Dual Exhaust

[TUNDRATTU]

I had Flowmaster dual 40's exhaust put on my Tundra before I joined TS. I guess my butt-o-meter is not working very well, but I'm sure I lost quite a bit of low end power according to some of the posts I have seen. I know I have gained in the top end though. Is there anything I can do to help the low end power without breaking the bank? Would an X-Pipe help? I have also heard that some High temp paint or exhaust insulator would help retain some of the heat in the exhaust pipes and mufflers.
I also have a K@n air filter. Should I go back to OEM?
Thanks for the help ahead of time.

Buck

[Hugemoose]

I'm in the same boat as you. I have a true duel set up with 50's on it and an x-pipe built in. I had all of this put on before I joined TS. Love my sound and top end did get quite a gain, but my off the line is sluggish. I'm in college and have no money to re-do my exhaust so that's out of the question.

I am courious about the paint though......I wonder if that would work....cause I would be up for that!

[gonzo59]

i have a bassani dual exhaust with x muffler. i cannot tell any difference on loss of torque on the low end. it sure seems that the top end woke up some. truck is a o3 4wd.

[IStan]

haha, putting on flowmaster before ts.. i'm glad i'm not the only one

[rcjunkie]

Would adding headers help with the low end torque? I've read that somewhere. I have the TRD headers and duals and the Tundra has nice pickup on the low end and good top end. I didn't expect it but I let a friend borrow my Tundra and he left me with his Lexus GS300, he told me that the Tundra was pretty quick.

[Tundrav8yamaha]

I have the borla dual with catback and I don't I like the system I may be going back to stock soon. The Borla is too dam Loud and doesn't meet my expectations it also seem I loosed Low end power as well . Performance gains slightly depends But overall I think the factory is better in my opinion...

[ProEdge]

On the Dual Exhaust issue..
I have an 06 Tundra D/C with the TRD Dual Exhaust..
My brother has an 05 Tundra D/C regular factory exhaust..
Both vehicles have the same kms on them..
Now.. At the higher RPM you can definetly feel more torque, power and acceleration with the Dual Exhaust Tundra..
At the lower RPM's, the low end torque feels the same between both Tundra's if not abit higher with the Dual Exhaust Tundra..
We have compared our Tundra's and the Dual Exhaust seems to out perform the regular exhaust at both the low and high RPM's..
The comparison's were done dry, not towing..
Feedback appreciated.. (I posted in the towing forum too)

[v8Toilet]

Sorry

[v8Toilet]

You can always try to find someone who will sell you a stock exhaust system and then you can sell the exhaust system you have on TS or e-bay to recoup your money. The headers will help get some of that back and if you can get the headers and then later a single exhaust system using the stock 2-3/8" pipe than you'll gain even more low end torque and mid range horsepower.

Here is an explanation on why you loose low end power from one of my earlier posts.

Originally Posted by v8Toilet

If you want the most power with a great sound than don't spend a lot of money on a pre made system. Buy a muffler that you like and have it welded in place of the stock muffler reusing the stock pipe. Do this and you’ll gain low end torque (with a Spintech anyway). If you want a tip than buy one and have it welded on. I've learned from experience that if you increase the diameter of the exhaust tubing beyond the stock 2-3/8" pipe that you'll loose some low end torque. If you go with a cat back dual system than you'll loose even more. The problem is that most of the cat back exhaust systems out there are 2-1/2" in diameter or larger. That’s too big for a 285 cubic inch truck motor. I have no experience with true dual systems on the Tundra but will tell you that they are expensive to make and don't offer any advantage over a properly engineered single exhaust.

I’ve changed the y-pipe with an SSautochrome y-pipe and felt no difference in power. The only thing I got was a leaky rusting pipe. That Y-pipe is actually a good flowing piece and isn’t worth messing with.

Don’t be too worried about top end horsepower either. What your heavy truck needs is torque in the 2500-3500 range to make driving in everyday traffic enjoyable. The engines torque peak is @ 3400 rpm so this is the area you want to make the engine most efficient. See my dyno graphs. Here is a cut and paste from one of my previous posts.


The factory pipe is 2-3/8" OD. I measured it with my dial caliper. The exhaust gases travel through the exhaust in pulses causing the exhaust flow to slow down and speed up with the firing pulses of the engine. The smaller factory pipe keeps the exhaust gas velocity up at lower RPM so that those exhaust gases keep moving with the firing pulses of the engine. With the larger pipe diameter or dual pipes the exhaust gas pulses actually stop and go now inside the pipe at lower RPM making it harder for the engine to pump them out because energy is wasted getting the exhaust moving after it stops. This causes the engine to pump less air at lower RPM. The exhaust gases may also tumble causing flow robbing turbulence because they are moving too slowly or stopping and moving with the firing pulses of the engine.

The factory 2-3/8" single pipe is a perfectly engineered part on the Tundra. Don't increase its size if you want the best compromise between low end torque and top end horsepower. For the best torque and horsepower I have found that replacing the stock muffler with a higher flower muffler and headers like the JBA or long tube headers work best.

If you install those headers with your duals you'll get that low end back but the single exhaust, high flow muffler with stock pipe, and headers will still make more power at lower RPM than the same setup with duals.

I disagree with them that the muffler alone decreases low end torque. If they do not have any leaks, bought a 2.5" inlet and outlet muffler, and reused all the stock piping including the rear tail pipe than they should have the same results that I got. I gained some low end torque with the addition of the Spintech muffler. My graphs didn't show it because I ran the truck in third gear but my 60-foot times at the track did and they improved. My dyno graphs start at about 3000 rpm. When you first install the muffler you might not notice anything until about 500+ miles because the computer will sense the change in air flow and richen the air fuel mixture at first and then lean it out as it relearns the new air flow characteristics of the engine. The same thing will happen with the addition of headers, and other breathing modifications.

I recommended the Magnaflow muffler because it is made of stainless steel and is cheaper than the Spintech. You can get the Spintech in stainless steel but it costs about $180 vs $99. The Aluminum coated muffler though is a stout piece and should last more than two years easy. The Spintech muffler is very well made! I don’t know for sure if the Magnaflow muffler will match the Spintech muffler for power; I can only assume they will be close based on dyno comparisons I have seen of them on other cars.

The Magnaflow muffler is a straight through glass packed style muffler much like the Borla and TRD muffler. All the glassed packed style mufflers have similar sound. The Spintech muffler is a chambered muffler but it is unique in that it has spiral shaped chambers (if you can call them that). Most chambered mufflers are more like a Flowmaster with triangular and baffled chambers to reflect the sound waves back at each other and cancel them out. The Glass style mufflers use sound absorbing insulation to absorb the sound waves. They both are affective at absorbing sound but glass packed mufflers usually have a more mellow deep sound to them and chambered style mufflers have more of a raspy crackly sound to them. Chambered style mufflers like the Spintech start out deep sounding and become more raspy and quiet as the engine rpm climbs. The sound of a chambered muffler will not change as long as the structural integrity remains but glass packed style mufflers loose there sound absorbing abilities as the miles pile on because the glass packing (sound insulation) breaks down and becomes less effective over time. Some people may comment that their TRD exhaust systems have gotten louder after 20+k miles.

Many people believe that if you loose back pressure than you loose low end torque. This misconception is complete BS. Pipe diameter has everything to do with Exhaust gas velocity and that is what affects how much torque you gain or loose with and exhaust.

[topher1254]

Just to ask a question (which I will probably answer myself)...

I currently am running the stock exhaust, except for TRD headers (which luckily came on the truck when I bought it used!!). Should my next change should be (based on v8Toilet's input) replacing the stock muffler with a TRD/Spintech/Magnaflow replacement?

I'd also like to create a more efficient intake system, but it seems there is conflicting advice about the intake kits...any suggestions?

[v8Toilet]

Originally Posted by topher1254

Just to ask a question (which I will probably answer myself)...

I currently am running the stock exhaust, except for TRD headers (which luckily came on the truck when I bought it used!!). Should my next change should be (based on v8Toilet's input) replacing the stock muffler with a TRD/Spintech/Magnaflow replacement?

I'd also like to create a more efficient intake system, but it seems there is conflicting advice about the intake kits...any suggestions?

Replace the muffler only is correct Leave the stock pipe in place. The intake system is again hard to improve because often what people here on TS have ended up with is a noisier system that gives you less low end torque in lieu of more top end horsepower. The same principals that apply to the exhaust system also apply to the intake system with the air moving in pulses with the firing rate of the engine. You need a balance of intake velocity (constantly moving air) with good flow in the RPM range that your engine is designed to operate in. Without changing heads, camshafts and intake manifolds you won’t get much benefit from a huge intake system in the RPM range your engine was designed to operate in. I did some testing of an aftermarket clone of the K&N intake system made by SSautochrome and the results where slightly less low end and more noise. My truck ran slower in the quarter mile because it got off the line more slowly. Not a big difference but it was there!

You might think that you can just replace your stock air filter with one of those K&N air filters because the marketing scams from that company have convinced you that it flows more air than the stock filter and They're right some what if you compare them one square inch to one square inch. Hey it sounds good in theory right and remember that flow contraption at the auto parts store that proves it! The K&N and similar TRD air filters do flow more air per square inch of filter area than a stock Toyota air filter but the stock Toyota air filter has 50% more surface area than the K&N filter and because of that the Toyota air filter flows better than the K&N air filter overall when it is new. This is only the case with the Toyota Tundra. I don’t know about other makes because I haven’t tested those and don’t plan on it.

The difference in power between the K&N air filter and stock Toyota air filter is not much of a difference but when I did one of my dyno runs we tested this theory and the Toyota air filter indeed made a little more horsepower to the rear wheels than a similar TRD air filter, which is just a renamed K&N filter. I also tested this at the drag strip and sure enough my average time with the stock filter was slightly better than with the TRD filter or K&N.

The Toyota engineers did a great job of engineering the intake and exhaust systems for the best possible compromise between low end torque and top end power in the Toyota Tundra and left little room for improvement in the intake and exhaust systems without revamping the entire system as a whole. The stock manifolds and muffler are about it for big improvements. The stock manifolds are designed more for cheap manufacture and good fit in close quarters at the expense of flow and the stock muffler is designed for less noise at the expense of some torque and horsepower. The stock exhaust pipe diameter is an engineered diameter designed for just the right amount of exhaust velocity at lower RPM without restricting too much flow at higher RPM. Mess with this and you upset the balance! After all unless you can make an exhaust system that gets bigger as the RPM of the engine climbs it will always be a compromise between low end power and top end power. Too many people are in the bigger is better mindset and just throw these parts on without a clue about what they are doing and upset the balance of the system as a whole.

Unless you’re an automotive engineer and you’ve done your homework than all you’re really doing a guessing and hoping that the $500 dual exhaust system you just bought that would be appropriate on a much larger engine is going to net you 20 horsepower just like the universal claim makes in the literature of the companies that advertisement it. Even if you are an engineer and you do your homework you’re most likely going to find out that the stock system is actually very efficient for the power range that Toyota engineers designed it for. Ever notice that when an aftermarket company claims you get 20 horsepower if you install their part that under that claim is 100 different applications. Do you really think that you are going to get the same results from one make of vehicle to the next?

I hope I have somewhat dispelled the misconceptions here and made some sense. If not than go ahead and put that 2.5” exhaust system on and that huge K&N system on that cost you a grand total of $750 of your hard earned money and you'll gain 20 horsepower at a useless 5200 RPM but don’t look at the toque numbers at 2500 rpm because you won’t believe that you lost 7-15 lb ft of torque and your truck will feel doggie off the line because Torque is what you feel not horsepower. In fact if you don’t already know that horsepower is just a mathematical calculation derived from torque than you don’t already know that torque is what a heavy truck needs to get it’s mass moving quickly and effortlessly. Toque is the actual twisting force produced at the crankshaft and horsepower is just a function of torque * RPM / 5252 or HP = TORQUE * RPM /5252.