custom y-pipe or stock y-pipe?

[grytundra]

im looking to get exhaust done on my tundra, but what should i do about the y-pipe leave stock or go custom ? 2.25 or 2.5?
thanks

[jkib]

What some say that have experimented with exhaust systems is to leave it stock and just install a good flowing muffler. Do a search in the engine forum under tundra exhaust or headers.

[v8Toilet]

The stock y-pipe looks restrictive but is actually a good merge collector. A supercharged Tundra with a stock y-pipe put down 300 rwhp on the same dynamometer where I put down 220 on the same day.

I’ve also changed mine for the SS-autochrome clone of the JBA y-pipe and didn’t notice any difference except more noise. It was leak prone so I went back to stock.

I say you should not mess with it because I believe it’s an engineered part made to support low and mid range torque. The kind of low and mid range torque a heavy truck like yours needs to get it moving.

From all my experience of trying different exhaust systems and headers, doing dynamometer runs, testing at the track, the only exhaust parts worth improving for more power on a naturally aspired V8 Tundra are the muffler (not the exhaust pipe) and the manifolds. Don’t change out the whole exhaust with a cat back 2-1/2” system but just change the muffler and keep the stock 2-3/8” exhaust pipe if you want the best most improved low and mid range torque.

[AC]

Your exhaust is only as good as the smallest restriction. When I removed mine, it seemed to be very restricted and replaced with the ss autochrome one.

[helica]

Sorry, but free-flowing is not always best. People complain about "restrictive" stock exhaust... but you NEED that restriction to create the low-end grunt. I agree with what was posted originally... Replace the muffler with a nice free-flowing one (I love my Magnaflow 18" Center/Offset) and leave the stock piping alone.

[Jetes03tundra]

helica, what is the part number on your 18" magnaflow?

[v8Toilet]

Originally Posted by helica

Sorry, but free-flowing is not always best. People complain about "restrictive" stock exhaust... but you NEED that restriction to create the low-end grunt. I agree with what was posted originally... Replace the muffler with a nice free-flowing one (I love my Magnaflow 18" Center/Offset) and leave the stock piping alone.

Helica I dissagree with you and here's why. This is from one of my previous posts. I just don't feel like writing it so many times.

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 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 it's 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.

[AC]

I think mine was extra pinched. Man, I felt like I was in high school again pinched. If I still had that piece, the cut-away picture would tell the story. It looked like someone had just smashed the the two pieces together. I like it better now with the 18" Mag. muffler. MO anyway.

[helica]

Originally Posted by v8Toilet

Helica I dissagree with you and here's why. This is from one of my previous posts. I just don't feel like writing it so many times.

I skim-read your post and it sounds like you do agree with me?