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Jeff W
DakotaEnthusiast
5/05/2003
06:49:30
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 Subject: Getting more bottom end out of a 4.7
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Message:
After seeing this pic of the under side of the 4.7 intake, I'm wondering if a new design with shorter runners wouldn't improve bottom end torque on the 4.7
Anyone with some real knowledge care to weigh in on this?
'02 Sport 4.7 auto, Gibson exhaust, homebrew K&N cold air, 275/60 BFG Radial T/A's, Infinity CD w/Pioneer & Infinity spkrs & Kenwood powered sub.
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.alex.
Dodge Dakota
JOIN HERE
5/05/2003
07:29:01
| RE: Getting more bottom end out of a 4.7
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Message:
Quite the opposite....
Longer runners get you more bottom end torque. Shorter runners provide a lot more top-end horsepower.
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RaZoR1
Dodge Dakota
JOIN HERE
5/05/2003
13:48:54
| RE: Getting more bottom end out of a 4.7
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Message:
I don't understand why people seem to think the 4.7 has no bottom end. If anyone watches Trucks, they had a show on rock crawlers. The Fire Ant was the world champion and guess wich engine they used. The 4.7. They said they used this motor because 80% (notexactley sure on numbers) of the torque was available right at 2000 rpm. That's right where they needed it. So wehat's the deal??? I have a 4.7 (recently S/C'd) but even before it was, i felt that this motor had lots of pull off the line.........
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Chris
Dodge Dakota
JOIN HERE
5/05/2003
13:51:47
| RE: Getting more bottom end out of a 4.7
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Message:
With just a few mods my truck had about 260-265 lb-ft at the wheels at 2200 RPM.... With the curve being flat there so it was probably available at 2000 as well... That ain't no slouch.... The real problem with the 4.7 is the dip inthe power curve between 4400 and 5200...
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Quadster
Dodge Dakota
JOIN HERE
5/05/2003
16:45:38
|  RE: Getting more bottom end out of a 4.7
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Message:
Dip in the power curve between 4200 and 5200? I thought the 4.7L made it's peak power at 4800 rpms?
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.alex.
Dodge Dakota
JOIN HERE
5/05/2003
17:16:05
| RE: Getting more bottom end out of a 4.7
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Message:
It does until you start modifying it. Then it increases the power all across the curve EXCEPT at 4800. It's the dumbest thing I've seen in this truck so far....
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Chris
Dodge Dakota
JOIN HERE
5/06/2003
08:46:58
| RE: Getting more bottom end out of a 4.7
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Message:
Exactly, my HP peak was at about 4400 RPM and the roque peak was at 3750 RPM..
Chris
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Quadster
Dodge Dakota
JOIN HERE
5/06/2003
09:22:49
| RE: Getting more bottom end out of a 4.7
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Message:
I have built a few race car engines in my days and quite often when the horsepower curve starts looking like the torque curve(very flat from midrange to peak), it can mean that there is a bottleneck on the intake side, usually in cylinder head flow. I have seen a couple of places on the net that are advertising ported head flow numbers, has anyone seen stock flow numbers on intake and exhaust for the 4.7L?
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Demon Dakota
DakotaEnthusiast
5/06/2003
15:47:21
| RE: Getting more bottom end out of a 4.7
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Message:
What we need is a variable length intake manifold (computer controlled, of course). That way we could adjust the powerband to suit our needs. Imagine the better throttle response, low end increase in TQ, and mid and upper end HP increases. That, coupled with a turbo or a S/C would be a phenominal increase in overall engine efficiency.
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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Demon-Xanth
Dodge Dakota
JOIN HERE
5/06/2003
16:09:39
| RE: Getting more bottom end out of a 4.7
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Message:
You can have anything you want. All it takes is money.
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Demon Dakota
DakotaEnthusiast
5/06/2003
16:24:35
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
I got money. What I need is someone who can build the damn product :)! Seriously though, if I could find a reliable hookup for producing a variable length intake runner design, I'd be all over it in a heart beat. I'm already committied to long tube headers. Some one else needs to take this one on...
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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Troy
Dodge Dakota
JOIN HERE
5/06/2003
17:01:22
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
What do you mean your committed to long tube headers? Are you getting some designed/ made? I want this style for my 2003, but nothing but shorty style is available. I had equal length, long tube headers on my 2000 5.9L and the torque was awesome. It also sounded great and helped with the top end as well. They were Kenne Bell (which no longer makes headers), and the pulse divider really helped the sound and power in my opinion.
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Chipster
Dodge Dakota
JOIN HERE
5/06/2003
19:42:55
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
Changing the length of the runners moves the
HP curve up or down the chart. Old Dave
Hughes has cut a couple of intakes open and
shortened the runners. The guys he sold them
to never dyno'd them after installation. So we
don't know if they took care of the dip in HP. I
was going to buy one from him, but he has
none modified and has no time to modify any.
The same old story with Dave, no time for the
4.7 guys.
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Demon Dakota
DakotaEnthusiast
5/07/2003
17:58:56
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
Troy,
Yes, I'm in the beginning stages for design on long tube headers for the 4.7L. And yes alex, my boy said he can make them with or without the precats, so you're in luck. They're going to be ceramic coated as well. There currently is no price available b/c we need to figure out everything and do dyno testing...blah blah blah. I'll tell you this, I'm not going to pass the R&D costs to the buyers. I'll just eat it and call it my contribution to the 4.7L Dakota performance world (along with the headers, of course).
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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Troy
Dodge Dakota
JOIN HERE
5/07/2003
18:14:16
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
Cool!!! Do you know when these will be ready for purchase. I'm really interested in this.
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.alex.
Dodge Dakota
JOIN HERE
5/08/2003
08:39:35
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
Dude, if you can get those to market and not charge any more than JBA does, then I bet you & your dude will move some serious headers!! Long tubes are gonna make some serious power over & above the shorties that are currently available. I can't wait to see what ya'll come up with!!
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Demon Dakota
DakotaEnthusiast
5/08/2003
10:55:27
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
Yeah, I can't wait either. It sucks spending all my mod money on R&D though, but in the long run it will be worth it. I'll keep everyone posted.
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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Billy
Dodge Dakota
JOIN HERE
5/08/2003
11:20:01
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
How are these long tube headers going to
help with the basic problem of the engine.
Which is the shrouded exhaust valve? Mopar
engineers developed thier exhaust system to
within 2% of headers.
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.alex.
Dodge Dakota
JOIN HERE
5/08/2003
11:31:09
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
They designed them to within 2% of SHORTY headers. LONG TUBE headers should make much more torque and a good bit more hp through the mid and top end rpm band. If you're worried about the shrouded exhaust valve, then take off the heads and clean up the bowls. That's what I plan on doing.
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y-pipe
Dodge Dakota
JOIN HERE
5/08/2003
12:59:46
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
Yea - only beacause of the wee wee 2" y pipe. You take it off, and the difference between the headers and the stock manifolds increases a bunch!
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.alex.
Dodge Dakota
JOIN HERE
5/08/2003
13:37:53
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
That's an excellent point.... are you sure it's a 2" y-pipe? It looks even smaller than that. Just crawling on our bellies(without jacking the truck up in the air to measure), me & the muffler dude thought it might even be 1 3/4."
That's my next project. Bigger y-pipe.
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Quadster
Dodge Dakota
JOIN HERE
5/08/2003
14:44:44
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
I have been comtemplating a change to my exhaust too and have finally decided on a way to eliminate the y-pipe altogether, see what you think. Cut the two pipes off before entering the y, then run each into a 50 series SUV Flowmaster which has two 2.25" in and two 2.25" out. This will eliminate the restriction at the y and using the single muffler will keep it lighter than using two AND give both exhaust pipes a balance effect (rather than using two mufflers and a crossover tube). If it's got a flowmaster on it, it's got to sound good:-) If you are curious about the 3rd cat, it will accidentally get forgoten when welding all this back together:-o
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Demon Dakota
DakotaEnthusiast
5/08/2003
15:45:59
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
Why even use a Y-pipe at all? Just go with a true equal length dual exhaust setup :)~
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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Quadster
Dodge Dakota
JOIN HERE
5/08/2003
16:06:23
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
The method I am talking about eliminates the Y pipe. I like the idea of a true dual exhaust but wish to have a crossover tube and the only way I see to have it in an "equal" location to both pipes is to make an S bend with the crossover tube and attach it 24" further back on the passenger side. This is assuming that I leave both pipes routed down the passenger side of the truck. If I remember correctly, there's not enough room to run a pipe and muffler on the driver side?
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Demon Dakota
DakotaEnthusiast
5/08/2003
16:49:11
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
Quadster, you are correct in that a muffler and exhaust tubing will not fit down the driver side (well, not without some serious modifications to everything under the truck). I think you're also in the ballpark with your measurements. An X-pipe would probably be more ideal overall to help with efficiency/scavaging, but where will you put one? Or where will I for that matter...
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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Quadster
Dodge Dakota
JOIN HERE
5/08/2003
17:02:28
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
I love the way an X pipe sounds and if I could find a way to fit one in the Dak, I will do it!
I have JBA headers on order that should be in by Friday and I'm trying to get my exhaust plan together so I can do it all at the same time.
Are you running a crossover tube on your true dual exhaust Demon? And what mufflers and pipe size did you go with?
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y-pipe
Dodge Dakota
JOIN HERE
5/08/2003
18:40:50
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
alex - you may be right. It may be 1 3/4"
To run "true" duals on a Dakota, you must run both pipes down the passengers side. The x-pipe crossover goes where the main cat is. If you want to keep your cats, then run two of them right behind the crossover. You need a tamdum x-pipe. It allows you run the pipes only one inch apart.
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Demon Dakota
DakotaEnthusiast
5/08/2003
19:47:50
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
Quadster,
I haven't yet found an off the shelf unit that will do the trick, so I'll have to fabricate my own. I went with Dynomax racing mufflers, and the pipes are 2.5" in diameter.
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
|
azdak
Dodge Dakota
JOIN HERE
5/08/2003
23:41:54
| RE: Getting more bottom end out of a 4.7
IP: Logged
Message:
longer runners do not increase bottom end short runners increase low end. take the tunnel ram intake manifold for instance. it does nothing till around 3000 rpm up to the 8500 mark hipo motors turning a lot of rpm run open plenum manifolds. also the crossover pipe in the exhaust only needs to connect the two pipes it has no flow value but rather pulse value. the standard rule is a line of paint down the pipes where it stops burning off after a couple minutes is where it goes. usually equal distance from the manifold ive said this before it works and it sounds good to, i got this from an old hot rod article as well as the differance between 2 1/4" to 3" exhaust and there flow properties on a motor (350)sb at below 6500 and it was not significant. the volumetric efficiency for a 2 1/4" pipe is more than you think the gases will flow faster than the 3" due to scavenging of course these numbers are per bank of cylinders
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Troy
Dodge Dakota
JOIN HERE
5/09/2003
07:49:32
| RE: Getting more bottom end out of a 4.7
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Message:
The stock y-pipe is 1-3/4".
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Quadster
Dodge Dakota
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5/09/2003
09:07:20
| RE: Getting more bottom end out of a 4.7
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Message:
I crawled under the Quad Cab last night and measured the stock pipes into the Y and they measured slightly over 2" in the straight section, which means they are 2" ID. I was a little dissapointed to find this out, I was thinking they would at least by 2.25" :-(
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