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Engine & DrivetrainDiscussions about the engine and drivetrain of your vehicle.
This is a discussion thread titled "conflicting exhaust info......", within the Engine & Drivetrain forum, part of the Technical & Vehicle Assistance Forums category.
So I have read on here that it is not a good idea to change our exhaust out to a 3" ( 2004 Tundra 4.7 V8). This is due to the motor setup for gas milage and compression.......
Looking on the Magnaflow website they manufacture a cat-back system that is entirely out of 3" which contridicts what others are saying on here. I was going to purchase a universal muffler from them that is pretty much dead on with what the factory specs are and change out to 3". Can anyone give me a reason not to......I figure that if Magnaflow is produceing a system with 3" for our truck and they have done the R&D then they should be right............
__________________
'01 IS 300 SOLD
'04 FX 45
70 240Z boosted/NO2 sleeper
'04 Tundra SR5 2WD DC
Many companies sell you on the idea that 'Bigger is Better', of course this is not always true. R+D needs to be done on a wide range of engine combinations. One size does not fit all in the case of exhaust. A totally stock engine will require less exhaust flow than an engine modified to flow better or one that has a supercharger for example. You will get many opinions here and out there, the best is to see how many are using what you are thinking of getting, what mods they have, and what they have experienced. My personal experience and suggestion would be to go no larger than 2 1/2", then install a nice 3 1/2" exhaust tip if you want the big look.
I agree. These companies live on selling things you like to hear not what works across the board.
Larry
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2004 Tundra V8 Limited Access Cab 4X4, Michelin 265/65/R17 ATX2 tires, Auto Dim Comp/Temp Mirror, Aero Turbine #2525 muffler, Access Roll Up Cover, Optima D31A battery, Multi-Vex adaptive outside mirrors, Eclipse AVN5510 Nav unit and Sirius SIR-ECL1 tuner as of 10/07 pictures in my photo gallery
If a combo of all these whizz bangs met their claims you'd have to syphon gas out of your tank every second day and sell the excess horsepower on the third????
Although you may not like this, the stock exhaust with a replacement muffler is the best all around set up.
Go bigger, and you lose your low-end torque. Go smaller...well...you choke your engine.
I used to have dual 2.5" pipes with an X-pipe and two F/M mufflers. My low end was....bad. I recently went back to a single 2.5" pipe with 1 F/M muffler. I simply reused what pipe I had, and put the stock y-pipe back in.
I have be VERY happy with this set up. Gave me my low end back.
__________________ David~2001 Toyota Tundra 4X4 TRD SR5~SSautochrome headers~Single 2.5" exhaust w/ Flowmaster 50 series delta flow muffler~K&N FIPK intake system w/True-flow filter~ASP underdrive pulley~Hellwig Anti-Sway Bar(removed)~Powertrax No-slip~Bilstein 5100 front and rear w/AAL~Diff breather mod~255/85 BFG M/T on Wheelers Black Steelies Type B~Custom Rocksliders~Skid Row front skid plate~Custom Transfer case skid plate
Many V8's need backpressure, the Tundra V8 will do just fine even with a 2 inch system. I have a 455 V8 and even that one does not really need a 3 inch system, but the two 3” pipes do look nice coming out at the back
Although you may not like this, the stock exhaust with a replacement muffler is the best all around set up.
Go bigger, and you lose your low-end torque. Go smaller...well...you choke your engine.
I used to have dual 2.5" pipes with an X-pipe and two F/M mufflers. My low end was....bad. I recently went back to a single 2.5" pipe with 1 F/M muffler. I simply reused what pipe I had, and put the stock y-pipe back in.
I have be VERY happy with this set up. Gave me my low end back.
You were probably running very rich with the higher flowing exhaust. Had you used electronics such as URD or Unichip to lean out the a/f ratio, it would have returned the low end without swapping back to the smaller system.
Last edited by Burger Steak & Eggs; 02-15-2008 at 07:47 PM.
I was planning on ordering my stuff from Magnaflow Exhaust Systems And Performance Mufflers - Justmagnaflow.com they seem to be the cheapest that I have found. I am thinking I am going to do a 3" from the resinator back. I will replace the factory resinator and from there back use 3". By the time that I buy the muffler, resinator, and do the install with 3" I will still be less than if I went with the Magnaflow bolt-on kit.......
__________________
'01 IS 300 SOLD
'04 FX 45
70 240Z boosted/NO2 sleeper
'04 Tundra SR5 2WD DC
Many companies sell you on the idea that 'Bigger is Better', of course this is not always true. R+D needs to be done on a wide range of engine combinations. One size does not fit all in the case of exhaust. A totally stock engine will require less exhaust flow than an engine modified to flow better or one that has a supercharger for example. You will get many opinions here and out there, the best is to see how many are using what you are thinking of getting, what mods they have, and what they have experienced. My personal experience and suggestion would be to go no larger than 2 1/2", then install a nice 3 1/2" exhaust tip if you want the big look.
then why would they post up a dyno showing the results with the 3" piping change. I personally know from experience on a 2JZ motor I-6 that the increase in piping achieved a higher TQ rating as well as HP on the dyno. I was N/A on a 3.0 liter motor....this is a 4.7...........I currently have 2.5 piping on my L24 2.4 motor......it just seems to me that 2.5 would be restrictive....
__________________
'01 IS 300 SOLD
'04 FX 45
70 240Z boosted/NO2 sleeper
'04 Tundra SR5 2WD DC
You can easily use bigger piping and it will make a difference, however too big can be defeating. I have an older Toy with a 20R bored out to 2.4L running 10:1 with a 500 CFM Holley, mid range high duration cam and long tube headers. I experimented with 2.5" and thought I had something good. Later on I re-did the system with 2.25" piping and saw a vast improvement in mid range. That 1/4" of cross-section made a big difference and gave me additional power where I wanted it.
The normal rule is that backpressure improves bottom end and open flow improves top end performance. The whole trick is to strike a balance for the best overall performance and sound quality, unless you have a specific RPM band in mind. Publishing a dyno number is meaningless if it is out of the normal RPM range you use for most of your driving. Simply having more high RPM power may not help if it takes longer for you to get there because your bottom end has suffered. I would suggest that whatever system you are considering, look at the dyno results carefully at all points and see where the curve concentrates the power increase, make your decision that way.
Smaller diameter pipes improve low end. Properly Designed back pressure tunes a Torque range to a specific RPM range.
Bigger is not always better!! Most of the time it is worse. Concentrate on your cats, resonators/mufflers or H pipes if your app. allows.
Full open pipes only benefit WOT. This is not where driveability is found.
LT
I thought that this rule held true for carborated motors and not TBI. By the way my Z is a Draw-thru carb turbo setup.....I have to keep the 2.5 to keep the turbo spooling earlier and faster ( due to the backpressure needed). People with a TBI set-up go with 3 inch and GAIN HP. Your rule is true for carborated set ups.
__________________
'01 IS 300 SOLD
'04 FX 45
70 240Z boosted/NO2 sleeper
'04 Tundra SR5 2WD DC
I thought that this rule held true for carborated motors and not TBI. By the way my Z is a Draw-thru carb turbo setup.....I have to keep the 2.5 to keep the turbo spooling earlier and faster ( due to the backpressure needed). People with a TBI set-up go with 3 inch and GAIN HP. Your rule is true for carborated set ups.
Not entirely correct due to cam overlap... loss of backpressure will steal some intake charge into the exhaust ( thus popping noise with low backpressure systems ). Although the EFI will compensate with fuel delivery, it is the partially lost air charge that you don't recover. EFI systems will not suffer as much as carbuarted systems but they will.
It is also important to qualify the exhaust components and their affect on back pressure. For example just to say a 3" exhaust system doesn't tell the whole story. A properly designed 3" exhaust may not give adequate back pressure for a particular engine, however a 3" system comprising of poorly bent piping, restrictive muffler, may work as it is really no better than properly designed 2.5" system. Pipe length is one variable that affects backpressure, since exhaust pulses from the engine, there is a pulse "wavelength" (similar to radio waves). Just like tuning an antenna's length will provide the best reception and transmission of band of frequencies of a radio. There is always an ideal frequency that peaks and the rest slope downwards on each side kind of like a bell graph. Exhaust works the same way, a proper length pipe will enhance flow while an improper length will cause the pulses to reflect back. A muffler is designed to cause some reflection of these pulse to cancel the noise, this results in backpressure even in a seemingly straight through muffler. Bends in piping can cause slowdowns just like bends in a river. A crossover pipe ( "H" or "X" ) will enhance flow by using the vacuum generated from one's bank exhaust pulses to help draw exhaust from the other bank, this also balances the back pressure of the engine. The position of the crossover will also have a bearing on it's effect. However do not take it as the crossover takes away all the backpressure, the length of pulse will only draw a certain amount of exhaust as compared to my statement about the loss of intake charge. The performance of a crossover is also affected by what is behind it, even in an open exhaust race engine, the pipe length is tuned.
There is a fairly complex set of calculations to design the ideal exhaust system, but even with those it will still be based on a particular RPM for best flow.
Am I suggesting you sit down and calculate it all out ?, no, just look at the whole picture and if reliable dyno results for a "particular" set of exhaust components is available then take the time to make sure it matches your primary driving needs. By all means consider the comments by owners that have upgraded their exhaust systems and what they have specifically used. Generalizing on size alone is not enough information to guarantee the best results.
conflicting exhaust info......
David~2001 Toyota Tundra 4X4 TRD SR5~SSautochrome headers~Single 2.5" exhaust w/ Flowmaster 50 series delta flow muffler~K&N FIPK intake system w/True-flow filter~ASP underdrive pulley~Hellwig Anti-Sway Bar(removed)~Powertrax No-slip~Bilstein 5100 front and rear w/AAL~Diff breather mod~255/85 BFG M/T on Wheelers Black Steelies Type B~Custom Rocksliders~Skid Row front skid plate~Custom Transfer case skid plate
