New Exhaust Question

I read a lot about how a drop in muffler moves your low end torque up higher in the RPM range. Does the same concept apply with a TRD cat back exhaust? Or does the low end torque stay the same with the TRD cat back system. Also does anyone have experience with the Gibson cat back exhaust?

 

I doubt there will be much of a change either way. Some people over play the back pressure idea, as long as you stay around the same size exhaust pipe diameter you shouldn't notice much of a change.

 

I think if you stay with the stock pipe it should be ok.... Just pick the muffler you want and change it out.... I went to 2 1/2" pipe and a 18" magnaflow, it lost low end but picked up top end...
Now I added the intake spacer and wow what a combination,the motor rocks....
Now it's good on the bottom and cranks above 3000 rpm...

 

You read wrong.
Tooter has headers AND an extended length runner intake to improve bottom end.
He dyno tested a Magnaflo against his stock muffler. The difference MIGHT have been 1hp.

 

I'm only talking about adding a muffler or car back not headers and an intake?

 

Muffler and cat-back will make no difference.

There is a period at the end of that sentence.
Even on Tooter's modified system, the muffler made no difference.

 

In absolute values you're right, Rich. They're essentially the same. But there was one slight difference...

Comparative dyno runs:

stock Toyota muffler: BLUE
Flowmaster Series 50 Delta Flow muffler: RED



On the dyno, the stock muffler torque peak was reached at 2,900 rpms. The Flowmaster muffler met and exceeded the torque peak of the stock muffler 100 rpms sooner at 2,800 rpms.

While everything I've done is with the aim of shifting the torque peak lower in the rpm range, I certainly didn't expect to discover that just changing out a muffler would also lower the torque peak by another 100 rpms.

This was a totally unforeseen side effect. And while it's very slight, I'm happy to add it to all of the other slight improvements. Because when tiny effects are cumulative, pretty soon you're talking real improvement.

My torque peak is now 2,800 rpms instead of the stock 3,800 rpms.

Greg

 

Hi Mike,

What muffler you choose makes less of a difference than does the diameter of your exhaust pipe. Just generally, if you go to a larger pipe diameter, you'll exchange some of your bottom end pull for top end performance.

I'm running long tube headers and an aftermarket muffler (Flowmaster 50 delta flow), and so actually went with a slightly smaller diameter exhaust pipe than stock just to make certain that I would not lose the low end pull.

Now what mufflers do add is sound... and that's the fun part. Listen to lots of YouTube videos so you can get a good idea of which sound you like the best.

I love the sound of a nice exhaust. It's like music.

https://www.youtube.com/watch?v=cMv-imsBZLI


Greg

 

But the curve is so flat and the difference so small that one can't really say that the improvement is worth the cost... and honestly, it is close enough to be within the margin of error for the equipment.
And as I mentioned, you've done other mods to optimize the engine for low end performance. Someone with a 100% stock engine may not see the same gains that you see.

But it does sound awesome, so if the goal is for a better tone, have at it... I'm considering it for mine.

 

Well guys hate to say you're wrong but you're wrong. I have been tuning race engine for over 20 years and the exhaust will make a difference...

I have the 6 so I know what the 4.0 likes...
Going larger on the exhaust and putting on a better muffler will move the torque curve up. The problem is we want our motor to pull like a V8 but it's a V6. On the Dyno it may be a few HP but the dyno can't measure acceleration and I can tell you my truck is night and day but I have to rev it. Above 3000 rpm it is a rocket and above 4000 it screams, stock hardly pulls above 3500 rpm.
Adding an intake will move the curve up but the stock exhaust is for low end so it won't help by it's self...
Tooter's testing shows there is no free lunch you want a better muffler it will have to be louder, get a straight ( no oval ) round and it will be louder but make more HP. He added a 22" oval and netted a few HP. You already have a quiet muffler. I'm a believer in the round muffler for HP, our motor has 4 cats so an oval is over kill. they are for V8 to make them quiet..
A 14" will be loud, I have a 18" and it's not bad and no drone unless I'm towing...

So for low end just replace the muffler with a round muffler with the stock exhaust, add the intake spacer to replace the lost low end, just replace the stock air filter and get rid of the silencer and reset the computer.
Your truck will be much faster than stock, I can guarantee it.....

http://www.tacomaworld.com/forum/performance-tuning/331394-mangnaflow-6-x-18-round-muffler.html

 

Good luck then, I'm out.

 

So you're saying that replacing the factory muffler with a drop in muffler is going to make a huge difference? No way, and what do you mean a dyno can't measure acceleration. A dyno measures horsepower. Horsepower is the rate at which work is done, i.e. acceleration.

Also tooter's testing shows if anything that a baffled muffler gave better gains that a straight through muffler.

 

And both marginally better than stock.

But Mr. "been racing the 4.0 for 20 years" knows more than anyone else about a simple muffler change on a stock motor.

 

I agree. When you open up your exhaust, you move the torque curve higher in the rpm range by trading less pull at lower rpms for more pull at higher rpms.

Heck, mine is only a 4!

What mods are you running so far?

Yes, it is. At low rpms, even the stock exhaust system is underutilized and needs to retain exhaust gas velocity to take advantage of the scavenging effect.

As far as I know, Magnaflow uses the same stainless perforated core in both their oval and round mufflers.

Oval:


Round:



The ovals are just quieter because there's more packing to absorb the sound.

At the very least, it will sound faster.

By the way your truck sounds great. Magnaflows have a very distinctive sound.

Here's my 4 cylinder with a Magnaflow...

https://www.youtube.com/watch?v=e2X9wPQE2Zw




Greg

 

I agree. Mufflers are for sound and not necessarily for performance. But if you can get a good sound it's definitely worth the cost.

We did three runs of each muffler, took the best run of each, and then SAE corrected all of the comparative runs for temperature and barometric pressure so as to confirm the results as being beyond the margin error.

And although the difference is slight, the results definitively prove that a chambered muffler can perform better than a straight through muffler. This flies in the face of the conventional belief that chambered mufflers don't flow as good as straight through mufflers.

Even before the tests, I read a lot about the acoustic and flow design principles utilized in Flowmaster mufflers, and these guys are really doing their homework on constantly refining their products.

That's true. I believe that mods working together can cumulatively yield more total gains together than each separate mod if done alone.

As a Magnaflow fan for many years... I love the Flowmaster sound.


Greg

 

.

I'm saying if you are trying to maintain the most torque don't go to a larger pipe and maybe a smaller pipe.
I'm also saying if you can't tell the difference when you put on your muffler you didn't go aggressive enough on the muffler what ever kind it is. You have to make it louder to get more power. I believe a round is the most efficient muffler so why use an oval unless you want it quiet but it wont make max HP. Race bikes don't use ovals because they make less power. Drag cars have no muffler.
I can have a motor make less power that will be faster in the 1/4 or pull better. Tooter can easy pick up 5-10 hp if he cuts the pipe at the cat but he may loose torque or shift the power curve up 500-1000 rpm.
I put on a 2 1/2" exhaust with the round muffler and the difference was instant lost low end power and picked up a ton mid and top end..
My truck was instantly faster but didn't pull my trailer as good. So on the dyno It could make the same HP and I just changed the power curve or I could have lost and gained... But the motor will respond when you remove that huge cork they put on there..

 

The problem is the 4.0 is not a 2000 RPM motor the cams and intake are not set up for max power at low RPM it is a great mid range motor so you have to tune for mid range to maximize the output, Toyota chokes out the exhaust to give it good low end but it can't rev with that huge muffler. Open it up and wow it is a rocket... I was reading post after post how the cat back did nothing, well they got the wrong one...

I put on the 2 1/2" cat back with the 18" round. I put in a K&N filter (old school) removed the silencer, deleted my pcv, iridium plugs, Mobil 1 oil and gear oil, and put on the intake spacer and reset the computer. The final touch was the spacer. The intake, exhaust and spacer all work together great. Filter did little, added the exhaust made a big difference but lost too much low end, added the spacer and it runs great, above 3500 the motor just rocks, perfect for running the dunes and passing. I still have to test the spacer with my trailer but it runs so good I'm going to keep the 2 1/2" exhaust.

I wish I would have done some before testing but I didn't expect it to run this good. I plan on going to the drag strip, dyno or both...

http://www.dirtydeedsindustries.com/

This where I realized why would I run an oval if a round will be quiet enough. most of his exhaust are rounds and everyone loves his systems. So I copied him and it runs great.

I would like to see someone use a smaller muffler with a smaller exhaust to see what happens...

But keep up the good work, thanks for sharing your results. I wish I would have done some before test, now I have to do some after testing.

 

I have a 2.5" straight through round exhaust that even dumps before the rear axle. Didn't notice any gains. You must have a more sensitive ass than I do.

 

Well works great on my truck.

Did you add an intake or filter?
Did you reset the computer so it can learn the exhaust?

A lot of post say the same thing but my truck runs much better...But I have to rev it.
Over 3000 RPM the motor is night and day...

 

OK I'm going to dumb this down....

Any exhaust mods will only increase power/torque above 3000 RPM, below 3000 rpm it will just sound cool or hurt performance...

So to maintain the most bottom end use stock or smaller pipe and just change the muffler...

Same for the intake, it will increase the power above 3000 rpm.

the trick is to gain power and not loose the bottom....

http://www.fjcruiserforums.com/foru...vals/16569d1192723493-hey-guys-515-l-dyno.jpg

Headers are the best exhaust mod you can make but the gains are over 3000 rpm...

so get the loudest muffer you can stand, intake spacer, air filter, delete the pcv valve and silencer filter and reset the computer.....

If you aren't happy with that I'll buy you dinner....