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Auggie
Dodge Dakota
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10/24/2003
00:34:47
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 Subject: 4.7 Exhaust Drama
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Message:
Hey guys, i know this subject has been beaten to death but after reading about 250 different post I'm just as unsure about which setup to go with when dealing with the 4.7. I'd say that for all the post that I read, half say its best to go with 3 inch single in single out cat back , while the other half say a 3 inch single in , 2.5 dual out is the way to go ..If I was able to take a ride in a truck that had each setup it would be easy to decide then but unfortunately i know of no one with our trucks with exhaust mods. I love the dual look out behind the rear tires but rumor has it that you loose low end , is this true. I have an appointment this weekend to have the exhaust done and the local shop states that I wont loose anything doing a 3inch single in dual out , but I see lots of conflicting post. Is there anyone out there that has duals other than the MBRP 2.23 duals and doesnt feel that they lost to much bottom end. Any advice that you guys can give me before this Saturday would be greatly appreciated. Thanks
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AndrewM
Dodge Dakota
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10/24/2003
09:48:42
| RE: 4.7 Exhaust Drama
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I'm thinking the true 2.5" dual exhaust from gsmotorsports is the way to go. That system looks bad ass.
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Chipster
Dodge Dakota
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10/24/2003
11:47:45
| RE: 4.7 Exhaust Drama
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Message:
I've had both. I now have the GS Motorsports
True Duals. It is not as throaty as the single 3"
system. But with my KB flash, I now can
peddle it from a roll and get second gear
scratch, with my 17" Nitto's ( it's an auto). I
went to the Truckin Nations in AZ a couple of
weeks ago. My truck ran in the middle of the
pack with the R/T's. Best time was a 14.86 in
98 degree.
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CThomp
*GenIII*
10/24/2003
12:09:40
| RE: 4.7 Exhaust Drama
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Message:
Chipster, what is your truck and what mods do you have?
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Chipster
Dodge Dakota
JOIN HERE
10/24/2003
16:57:17
| RE: 4.7 Exhaust Drama
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Message:
2001 CC 4.7L Auto, KB Flash, HO Intake, HO
Cams, 4.10 Posi, GS Motorsports True Duals,
Shaker Hood, 72 F/B Throttle Body and
Hotchkis Drop.
Hey CT.............That flash your looking for!!! The
only two people that do them right are Kenne
Bell and Mike Leach (stay away from ASE).
Anybody else just sends them to Mike Leach.
So don't bother with these third party vendors.
Go directly to the source.
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ErnieQuad03
Dodge Dakota
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10/24/2003
21:16:05
| RE: 4.7 Exhaust Drama
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Message:
I just had a 2.5 center in offset out stainless flowmaster delta flow 40-series installed. All I did was replace the muffler, left all stock pipes and no tip. Honestly, it sounds loud as hell and I did not lose any low-end. It accelerates much better now and really rumbles, no crackles no pops.
I REALLY recommend this setup. You will not be disappointed if you like it 60's mopar loud on the outside with a nice mellow tone in the cab, no drone. I will do my best to get a sound clip up. I will have pictures real soon on Dodge Truck World gallery, user hemimopar426.
Next I am looking to upgrade the intake a little, currently just have a drop-in K&N.
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ErnieQuad03
Dodge Dakota
JOIN HERE
10/24/2003
21:27:51
| RE: 4.7 Exhaust Drama
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Forgot to mention the truck I installed that on, my bad.........
2003 Quad Cab 4x4 4.7L with 5spd manual.
Good luck!
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MD
Dodge Dakota
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10/24/2003
21:57:49
| RE: 4.7 Exhaust Drama
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Message:
Concerning the issue of low end loss - While you will NEVER get 100% agreement on anything having to do with performance, there is certainly a degree of consensus among the "regulars" here (those into performance, not just sound) that for the 4.7 you will lose low end with a 3" set-up. The general consensus is that for a 4.7 a single 2 1/2 inch pipe is best from a performance standpoint.
Now, you can go out and pay $300+ for a 3" cat-back system and lose some low end and gain some top-end, or spend even more for a dual 3" set-up and lose even more low-end while gaining some top end, OR . . . .
You can make use of the single 2 1/2" pipe you have and replace the stock muffler with a flow-through design and PERHAPS gain a little power throughout the powerband. A Magnaflow #14256 is a good choice, as is the Borla #40665 (I think that is the correct #) - these will open up the exhaust and enhance breathing, while providing a bit more refined rumble than the Flowmaster 40 Series, which to me sounds like a Mack Truck with blown exhaust manifold.
PS: If you insist on duals, ask some folks on here if they prefer running 2 1/2 or 2 1/4 pipes behind the muffler (mufflers if you run true duals). All motors require some critical level of back pressure to run strong - but, I'm not an engineer of flow dynamics).
Now, I think I'll just kick back and read those cards and letters as they come pouring in. LOL
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Demon Dakota
DakotaEnthusiast
10/24/2003
22:08:56
| RE: 4.7 Exhaust Drama
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Message:
The loss of backpressure is still and always has been a myth for the 4.7L crowd. I've done nothing but gain HP and TQ during all of my exhaust mods, but I do not personally feel the need to go to true 3" duals. I think that 2 1/2" true duals are more than sufficient.
Here...some light reading for you folks...
http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
Custom tranny VB Mod
Demon long tube headers
Ported/polished heads w/ 1.92" Intake/1.60" Exhaust Valves
One dead stock LSD unit (POS...)
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Frank
Dodge Dakota
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10/25/2003
07:30:17
|  RE: 4.7 Exhaust Drama
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I have a 2000 CC 2WD 4.7L 5-speed and had a Flowmaster 40 Series catback system put in about 2-1/2 years ago. The muffler has a single 3 inch inlet and two 2-1/2 inch outlets. I have a 12" long x 3 inch diameter chrome tip on the end of each pipe and have the pipes exiting the rear end angled at 45 degrees (instead of straight out the back). The truck sounds pretty mean and the angled outlets tend to "spread the love" a little better. After having the system installed I didn't notice any decrease in power whatsoever. In fact, I noticed that the power began to come on a couple or few hundred rpms sooner than with the stock exhaust. At ~1,700 rpms, the exhaust note changes noticeably and the muffler begins to resonate (as the engine begins to move into its power range). The Flowmaster muffler is built like a tank and sounds great, even with the cat still in place.
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MD
Dodge Dakota
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10/25/2003
09:34:22
| RE: 4.7 Exhaust Drama
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Message:
DemonDak - I would agree with you to this extent: If he really opened up his intake system (you have P&P heads, valves, a 70mm TB cams and intake) he could probably make use of the 3" system and benifit from it without any lose of low end - in fact, he would likely gain power throughout the powerband with a larger flow exhaust system.
However, I think there is a consensus among 4.7 owners on this site who have used a 3" system on a near stock engine that a 3" is counter-productive relative to low end torque.
Like I stated earlier - when it comes to performance mods, you can never get 100% agreement on anything.
MD
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Demon Dakota
DakotaEnthusiast
10/25/2003
11:31:26
| RE: 4.7 Exhaust Drama
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Message:
MD, while many others have said they "felt" a loss of TQ at low end, others (like myself) have actually dynoed and shown gains throughout the entire powerband (we're talking from TQ converter lockup until redline on the dyno). Butt dynos are extremely inaccurate, as we all know.
While searching through the posts (and there are literally thousands here) on exhaust threads, the true people in the know are the only ones who have gone to the dyno. All the others that claim loss of low end TQ never said a word about going and getting their mods dynoed. If I keep losing TQ on the low end (and I just recently did the heads/valves, so my time does not reflect those mods) and could run a 14.52 in the 1/4 with just lite mods, then I say again that the exhaust loss of TQ theory is nothing but myth. It is a physics fact at this point...you do not need backpressure to run the engine. You have an ECU that handles that...it is a self regulating system.
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
Custom tranny VB Mod
Demon long tube headers
Ported/polished heads w/ 1.92" Intake/1.60" Exhaust Valves
One dead stock LSD unit (POS...)
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xplikt
GenIII
10/25/2003
13:51:40
| RE: 4.7 Exhaust Drama
IP: Logged
Message:
Actually, I'm looking at true dual 3". I was going to go 2.5", but I decided I should probably just go ahead and do 3". I am running 4.56 gearing (5.28 with my R/T rims), so low end really ins't a big problem. More importantly, I'm going to Nitrous next Spring and it loves nice open exhaust systems. 3" has it's use, just not for a stock N/A. It's a bit extreme.
-Mike
http://www.dodgetruckworld.com/xplikt/
2002 2WD RC SLT 4.7L 5spd 3.92 LSD
MBRP Single in/out | straight piped 3rd cat | turndown tip
Full Hotchkis and RAS
Shaved emblems and antennae
150BM fan | removed clutch | HD Radiator
R/T wheels on 275/40/17 Dunlop 9000s
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Auggie
Dodge Dakota
JOIN HERE
10/25/2003
20:22:45
| RE: 4.7 Exhaust Drama
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Message:
Ok guys, first off,thanks for all your inputs here, it helped me with my final decision on my exhaust setup. So here it is, this morning I had the local custom shop do their magic and away they went like busy bee's cutting, bending , and welding. Final result 3 inch in , dual 2.5 out, behind the rear tires, 3.5 polished stainless pipe cut 45 degrees and angeled back..Oh, 22inch magnaflow muffler. Like a kid looking at all the gifts under the Chritmas tree and anticipating to open them, I couln't wait for them to fire up my truck to hear the result. And Wow, what an awesome sound. Nice low growl...not to loud , not quiet at all. So lets see, its 8:45 pm right now , i was out of the shop on my way at 10:30 am this morning.. The fact that I spent the day driving all over creation speaks for itself..What a difference, such an awesome sound. And peformance wise, I honestly cant feel any loss in low end torque or horsepower, actually the throttle response is very quick now and rev's up to 4 grand very quickly when getting on it in all gears. I actually think the truck is pulling much harder from 2000 rpm's and up...So to sum it up, it doesnt not seem at all to loose any low end at all and its definetly gained an incredible sound which isnt overbearing inside the cab. But one word of caution, be careful , could lead to the constant abuse of the accelerator..
Thanks guys for all your help, now off to research an intake:) Any suggestions:)
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MD
Dodge Dakota
JOIN HERE
10/26/2003
10:00:32
| RE: 4.7 Exhaust Drama
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Message:
DemonDak
I in no way wish to appear argumentative on the issue, but I will say this - in my youth I ran a '57 "C" Gas Chevy in the early days at Pomona, Irwindale, Lions drag strip in Long Beach, and at Half Moon Bay in northern Cal. - I went to high school with Gary Hooker who built the headers for my car - the second set he ever built. I've been away from the performance scene for many years, and there are many things I learned way back when that no longer apply - and you may be correct in your statement about backpressure - but I doubt it, as the physics/principles of flow dynamics have not changed.
I encourage you to read some recent research on the subject at the following site:
http//modernmusclecars.net/articles/exhaustdynamics.html
Dr. Michael Brown
Phd, Mathematics
Berkeley, 1969
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rockgod
Dodge Dakota
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10/26/2003
11:07:16
| RE: 4.7 Exhaust Drama
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Message:
I'm going in this week and having a Flowmaster 70 installed with 3" in and dual 2.5"s out with pipes out the back. Everything aluminized. I'll be adding a K&N intake also.
I'll report back on how this works out on my '03 qc 4.7,auto,4.10's.
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Demon Dakota
DakotaEnthusiast
10/26/2003
12:23:50
| RE: 4.7 Exhaust Drama
IP: Logged
Message:
MD, as I said, they do not apply to the 4.7L V8 b/c it is an ECU (computer) regulated FUEL INJECTION system...
I should have been more specific in my point of view.
Of course vehicles with carbs would run differently if you open up an exhaust entirely. They are jetted for a certain amount of fuel and air, and if you change the flow of air without changing the fuel, then you may see losses (running lean or rich, whichever way you change the system), which would, of course, change the amount of HP and TQ throughout the entire system.
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
Custom tranny VB Mod
Demon long tube headers
Ported/polished heads w/ 1.92" Intake/1.60" Exhaust Valves
One dead stock LSD unit (POS...)
|
Demon Dakota
DakotaEnthusiast
10/26/2003
12:40:16
| RE: 4.7 Exhaust Drama
IP: Logged
Message:
MD, the article you posted is only partially correct. Backpressure is still not what is needed to run the engine...it's velocity of gas. And moreover, he was specifically describing (and poorly) forced induction systems. As you might have noted in my previous posts, I said that 3" true duals may be pushing the limits of performance for our N/A 4.7L's...you can't just use open headers right off the engine and expect to make power with the ECU tuned as it is.
You know, this issue is just far too complicated to really discuss here on the web simply b/c people have been misinformed for far too long, and I can't really teach everyone here about the dynamics of gas flow unless I am talking to you personally. If I could teach you all personally, you would be able to see that I have all the documented evidence to support my claims on fuel injected street driven vehicles. My statements are meant to directly correlate to these vehicles...
I guess there are just too many variables, is what it comes to. But I will say this with a guarantee...you will make more power with the proper intake and exhaust setup on your 4.7L engine without having to change very many things. If you go as far as I have, then of course you'll realize more gains.
Baseline auto 4.7L's usually put out 175-180~ish to the wheels. Everyone who has exhaust mods to increase flow should dyno their truck to see what happens after they dyno it. My truck is over 250 RWHP N/A at this point (mostly dependant on atmospheric conditions...I don't use the SAE corrected numbers b/c it's not a perfect world, which is what the SAE numbers reflect). My stock LSD is absolutely dead due to the massive increase in TQ over the powerband. These are simply facts in the case supporting what I know...that the true dual exhaust setup is the best for performance with this engine (in a N/A state of tune). Now I can get off into the forced induction tangent as well, but I'd rather not at this time...
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
Custom tranny VB Mod
Demon long tube headers
Ported/polished heads w/ 1.92" Intake/1.60" Exhaust Valves
One dead stock LSD unit (POS...)
|
Chipster
Dodge Dakota
JOIN HERE
10/26/2003
14:21:13
| RE: 4.7 Exhaust Drama
IP: Logged
Message:
Guys...... Have you seen the size of the
exhaust port on the 4.7 head? It's tiny. Anything
more than a 2.5" dual or 3.5" single would be
a waste of money.
Hey MD.... I was probably there with you at
Lions. Nice to know that I'm not the only
seasoned veteran on this board.
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Demon Dakota
DakotaEnthusiast
10/26/2003
14:43:11
| RE: 4.7 Exhaust Drama
IP: Logged
Message:
Stock exhaust port is about 1.46"...
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
Custom tranny VB Mod
Demon long tube headers
Ported/polished heads w/ 1.92" Intake/1.60" Exhaust Valves
One dead stock LSD unit (POS...)
|
01Motorsport
Dodge Dakota
JOIN HERE
10/26/2003
15:29:54
| RE: 4.7 Exhaust Drama
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Message:
Finally, an excellent exhaust post! The newbees need to come back to this one. I had a Flowmaster 70 single-in with 2 1/2" duals installed as my first "new vehicle" mod in 2001, besides a K&N drop-in. I do recall the performance change was minor, but the addition of homebrew 3" alloy intake and Fernco inlet with rubber flap removed absolutely brought the 4.7 to life. Good air in + good air out has worked on every Mopar I've owned since 1977.
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