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Old 06-07-2013, 12:13 PM
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Doing exhaust on 5.7L WK...What's your opinion?

Just got caught up on the maintenance needed on my 05 Limited 5.7L hemi WK, and now I'm thinking about getting an intake and exhaust system for it. probably wont be for a few weeks and I'll definitely need to shop around for a great deal, but I'd thought I'd reach out to the JG community to see what you all think.

Which should I do first?

What is more bang for my buck? (gas mileage, performance, etc)

What brands are other people with the 5.7L running?

What's your opinion on the different options available for intake/exhaust systems for the 5.7L?

Where are good places to shop?

Do you happen to have either of these for sale? (and is it a bad idea to buy used intake/exhaust systems?)

Any help on answering any of these questions will be greatly appreciated!
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Old 06-07-2013, 03:17 PM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

My opinion. Start with a tuner like the Diablosport Intune. It will increase both performance and fuel economy so it's a win-win. Don't waste your money right now on an exhaust or air intake. You may also want to consider an 85mm ported throttle body. That's my next mod so I don't have any personal feedback yet but I've heard nothing but good things about doing it. Good luck.
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Old 06-07-2013, 08:39 PM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

My opinion, FWIW, based mostly on my experience. You're going to get many different takes on your questions, but remember that without dyno testing (generally a waste of $$$), most of these mod. benefits are just as I am saying.....opinions, and ultimately you'll have to decide which course to take. Also, most mods, by themselves, don't make a noticeable difference, but cumulatively they all add up.

As said above, start with a tuner. I have both the DS and the SC units for my somewhat modded Hemi (see signature). Also, in addition to the mods. listed, I have an SLP 25% UD crank pulley, and have, just last week, installed a BBK true 85mm throttle body. Depending on what your ultimate goals are should determine which tuner to purchase, as they both have their benefits. It should also be your guide on choices of other mods. to go with.

The DS allows you to update the PCM/TCM CALID flash files, gives slightly (less than 1 mpg) better than the SC tuner, gives slightly better performance (hardly noticeable), allows you to modify WOT air/fuel ratios and ignition timing, allows you to purchase ChipMaster Revolution (CMR) custom tunes, and the rest of the features are similar to the SC.

The SC's biggest and best feature is the add-on (~$40) Advanced Transmission Tuning Application (ATT). It allows you to modify all up/downshift schedules and torque management for both light and WOT throttle. Personally, having the transmission working about 100 times better than stock is a no brainer, and that's why I now use the SC probably 90% of the time.

The exhaust system is probably the biggest weak points in the 5.7 WK/XK. Here's a couple threads on my system and a recommendation I made to swap out the stock WK logs for the LX logs that, so far, I don't believe anyone has tried. Personally, I think this would be, by far, the best bang for the buck, as long as you add a good 3 in. cat. back to go with it.
http://www.jeepgarage.org/f5/a-better-exhaust-system-for-the-5-7-wk-19490.html
http://www.jeepgarage.org/f5/headers-for-my-5-7-hemi-18229.html

For the intake, I'd use the stock airbox, K and N or TruFlow air filter, and an Airaid Jr or WK SRT-8 intake tube. I'd also add one more air inlet to the bottom of the airbox. See attached pix. Remove the drain cup and add a 3 in. tube routed to the grill area. Be aware that the stock airbox is capable of flowing much more air than the stock/relatively stock hemi can process.

The SLP UD pulley makes a negligible difference, and an 85mm throttle body (TB), IMO, is useless.....but then I was quite sure of that before I bought it. I was just hoping for hope's sake that there would be a slight difference because of my mods. So far, my observations on the TB (a little less than .2 in. larger than stock) are that the throttle is a little less responsive and the top end performance appears to be slightly less than the stock TB. It's difficult to access using the "seat of the pants" method, but that's the way it feels to me. Remember, the stock 80mm TB is used on 5.7's, 6.1's, and 6.4's, so it obviously is capable, CFM wise, of handling anything even a moderately modified 5.7 can process. If you're just dying to waste your $$$ on a TB, I'd probably choose a ported 80mm unit, but I seriously doubt that they flow much better than a stock unit.

Another low buck thing you could do (probably less than $200), again that I think no one has tried, is to advance the cam one tooth, about 7 degrees. This will move the power/torque ranges to a lower RPM to increase performance and torque at lower RPM. On my WK aftermarket cam which already has a 6 degree advance ground into it, I added 2 degrees more. My fuel economy went from ~17-18 mpg stock, to ~20-24 mpg (most of the time ~22 mpg) as currently modified. I did the same cam mod. to my Hemi LX, advancing the same grind aftermarket cam 6 degrees, for a total of 12 degrees. The top end (above ~5000 RPM) on it is pretty dead, but the WK stills pulls well to 6200 RPM. But, then again, how often do you run the RPM up to or above 5000 RPM?
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Old 06-08-2013, 05:50 AM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

Quote:
Originally Posted by jeepgcoman View Post
My opinion, FWIW, based mostly on my experience. You're going to get many different takes on your questions, but remember that without dyno testing (generally a waste of $$$), most of these mod. benefits are just as I am saying.....opinions, and ultimately you'll have to decide which course to take. Also, most mods, by themselves, don't make a noticeable difference, but cumulatively they all add up.

As said above, start with a tuner. I have both the DS and the SC units for my somewhat modded Hemi (see signature). Also, in addition to the mods. listed, I have an SLP 25% UD crank pulley, and have, just last week, installed a BBK true 85mm throttle body. Depending on what your ultimate goals are should determine which tuner to purchase, as they both have their benefits. It should also be your guide on choices of other mods. to go with.

The DS allows you to update the PCM/TCM CALID flash files, gives slightly (less than 1 mpg) better than the SC tuner, gives slightly better performance (hardly noticeable), allows you to modify WOT air/fuel ratios and ignition timing, allows you to purchase ChipMaster Revolution (CMR) custom tunes, and the rest of the features are similar to the SC.

The SC's biggest and best feature is the add-on (~$40) Advanced Transmission Tuning Application (ATT). It allows you to modify all up/downshift schedules and torque management for both light and WOT throttle. Personally, having the transmission working about 100 times better than stock is a no brainer, and that's why I now use the SC probably 90% of the time.

The exhaust system is probably the biggest weak points in the 5.7 WK/XK. Here's a couple threads on my system and a recommendation I made to swap out the stock WK logs for the LX logs that, so far, I don't believe anyone has tried. Personally, I think this would be, by far, the best bang for the buck, as long as you add a good 3 in. cat. back to go with it.
http://www.jeepgarage.org/f5/a-better-exhaust-system-for-the-5-7-wk-19490.html
http://www.jeepgarage.org/f5/headers-for-my-5-7-hemi-18229.html

For the intake, I'd use the stock airbox, K and N or TruFlow air filter, and an Airaid Jr or WK SRT-8 intake tube. I'd also add one more air inlet to the bottom of the airbox. See attached pix. Remove the drain cup and add a 3 in. tube routed to the grill area. Be aware that the stock airbox is capable of flowing much more air than the stock/relatively stock hemi can process.

The SLP UD pulley makes a negligible difference, and an 85mm throttle body (TB), IMO, is useless.....but then I was quite sure of that before I bought it. I was just hoping for hope's sake that there would be a slight difference because of my mods. So far, my observations on the TB (a little less than .2 in. larger than stock) are that the throttle is a little less responsive and the top end performance appears to be slightly less than the stock TB. It's difficult to access using the "seat of the pants" method, but that's the way it feels to me. Remember, the stock 80mm TB is used on 5.7's, 6.1's, and 6.4's, so it obviously is capable, CFM wise, of handling anything even a moderately modified 5.7 can process. If you're just dying to waste your $$$ on a TB, I'd probably choose a ported 80mm unit, but I seriously doubt that they flow much better than a stock unit.

Another low buck thing you could do (probably less than $200), again that I think no one has tried, is to advance the cam one tooth, about 7 degrees. This will move the power/torque ranges to a lower RPM to increase performance and torque at lower RPM. On my WK aftermarket cam which already has a 6 degree advance ground into it, I added 2 degrees more. My fuel economy went from ~17-18 mpg stock, to ~20-24 mpg (most of the time ~22 mpg) as currently modified. I did the same cam mod. to my Hemi LX, advancing the same grind aftermarket cam 6 degrees, for a total of 12 degrees. The top end (above ~5000 RPM) on it is pretty dead, but the WK stills pulls well to 6200 RPM. But, then again, how often do you run the RPM up to or above 5000 RPM?
Very thought through response there.
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Old 06-09-2013, 09:40 AM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

Intake and exhaust are just noisemakers and a waste of money on the 5.7. First thing to get is a catch can, then a Diablo intune and taper ported 85mm TB. The above post about 85mmTB is using a straight bore, not a taper bore, and I can assure the taper bore gives improved performance, as I did back to back testing with and without CAI.
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Old 06-09-2013, 10:29 AM
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Nice, I greatly appreciate everyone's input so far on this thread, strongly reconsidering my first performance mods now!
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Old 06-09-2013, 10:57 AM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

Until an improved way for spent gasses to escape and use the exhaust pulses to help pull the next charge in is available, all the money in the world can be spent on the intake side of the head with little performance improvement. The 5.7 likes a fast moving intake charge to fill the cylinders. Intakes with bigger runners have been tried and performance was negatively affected. Why? Combination of cam timing/duration and poor exhaust design.
So whatever we do behind the manifold...same thing, very little change in performance only noise factor.
I like the intake noise, reminds me of when I was a kid and took out the old mans truck. First thing I did was flip the air cleaner lid so you could here the four barrels open up. Thats right we used to have a thing called a carburetor on top of the intake manifold. Lol
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Old 06-09-2013, 01:06 PM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

X2, all the way down on SweetWilliam's comments. I used to do the same thing with my dad's '57 Dodge Custom Royal 354 cu. in. Hemi. I also used to climb under it and lower the front end by adjusting the torsion bars.....no front springs on them. One time I didn't quite get it back up to the right height and he caught me. What a hoot.

Also, like dmsfun says, a catch can on a Hemi is a must, and the sooner the better. While you're at it, clean the throttle body, which I am sure is all gunked up.
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Old 06-09-2013, 06:38 PM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

Quite often I read about what cat back exhaust to put on and this always comes up... dont run this cuzz it's too big of diameter and wont have enough back pressure.
A; someone please tell me what is too much and what happens when there is too little? How does it effect an engines performance?
B; do you really think, given the junk exhaust manifold, piping and cats that are in front of any bolt on system, the size can be so big as to effect performance?
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Old 06-09-2013, 10:43 PM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

Dang, SweetWilliam, you sure have a lot of questions, LOL! Designing and building a quality, effectively tuned exhaust system is not kid's stuff. My uneducated guesstimate is that there is maybe only one knowledgeable exhaust builder (normal local shops) in 1000 that has a good, complete understanding of the how's and why's of building a good system.

The mfger's probably don't put that much research into their systems, mostly because of R and D costs. I think, in our case, they dragged some exhaust manifold off the shelf that would fit between the tight frame rails, stuck in on our Hemi's and called it good. Why didn't they pick the LX ones instead? Maybe because Jeeps aren't normally supposed to be race cars, and need more low end power, especially when off-roading or towing. Hence the smaller outlets in the manifolds. Here's a bunch of info. (quotes) I've gotten off the internet. They address everything from theory, design, building, testing, and so on. I guess it's easist to say, it's all about a balance of exhaust pressure pulses and velocity. I don't pretend to understand all I know about exhaust systems but, IMO, anything is better than what we have, if we're after performance and economy.

"All too often the engine exhaust is an afterthought for the engine and chassis builders, yet its design and construction impacts significantly upon car performance. The exhaust system can be a vital tool for optimizing the performance of the engine, through the way in which its design manipulates the pressure waves that can crucially assist cylinder filling and scavenging. On the other side of the coin, the exhaust system presents many challenges. It is a major loss-path for thermal energy; and it can be a car packaging nightmare."

"There are two separate components to the exhaust event. The first is the removal of exhaust gasses from the cylinder, which occurs as a pulse of hot gas exiting the cylinder and flowing down the header primary tube. The second is the (much faster) travel of the pressure wave in the port caused by the pressure spike which occurs when the exhaust valve opens, and the various reflections of that wave. Taking proper advantage of these pressure waves (component two) can produce dramatic improvements in clearing the cylinder (component one) and can strongly assist the inflow of fresh charge."

Note: Our Hemi firing order and cylinder numbering is the same as the GM engines. When they're talking about the "cup", it's the NASCAR Cup rules. The headers my guy built for me are a 4-1 mid length system, like they're talking about. My primary tubes are also unequal length. A 4-2-1 system with equal length primaries would have been better, but the tight space and $$$ limited both him and me.

"With the GM cylinder-numbering system (1-3-5-7 on the left) and firing order {18436572; the 4-7 swap is not allowed in Cup} ), the exhaust pulse spacing on the left side (expressed in terms of degrees of crankshaft rotation) is 270-180-90-180 while the spacing on the right side is 90-180-270-180. This uneven pulse spacing gravely impedes the achievement of a well-tuned exhaust system such as can be achieved with evenly-spaced pulses and a 4-into-1 collector."

"The instantaneous velocity of the exhaust gas flow at any point is determined by the pressure gradient and the cross-sectional area at that point. In the header, a smaller tube diameter will increase the velocity at a given RPM, which might enhance the pressure wave tuning (the second component) and can be beneficial with regard to inertia effects. However, if the diameter is too small, there will be flow losses and consequent pressure gradient increases which can offset any tuning gains. So the selection of proper tubing diameters is an important part of the design."

"Using a 4-into-1 system as an example, the four primary tubes will ideally have the same centerline length and will sharply transition into an area having roughly three to four times the area of the primary.. The larger the cross-sectional area of the collector tube plus the area of all other tubes at the same junction compared to the area of the active primary tube (area ratio), the larger will be the amplitude of the reflected wave. However, the collector has an optimal size: too much area and the wave tuning in the collector will be diminished. The optimal length is related to the number of cylinders feeding into it."

"In the case of the currently-flowing header primary, the EVO-initiated positive pressure (compression) wave is reflected back as a negative pressure (expansion) wave. If the arrival of the reflected negative pressure wave back at the exhaust valve can be arranged to occur during the latter part of the exhaust cycle, the resulting lower pressure in the port will enhance the removal of exhaust gas from the cylinder, and will reduce the pressure in the cylinder so that when the intake valve opens, the low pressure in the cylinder begins moving fresh charge into the cylinder while the piston is slowing to a stop at TDC."

"The instantaneous velocity of the exhaust gas flow at any point is determined by the pressure gradient and the cross-sectional area at that point. In the header, a smaller tube diameter will increase the velocity at a given RPM, which might enhance the pressure wave tuning (the second component) and can be beneficial with regard to inertia effects. However, if the diameter is too small, there will be flow losses and consequent pressure gradient increases which can offset any tuning gains. So the selection of proper tubing diameters is an important part of the design."

"Several experts agreed that the rules-of-thumb still apply: better low end needs smaller and longer tubes; better high end needs bigger and shorter tubes."

Again, IMO, this holds true for the cat. back portion of the system too. Every exhaust guy I ever talked to says the 5.7 Hemi (with a good set of headers) will work best with a 3 in. single system, or 2.25 in duals. If you leave the stock exhaust log "choke point" in, stick with the stock cat. back tubing size too.
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Old 06-10-2013, 04:41 AM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

Best thing to do is look at before and after dyno results of the exhaust system you are looking at. That is what I did before I choose my long tube headers and cat back. Typical gains on the dyno were 20-25 hp.
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Old 06-10-2013, 09:50 AM
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Re: Doing exhaust on 5.7L WK...What's your opinion?

Gojeep, that sounds about right, depending on muffler(s), cats. and tubing size(s). I was figuring on mine ~30 hp, as my elapsed time at the drags went down ~.3 second after the install. The old drag racers rule of thumb was 10 hp. increase for every tenth of a second reduction in elapsed time. You're right though, there is no real substitute for dyno testing but, I for one, am to cheap to spend the money on it, especially if I can use that same money for another mod., LOL. I've always relied on the drag strip for my testing, because it's more fun and doesn't cost as much. I've only dyno'ed one vehicle over the years, and I didn't really care for standing next to my ride when it was cranking 6000 RPM with open headers. My first thought was, when is it going blow. Back then things were different though.....had to properly jet the carburators, and adjust the advance curve and timing. Are you running the SRT long tubes? What kind of cat. back are you using?
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