Dynomax VT Muffler Test! Does Quiet Mean Slow? 

Dynomax VT Muffler Dyno Test!  Does Quiet Mean Slow?
By Mike Kojima


Our web guy Frank is getting old.  The Frank we used to know once built a 500 hp turbo SR20 engine himself and owned a daily driven 11 second Sentra.  Now a few years later and Frank has turned into a uh, puss.  Something about getting married and having a kid screws up one’s priorities.

We had been bolting stuff onto Frank’s Infiniti G35 sedan, including a really cool prototype exhaust system from Berk Technology.  All this did was cause Frank to complain about how loud the car was.  Did we even know this guy anymore?  Anyways, to appease Frank who also happens to be the best web guy we know by far, we had to do something about the noise.


Dynomax VT Muffler Test! Does Quiet Mean Slow?
Domesticated Frank's family hauler.


The prototype Berk exhaust was a 3” diameter system with a straight thru racing muffler and a small resonator.  Unlike the Nissan 350Z, the G35 has a lot less space in the back to put a large muffler and it was hard getting the exhaust acceptably quiet for a typical sedan driver.  What is acceptable for someone with a sportscar like a Z probably will be too loud for a sedan driver like family man Frank.  

Frank was willing to trade off some power to get a really quiet exhaust note and we were challenged to find a high performance muffler that could quiet the car down enough to satisfy Frank’s age induced pickiness.


Dynomax VT Muffler Test! Does Quiet Mean Slow?
We really like Frank's car, but the family is not happy with its high performance tone.


Frank's biggest issue was part throttle drone.  Something about his daily drives over hilly terrain put his car in the drone throttle position for miles at a time.  It was bad enough that he had taken to wearing earplugs on his daily commute.  My suggestion that he simply turn up the radio didn’t go over very well with him either.


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Wednesday, September 28, 2011 1:02 AM
Did you WPC the muffler bearings? ;-)
Wednesday, September 28, 2011 3:33 AM
I need a 4" inlet/outlet muffler like this for my turbo miata. Current one is straight through and a bit loud.
Wednesday, September 28, 2011 4:43 AM
this is fantastic, i don't know why i've never heard of this muffler before.

I've built lots of custom exhausts and i've never really been happy with the part throttle noise of a free flowing exhaust. when i checked the price on these i am happy to discover that these are pretty cheap.

do you have any before/after audio clips with the car from the article?
Wednesday, September 28, 2011 5:31 AM
I have heard that the flapper in these tends to loosen up and rattle. Keep us updated on how it goes.
Wednesday, September 28, 2011 5:33 AM
Does anyone have suggestions for a dedicated race muffler to be used at a track that as a noise limit? 3" inlet and outlet would be lovely.
Wednesday, September 28, 2011 5:51 AM
I'm with @Wrecked... I'd be interested to know 10K, 20K, 50k, ect miles down the road if he has any problems with this. But then again this is the aftermarket branch of an OEM supplier so surely they would have done plenty of longevity testing. (I'd like to see the results of that)
My worry would be the spring rusting and breaking due to moisture and heat cycling.

+1 @Marc on the before and after audio clips.

Another good article Mike Kojima!
Wednesday, September 28, 2011 7:09 AM
The VT muffler is a stainless steel muffler with a lifetime warranty, according to the Dynomax link in the article, so my guess is rust shouldn't be a problem.

Mike, why the two-y pipes?
Wednesday, September 28, 2011 7:10 AM
I've always loved the idea of this muffler. If it had been around when I did my exhaust it would have saved me from having to put 44" of resonator (3 total) under the car in addition to the muffler out back. Money and weight savings, and even quieter when you need it.

I've heard about the valve rattling problem too. And then I've heard they fixed it.

I'm very curious to hear how this thing holds up after some good miles. It is still on my list of upgrades to consider.
Mike Kojima
Mike Kojimalink
Wednesday, September 28, 2011 7:10 AM
The flapper door is OEM validated so I don't think long term durability will be an issue.
Wes Dumalski
Wes Dumalskilink
Wednesday, September 28, 2011 7:32 AM
Great article for the muffler... for Frank... not so much...
Der Bruce
Der Brucelink
Wednesday, September 28, 2011 8:13 AM
I 2nd Steve's question regarding the 2 y-pipes!

I like how Dynomax has created a performance muffler capable of appeasing the "Happy Wife, happy life" theory :)
Wednesday, September 28, 2011 9:03 AM
OK, before I comment on the VT muffler, let me preface this by saying that this is my daily driver which I use for a daily 3 hour commute up and down the 405 (From Ventura County to Santa Monica).

The first exhaust installed was a straight through 3" that was so loud, I LITERALLY had to wear ear plugs while driving. I have a friend with a turbo 240 who rode in my car and had his hands over his ears the whole time. So while Mike may call me a wuss, he's the one driving the cushy Tundra to the office every day :)

The new exhaust REALLY is fantastic. Not only did the MotoIQ guys go above and beyond to get this done, but the team at Berk Technology is a class act.

The new exhaust sounds a lot like my 350Z when it had a Nismo exhaust. Deep, throaty, but quiet enough to lift off the throttle when passing a police car to not get noticed. At WOT, it has a loud but beautiful tone. I've owned an S2000, 350Z, several SE-R's and this is by far the best sounding car I've ever owned.

I'll be checking in on this thread, so if you have questions, AMA!!
Wednesday, September 28, 2011 9:48 AM
Wow, glad to finally see some real results with this!

The maxima.org guys have been using these for over a year, but no one really has any performance results. Also, the design was updated from the original one and should rattle less-- the original VT's did rattle over time according to what's been found. Not sure on the newer ones.


Anyway... awesome to see real dyno results and a real review!
Wednesday, September 28, 2011 10:28 AM
Did I miss an article? When did the exhaust get installed? Dyno shots also show different wheels (nice choices too)... curious.

Love the background info of Mike calling you a wuss while Mike drives the Tundra to work. hahahah. Looks like Mike is flexing/streching/abusing his editorial powers a bit, eh? =)
Mike Kojima
Mike Kojimalink
Wednesday, September 28, 2011 10:31 AM
I also drive a loud EVO to work and I still remember how to work on cars.
Wednesday, September 28, 2011 10:56 AM
Lol, touché Mike.
Der Bruce
Der Brucelink
Wednesday, September 28, 2011 10:57 AM
Frank - Thanks for chiming in! I constantly forget the PoPo is so hard on guys down there :( How would you say throttle response is now in that 40-70 mph range? Were you planning on beefing up the tranny at all? For some reason I thought you were going to take it out for the occasional track day.

Speedball - I asked myself the same question about the missing article. Although, Mike had worded things in such a way where I understood that they tried the Berk exhaust but due to Frank's displeasure, this was the fix and final result for exhaust upgrade.
Wednesday, September 28, 2011 11:17 AM
@Mike Kojima - "The flapper door is OEM validated so I don't think long term durability will be an issue."

Cool, they are less than $100 on summit racing. I'm going to consiter this muffler on my daily driver a 96 GMC Jimmy with a 4.3L
Wednesday, September 28, 2011 11:24 AM
The flapper in the muffler tech should be very well developed. My 2005 Evo had it. Vettes have them. I want to say Nissan Maximas do too. And BMWs have them. Granted, I don't know which ones are electronically controlled and which are passive. The Evo was passive like this one.
Mike Kojima
Mike Kojimalink
Wednesday, September 28, 2011 11:26 AM
The Spec-V has it too.
Wednesday, September 28, 2011 12:08 PM
@Der Bruce... Yeah Simi Valley (where I live) has cops at every corner, and they absolutely detest loud import cars.

Throttle response was just slightly better without the VT muffler, but for what I get back in quietness, I don't mind it one bit. It still is VERY crisp.
Wednesday, September 28, 2011 5:52 PM
If I ever get sick of my magnaflow this may be the way I go, the magnaflow is too quiet WOT but it's slightly unbearable in stop and go and cruising 65+. Resonator and a cut out might fix that but I don't know though, I am possibly thinking about something like a Flowtech Warlock, just turn three wing nuts for loud mode!
Eric Hsu
Eric Hsulink
Wednesday, September 28, 2011 11:28 PM
It would be the bomb if they made these with different rate springs on the flapper. That would add a whole additional dimension in tuneability.
Dusty Duster
Dusty Dusterlink
Thursday, September 29, 2011 2:15 AM
What Eric said. Can you get different spring pressures?
Thursday, September 29, 2011 3:27 AM
that's what the above or below 4.0L choice means. the above 4.0 is a stronger spring and if you browse the forums many people recomend them even on smaller cars to increase the backpressure a touch more and keep cars quiet until WOT.
Micah McMahan
Micah McMahanlink
Thursday, September 29, 2011 4:50 AM
I wonder how much noise and performance effect would be with a lighter spring.
Did you mount it so that the hinge was on the top or bottom? basically was gravity helping keep the flapper shut or not?
Micah McMahan
Micah McMahanlink
Thursday, September 29, 2011 4:54 AM
Just read Eric's post. I was thinking the same thing about various spring rates or have an external tensioner/rod for adjusting spring tension.
I guess to make a 1 muffler to suit all, rod adjustment at a weight penalty (but it's a street car, really who cares?) OR if it were a serviable muffler have various springs rates that could be installed. Also not a bad idea for a fiberglass muffled exhaust.
Thursday, September 29, 2011 5:16 AM
Micah -> there's no reason you could not cut a small access hole if that's what you wanted to do. but they are claiming the thing opens fully at less than 1psi so i suspect there's not much to gain bu tuning that spring. if you want ultimate power use a strait through.
Micah McMahan
Micah McMahanlink
Thursday, September 29, 2011 10:08 AM
Marc: Well they rate it at 1 psi but never do state in which mounting orientation. Gravity helping or gravity fighting to keep the flap shut. With that being said and the note of the spring/flowrate potentially being the culprit for mid power drop off, I think tuning the opening point and cracking pressure point could be advantageous. You could potentially dial it away by slowing the velocity drop or being able to use a different weight spring to help shift the turbulent flow spot to a more favorable point (for a given powerband).
Perhaps it's is just my anal, inner, IC engine, engineer coming out...?
Thursday, September 29, 2011 10:42 AM
rough back of the napkin type math says that gravity would contribute about 0.5% difference in the opening pressure. but it does not matter, you'd always want the sealed side to be on top to avoid giving moisture a spot to sit and corrode the pipe if at all possible.

i just think this product isn't for you. it's for people that want a quiet but powerfull car without having an extra switch inside.

it's only $90.
Micah McMahan
Micah McMahanlink
Thursday, September 29, 2011 11:35 AM
yeah, I do want it for my DD beater WRX. So I've been looking into it and every single turbo application of this, people complain of the flapper clanking lol. Most of them have issues with it clanking at light load/parking lot driving. An adjustable spring to tune that out would be nice.
Also didn't Apex'i or one of those companies have something similar to this years ago? Use to be an add in the magazines.

This would not be on my track car by any means! I'm actually going to try my hand at an expansion/resonance chamber to muffle it...or get lazy and call up Burns ;)
Mark F
Mark Flink
Friday, September 30, 2011 12:21 PM
IS300 has one of these as well. It is a passive system without an active controller.

It is very simple to add an active actuator like they do on Ferraris or Corvettes. Something tied to RPM could be done.

Hell, you could even have the TPS as an input and then you could make a 2d lookup table to have it more tunable. Or, if you have a dual runner system in your intake, you take the vacuum or electronic feed from that to an electronic or vacuum actuated flapper. Sort of like the exhaust cutouts.
Bob Holmes
Bob Holmeslink
Friday, September 30, 2011 5:51 PM
Man I wish this had come a little sooner. Just bought an AeroChamber, although this was another option.

I know what Frank has gone through, I spent a bunch of time sound insulating my car after a trip to LA. I didn't get an hour down the road before I stopped at a gas station and purchased ear plugs.
Friday, September 30, 2011 9:10 PM
So, 2 Y-pipes? :)
Mike Kojima
Mike Kojimalink
Saturday, October 01, 2011 9:06 AM
Its what we had to do to fit the hugest muffler made in there. Didn't want Frank's easy listing music to get bothered while he sips his latte on the way to work.
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