the DECS is a great system, lot of auto shit, and its electronically controlled

but around $550 USD if you can find them anymore!

I must stress you don't try and boost hard when the valve is shut!!!!

the apexi EVC is exactly the same as the one I installed

[(B1) MR_fanny]

thats tough when you get in a sticky situation and need some power to get out of. my mates got the apex silencer thats spring loaded so it opens up quite well when under boost and is very quiet, obviously not as good as free flowing but at least you dont have to remember to open and close all the time.

i was seriously considering these kits when i got my defect but in the end i couldnt justify it though the DECS looks pretty good.

[godzl1975]

had one fitted to mine and when it came to dyno tuning it...it was causing problems..so i took it out.

[Adriano]

You could always somhow attach it the the throttle, so when you give it full throttle, it automatically opens. If you want a cheaper alternative, or a bigger one, go to a truck wrecker and buy an exhaust brake flapper(actually, these are usually vacuum operated, so you may be able to hook it up to manifold vacuum, give it boost and it will open)

Edited April 9, 2008 by Adriano

[GeeTR]

OEM there's dozens that use something similar, Dancing horse, Maserati, Bentley, Jag, Aston Martin and so on. Some, like the 360 though, i think are for sound.. not noise suppression.

I've a mate with one, though theres a 4" "Y" pipe. Closed the zhaust works normally, open and it sounds like an open pipe bridge ported 13B *cough* ... So he has an option of loud (100dB) and even louder...

Most are stepper motor controlled, so you could make it open (any angle) by any system with a spare output, like an aftermarket ECU. Im sure a simple PIC could help those with OEM ECU's.

I figured most people used a Y pipe, and diverted the exhaust gases straight to atmosphere, but it seems not of late. The large 3.5" - 4" units from teh US seal COMPLETELY for this reason.

BTW, I would expect the roadside RTA to rape you dry if caught.

I would be VERY cautious of exhaust temps (straight through, non Y style) when cruising on the freeway, as the back pressure plus closed loop lamba correction, would make for some very hot exhaust valves i would have thought...

Juz my thoughts

Edited April 9, 2008 by GeeTR

[BHDave]

They blow shut if used in a single pipe. If used in a Y pipe arrangement they are ok. Have a look at how the OEM gear is used, It's always on a second pipe or a diversion in a muffler, it's never blocking the primary pipe.

godzl1975 has obviously experienced it.

rubbish things. get a decent rear muffler and throw the cannon in the bin. Maintain power while avoiding headaches (both literal and metaphoric).

[R34NRG]

it be great if they had this in something bigger then 3"

[dead32]

even the brand new falcon has this system, although it wasnt fitted for noise, it was fitted for emission's so i was told....

regardless if the epa catch's a temporary silencing device, your even more f**ked then if you just went over the normal limit.... trust me its not worth the hassle. just make your car a reasonable noise level.

[GeeTR]

it be great if they had this in something bigger then 3"

.... as i mentioned, a mate uses a 3.5" one

Look in the US dood, not JapScatLand for a larger one.

Edited April 9, 2008 by GeeTR

[Adriano]

Why does everyone think the rta would have an issue with it, it can only make the car quieter, and should improve emmissions when its shut, as it would be similar to EGR.

[R31Nismoid]

In Vic its an issue only, probably legal in other states.

Vic it isn't legal because of the fact you can leave the testing centre and then be XXdB over instantly as its adjustable

[dead32]

Why does everyone think the rta would have an issue with it, it can only make the car quieter, and should improve emmissions when its shut, as it would be similar to EGR.

the epa in particular heve an issue with such a devcie, as its a device that can temporarily alter the emissions of the car, be it noise and actual gase's.... any temporary emission control device is illegal, aswell as anything that can alter the emission's other then factory, e.g aftermarket computer,bov etc

[Adriano]

But if it was setup to open and close automatically, then it should be legal?

[scathing]

Yeah, I've been emailing around and I'm now in contact with AES / Hyperflow (Autospeed did a couple of articles on their system) and they've got a few of these things.

Their top-of-the-line one is fully active with a pressure sensor and a configurable control unit, so it can adjust itself to maintain only a certain amount of backpressure. It'll take inputs from the TPS and an RPM signal wire too, so you can also set it to only open at WOT or a certain RPM. Not cheap, but a pretty funky piece of gear.

I'll probably end up going for the dumbest one, which is just a simple on-off switch that I'll conceal somewhere.

a lot of exhaust stores can get them in, but 3" is the largest size i think.

Hyperflow's comes in 4" bore size, but they recommend going half an inch bigger than the rest of your exhaust to retain flow.

But if it was setup to open and close automatically, then it should be legal?

If its set up so it cannot be controlled by the user and, in its automatic mode passes all noise and emissions regulations for the vehicle, then yes it could conceivably be legal. That's how Ferrari, Aston Martin, Lamborhini, etc get away with theirs.

Edited April 10, 2008 by scathing