Y pipe vs dual inlet muffler?

Cool. That is a pretty interesting design. Thanks for sharing this.

 

At the muffler shop right now getting an 02 sensor stitched in, x pipe, y pipe, and single 3” in/out muffler. Kid working on it was scratching his head for a minute but figured out was I’m looking for. The last muffler that was welded in (5 or 6 years ago) was placed further forward than I liked which I suspect contributes to the mild drone at 1500-1700 rpm. They are moving this one back further to the stock location so hopefully it’s quieter in the right way.

Can’t wait to hear it, mild as it should be.

 

Good news, bad news.

Muffler shop got everything put together without issue. I haven't put many miles on it but I did take it up to 90 mph and cruised around 65-70 mph for a few miles. Initial impressions from the butt dyno and ear-mometer are positive. Comparisons below are drawn between the way the truck has driven for the last the several years as well as my 5.7 sequoia.

First, I feel like I got that bottom end response back, and maybe a bit more. I find myself jumping out a little more at stop lights or merging in to traffic then getting up to speed a tad faster with less RPM. In fact, I'm overshooting the speed limit a few mph before backing out of the throttle - and I'm not giving it the beans by any means. Like 2500 RPM or less. I can even putter around below 2000 rpm and still make it to speed without feeling like I'm sludging through some much. So I think that's a big win.

Second, the engine pulls better/more consistently throughout the RPM band. The previous exhaust - a Flowmaster Delta 50 - felt a little sluggish below 2200 rpm, then woke up a bit and pulled well above that. I don't necessarily think I was "losing power" below 2200 RPM, but that above 2200 RPM it was making a little more power under the curve. In all fairness, I've added 800 lbs to my daily load out since I ran a stock muffler, so I'm basing some of that supposition on how my sequoia drives fully loaded down with kids, gear, and dogs. Anyways, with the new setup it pulls a little smoother throughout with a little extra sauce around 4k and up, but I'm haven't done enough heavy throttle pulls to really know it pulls up top. Still, it feel stronger and smoother than both stock and the delta 50.

Third, the sound. It's nice; smoother, quieter in some ways, not raspy or sloppy sounding. I've listened to just about every tundra exhaust clip I could find on this site and the inter webs and it seems to me that many of them to have a harsh rasp which I was trying to avoid. The Delta 50 sounded a little sloppy below 2k and good above that, but not as tight as this setup. Noise level is kind of weird. It's a tad noisier in park and maybe at idle in gear, but quieter everywhere else. Well, quieter everywhere else except for one spot. But I'll get to that. The engine racing sounds more like a super clean stock motor; I can hear a little more of the motor at higher RPM like a stock exhaust, but with a stronger exhaust note. I know that sounds weird, but so far, that's the best way to describe it. And I'm happy with it. Should be great for towing.

Now for the bad. That one spot that wasn't quieter than the previous exhaust? 1600-1800 RPM. The drone zone. And it's very pronounced. Oof. But, again, it has some peculiarities. Cruising around town at low RPM and low throttle input, the drone is very pronounced as the engine runs through it but immediately cleans up at 2k. Driving down the highway at 65/70 mph, it's louder but doesn't drone in the same way as it does when running through the gears. Hopefully it's tolerable for a while, and when towing, I'm rarely in that RPM zone except the few 55 mph zones, but I can shift down a gear at that point without much detriment to mileage and noise.

I wonder if removing the additional tail pipe extension that had previously been stitched in with the flow master contributed to the additional drone. Maybe, maybe not, but I'm sure I'll be making another trip to the muffler shop to have them put in a helmholtz resonator. That might be fun to explain to the new kid.

The other negative is that the work wasn't as good as they usually do. It was the younger kid doing the work and, while it appears to be functionally just find, there as few things that I'm not super pleased about. But it's not such a big deal that I'm gonna bring it back and make him redo it. Well, probably not.

Here's a few pics from the middle of the night. Might try to get some better ones tomorrow. Ignore the junk in the background; we've been doing some late spring cleaning.. Ha.

 

So I made myself a little cheat sheet last night to find the frequency, wavelength, and 1/4 wave resonator length at a specified RPM. I'm getting drone between 1600 and 1800 RPM judging by the Ear-o-meter.




To verify, I used my laptop and an inexpensive but much better than built-in-computer-mic Dayton iMM-6 to measure the in-cab resonance. The mic isn't calibrated below 50 hz or so, so you can ignore some of that. But it shows very clearly a resonance peak around 105 hz and 120 hz - EXACTLY where my spreadsheet calculated it to be based of off RPM. So the drone is, in deed, from the the exhaust.



I have an appointment this afternoon to have a Helmholtz resonator built and stitched in to the y pipe.

How exactly is the all this determined? Well, sound travels a specific speed through specific mediums. Through air (at seal level, temp 68F-ish, humidity IDunnutRMmbr) it travels around 1125.3 ft/s. We measure frequency in Hz, or cycles per second. The lower the frequency, the longer the wavelength. Think about bending a ruler on the edge of your desk in grade school and letting it buzz as it oscillates back and forth - the longer the ruler, the larger the oscillation and the lower the pitch. So wavelength is longer at lower frequencies.

We can use engine RPM to determine frequency because it fires cylinders at a regular interval - or cycle. An 8 cylinder motor fires all 8 cylinders once every two rotations of the crankshaft (we us the Otto 4 cycle), so for every RPM we get 4 cycles or distinct combustion events. Multiply that by the RPM and you get the frequency - but in cycles per minute, not cycles per second as Hz are measured. So we we simply divide by 60 to get the frequency in hz at that RPM.

Example: 600 RPM = 4 combustion events * 600 = 2400 cycles/Min Divide 2400 cycles/Min by 60 sec/min (same as multiplying the inverse: 2400 cycles/min * 1/60 min/cycle), the minutes units cancels out and we are left with 40 cycles/second, or 40 hz.

To get wavelength from the speed of sound and the frequency, we simply divide the speed of sound by the frequency. Again, at 600 RPM, or 40 hz, the wavelength is 1125.3 ft/s divided by 40 cycles/s = 28.1325 ft. Check the units - 1125.3 is ft/s, hz is cycles/s, so the seconds drop out and we are left with feet. But we want it in inches, so we simply multiply 28.1325 by 12 and we get 337.59 inches.

So where the heck does the resonator length of 84.4 inches come from?? Well, we want to cancel out the frequency that we are targeting. One way to do that is by using destructive interference. What is destructive interference? In this case, it's simple. Sound energy travels in waves, like whipping a jump rope and watching the wave travel the length of the rope. If we introduce and equal an opposite energy to that wave, it will sum to zero and no sound will be heard.

Think back to middle school or high school maths when you had to plot a wave function - sin wave, in particular, which your teacher called a sinusoidal wave to use big words and confuse and intimidate you.. The wave started at 0, ramps up to 1 on the y axis (at pi/2 on the x axis), then back down to zero (now at pi on the x axis), then continues back down to negative 1 (or negative pi), then back up to zero, where the function then repeats itself. Like so..



Now imagine you shift that wave by pi/2, either to the left or the right, it doesn't matter. Like so...




Now add the values of each of the waves ANYWHERE on the x axis - you will find that it will equal zero. This is the principle behind noise cancellation.

So what's that gotta do with a resonator tube? Well, we want to shift the sin wave by 1/2 the distance, or half way through each cycle, we want to introduce a new cycle. But how? The simplest way is to use a resonator tube 1/4 the length of the targeted frequency. Why, and what does that do? If you take that same wavelength that you are targeting, run it down a tube 1/4 the wavelength you are targeting, then run it back down the tube another 1/4 wavelength to reintroduce itself into the main exhaust tubing, it's now at 1/2 the regular interval or frequency and will interfere with and disrupt the original problematic frequency. So, a tube with a capped end, 1/4 the length of the targeted frequency wavelength should create a destructive resonance.

But doesn't that little tube have it's own resonance that could be constructively bad and amplify sound at a certain RPM? Yep. BUT... since we are using 1/4 wavelength tubes, it's natural resonance is now FOUR times that of the targeted frequency. If you are putting in a tube to target 1700 hz as I will be, that tube itself will resonate at 4*1700 = 6800 RPM - WHICH MY MOTOR WILL NEVER SEE. Frequencies below 1500 RPM *could* be problematic, but most drone happens above that, unless you use 8 inch sewer pipe to plumb your exhaust, then you probably don't care about a little drone.

A few other items to note: while the tuning frequency is specific, it should have an effect on frequencies 1/4 octave up and down (really 1/2 octave up and down, but the effect is limited past 1/4 octave). So what should that mean for me in my case? If I target 1700 hz, then I should get some noise cancelation down to just below 1500 hz and up just past 2100 hz. Should theoretically work perfectly to fix my drone.

I'll remeasure after they weld in the resonator tube this afternoon and see if that was all just a bunch of malarky.

 

Or not…

After discussing it in person yesterday with the muffler shop and making an appointment for today, I waited an hour for them to pull the truck in to the bay just to back it out two minutes later. The ‘boss man’ changed his mind and refused to add the resonator. Perhaps he could have told me that yesterday…? Said it would cause problems and that he would cut out the x pipe if I wanted instead. I suppose that could cause some of it, but it didn’t sound like a solution to me. Oh well. Guess I’ll have to figure out something else. Not a lot of exhaust shops around me. Ugh.

 

Might try out a Flowmaster Pro flow through muffler. Why not...

 

That’s a lot of frustration when you have a guy right here with literally hundreds of exhaust system experiments for tundras under his belt. Tens of thousands of exhaust builds for tundras. What exactly is the point of this? Just curious

 

Just buy the resonator from dirty deeds and install it. Took me 30mins and killed my drone that was at the exact same range as yours. I’m running an x-pipe to a Borla pro xs dual in single out muffler in stock location with stock size pipe. The drone was insane before the resonator. Resonator solved it all.

 

Have you decided on your solution? I would weld in a j-pipe resonator about 27-26 inches long in between the y pipe and muffler. Should kill your drone. @dirtydeeds knows the resonator deal with Tundras and has been helping the Ford Raptor folks out too since 2014.
I'm butchering my system, thanks to @reywcms, and been running it dumped after the muffler. Removed about 5 ft of pipe. Will be welding in the relocated resonators to solve the drone, choppa choppa sound, at 1900rpm. In the pic I'll be welding in the 27-26 inch resonators after the x and before the mufflers. Keith advised me to keep it original but wanted to experiment...
and yes I'll recoat with some fresh BBQ paint.

 

I’m trying out the flowmaster muffler posted above. I should have it stitched in Friday, hopefully, then I’ll measure the resonance again and see what needs to happen. As of now, a 26” resonator would not suffice given the measured resonance peaks.

As an aside, I was thinking about exhaust pipe diameter for a SC system compared to a stock system. If we increase output by 50% (assuming some losses from the SC that aren’t seen on the dyno in the form of extra HP), the stock 2.25” piping would need to move up to 2.75” pipe to retain the same pipe area to HP ratio. Tailpipe would need to increase from 3” to 3 5/8”. Yes, I know those aren’t standard pipe sizes. Curious if 2.5” pipe to the muffler, with a single 3.5” muffler/tailpipe would flow well while maintaining good exhaust velocity. Rey’s new exhaust is 3” all the way from the collector back. Just musings…

Once I get the new muffler installed and then remeasure the resonance, I’ll see what needs to happen with a resonator. Might have to go get some stainless wire from the welding supply store and stitch it in myself.

 

I'm running 3 inch from long tube all the way with a 2 inch resonator. I'm re-using my 26 inch resonators. Good luck figuring out your system. Everyone has a different ear for the sound they like. Some actually like drone but I couldn't handle it especially at 1900-2000rpm.

 

I needed a little break from work today so I had a little fun with the bandsaw, grinder, and welder. Everything went great until I got to the tailpipe - darn thing doesn't measure 3"! So had to stuff some welding rod in and fill the gap. Hindsight - I probably could have sleeved it with a piece of 3" ID pipe and made it work, but I ended up borrowing a bay at my buddy's shop to stitch the muffler in place. Everything else I welded up at my place to make it go faster.

Man, I'm surprised at how quiet this Flowmaster is. I've barely driven it around and haven't been on the highway yet, but it appears that the everything is quieter, and that the drone is quieted down as planned. I'll drive it a bit before I post any real impressions, but I was hoping for quiet and expecting less quiet. So far, I'm pleasantly surprised.

Oh, and ignore the booger welds. Of course, I ended up blowing through the tailpipe in a couple of spots and had to go back over a few spots. And by that time, some slag dripped in to the nozzle while welding the underside before I noticed working my way up the backside. Oh well. I'll just throw some Weber Black on it after I make sure it's not leaking and call it good.

 

At the end of the resonator you may want to weld in a support to the muffler end. May not be needed but cheap insurance. Looks good!

 

Ah, right. Thanks. I had planned to but, of course didn't. I did get a support on the muffler body at least.

 

I talked to Keith at DD earlier concerning the location of the j-pipe resonator. I noticed a lot of exhaust shops located it before the muffler and he locates them just after the axle. He stated he saw better results. Like you I did mine before the muffler and did notice a reduction in drone at the 1900-2000 rpm. Just a FYI if drone is still an issue.

 

Got out on the highway for a minute today to get a few initial impressions.

This Flowmaster laminar flow muffler is actually quieter in most scenarios so far than the outgoing Spintech, which surprises me. I only towed around town and didn’t get up last 70 on the highway, but so far, that’s how it is. When I fired it up to pull out of the bay, I was surprised at how NOT loud it was.

The sound is more mellow but distinct; for me, a happy combo of not being obnoxious while sounding like an exhaust note should sound. Good tone, not loud.

There is less resonance in the cab. I had twin peaks at 1600 and 1800 rpm before, so I split the difference with the resonator length and targeted 1700 rpm. On the highway, those resonance peaks are reduced significantly. 1700 rpm is even quieter - like, kinda spooky quieter - so my maths appear to have been correct. When accelerating a few mph on the highway, it gets a little louder, then settles right back down to smooth and quiet. You can still hear some tone, but most - if not all - of the drone has been knocked down. I can’t say for sure yet because I don’t have a lot of seat time yet.

There might be a little more resonance around 2100 rpm but it really doesn’t seem louder if pushing right through 2100 rpm, but rather when puttering and it shifts just past 2100 rpm, then motors back through it briefly, if that makes sense. I can shorten the resonator if I feel like 2100 rpm is the trouble spot, but it would be much harder to lengthen it again if I were mistaken. So I’ll let it play out first.

At cruise from 40 mph and up, its definitely quieter.

Overall, I’m happy with the improvements and surprised by how quiet it is for a straight through type muffler. I’ll put some miles on it next week and really be able to tell. Might pull out the microphone and measure again at some point just for fun.

 

Supercharged doesn’t require bigger diameter tubing.

 

@blenton What Y pipe did you purchase for this setup?

 

Can anyone confirm if the tailpipe from the standard stock exhaust is the same exact tailpipe from the passenger side of the TRD exhaust and does Toyota sell the driver side tailpipe separate or does it sell as a pair only?

 

They are different tailpipes. TRD tailpipes have a particular 3 bolt flange, tip, and possibly even diamater. I think they’re only sold as pairs.

 

Thank you

 

Amazon special stainless steel dual 2.5” to single 3”. I think this one..

$28 Universal 409 Stainless Steel Exhaust Y Pipe, 3" Single to 2.5" Dual Exhaust Adapter Connector for Car Truck, 10" Overall Length, Weld-on

https://www.amazon.com/dp/B0BXSWG54L

 

TRD tailpipes are completely different. They’re 2.5” diameter. Stock single is 2 3/4” diameter. TRD tailpipes are also a unique flange design. We make and sell them separately

 

Thanks Keith I'm gonna send you a DM

 

You sell exhaust stuff?? I would have never guessed…

 

It’s true. The TRD flanges, we make them. Nobody else does. This customer didn’t know. Now he does. And so do you

Keith 760-877-4234

 

Ok, Keith. It appears that you don't take subtle hints well, so I'll be more blunt. In a thread that's two pages long and fewer than 60 posts, you have posted your phone number 5 times - almost 10 % of the total post count is you trying to hock your wares, and about the same number of additional posts from you disparaging or attempting to dissuade any discussion or experimentation with the topic at hand. That a lot sounds like spamming to me. And it happens on just about every exhaust-related thread here in the last several years. Your childish elementary school bullying tactics and FOMO insinuations are simply obnoxious. Please stop. I can't recall a single respectable vendor on this site that uses I'm not interested in purchasing anything from you. I WAS interested - several times in fact. I've had more than one system or muffler in my cart on your website at one time or another. But I've decided against it.

I used to value and respect your opinion - that was years ago when the hot platform was Tundratalk. You contributed to discussions and respected folks with differing options. As I see it, now, you simply criticize and berate any and all other exhaust brands, systems, setups, and thought processes different than the product you sell, as well as attempt to belittle and undermine the decisions others have made when they DON'T buy something from you. Your opinion and expertise is not longer respected because you no longer act respectable. I appears to me that you no longer value the members of the community, but the dollar bills that you can squeeze out of said members.

I'm glad you have been able to build a business for yourself. Having started from nothing and done the same thing for myself, I respect that. But I no longer respect your actions or behavior. I am tired of you bashing somebody or something on every exhaust thread that I can recall (several that I'm currently or have recently engaged in right here, even). We are tired of it. I don't want to buy your stuff. It has very little value to me.

I do value the experience of tinkering and figuring things out for myself. If you are still questioning the purpose of this thread as you clearly stated earlier, it should be obvious: I'm searching for further understanding on the subject. You used to be the kind of guy that would pitch in share what knowledge you have; now it seems the only things you share are your phone number, your opinion that you already know everything and it's a waste of time to ask questions that don't involve dollar signs, and your disdain for anything other than DD's gear. If I wanted someone to opine on the supposed best system for my truck, I would ask for opinions and for somebody to point me in a direction for me to spend my money. I am not, nor did I ever inquire anywhere in this thread.

I'm sorry to be the one to tell you this. Perhaps you are used to people worshipping the ground you walk on. I'm here to learn a few things, share what I know, and enjoy the sense of community - not to be bombarded constantly with adverts and fear mongering. Please, butt out if all you have to contribute is shoddy sales tactics.

 

There’s no way I’m reading all of that. I’m clearly living rent free in your head. If you don’t like my posts feel free to scroll along sir. Have a great rest of your night. LOL

 

@blenton Wow...hope all your endeavors pan out for you. Always thought of a guy trying to get ahead. We all have different ways. Some flourish and some try to stay afloat. (In our current economy)