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Not to jump in the middle of a forum battle here... but the mention of the silencer made me think of a thread by xluben over on Nasioc (one of the better known guys there) who actually did some testing including tuning and dyno runs with and without a silencer on a single exit Greddy exhaust for a 2011 WRX.

Short version, he had fairly significant power levels (a bit under 500whp if I remember right) and found that going to the single exit exhaust gained him about 25 whp while putting in the silencer lost a lot... 60+ whp down and did actually make the car run a bit rich.

Here's the thread:

xluben's Greddy Racing Ti-C Single Exit Cat Back Exhaust Review - NASIOC


In any case, I have a Tomei currently on my STi and have run one on my previous STi as well... I definitely wouldn't consider the silencer for any purpose other than to muffle cold starts. Mainly because it looks and sounds terrible with the silencer in.
 

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Not to jump in the middle of a forum battle here... but the mention of the silencer made me think of a thread by xluben over on Nasioc (one of the better known guys there) who actually did some testing including tuning and dyno runs with and without a silencer on a single exit Greddy exhaust for a 2011 WRX.

Short version, he had fairly significant power levels (a bit under 500whp if I remember right) and found that going to the single exit exhaust gained him about 25 whp while putting in the silencer lost a lot... 60+ whp down and did actually make the car run a bit rich.

Here's the thread:

xluben's Greddy Racing Ti-C Single Exit Cat Back Exhaust Review - NASIOC


In any case, I have a Tomei currently on my STi and have run one on my previous STi as well... I definitely wouldn't consider the silencer for any purpose other than to muffle cold starts. Mainly because it looks and sounds terrible with the silencer in.
Hwve a look at the reducer used with the muffler, it looks like it drops down in size heaps.

Not a real comparison when comparing a reducer or muffler which is the same size as the pipe.

I guesstimate the funnel for retaining the baffle drops the pipe size down 100%, of course a 1.5" outlet will cause a bottle neck.

That greddy rear can with the baffle, IMO, is rubbish.
 

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U claimed it, now explain it ... lol

Hahahahahhha keep name calling, I don't mind coz I'm waiting for your explanation. Car runs rich with silencer haahaahhahahahhaha, maybe I should add more timing advance then tune out the detonation with a silencer hahahaahhahhhahhahah

Sent from my SM-N9005 using Tapatalk
Alright, in general if you remove restriction to the intake or exhaust without tuning the car will run lean and vice versa. Why this happens, you can research the details yourself, but the car expects to see operating conditions in a fairly narrow range and is in open loop under boost. While the CBE portion isn't as big of a deal vs the downpipe it's still significant and necking the exhaust down from about 7 to 1.8 square inches is a major change and is almost certain to make you run a bit richer. If farmboss is down to 2.5" after the cutout that's about 5 square inches, not nearly as extreme as a silencer.

I suppose you could have a map just for the silencer, but the backpressure has other negative effects that are undesireable, it's just best not to try to shove so much exhaust gas through such a small hole.

Basically, the results of using a silencer are almost exactly what I expected in brapp's link, I'll post it below.


brapp, thanks for the post! That clears it up I think.

Update 3: I did some logging, and I don't think I'm going to be keeping the silencer on. I was having trouble logging, so I was only getting logs up through 4-5k rpm's and then they were cutting out, but after looking over my partial logs some more and talking with my tuner, I decided it's not really worth it for me. With the silencer installed I was losing 1.5psi of peak boost and going 0.5 points richer in AFR, which means there is some serious restriction going on!

My logs only went out to just below 5k rpm's but even at that point it was already down close to 60WHP! If I had to guess I think it would probably be about that much drop all the way up through redline. So the car was probably down to close to 430WHP peak. Definitely a huge drop from what it was at with the Greddy and no silencer (and even a step down from the stock exhaust).

It was down by maybe 10WHP prior to peak boost (compared to the Greddy without silencer). Peak torque was also down by about 60ft-lbs. The logs cut out right about where peak torque occurs, so I think this is an accurate peak number. As you can see, the silencer shifted the whole powerband down, and anything after spool up, it shifted down a LOT.

Now if I had gotten retuned and pushed the boost back up, and leaned the AFR back out, I probably could have gotten quite a bit of that power back. Maybe I could get it into the same ballpark as with the stock exhaust, but I don't have an AP so I'm not switching tunes when I throw in the silencer, and it's a big enough change that it would be less than ideal to install the silencer with the current tune.

Even if I could swap tunes easily I don't think I would want to try and push the power back up because that's it's just going to be making everything work harder. My turbo is already being pushed, and bumping it up to try and compensate for a restrictive exhaust doesn't seem like a good choice. I may install it for long trips if I want it quiet and don't car about power, but I don't plan on using it for romping around town.

Now I'm not sure how much it would change power in a stock turbo setup, but I know that for my car it does not look like a good every day option. I don't plan on using it very often, if ever. If someone on a stock turbo wanted to test it out I would be interested in seeing the results! The silencer is really quiet, and still sounds good, but I don't think it's worth the performance drawbacks.
 

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I guesstimate the funnel for retaining the baffle drops the pipe size down 100%, of course a 1.5" outlet will cause a bottle neck.
For flow you look at cross sectional area. 3" diameter is about 7 square inches, 1.5" diameter is about 1.8 square inches. So 388% difference.

I just measured the Tomei silencer and it's about 1 7/8" diameter... not as bad as I thought but still a significant restriction.
 

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For flow you look at cross sectional area. 3" diameter is about 7 square inches, 1.5" diameter is about 1.8 square inches. So 388% difference.

I just measured the Tomei silencer and it's about 1 7/8" diameter... not as bad as I thought but still a significant restriction.
All that mucking around when all that was needed was a long resinator and a rear box not engineered by a monkey.
 

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Yup.

Had my guys, Lachute Performance, swap in this:

5 x 11 OVAL 14589

to replace the existing resonator.

So much quieter, no real difference performance wise, under 500whp.

I used Magnaflow on a DSM years ago, it was quiet... If/when I swap out the stock DP I might have the resonator upgraded similarly as the Tomei is pretty loud.
 

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Hey guys ,

I have a catless invidia pipe and q300 cat back

Its just too dam loud , failing passing registration and police catch my ass everywhere.

I need to swap out this exhaust system but consideing im putting down now 445 WHP i need to keep around this figure although i dont mind dropping a little power to drop the huge noise of the q300

Any ideas.????
Yo Ian, what's up bud? It's Glenn
 

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Cobb GD exhausts are not exactly quiet. Yes I have been ticketed for load exhaust with one, and they're not full 3". They are not all bad though, they are well made and sound decent.
 

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Hwve a look at the reducer used with the muffler, it looks like it drops down in size heaps.

Not a real comparison when comparing a reducer or muffler which is the same size as the pipe.

I guesstimate the funnel for retaining the baffle drops the pipe size down 100%, of course a 1.5" outlet will cause a bottle neck.

That greddy rear can with the baffle, IMO, is rubbish.
My understanding was that the debate was whether or not running a Tomei Ti exhaust with the silencer would cause loss of power and/or running rich.

I own the Tomei exhaust in question, and the silencer looks exactly the same as the on used on that Greddy exhaust. Therefore, I do believe that Xluben's findings would be consistent with the results that would be found with the Tomei exhaust.
 

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My understanding was that the debate was whether or not running a Tomei Ti exhaust with the silencer would cause loss of power and/or running rich.

I own the Tomei exhaust in question, and the silencer looks exactly the same as the on used on that Greddy exhaust. Therefore, I do believe that Xluben's findings would be consistent with the results that would be found with the Tomei exhaust.
The OP asked about a Q300, the Tomei/Greddy Ti exhausts are rubbish with the silencer and to loud without.

Reading the link suppied to support the increased back pressure claim only provided evidence that they may be fine for a stock power car but due to huge reduction and therefore restriction from the silencer they are not a viable option.

Disclaimer: I have a INVIDIA Q300, there is a ton of room for a larger resinator in the mid pipe. So for between $100 and $200 it could be fixed without any detriment to power.

This thread lost its way from what the OP asked, it did however turn into a immature I'm right and your wrong pissing contest.

This is why it is so hard finding information on this site, the thread has many pages, but few relevant posts to the original question.
 

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dang.. I have invidia catless dp and q300 as well and would like something a little bit louder. I'm also 35 years old so not a snot nose kid. ;)
 

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This thread lost its way from what the OP asked, it did however turn into a immature I'm right and your wrong pissing contest.

This is why it is so hard finding information on this site, the thread has many pages, but few relevant posts to the original question.
Lol on saying the Tomei is junk but you run a Q300? I don't consider Invidia all that great, the Q300 comes with what, a 1-year warranty and I've seen them look like crap after a few years, badly corroded, built with what's obviously two different materials... The y-section was much more corroded vs the mid pipe section. Garbage imo, but they do polish their turds so they look nice before installation. Invidia is one of the worst value for money brands out there, highly over-rated.

As far as immature pissing contest I suppose we should not challenge bad information so it can get perpetuated and some poor dude will buy a Tomei, throw the silencer on permanently without understanding it shouldn't be used for more than cruising? Better to be more crap to sift through then get bad information... In any case you've mostly just whined and gave ridiculous opinions about what you think is too loud, people have to wade through that BS?
 

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Discussion Starter #57
You are right , Invidia is crap.

I solved the problem eventually by buying 2 vibrant cans and custom welding them at 45 degree angles.

High flow now and as quiet as stock.

Love them
 

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You are right , Invidia is crap.

I solved the problem eventually by buying 2 vibrant cans and custom welding them at 45 degree angles.

High flow now and as quiet as stock.

Love them
In what way did you find the Invidia "crap".

Have welds broken?
To restrictive?

I ask this as I have not had any issues with mine as yet.

If it's the discoloration I'm not fussed about that, generally all stainless will oxidize over time, more so if it sees high salt levels.

If it was because of the noise level, then that is a consumer purchasing the incorrect system.

In the 2 years of having the Invidia TBE mounted I have never been pulled over for noise, and it's not like I drive around like a grandma, I'm not happy unless I can hear the induction and exhaust note for the thing running up on boost.

Overall I have found mine to sound great, I did do alot of research on it prior to purchase, in being, I found typical cars to mine and went and listened to them in person, sound clips of cars revving will not give you a idea of what an exhaust really sounds like in the flesh.

Anyways, I'm glad you have gotten the car to the sound you are after by replacing the rear boxes.

Have you got some pics?
 

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Discussion Starter #59
In what way did you find the Invidia "crap".

Have welds broken?
To restrictive?

I ask this as I have not had any issues with mine as yet.

If it's the discoloration I'm not fussed about that, generally all stainless will oxidize over time, more so if it sees high salt levels.

If it was because of the noise level, then that is a consumer purchasing the incorrect system.

In the 2 years of having the Invidia TBE mounted I have never been pulled over for noise, and it's not like I drive around like a grandma, I'm not happy unless I can hear the induction and exhaust note for the thing running up on boost.

Overall I have found mine to sound great, I did do alot of research on it prior to purchase, in being, I found typical cars to mine and went and listened to them in person, sound clips of cars revving will not give you a idea of what an exhaust really sounds like in the flesh.

Anyways, I'm glad you have gotten the car to the sound you are after by replacing the rear boxes.

Have you got some pics?
Yes , Discolored and basically all rusted up and trashed. Really poor quality from my point of view as well as way more loud than necessary.

The Vibrant silencer/cans i have fitted are awesome. So dam quiet yet maximum flow as recommended by my tuner. when low in the rpm range then when WOT they really let go Really happy with them compared to the Q300 i hated for last 3 years as keeps local 5-0 at bay not pulling me when i go past them.

How do i upload photos on here.? i forgot as been such a long time.??
 

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......The Vibrant silencer/cans i have fitted are awesome. So dam quiet yet maximum flow as recommended by my tuner......
What is the part number of the Vibrant you have ?
Did you add a resonator in the mid-pipe ?
A picture of the setup please .....
Better yet.... a video ....
 
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