You are currently viewing our community as a guest, which gives you limited access to view most discussions and access our other features. By joining our Member Supported community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload photos, content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!
If you have any problems with the registration process or your account login, please contact us.
Engine & DrivetrainDiscussions about the engine and drivetrain of your vehicle.
This is a discussion thread titled "TRD Duals vs. Banks Monster Exhaust", within the Engine & Drivetrain forum, part of the Technical & Vehicle Assistance Forums category.
Well I need to make a decision here of what i am going to do. I have an opportunity for some TRD Duals at a great price (used) or to try the Banks system, again at a great price.
I guess my last question is this....The TRD is not a true dual system w/ the air exiting 2, 2.5" pipes. Is this worse than having a system w/ a single outlet w/ a 3" pipe?
I my logic, it seems the single outlet would be better w/ less power loss.
Anyone Anyone....Help me out here.
Well you know you won't be happy with the power of the TRD, but you know you like the sound. You aren't sure of the power of the Banks, but it is probably better. What kind of muffler does the Banks use, chambered or stuffed? I'll bet the Banks sounds great and will probably give you better results. I say try the Banks and see what happens.
__________________
"You play the hand you're dealt. I think the game's worthwhile." -C. S. Lewis
I saw the add for the Banks system too and wondered if anybody had tried it. I've seen everything on this site - Bassanni, TRD, no muffler, Flowmaster... From everything I've read/heard, the smaller pipe seems to work best for the NA engine. Has anybody ever done a dyno comparison of the various mods?
I've read so much stuff on this site, that I've just left my stock pipe/muffler in place. I'd really like to have the rumble of my old Chevy, but I don't want to kill the performance to get it. I've never changed the air intake for the same reason. The cost of the K&N FIPK seems to outweigh the performance increase...or decrease depending on who you talk to.
Why does less back pressure seem to kill the low-end on the 4.7L? Does the lack of back pressure scavenge too much of the inlet charge from the cylinder during valve overlap?
Well I need to make a decision here of what i am going to do. I have an opportunity for some TRD Duals at a great price (used) or to try the Banks system, again at a great price.
I guess my last question is this....The TRD is not a true dual system w/ the air exiting 2, 2.5" pipes. Is this worse than having a system w/ a single outlet w/ a 3" pipe?
I my logic, it seems the single outlet would be better w/ less power loss.
Anyone Anyone....Help me out here.
Not going to tell you one way or the other, but be sure to let us know how you like, it and if you don't (sell it on here for cheap)
just kidding.
I saw the add for the Banks system too and wondered if anybody had tried it. I've seen everything on this site - Bassanni, TRD, no muffler, Flowmaster... From everything I've read/heard, the smaller pipe seems to work best for the NA engine. Has anybody ever done a dyno comparison of the various mods?
I've read so much stuff on this site, that I've just left my stock pipe/muffler in place. I'd really like to have the rumble of my old Chevy, but I don't want to kill the performance to get it. I've never changed the air intake for the same reason. The cost of the K&N FIPK seems to outweigh the performance increase...or decrease depending on who you talk to.
Why does less back pressure seem to kill the low-end on the 4.7L? Does the lack of back pressure scavenge too much of the inlet charge from the cylinder during valve overlap?
Larger pipe diameter lets the exhaust gases cool more while in the pipe causing the gases to expand. This creates back preasure at low RPM's. High RPM's force the exhaust through the pipe before it can cool off.
Bigger exhaust pipe actually has MORE backpressure at low RPM
Quote:
Originally Posted by ThomasMore66
Why does less back pressure seem to kill the low-end on the 4.7L? Does the lack of back pressure scavenge too much of the inlet charge from the cylinder during valve overlap?
The reality is the bigger aftermarket pipes (or duals) actually have more (NOT less) backpressure than the smaller stock pipe at lower RPM. Bigger pipe does have less wall friction per square inch of cross section than a smaller pipe and that's what causes people to intuitively assume that the larger pipe will present less resistance to the flow. And that would indeed be the case if exhaust gasses were the same temperature as the surrounding air and if the gasses were a uniform steady flow.
But exhaust gasses start out at the engine many hundreds of degrees hotter than the surrounding air and they also are composed of pulses with leading and trailing wave edges. As the gasses flow down the pipe, they cool, lose energy and become more dense...IOW they lose their velocity and become harder to push out. To minimize loss of energy, the gasses must not be allowed to expand before they exit the tailpipe. Furthermore, if the wave forms aren't handled right, you get an enormous amount of turbulence inside the pipe which causes much resistance to flow. A larger than optimum pipe size (IOW anything larger than stock) allows way too much adiabatic cooling due to gas expansion...and it allows too much loss of wave form/increase in turbulence. The net result is a larger pipe presents more, not less, backpressure to the engine at lower RPMs than the smaller stock pipe...and that is what kills the low end torque.
As for overlap, first of all this engine has little to no valve overlap since it was optimized for low RPM torque and not high RPM horsepower (that's why it has such long intake runners). Second, if a lack of backpressure were to cause problems with scavenging, headers would cause power losses (and not produce the dyno proven power gains) since headers do actually reduce backpressure at the valves.
The bottom line is that scavenging is good and backpressure is bad. That's why headers improve the low end torque on this engine. And it's also why a bigger than stock pipe kills torque because it actually increases back pressure at low RPM.
__________________ Ray
Natural White '03 Access Cab V8 SR5 4X4 with TRD Off Road Suspension, Limited Slip Differential, and Towing Package
Towing & Performance Mods: JBA Headers, Gibson Muffler, 4.30 gears, Michelin LTX M/S Tires, Hellwig Anti-Roll bar, Prodigy Trailer Brake Controller, Autometer Z-Series Transmission Temperature Gauge, Magnefine Transmission Filter
Utility & Misc Mods: Genuine Toyota OEM Step (Nerf) bars, Peragon Tonneau Cover, TracRac Rack and Rail System, Muth Signal Mirrors, Pop&Lock tailgate lock, TruSpeed speedometer calibrator, "$20" RS-3200 Upgrade, Auto-Dimming mirror w/ Temp and Compass, Clear/Red/Clear Taillights with Silverstar Signal bulbs, 3M Clear Bra
Sorry Ray, just a little humor on my part! Fact is though, if it wasn't for your in-put, into these discussions, we'd ALL be... a lot less wise about this. So, for all TS members...
Dave
__________________ 2004 SR5 Double Cab 4x4 w/TRD Pkg. Mods to Date:
16" 5 Spoke Brawn Enkei Wheels, Keyless Entry, Line-X Bed Liner, Challenger Running Boards, Husky Floor Liners, Bug Flector II (painted to match), Colegan Bra, Borla Dual (Side-Exit) Exhaust System, 2" Wheeler's Coil Lift, TRD Add-A-Leafs Mods to Come:
265/75/16 BFG A/T's, Possible Mods:
Seat Covers, 3M Clear Bra (hopefully... just cost so friggin' much!)
Sorry Ray, just a little humor on my part! Fact is though, if it wasn't for your in-put, into these discussions, we'd ALL be... a lot less wise about this. So, for all TS members...
Dave
LOL. Yep, a little humor was needed here. And I'm glad my lessons on the deeper thermodynamic and acoustic physics of exhaust flow are being appreciated by at least some.
But on a slightly more serious note, if we Tundra owners are going to achieve usable gains in power through bolt on modifications, we've got to get beyond what I refer to as the "garden hose model" of exhaust or intake air flow where "bigger is always better". A big (and loud)...or dual...exhaust pipe may indeed build up self-esteem and impress other guys...though it may also cause a lot of women to laugh, point, and make derisive remarks about "trying to compensate for other inadequacies". But choosing pipe size without a thorough understanding of the underlying physics, including a good understanding of thermodynamics, fluid wave forms, effects of turbulence, etc., is generally going to result in torque loss, not a torque gain.
__________________ Ray
Natural White '03 Access Cab V8 SR5 4X4 with TRD Off Road Suspension, Limited Slip Differential, and Towing Package
Towing & Performance Mods: JBA Headers, Gibson Muffler, 4.30 gears, Michelin LTX M/S Tires, Hellwig Anti-Roll bar, Prodigy Trailer Brake Controller, Autometer Z-Series Transmission Temperature Gauge, Magnefine Transmission Filter
Utility & Misc Mods: Genuine Toyota OEM Step (Nerf) bars, Peragon Tonneau Cover, TracRac Rack and Rail System, Muth Signal Mirrors, Pop&Lock tailgate lock, TruSpeed speedometer calibrator, "$20" RS-3200 Upgrade, Auto-Dimming mirror w/ Temp and Compass, Clear/Red/Clear Taillights with Silverstar Signal bulbs, 3M Clear Bra
This is why I love this site. I got some info from Banks and the exhaust looks really really nice, BUT they did not send me any #'s on dyno results.
Thanks again for your input, I have learned a lot about how the exhaust works on our trucks and have done a lot of weighing out of what is important to me in terms of buying one.
Thanks again for everyones input. It has been a huge help.
It’s been a while since I was in college, but I do remember that the exhaust gas expands reversibly and adiabatically to atmospheric pressure. Also the gas exiting the gas will attain a high velocity (progressively slower with each molecule of gas exiting the cylinder). The entire process takes on a wave form due to the other cylinders exiting into the same exhaust. So, you end up with the expansion process (nice for turbo’s which are an isentropic expansion if I remember right) and a wave pulsation.
Now, my last Chevy seemed to thrive with the open exhaust, but I did have two different sets of headers (collector length/diameter changed the torque curve) which did affect the low-end of the car. The longer collectors made a positive change in the low-end.
The only other vehicles that I’ve had that did not seem to like the open exhaust were 2-stroke Yamahas. Now I realize the 2-stroke and 4-stroke models are not the same, but too little back pressure resulted in the inlet charge partially leaving the cylinder. Back then my teenage mind had some trouble understanding that concept.
So, that brings me back to the 4.7L. Does the design of the headers (JBA, TRD, etc) create a slight suction on each cylinder as the other exhaust valves open? I noticed that you have the JBA headers and only a Gibson muffler on your truck. I’ve seen other header manufactures make this claim-the Doug Thorley Tri-Y comes to mind. Does anyone have an opinion on the Bassani exhaust? I’ve sure seen that name on this web site quite a few times.
For the Tundra...only cat back. Other trucks I am not sure of. Did not look into them.
I got some info from Banks...they are VERY well made exhausts and look great, but they did not send me any dyno #'s. Kind of a let down that they did not pony up the #'s. Just too bad.
JOHN
Fact is though, if it wasn't for your in-put, into these discussions, we'd ALL be... a lot less wise about this. So, for all TS members... 
Glad the physics lesson was appreciated.
But choosing pipe size without a thorough understanding of the underlying physics, including a good understanding of thermodynamics, fluid wave forms, effects of turbulence, etc., is generally going to result in torque loss, not a torque gain.
thanks for posting up your thoughts 
