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Discussion Starter #1
I have done a ton of research on this subject and thought it would be helpful to a lot of member's here if I shared some general knowledge.

There are 3 general ways to quiet down an exhaust system on a vehicle. Restriction, Reflection, and Absorption. Guess what OEM uses. Unless it's an exotic car it's likely restriction. Reflection is what some aftermarket companies use but on the top end of the RPM range they will actually restrict flow as much or more than stock. Absorption is what exotic car manufacturers and high end muffler manufacturers use. On a medium level production line the reflection style muffler is the cheapest to manufacture.

Let's touch on the subjects of restriction and backpressure. Most engines need some backpressure in order to scavenge properly. Backpressure and scavenging are 2 different things yet they work together. Everybody has a friend who has violently shouted, "you need some backpressure to make power!" But has anybody ever thought about why you need that backpressure? Without backpressure you wouldn't have scavenging. Scavenging is what makes power, not backpressure. That's why you lose power by putting on a huge cat back but leaving your stock manifolds and y pipe.

Take my truck for example, how can I get away with true dual 2.5" tubing with flow through mufflers? The backpressure and scavenging has been greatly improved by adding Long Tube Headers. All the backpressure this engine needs is in the headers since the exhaust is able to scavenge so efficiently. In other words at peak volumetric efficiency the headers actually 'siphon' the exhaust out of the head. Unlike stock manifolds which have much less scavenging, the exhaust needs to be pushed out of the head into a high backpressure low flowing manifold.

The next most restrictive area the exhaust needs to overcome in a stock exhaust system is the 'y' pipe. Whether crimped to nothing like stock, or crafted together professionally by an exhaust shop the 'y' pipe is VERY restrictive. Then hit the cats, the resonator, the muffler, and finally the huge crimp bend to go up and over the rear end. Each of these things by themselves are very restrictive not to mention when you put them together on an entire system.

Exhaust flows exactly like traffic on a freeway! Put 4 on ramps like 20 feet away from each other with no runway and expect the merging cars not to slow down traffic(manifold). Then line the lanes with 6 foot high poles just far apart enough to squeeze your vehicle through.(cats) Now merge 8 lanes into 4. (y pipe) Then make 20 off ramps on each side of the freeway and no runway's.(resonators) Put a maze of different roads going all different directions but ending up in the same location to exit the maze.(muffler) Finally put a huge curve with 2 less lanes.(up and over the axle.)

If properly built the exhaust would flow like 4 long sweeping on ramps, (headers) Each bank would never merge but instead flow out of the tailpipe using long sweeping curves that never lose a lane.

The above analogies are EXACTLY how exhaust flows. For all you hydraulics experts out there, you can also picture the exhaust as water traveling through pipes. The OEM didn't design the manifolds to lose power, they didn't design the crimped 'y' pipe to lose power, nor the resonator, muffler, tailpipe. They designed them to make the system quiet and lose the least amount of power possible while targeting a specific decibel at a target price on a large scale production level! So in other words, cheap, quiet, fast. I was always curious as to how much was lost so I built my own system using S&S Longtubes, 32 horsepower to the wheels! Mileage has also increased as long as I don't drive like a jack-***.

Since most aren't going to spend the money on a full race exhaust system, I'll stay focused on the 2 systems that would make the most power on these trucks. I have tried almost every configuration possible with dyno testing on some of them. I will write part 2 of this when I have time.
 

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Very informative. Please post up more on this a I am just beginning my research into this area.
 

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Discussion Starter #3
Very informative. Please post up more on this a I am just beginning my research into this area.
Hey, I just edited the article, I fell asleep last night punching the keyboard:first: I woke up in the middle of the night and pushed submit.

I'll write part 2 tonight.
 

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BUMP BUMP - More articles? please?
 

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BUMP BUMP - More articles? please?
Thanks for the reminder!

Most Tundra owners aren't going to go 'full race,, meaning no cats'. To me it's still up in the air as to whether it's even beneficial. I've read lots of fact and opinion on the subject. I have recently built a new 'h' pipe for my 'full race' system. This pipe removes the cats. I can tell you this, when I went from single to dual, with cats, there was a REAL noticeable difference! The truck came alive. Going cat free, can't say I notice much. I am in the process of experimenting with new mufflers since my current design is waaaay too loud with tri y long tubes and no cats. Once I've made the mufflers I'm gonna stick with, I'll put it back on the dyno. In the mean time back to the subject.

Once again most people won't go full race, it's too expensive. From what I've seen there are 2 types of guys. Both want more sound and power. One is willing to spend some money and the other either can't or isn't willing. The guy willing to spend the money will usually buy a cat back, and the guy with not so much money is gonna just buy a muffler. The guy with the money doesn't want it too loud, but the guy without the money wants it loud.

I understand both guys since I've been both guys at some time in my life:afro:. I am kinda in between right now, I want it loud, but not open pipes loud. But back on subject! Both scenarios above can be done a right way and both can be done a wrong way.

I'll start with the cheaper way. (and there's nothing wrong with this way if done correctly) To simply cut out the stock muffler and replace with a louder one. I won't mention any names, that's not the point of this article, but I've seen this all too often! Guys cut out the stocker put on a 'v' style baffled muffler and let it dump under the truck! HUH! First off you need some tubing after the muffler, second, to put a big wall and a bunch of baffles right in the way of the exhaust flow, and third, to let the muffler resonate under your truck like that! WTF? Not to mention, you're breathing all that toxic exhaust at every stop light. Then we need to consider the flow capabilities of the muffler. The specific muffler that I am talking about was originally designed to make a V8 muscle car sound cool and flow 4 cylinders through it, not all eight!

When you put this muffler 'in the way' the back pressure increases as the rpm increases. This is the opposite of what you want. So now you ask yourself, what's the alternative? A flow through style muffler! Some guys call it a glasspack, but rest assured, a glasspack isn't what you want. Glasspack is louvered and mild steel core, outer case is too small, and they neck down to 1 7/8" on a 2 1/2" muffler. No good. You want a muffler with a Stainless Steel Perforated core with a properly sized canister and true sizing in and out. Your high end sports cars use this type of muffler why not you? If you insist on dumping this under the truck go ahead, but let me assure you, it's well worth the money/effort to run a tailpipe to the side just before the rear tire. Cut up the old tailpipe and re-weld it to exit the vehicle, don't breath that poison! You will gain at least 5HP with this set up, not lose it. You will also gain a pretty substantial throttle response and mpg.

For the guys who want it quiet and aren't afraid to spend a little money, I've got news for you,in most cases there's no need for a catback! Most lose power! Most have much larger tubing and that causes the velocity to slow creating backpressure. Unless you replace the manifolds and open up the restrictive y pipe and all the tubing from the headers to the single tailpipe you're wasting your money. If it's just about the growl and a little power/throttle response, cut out the stock muff and weld in the above flow through. It will be much quieter with the tailpipe and you will gain power!

The above scenarios are based on the 1st gen 4.7 Liters. I will continue this article in the next few weeks after I do a true dual 'h' pipe 5.7L with 2.25" tubing. I will try and include before and after dyno proof and lots of sound clips and pics. Will probably start a new thread and put a link here. Stay tuned!
 

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Looking forward to that next post. I've been itching for a better exhaust. I'll wait for more info so I can do it right.
 

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Interesting reading. Can anyone tell me how I can bookmark a thread like this in the future without having to post a comment? Do I use the permalink tab or "subscribe" tab?
 

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Discussion Starter #8
Interesting reading. Can anyone tell me how I can bookmark a thread like this in the future without having to post a comment? Do I use the permalink tab or "subscribe" tab?
Top right...click on thread tools.... In your usercp you can turn on or off automatic subscriptions
 

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I agree with everything you said, good job.:tu:
Glad somebody is using logic rather than making assumptions, can't tell you how many times I've heard people say go with a bigger tailpipe, it opens up for more HP!
 

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Discussion Starter #10
I agree with everything you said, good job.:tu:
Glad somebody is using logic rather than making assumptions, can't tell you how many times I've heard people say go with a bigger tailpipe, it opens up for more HP!
hahahahahaha, bigger pipes actually make MORE backpressure! The velocity of the exhaust slows and actually goes stagnant, the exhaust trying to exit the system hits this stagnant exhaust and it slows down, causing a back up (back pressure) in the entire system. Now instead of scavenging (siphoning) out, the engine has to push out the exhaust. This takes horsepower away from the wheels.
 

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Worse flow at lower rpms, but once the revs increase, scavenging can begin again. Had this experience with my MagnaDrone dual system. They use 2.5" tubing which seems to be a bit too big for a stock 5.7. It did wrap the tach needle over better, but so much torque was lost the truck would barely break traction off the line.
 

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Discussion Starter #13
any good flow through muffler, Borla, Magnaflow (a straight through not chambered) Gibson, BAMuffler.

The thing that is most important when choosing a muffler is that the case, perf. tubing and end caps need to be 16GA or thicker. I bought a really awesome no name brand from PepBoys. All stainless, flow through. Sounded really good. Not too loud, but you could hear it. Nice deep pitch.

One trip to Pismo and it got really loud and pieces of rusted metal began spitting out my tail pipe. It actually rusted through in a couple months. The outer case was 304 stainless (the best grade stainless there is) but the core was mild steel:confused: That's backwards! The core needs to be stainless, not necessarily 304 stainless, but mild steel 20GA is obviously going to rust.

I didn't even check this stuff out when I bought it because I just assumed it was good. I was wrong! And I paid $100! I replaced it with a Borla and it lasted until I cut it open to see what was inside.:first:

All the best stuff is used! The mufflers that I built have many similarities! The only thing that I do different from Borla is the outer case isn't all pretty with 304 stainless. It's aluminized with 3/16" end caps. It would take years to rust through metal that thick. Plus, you can throw it out your window barreling down the freeway. If you can find it you'd still be able to install it. This thing is built like a tank. You can use em for rock sliders:D

But like said before, I recommend a flow through style muffler, the same diameter as your stock tubing, 409 stainless core, about 12" long, packed with course fiberglass strands, with a 5" diameter body. Bigger is too much backpressure, smaller is not enough backpressure and it gets too loud as well.
 

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Discussion Starter #15
I have heard real good things about the Corsa. I haven't seen a cat back for the first gen tundra in person so any information I gave would be opinion not first hand. The concept is great and makes a lot of sense. I haven't personally tested it so I can't really give any good advice.

If you get one I'm sure everybody subscribed to this thread would love to see before and after dyno results. If you do it could you post the link here so we can see it? It would be nice to see another option for our trucks.
 

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More write ups? How about some observations about back pressure at idle and take-off vs back pressure at speed (like 2200-3000 RPM)?

Thanks,

Lizard
 

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More write ups? How about some observations about back pressure at idle and take-off vs back pressure at speed (like 2200-3000 RPM)?

Thanks,

Lizard
Well............I built a true dual with H-Pipe on a 5.7L Tundra a couple weeks ago. I built it out of 2.25" tubing with dual exits just before the rear tire on the passenger side. After what Mr Creosote said and what I thought would work best considering the truck is really heavy, I thought that would be the best choice for that engine. I was wrong! You could stand 8 feet away from the tailpipe and with the truck at idle it blew the exhaust on you. And not just a little, but it felt almost like a leaf blower. HAHA that is an exaggeration, but seriously, at 8 feet away the exhaust was blowing pretty hard. It reminded me of an old Mustang or something. When you stepped on the throttle at high rpm's it made this weird hissing sound, kind of like the sound coming out of a 70's land yacht with really restrictive exhaust but a 600 cubic inch big block. Modern fuel injected vehicles don't need that much back pressure. It just felt corked up. I drove it around like that for about 5-10 miles. A lot of it with a brick wall on the passenger side so I could hear the exhaust reflection. I then built a brand new system using 2.5" tubing. Waaay better. I wish I had done it from the beginning! There was zero loss of low end torque. The top end opened up too. The sound is unreal! It makes sense, these trucks make almost 100 hp more than my 03 and I gained 32 HP switching to Long Tube headers on the 03, and true dual 2.5". I was afraid that since the 07 didn't have headers it wouldn't be able to flow what the 2.5" tubing needed. I now know, these trucks really do benefit by stepping up to a little larger tubing.

I have been hesitant to post up video or a write up on this truck because the owner complained about droning on the freeway. I never took the truck on the freeway, but I did drive it on the road out by the wild animal park (in the middle of no where in the middle of the night, it's a country road that's straight) I was able to maintain freeway speed for about 3-4 miles. I only experienced droning when the lid was removed from the Volant. It actually droned stock with the lid removed. It's a weird drone that I have never heard. It's kinda high pitched yet deep at the same time. Very annoying! I didn't hear it stock or with my exhaust when the lid was on. I am kinda waiting on feed back from my friend who's truck I installed this on before I start posting up a bunch. I don't want to risk my reputation by recommending something that is going to drone.

Very simply put, drone occurs when the harmonics of the engine at a certain rpm matches the harmonics in the exhaust and body of the vehicle. As the sound and vibration exits the exhaust tubing it causes it to vibrate, that vibration will sometimes be amplified by the body of the vehicle. The sound will usually come out as a deep pitch annoying sound that rattles your head.

There are only a few main 'fixes' for drone. Obviously running tubing after the mufflers which completely exits the vehicle is the most important thing to consider when combating drone. Another way to combat drone (I've seen this on many Tundra's) is to get a video camera, like a gopro, and film the exhaust system during the drone. You will actually see the tubing vibrate. Once you pinpoint the section of tubing that is vibrating you weld thick pieces of steel to it. The steel will absorb the vibrations substantially cutting/eliminating drone. You can also weld extra hangers in those areas.

Another way to get rid of the drone is to put the muffler after the tubing that drones. I know this first hand. My 01 Dodge Ram Cummins has 4" exhaust and like every diesel I have ever owned, the first day I bought it I removed the muffler. The turbo restricts the system so much there is hardly any sound and it gets a big rig sound without being too loud. Well come to find out that when you tow heavy with a Cummins, you know a 12,500 LB trailer (empty weight) with a 4500 LB Tundra inside, the exhaust drones real badly! I searched and searched everything that I could on a Cummins forum. There was a guy who made several posts regarding his terrible drone while towing. His solution was to cut off the tailpipe just after the rear end and the drone completely went away. That got me thinking! I welded on several thick pieces of steel on the tubing just after my rear end. The drone was cut down substantially! But it was still there and it was still annoying! I then made a muffler and put it right after the rear end with the tail pipe exiting the truck completely. Like this:
Sorry Chevy, I stole your exit location:first: It still has that big rig sound at idle, and frankly it's just as loud. But now cruising on the freeway there is no drone! The muffler is right in the section of tubing that drones and it kills the vibration!

Back to the 5.7L Tundra. IDK? I need to get in the truck and hear what my buddy is talking about. I'm not sure he actually has drone, or if he's just not used to being able to hear the exhaust. He texted me a week or so ago saying that he now loved the sound and he's getting used to it, but like I said I'm not going to recommend it until I'm sure it's good. I have a friend with a gopro and we use it all the time to watch what our suspension is doing when mobbing through the whoops in Ocotillo Wells. I do have that as a resource if there is indeed a drone. I will also build resonators if necessary as they don't cut flow too badly if correctly sized. I will post pics and video of the build as soon as I get the bugs sorted out.
 

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Were you able to dyno your friends 5.7 truck before and after? You want to look at my set up sometime? I'm not too far away...right now I'm set up with DT longtubes, volant, and dual 2.25" powersticks with h-pipe. This is the last thing I need to finish on my truck before the wifey gives me the walking papers. I've been messing with it for almost a year now.
 

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yep...what I consider drone anyways (this is my CYA statement). Right around 1600-1900 rpm.

Also, forgot to mention I run dumps right after the muffler.
 
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