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D Denney
Dodge Dakota
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3/18/2002
08:04:33
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 Subject: Damn Flowmasters
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Message:
Ok so i go and have a 50 series flowmaster 1 in 2 out, 2.5" all the way out to stock location. Sounds great havent listened to radio much the past 4 days. I have 00 Dakota Quadcab 4.7 . My zero to sixty times went down .8 seconds, man was i pissed off. So i guess i gained horsepower at the expense of torque. If the truck didnt sound so good id have my stck exhaust back on.Would a fresh air intake help me regain some of my lost power? anyone else expirience same problem? any thoughts?
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CThomp
Dodge Dakota
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3/18/2002
08:30:08
|  RE: Damn Flowmasters
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Message:
I haven't experienced the problem yet but you should have the in as well as the out for your engine to breath properly. I have a 360airintakez. I did this first. I'll probably do a catback next. I'm also going to look into a free-flow cat because I've heard that 4.7L's like them. I have a '00 4.7L CC.
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D Denney
Dodge Dakota
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3/18/2002
08:35:01
| RE: Damn Flowmasters
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Message:
Thanks for the reply , im lookin to get a 360 soon. Hopefully it will help.
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mopar2ya
Dodge Dakota
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7/31/2002
22:07:31
| RE: Damn Flowmasters
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Message:
I have the same problems with my flowmasters-loss of low-end torque.
Did your 360 intake help?
Thanks,
mopar2ya
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mopar2ya
Dodge Dakota
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7/31/2002
22:47:20
| RE: Damn Flowmasters
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Message:
I have the same problems with my flowmasters-loss of low-end torque.
Did your 360 intake help?
Thanks,
mopar2ya
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R/Truck
Dodge Dakota
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8/01/2002
10:53:15
| RE: Damn Flowmasters
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Message:
I know what will help your power loss, get a new muffler. I went from the flowmaster 50 to a magnaflow and it was like driving a new truck. Flowmaster is not a performance muffler it just makes noise.
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Thrush
Dodge Dakota
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8/01/2002
12:44:39
| RE: Damn Flowmasters
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I have the single 3" Flowmaster catback. I have noticed a tremendous loss of low end torque since I added headers. Do you guys think that by switching to another muffler would restore my low end grunt?
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R/Truck
Dodge Dakota
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8/01/2002
13:14:50
| RE: Damn Flowmasters
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Message:
Have you upgraded your intake? You really need a larger TB with those headers, and yes anything but flowmaster.
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bailey
Dodge Dakota
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8/01/2002
13:23:18
| RE: Damn Flowmasters
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Message:
It's not the muffler that kills the low end, it's the incorrect pipe diameters. Anything more than a single 2.5" on the 4.7 isn't good for low end. (unless your using forced induction) When you change a factory exhaust from single to duals or just simply a larger single pipe, you lose low end. Works this way on all vehicles. I dont care what anybody says. The more airflow space you have the slower the exhaust exits. The slower it exits, the more cool and heavy the air becomes making it harder for your pistons to push it out. Flowmaster mufflers just reduce backpressure which isn't good for high or low end despite what many believe. It's not the loss of backpressure that kills your low end, its loss of velocity. Sure I love the sound of dual exhaust or a bigger pipe but it's most always a trade off with low end.
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dr0p0ff
GenIII
8/01/2002
13:31:14
| RE: Damn Flowmasters
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Message:
bailey would be correct
Keep On Truckin!
Sgt G
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dak-quack
GenIII
8/01/2002
15:49:14
| RE: Damn Flowmasters
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Message:
NEWSFLASH!!! I've got great news for you... if your 0-60 went down .8 seconds it's faster!!!
;)
2002 QC, 4.7 3.92 4x4 AT LSD
Formerly dakquad
NO MODS.....NONE!!!
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WallyR
Dodge Dakota
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8/01/2002
16:04:23
| RE: Damn Flowmasters
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Message:
That's the way it is. Larger diamter = lower velocity = less cylinder scavenging = less low end torque.
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rtdkota
R/T
8/01/2002
17:04:05
| RE: Damn Flowmasters
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Message:
People still don't believe me but here goes again-- the 4.7L is very finicky on backpressure-- Not enough, you'll lose low end, but gain on the top end.
The flowmaster is a high flow muffler-- running a fm on a 3" cat back will drop your low end (torque & hp). Dropping in a more restrictive magnaflow the truck will actually pick up more low end (to a point) than the flowmaster.
I've gone through this with my '95 SLT-- Ran an utltra flo (basically a straight through muffler) and headers.. .was great, some low end loss, not much. Then changed the cat to a Carsound high flow-- YIKES! NO low end... the truck was a dog until 3000 rpm then was a rocket until 4600 rpm... 1600 rpm worth of driveability wasn't working out so well... Ended up dropped the Ultraflo, went with a Superturbo-- Got all of my low end back, plus more, and it ran real good at the top end.
It's all about balance-- I run mopar headers, 3" into the stock cat (opened up from 2.5") and 3" out to a flowmaster 40series-- to 2-2.5" through the roll pan... If I swapped out the cat to a higher flowing carsound, I'd kill my low end. The setup seems to be the best balance there is (I could probably go back to a Superturbo and get MORE low end, but sacrafice some top end... NAH.. I like it the way it is!)
Sam
RTDKOTA
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alex
Dodge Dakota
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8/01/2002
17:15:33
| RE: Damn Flowmasters
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Message:
It's been a common rule of thumb with me & my racin' buddies...
If you want to make noise, go with Flowmaster.
If you want to make power, go with Dynomax.
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pbxr1
Dodge Dakota
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8/01/2002
18:27:10
| RE: Damn Flowmasters
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Message:
Whew, I was getting worried. I just ordered a DynoMax, 2 1/5 single in and out. I really would have been upset if I lost anything, by adding a mod. Thanks to this forum and reading alot of posts I think I made the right choice for now.
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Throttle
Dodge Dakota
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8/01/2002
20:53:59
|  RE: Damn Flowmasters
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Message:
I bought the 50 series FM (part# 52558) for my 02' 4.7 and really noticed no diff. in performance or sound. I then got the idea to go without a muffler altogether (after all there are 3 cats on the truck). I then found a guy who bends pipe and had him make me a tailpipe over the frame rail and dumped it out before the rear tire. Again, I noticed no diff. in performance, but it sure looks good and sounds even better.
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Muzzy
GenIII
8/03/2002
05:24:31
|  RE: Damn Flowmasters
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Message:
I must have a very odd Dakota then. When I installed my Flowmaster cat back system, I noticed more top end and about the same low end. The biggest difference I noticed is my tires break loose (dry cement) in 2nd gear at about 3500 RPMs. They didn't do that with my stock exhaust. That's just easing it into gear and then stomping on it. I then gutted my 3rd cat. I noticed even more of a gain. In fact, on the highway when I am in 5th going 60, I just mash the peddle and it will pull pretty good. Before, I used to have to downshift into 4th.
Would someone like to test this theory on a dyno? The one person I know of who has (Duner), showed the opposite of what all of you are agreeing to. Duner dyno'd his truck with a 3" high flow cat and 3" exhaust and showed a gain in performance. This was before his turbo was installed.
As long as I have been modifying motors, I have never seen any gains in anything by restricting exhaust flow. I know for sure you can expect higher exhaust valve temps and more combustion gases being left in the cylinder.
-Muzzy
2001 EC Dakota 4x4 - 287ci V8 - 5 Speed - 3.92 gears/w Sure Grip
Borla Stainless Steel Headers - IAT Adjuster
Flowmaster Force II Cat Back - Ported TB/Custom Cold Air intake
H&K USC Security System
Coming Soon - head porting/ install HO cams & valve springs
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Bruce P
Dodge Dakota
JOIN HERE
8/03/2002
22:33:09
| RE: Damn Flowmasters
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Message:
I have to agree with Muzzy on this one. IT IS NOT THE "BACKPRESSURE" THAT IS MAKING TORQUE.
Instead, after careful measurments, you may find that it is the VELOCITY of the exhaust gasses that are affecting low-end torque. Basically explained... A column of liquid (in this case exhaust gas) will have LOWER velocity in a larger pipe.
This is why, that unless you are forcing induction into the 4.7L V8, it is best to not go over 2.5inch diameter exhaust piping. The VELOCITY will become so weak at low RPMs that the engine scavenging will be non-existant. Thus, reducing torque at those RPMs.
This EXACT same phenomonon holds true for an INTAKE system. Smaller diamater piping improves the VELOCITY at low RPMs creating better induction into the engine.
In both cases, the "trick" is to not reduce the diameter to the point where the FLOW RATE is restricted.
Folks that tune engines for a living will tell you that in general "long-thin pipes help the low end while short-fat pipes make high-RPM power."
Choose your path and tune your intake-exhaust accordingly.
As rtdkota says..."It's all about balance--"
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WallyR
Dodge Dakota
JOIN HERE
8/03/2002
22:57:47
| RE: Damn Flowmasters
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Message:
bruce,
backpressure does have something to do with it, but it is the end result.
for a given flow rate, being what the engine can move in and out of the cylinders, the velocity and cylinder scavenging will be lower with a larger pipe (as I pointed out two days ago!) but there is a very well defined relationship between flow rate, velocity and static pressure, which most refer to as "backpressure". for this given flow rate, if the velocity and the velocity pressure are decreased because of an increase in diameter the static pressure, or backpressure, will decrease as well. basic laws of physics.
wally
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HSKR
Dodge Dakota
JOIN HERE
8/04/2002
14:07:22
| RE: Damn Flowmasters
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Message:
It's just the shytty flowmaster that is causing his problems. The might make the truck sound good, but they have been proven(on the R/T's at least) to actually lower hp and tq on the dyno. Spintech is a really good muffler and helps more for sound and performance over the Flowmasters(especially the really restrictive delta flow models)
\
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handi2
GenIII
8/04/2002
23:41:39
| RE: Damn Flowmasters
IP: Logged
Message:
On the 4.7 trucks why not just leave the damn exhaust alone..!
I read all the posts "I lost low end torque so I had to get a larger throttle body"
Now your back to where you started.
http://photos.yahoo.com/handi254310
2002 Quad Cab SLT Plus 4.7 Every Available Option
Access Tonnoue Cover/Bedrug/360 Air Intakez/Jet Stage 2
180 Robertshaw/Roadmaster Active Suspension
Street Scene Grill Inserts
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