Custom exhaust or stock Exhuast for Tundra.

[skater911]

I have a 2005 Tundra V8 Sr5 with TRD off road package and the TRD limited slip diff. I was thinking about adding an exhaust for maybe a little bit of a performance boost, but mainly for sound. Here's the deal, I will in the future be towing a sandrail and a couple of quads probably no more than 4000 lbs. I have seen the threads about cat back systems being detrimental to torque. That is the one thing I refuse to give up. I spoke to a local shop who advise the best route is to go 3 inch pipe for the intermidieate pipe to the muffler (he advised on flowmaster) then 2.5 for the tail pipe. He said that going back down to the 2.5 will regain any torque the 3 would have lost, thuis creating more back pressure. Should I go with this or just stay with my stock exhaust?


Thanks again.

Also do intakes hurt your torque curve???

[RockyMtnRay]

Originally Posted by skater911

I have a 2005 Tundra V8 Sr5 with TRD off road package and the TRD limited slip diff. I was thinking about adding an exhaust for maybe a little bit of a performance boost, but mainly for sound. Here's the deal, I will in the future be towing a sandrail and a couple of quads probably no more than 4000 lbs. I have seen the threads about cat back systems being detrimental to torque. That is the one thing I refuse to give up. I spoke to a local shop who advise the best route is to go 3 inch pipe for the intermidieate pipe to the muffler (he advised on flowmaster) then 2.5 for the tail pipe. He said that going back down to the 2.5 will regain any torque the 3 would have lost, thuis creating more back pressure. Should I go with this or just stay with my stock exhaust?


Thanks again.

Also do intakes hurt your torque curve???

Your muffler shop guy so full of ignorant crap that I would run as fast as I could as far as I could from that shop.

First of all, you don't want any backpressure ever...it's evil and kills performance. Second, oversized pipes (and 3 inch pipes are definitely oversized) actually produce more backpressure than the stock 2 3/8 inch pipe below about 3500 RPM. Even 2 1/2 inch pipe is too big for this engine, particularly at low to mid RPM and produces more back pressure than the stock pipe. Finally, a Flowmaster is the worst possible muffler you could ever choose for towing if you want to keep your low to mid range torque and your hearing. Even a 40 series FlowRestrictor muffler has barely a third of the flow of a decent muffler like a Dynomax...and the 50 and 70 series (particularly the Delta series) are even worse. And compounding the problem, a FlowRestrictor makes so much noise that your hearing (and brain) will be numb and fatigued after just a couple of hours of towing.

The reason that any exhaust over 2 3/8 hurts low/mid performance...and produces more backpressure than stock...is that it allows too much expansion and cooling of the exhaust gas. The expanded/cooled exhaust gas acts like a huge plug inside the exhaust system...and creates increased backpressure. Allowing the gas to first expand/cool inside a 3 inch pipe and then constricting it back to a 2 1/2 inch pipe is even worse.

If you're not ready to do this correctly (i.e. install headers first), then at least install a decently flowing muffler in the stock tailpipe. If you want a noticeable sound, use a Magnaflow or possibly a Dynomax. If you want quiet, use a Gibson. But whatever you do, don't be so stupid as to install a noisy, restrictive FlowRestrictor in the hopes you will improve your towing performance.

And in any case, keep in mind that you don't own some domestic truck that was severely underengineered and has lots of easy to grab performance increases. As been said here many times before, Toyota's engineers have gotten all the "low hanging fruit" from a performance perspective. You will be extremely hard pressed to get any performance gains from an aftermarket exhaust until you remove the real "plug" in the exhaust system which is the stock manifold. In most cases, you will actually hurt your performance by going to an aftermarket exhaust unless you first replace the manifold with headers.

As for intakes, yes, most (particularly AEM and K&N) do hurt the torque curve below about 3000 RPM. There's very little dyno data for RPMs under 3000 but there are several reports here at TS from very credible members and they've universally reported loss of low to mid range torque, particularly for towing, on trucks with K&N intakes. The one possible exception to this loss of low end torque is the Volant intake; there are some indications that it actually helps low end torque.

[skater911]

Awesome info, thanks alot I was hoping you would see this post, I saw a lot of earlier posts you did.

I guess it is back to the drawing board.

[07 firecrew]

sorry to but in guys, but i installed the magnaflow(5x11x22) stainless, i think it's a #13586. i can tell you from experience, the 2.5 pipe, will out perform the factory system, everywhere. take it to the bank.

[skater911]

What about your low end, how much did you lose?

[H2O_MAN]

Following Ray's advise I have installed my JBA headers and will put at least 500 miles on the truck to let the ECU adjust.
I will then weld in a Gibson Superflow muffler and be done with my exhaust mods.

Sidebar: I purchased the Gibson 788500S muffler and found
it was a little to long (24" body vs. 22" stock body length) --
This would require unwanted extra cutting to weld in place.
Stylinconcepts.com is letting me exchange the muffler
for the next smaller one (p/n 788200S with a 19" body).
The 788200S should weld into place easily

[dsrtrcr01]

Originally Posted by skater911

I have a 2005 Tundra V8 Sr5 with TRD off road package and the TRD limited slip diff. I was thinking about adding an exhaust for maybe a little bit of a performance boost, but mainly for sound. Here's the deal, I will in the future be towing a sandrail and a couple of quads probably no more than 4000 lbs. I have seen the threads about cat back systems being detrimental to torque. That is the one thing I refuse to give up. I spoke to a local shop who advise the best route is to go 3 inch pipe for the intermidieate pipe to the muffler (he advised on flowmaster) then 2.5 for the tail pipe. He said that going back down to the 2.5 will regain any torque the 3 would have lost, thuis creating more back pressure. Should I go with this or just stay with my stock exhaust?


Thanks again.

Also do intakes hurt your torque curve???

I live in Esco as well. I took mine to Precision mufflers right off the 78. It is in San Marcos. I had a muffler welded in place of the stock one for I think around $60 (Not including the muffler price)???? It is off the rancho santa fe exit on the right side of the freeway when you are going west bound. It is a small hole in the wall shop but the guy does good work and knows alot about exhausts.

[Jordansrealm]

I have your truck and currently I am running the JBA Headers and 2.5" Exhaust. I love it and it sounds awesome. The power band is now much smoother and much quicker. Dont get caught up in low-end loss with exhaust systems like everyone seems to. Adding an exhaust ONLY to your truck isnt going to hurt your system and even if you lose lets say a few pounds of torque the power, flow, and sound you gain are more than worth it. If you are ever in Orange County let me know and I will give you a ride.

Jordan

[ThomasE]

It would be best for your situation to cut out your stock mufflfer and weld in a new one. I did that after I already installed the JBA headers. With the headers I immediately felt more power. After I added a Magnaflow (2.5" in/out) keeping stock piping, it sounded a lot nicer. But I can't say I fell any gain. At the same time, I'm sure I didn't lose any torque either.

[skater911]

Thanks for all the replies, I appreciate all the info. I will let you guys know what I end up doing.

[Burl]

Why or how does the TRD dual system work when other duals don't?

[RockyMtnRay]

Originally Posted by Burl

Why or how does the TRD dual system work when other duals don't?

It doesn't...the TRD duals suffer from the same loss of low to mid range torque as all the other "systems" that use dual 2.5 inch pipe from the muffler back. There have been several credible TS members who have tried the TRD duals and then gotten rid of them because of unacceptable low end torque loss.

Some muffler back dual exhausts (TRD is one) do improve top end horsepower (3500 RPM and higher) plus, to some people, they sound and look better than the stock exhaust.

The only dual exhausts that don't hurt low end torque are those custom systems that use a true dual pipe all the way from the cats back...and that's only if small (not larger than 2 1/4 inch or 2 inch) pipe is used as well as having an H- or X- crossover right behind the cats. A properly designed and crafted custom system like this with stainless pipe, a Dr Gas X-crossover, and quality stainless mufflers (Borla, Magnaflow) will typically run $800 or higher. And even then, the low end torque is not any better than you can get by simply replacing the muffler in the stock single exhaust with a good flowing aftermarket muffler (Magnaflow, Dynomax, Gibson).

[PagalDesi4Life]

Originally Posted by RockyMtnRay

First of all, you don't want any backpressure ever...it's evil and kills performance.

When I went to a muffler shop to see if it was possible to install cutouts on my Sequoia, he said he didn't reccomend it since its only used for racing and that the car wouldn't have enough backpressure which is needed to run the v8.

RockyMtnRay, are you saying that no backpressure is good when towing or just in general driving?

[dsrtrcr01]

Originally Posted by RockyMtnRay

First of all, you don't want any backpressure ever...it's evil and kills performance.

Is this just for the Tundra? I know that the older Toyotas, late 80's early 90's run a whole lot better and have more low end with back pressure. Also the smog does not work with no back pressure on these older trucks. I had an 84 with open pipe 2.5 inch all the way. Once I put in a spintech and dropped the size to 2.25 after the muffler it had much more grunt on take off.

[Xtrema]

One thing we all should remember is that backpressure is something that the engine designers consider when specifying the intake and exhaust valve overlap. It is not backpressure that is bad. It is removing backpressure when the engine designer wants it. The exhaust valve is normally coming to its closed position as the intake valve is opening. (Even in DOHC engines there can be valve overlap.) The fresh air / fuel charge displaces the residual burned inert exhaust gas. When backpressure is reduced, some of the fresh air / fuel charge leaves the cylinder and goes out the tailpipe, right before the exhaust valve closes. So, your engine has less air / fuel to burn, and creates less cylinder pressure and torque to move your hot rod. Sounds crazy, perhaps, but it can and does happen. Perhaps you can hear my deep baritone voice of experience?

Other elements of gas flow dynamics include the resonance of the pipes. Diameter, changes in diameter (i.e. mufflers), location of mufflers relative to the previous diameter change, all have an impact on flow and flow resistance. This is more commonly seen on intake manifolds, such as those cars with two runners per cylinder for different rpm ranges.

The Toyota VVT-i cam adjustment attempts to maximize torque by changing the cam timing with respect to engine speed. The flow rate and when the flow reaches the cylinder are very important to maximizing torque.