I know many had this removed, do you guys feel like do something. I just did it and it feels kind of slower. or is that it make more sound and seems to be slow.

Shiv conducted a number of dyno tests comparing the silencer in and the silencer removed, and they all showed a loss of approximately 1 horsepower or so. However, the removed silencer results in the turbo spooling a few hundred rpm's earlier... and a lot more noise :D

ive done this. its alright. it give more noise. and since im an auto, i cant hear the bov very well. ive sad in some manual's without the silencer, and its loud. but its a free mod, no harm. you can always go back, unless you hacked it.
:D

It's a sound thing. If there is any loss or gain in HP, you will never notice. I did it and like it.

/\rcanum

That was the first thing I did...Over a year ago now...Makes it sound better, didn't notice a power gain or loss.

Originally posted by ScoobyBoy
ive done this. its alright. it give more noise. and since im an auto, i cant hear the bov very well. ive sad in some manual's without the silencer, and its loud. but its a free mod, no harm. you can always go back, unless you hacked it.
:D

I have a 4EAT WRX also and I still hear the Bypass valve all the time. Maybe my car is just special. :p

I couldn't feel a difference either way. I left the silencer off because I like the sounds it lets out.

i heard you gotta cut it out....can you take it out and still be able to put it back?

Originally posted by scsi
i heard you gotta cut it out....can you take it out and still be able to put it back?

if you didnt hack it. if you took out the entire thing, then you should be able to put it back.

ImprezaRSDriver - really? i tried listening really hard, and i couldnt hear it. the only thing i could hear was the turbo spooling.

Ok... so Shiv's proven that you lose 1 hp... but do you gain any torque? If the turbo is spooling earlier, are you getting better acceleration?

ScoobyBoy,

I can hear and so can all my friends who ride in the car. They say that is cool. :p I am still runing all the stock components like pre-cat, stock turbo and I can hear it just fine. I know that if you put a CAI, you will definitely be able to hear it much more. But I am still running the stock airbox because I scooped up quite a bit of water from the last storm in California. So I am just taking a precaution at this point.

I know some people have bought, I guess you would call it a plastic block off plate, that blocks off where the little cheesy "ram air" vent goes from the front of the hood to fender. It is a stock part from what I've heard on the RS. Anyone do this and what is the part#

/\rcanum

Originally posted by Monolith
Ok... so Shiv's proven that you lose 1 hp... but do you gain any torque? If the turbo is spooling earlier, are you getting better acceleration?

IMHO, Shiv seems to be a good guy. I have no personal experience with him, but how could you prove a 1HP loss? I've seen dyno runs of the same car back to back show differences of 5 HP.

/\rcanum

I know what part you are talking about. It is a part that had come with the original RSs when they started using the Phase II motors. I cannot remember the part number off the top of my head but I will look for it.

Thanks :)

My car will be needing to hit the dealership in about 2 months for a checkup/oil change. So I thought I could get the part # and have it waiting for me there.

/\rcanum

PN46059FA000 couple bucks IIRC

Originally posted by Arcanum
My car will be needing to hit the dealership in about 2 months for a checkup/oil change. So I thought I could get the part # and have it waiting for me there.

When I traded in my '00RS that blanking cap mysteriously went missing the day I took it to the dealer. :)
I don't have the part number or anything but I did manage to 'find' one of those caps for my WRX ;)

I got tired of it and put mine back in. It was takeing up space in my room. :D And my HKS BOV takes care of that "cool" sound. And if you want your BOV to sound even LOUDER in the cabin just remove the firewall plug behind the clutch pedal. (blue ej20) told me this and it works, but your feet get cold

Originally posted by Arcanum
IMHO, Shiv seems to be a good guy. I have no personal experience with him, but how could you prove a 1HP loss? I've seen dyno runs of the same car back to back show differences of 5 HP.

/\rcanum

Bad way to put it... I meant a nominal horsepower loss as opposed to literally 1hp. Sorry! :D

I feel that if you put that plastic cover on the new hole in the fender well you will increase your chance of sucking up water into the filter.

:grabs flame suit and runs for the hills:

~v6

Originally posted by V6turboTA
I feel that if you put that plastic cover on the new hole in the fender well you will increase your chance of sucking up water into the filter.

:grabs flame suit and runs for the hills:

~v6

How?

the firewall thing that nevz was talking about works. i used that to route my boost line to the TT, and after that i heard the turbo much louder. i left the plug in, but i taped it on, so it wouldnt fall out. if you do decide to take it out watch out for it, dont let it fall out, itll be a ***** to fish it out.
:D

Where else does it draw air from?
I would imagine it would suck air from the holes in the bumper cover. When you block off that large hole it will have to suck more air thru the same holes in the bumper. Therefore it will create more of a vaccuum and could possibly draw in water if you drive thru a puddle under throttle.

At least thats my guess.

~v6

Myself and another member did some Delta Dash testing of the intake silencer mod. We tested three scenarios:
1. Stock intake
2. Silencer removed
3. Silencer removed and dryer hose to connect airbox to scoop

All testing was conducted on the same day on an otherwise stock WRX. Results shown are for three WOT runs up to 4th gear. #3 run was cut off due to police presence.

In the attached pictures/files I will show three charts:
MAF vs MPH
MAF vs RPM
MAF vs Time

JC

This chart clearly shows that MAF is highest for all MPH ranges with the stock intake. This indicates that a "ram air" effect is occurring at higher vehicle speeds due to the ram air effect in the front of the car. Note that this is good.

Caution - this chart does not take into account RPM yet and thus, these results seem to indicate an obvious advantage for the stock setup at this point...

This chart clearly shows that MAF is better for the modded intake silencer but starts to fall behind in the upper revs. Nontheless, its not so much worse in the upper RPM ranges that it offsets the obvious gains obtained in the lower RPM ranges.

Also note the significant amount of scattering of the data in the stock setup. This shows that the intake silencer mod provides much smoother airflow due to decreases in turbulence in the intake.

As can be seen by this chart, the silencer seems to hinder spool-up time and the MAF increases more rapidly for modded silencer options.

So, as you can see from the attached graphs, the stock setup seems to be better than the others in the upper RPM's and the silencer mod results in low end gains. I also did a statistical analysis (multiple linear regression) using MAF, MPH, RPM and IAT and the MAF reading seems to correlate well with MPH and RPM, but not IAT.

So, based on what I see in this chart, there is either some "ram air" effects from the stock intake or it is accessing colder air at high RPM/MPH (most likely the former). Note that the MAF takes into account air velocity and temperature to be able to calculate the "mass of air" entering the engine. Of course, the more air you can get in, the more power you are going to make.

My experience with the silencer mod (I currently have the hacked version) was that it provided increased smoothness and low-end gains. These charts support my hypotheses based on the 'ol butt dyno.

JC

bravo! this monday's learning points goes to thejean....thx for the footwork;)

Originally posted by V6turboTA
I feel that if you put that plastic cover on the new hole in the fender well you will increase your chance of sucking up water into the filter.

If you're going to be crossing rivers you should be getting one of those safari snorkel intakes, not shortening the stock one!
I could be wrong but I don't think under normal conditions water should be a problem.
I had a hybrid Civic and was running a cold air intake with the cone filter mounted directly behind one of the fog light cut outs (with no fog light). The car was pretty low, I live in Vancouver (rainy winters like Seattle) and never had any problems.
Maybe somebody can chip in with a water on filter hydrolocking disaster story for us. I personally have never heard one.

ok, so does anyone want to sell me their factory resonator because I already hacked mine... :(

thejean must be a math major... or really hardcore on stats :D Thanks for the info! But I still wonder if it's a good idea to remove now... anyone know how much louder it is? Like unbearably loud?

Hey i have a Dual Vent Blow Off Valve, i was wondering if taking out my silencer would make it a little louder since half of it is venting back into the intake system..

Originally posted by Choku Dori
thejean must be a math major... or really hardcore on stats :D Thanks for the info! But I still wonder if it's a good idea to remove now... anyone know how much louder it is? Like unbearably loud?

haha. Nope, not a math major. I'm an engineer who designs water and wastewater treatment plants. But, as part of my masters I did have to do an graduate level applied regression analysis course. Not fun. Not fun at all.

Anyway, glad to hear this data will be of some help. FWIW, I have the hacked silencer with the hole left venting to the fenderwell. That way, if the air is colder in the fender, I can access it. This would also help to reduce pressure loss in the intake tract since the suction piping is effectively shorter. Plus, I likely still get some of the slight "ram air" effect that stock scoop gives by allowing the whole fenderwell to be "pressurized" by the scoop.

An added advantage, if by chance any rain did get in the intake (we get a lot of rain up here in Nova Scotia), then the hole where the stock scoop is could vent that water downwards. My thoughts is that in the stock setup, the incoming air goes down into the silencer, which is shaped to project the air flow back up towards the air box. My feeling is that Subaru put the scoop there for a reason and I like the idea of keeping it in the equation as a minimum.

I guess I was trying to get the best of all worlds. Unfortunately, there's always a trade-off isn't there?

JC

I left my silencer in place :)

How about leaving the snorkel that feeds air in from the front. Gut the silencer, and making sure you seal the airbox between the airbox and fenderwell. And don't forget the K&N filter!

-scu

Originally posted by kenchan
ok, so does anyone want to sell me their factory resonator because I already hacked mine... :(

hacked mine too! i haven't really looked around but i'm sure they aren't that hard to get a hold of....;)

Originally posted by thejean
applied regression analysis course.

:confused:

How does the sound compare to a CAI? My friend has the aem and it doesnt seem very loud at all, maybe I am just used to NA cars, but his doesn't seem very loud at all.

Originally posted by Obi-Wan
:confused:

hahahaha
Thats exactly the look I had on my face for 99% of that course.
jc

Would this mod effect the warranty in any way? Like if they see it modded, they would reject service to my car?

Probably. So slap it back on when/if you go into your dealership ;)

kinda revivin the thread.... but i just did the silencer removal and i DID get a CEL. But i reset the ECU and it went away. Did that by disconnecting the battery for a minute and reconnecting it. Great first mod :)

Good reminder for people to reset their ECU when this or nearly any other mod is done. Thank you :)

Well... I did this mod about a month ago. Just wanted to add my impressions.

First try: Took out silencer. Could hear turbo spool much better. Ran it for about a week. Felt slower than usual on the "butt dyno". Felt like I had less torque. RPM revved slower and turbo seemed to spool slower. (When I say "spooled slower"... I don't mean like significantly, maybe like by a few hundred RPM's)

Second try: Added GP Moto Delete Elbow. Felt slow still. And lost most of the spooling sound now. Almost sounded like stock again. Turbo still spooled slower. Checked cables/hoses. Got pissed off.

Third try: Put silencer back in. Tossed GP Moto Delete Elbow onto junk parts box (waste of $40). Runs like normal now. Turbo spool is back to normal. Torque is back to normal.


All this was done on a stock 2004 WRX with ECU being reset. I could just be all psychological. Others I've talked to have had the same problem. Some people don't have any problems. Logically you shouldn't have any problems with it, but I guess some of us just have bad luck.

So, this being said... Anyone want to buy my used but pretty much BRAND NEW GP Moto Delete Elbow? $30 free shipping :-P

I'll take it, check your PMs.

how could it feel slower, the only thing it does is straighten the path of the intake air flow.