question for exhaust gurus

[duke boy]

I would like to do true duals and headers on my '05 Tundra 4.7L for power and economical reasons. I understand the concept of scavenging and why you don't want large diameter exhausts and why maybe a single pipe exhaust would be better. If I were to do true duals, would I want to run 2" or 2 1/4" pipes? Would a high flow cat make a big difference or should I just get a pair of regular cats? Can you recommend some mufflers that won't be too loud but won't be restrictive? I like a v8 rumble, but don't want to tick off the neighbors and would still like it quiet inside the truck unless I punch the throttle. Quieter is better (no 40 series flowmasters). Also, I have another thread on the topic, but if anyone has comments on the SSAutochrome headers (which I am considering getting) that hasn't posted on my other thread, this is also a good place to respond to that. Also, the JBA headers fit all years of Tundra, but the TRDs only say that they fit to '02. Will they fit all years as well without modification?

[Jack Burton]

Originally Posted by duke boy

I would like to do true duals and headers on my '05 Tundra 4.7L for power and economical reasons. I understand the concept of scavenging and why you don't want large diameter exhausts and why maybe a single pipe exhaust would be better. If I were to do true duals, would I want to run 2" or 2 1/4" pipes? Would a high flow cat make a big difference or should I just get a pair of regular cats? Can you recommend some mufflers that won't be too loud but won't be restrictive? I like a v8 rumble, but don't want to tick off the neighbors and would still like it quiet inside the truck unless I punch the throttle. Quieter is better (no 40 series flowmasters). Also, I have another thread on the topic, but if anyone has comments on the SSAutochrome headers (which I am considering getting) that hasn't posted on my other thread, this is also a good place to respond to that. Also, the JBA headers fit all years of Tundra, but the TRDs only say that they fit to '02. Will they fit all years as well without modification?

Hey,

Let me introduce you to the SEARCH FUNCTION
You are asking ?'s that have been answered MANY times before....

Search on JBA or TRD headers and dual exhaust. You'll have more than enough info to make an informed decision..... Good Luck. JB

[duke boy]

yes, i have searched previous threads. It is a lot to go through to find answers, especially when you just got a new truck and have lots of questions. Also, there is lots of condradictory information on these threads. Some people like certain parts, others don't. It's hard to get factual answers to questions that should be pretty much cut and dry. From the best I can tell, the SS Autochrome headers are going to be bad for low end power and I would need to go with JBA or TRD. Are there any other manufacturers that are affordable? Does anyone know if TRD headers will work with an '05? I'd call the dealer and ask, but they are dumba$$s and I don't trust a word they say. Also, as long as you picked the right diameter pipes and the right mufflers, a dual exhaust would not hurt low end performance, would it? I'd like to run duals. They look and sound cool. Also, why are rear exit duals contraindicated for towing? I understand that they will blow the exhaust back toward the trailer but who cares? I am not transporting livestock, and not going to be towing that often anyway. Just a boat or car on occasion. Can I do rear exit or is there a reason not to?
From the other posts, it seems like people not looking for loud mufflers like Gibson. Any other suggestions of good mufflers for low-mid range power that won't be too loud but will still have a good v8 sound? Also, has anyone switched out there cats for hi flow cats?

[RockyMtnRay]

Originally Posted by duke boy

I would like to do true duals and headers on my '05 Tundra 4.7L for power and economical reasons. I understand the concept of scavenging and why you don't want large diameter exhausts and why maybe a single pipe exhaust would be better. If I were to do true duals, would I want to run 2" or 2 1/4" pipes? Would a high flow cat make a big difference or should I just get a pair of regular cats? Can you recommend some mufflers that won't be too loud but won't be restrictive? I like a v8 rumble, but don't want to tick off the neighbors and would still like it quiet inside the truck unless I punch the throttle. Quieter is better (no 40 series flowmasters). Also, I have another thread on the topic, but if anyone has comments on the SSAutochrome headers (which I am considering getting) that hasn't posted on my other thread, this is also a good place to respond to that. Also, the JBA headers fit all years of Tundra, but the TRDs only say that they fit to '02. Will they fit all years as well without modification?

True duals and headers will NOT improve your economy. No one here at TS.COM has ever gotten better mileage from exhaust mods. Generally the mileage drops badly because of a great tendancy to frequently step heavily on throttle to hear the V8 sound.

The stock cats are high flow cats. You won't gain anything from going to aftermarket cats.

Magnaflow mufflers sound about right for you.

SS Autochrome headers won't work on an '05 because your engine has air injection in the exhaust manifolds (to control emissions) whereas the '04s and earlier did not have air injection.. Pre-05 headers in general won't work on an '05 engine for that reason. TRDs will only fit '02s and earlier because Toyota moved the cats closer to the manifolds starting in '03 and the TRDs couldn't be fitted without moving the cats and thereby affecting the emissions testing. Emissions testing for CARB certification is very expensive; TRD never saw enough market to do that.

Your only, repeat only, header option for an '05 is the new JBA header...a header that is tuned for top end. All the previous reports about JBA header characteristics are pretty much null and void for an '05 engine.

To be honest, I strongly suspect that just about all the knowledge about what exhaust mods are best for improving performance on the '04 and earlier models is null and void for the '05 models...because of the VVTI and dual intake runners, the '05 has almost totally different performance characteristics over 3500 RPM.

You will be exploring new ground if you start modding the exhaust on an '05. Please let us know what works and what doesn't.

[duke boy]

When you say JBAs are tuned for top end, what RPM range are you referring to? 3500+ or just a little bit higher than what you were mentioning for pre '05 trucks? Do you think it would lower low end performance or would that stay the same? Maybe a 1 in 2 out Magnaflow catback is all I should do. It would be cheaper and less complicated than duals and serve the same purpose, especially since I don't want volume. People have mentioned the 2000RPM resonance in the Gibson. I do not want this. I had a car that did it real bad with flowmaster 40s and I hated it. I know the Gibson won't be that bad, but will the Magnaflow be quiter inside the truck? Also, I am a fan of the way rear exit duals look more than side exit but manufacturers contraindicate them for towing. I am not going to be towing all the time and not planning on towing livestock or anything but will occasionally tow heavy loads. There isn't anything wrong with rear exhaust for me, is there?

[RockyMtnRay]

Originally Posted by duke boy

When you say JBAs are tuned for top end, what RPM range are you referring to? 3500+ or just a little bit higher than what you were mentioning for pre '05 trucks? Do you think it would lower low end performance or would that stay the same?

The only real evidence so far is the Dyno chart that JBA published for the '05 header...by comparison to the stock torque curve, it shows a big bump in torque around 3800 to 4000 RPM (peak torque RPM is around 3900 with headers vs 3400 with the stock manifold). Furthermore, this Dyno chart shows a really big...and I mean BIG...drop in torque versus stock at RPMs below 3000. Since the '05 engine essentially retunes itself at about 3500 RPM, JBA pretty much had to pick the low-mid range or the top end range to optimize for (since headers don't retune themselves) and my impression is they went with torque optimization in the 3500 RPM and up band. Looks to be a great header for folks who want to increase the "sport" (top end) performance of the truck; seriously doubt if it will be a very good header for those who want to improve towing torque in the 2000 to 3500 RPM range. By contrast, the JBA headers for the pre05s seem to be optimized for the 2600 to 4000 RPM band and work very well for enhancing towing torque. With JBA headers and a Gibson muffler on my '03, the peak torque RPM actually was lowered from 3400 to 3200.

Maybe a 1 in 2 out Magnaflow catback is all I should do. It would be cheaper and less complicated than duals and serve the same purpose, especially since I don't want volume.

Single inlet/dual outlet catbacks are a guaranteed way to lose low end torque. I can't think of a single such 1 into 2 system that hasn't hurt torque.

People have mentioned the 2000RPM resonance in the Gibson. I do not want this. I had a car that did it real bad with flowmaster 40s and I hated it. I know the Gibson won't be that bad, but will the Magnaflow be quiter inside the truck?

Gibson has very minor drone, especially if you do a muffler replacement and not install a catback. I haven't driven with the stereo on for nearly a year, have very sensitive hearing, and hardly can hear any drone from the Gibson on my truck. A Magnaflow will make more noise in the cab; it will be a lot noisier in the cab at the higher throttle openings that are needed for towing. Gibsons don't produce any V8 sound above idle...since you want that sound, you'll have to use a louder muffler...Magnaflow, Borla, Dynomax are all reasonable alternatives.

Also, I am a fan of the way rear exit duals look more than side exit but manufacturers contraindicate them for towing. I am not going to be towing all the time and not planning on towing livestock or anything but will occasionally tow heavy loads. There isn't anything wrong with rear exhaust for me, is there?

There are two primary reasons for the contraindication of towing with rear exit duals.

The first is the strong likelihood that you'll get hard to remove soot and other exhaust contaminants plastered on the front of whatever you're towing. Tundra V8s do produce some unburned carbon which accumulates in the exhaust pipe...they also produce liquid water condensate in the exhaust during the warmup process (especially in cool weather). The '05 engine has more valve overlap at high RPM (one effect of the variable valve timing)...more overlap means more unburned/partially burned fuel gets into the exhaust (the reason that Toyota had to resort to air injection)...and that all adds up to a greater likelihood you'll have noticeable amounts of carbon in the exhaust pipe. Stomp the throttle hard to get a heavy "rig" up to speed and you'll likely splatter black crud all over the front of whatever you're towing.

The second reason is reflected noise. This is particularly an issue when towing travel trailers (or any other trailer with a large, hard front surface that readily reflects sound). Since aftermarket dual exhausts are almost always associated with much louder than stock mufflers, the sound reflecting off the front of the trailer can produce nearly deafening sound pressure levels in the cab. At certain RPMs and truck/trailer distances, there can also be very strong resonances. One of my neighbors has a Chevy truck with dual exhausts (each pipe equipped with a fairly sizable (30 inch) glasspack muffler) and originally he had the muffler shop route them out the rear. Then he got a travel trailer and it only took one towing trip to convince him that the in-cab sound level from reflected sound was so high that he and his family were going to have major hearing problems (he was still partially deafened 2 days after returning from just a 200 mile trip and just kept saying "loud" over and over again ). Before he towed again, he had the muffler shop aim the exhaust tips to the side of the truck so the sound wouldn't be aimed directly at the front of his travel trailer. He told me later that just re-aiming the exhaust outlets made a huge reduction in sound levels and that he and his family (especially their little girl that rides in the back seat) could still hear pretty well at the end of a trip.

[mtnsports]

wow..very very helpful stuff! thnks a bunch sounds like i might not do to much to my 05 as far as exhaust goes ..still thinkin of airbox/airfilter stuff
also, VVT..sounds good..but also sounds pretty complex....

05 dblcab v8 4x4

[rexallen13]

The standard air box is better than the K & N FIPK system. I can attest to that as I switched back to the Toyota system. Most posts I've seen say to stay stock. If you must waste your money than change.