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MD
Dodge Dakota
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10/26/2003
19:10:46
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 Subject: RE: 4.7 Exhaust Drama
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DemonDak - you are absolutely correct that we are, or should be, talking about gas velocity and not backpressure, to explain the exhaust process.
My expertise is not in that area. However - one final point - given the mods of a particular engine (or lack of same) - an optimum diameter of the exhaust pipe is one that optimizes exhaust flow. Larger, contrary to the belief of some here, is often not better, and can actually have a delitorious effect on the flow. The application of equal or unequal header pipe lengths can also have an effect on velocity. Gary Hooker and I had this same discussion 35 years ago. He, along with other makers, can and does manufacture exhaust systems that utilize differential piping diameters and header pipe lengths to affect torque and power curves up and down the RPM range. Modern computer controlled engines can and do make running, real-time adjustments to account for myriad variables that impact engine performance - and to some extent these computer generated real-time adjustments can make up for some, but often not all, physical shortcomings of various components - of which a given engine's exhaust system and its ability to scavenge exhaust gases at optimal velocity is but one of those components.
BTW - your comment about "Butt Dyno" was not only humorous, but spot on accurate. A whole bunch of folks on here mistake noise for power.
MD
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j
GenIII
10/26/2003
19:22:37
| RE: 4.7 Exhaust Drama
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I can only speak of my own experience. When I switched from the stock exhaust to my 3" Magnaflow catback there was definitely a loss of low end torque. There was no question about it. With the stock setup I could spin the wheels way too easily and the loss was actually somewhat of a benefit. I don't think it is going to show up on a dyno, since most dyno graphs don't go below 3000 rpms. If you optimize flow at one rpm, you are going to sacrifice it at another.
2000 4.7 CC auto, clear corners, Spintech true duals, Kenne Bell s/c, Aquamist water injection.
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Chipster
Dodge Dakota
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10/27/2003
12:08:02
| RE: 4.7 Exhaust Drama
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Message:
J..... I had the same thing happen to me. When
I got on it, (after my exhaust mod), it would
make this sick sound and do nothing. Then I
put an Optimizer II on it, which bumped up the
timing and that made things all better.
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.alex.
Dodge Dakota
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10/27/2003
13:43:41
| RE: 4.7 Exhaust Drama
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Message:
Jeez, i hate to add fuel to the fire, but I have to put in a vote for the 2.5" true duals set-up.
I have run a 3" single exhaust since about 2 months after my truck was new. The factory y-pipe into a 3" cat into a 3" Dynomax cat-back system. When i started out, it was just the cat-back system..... Then Duner told me to add the 3" cat and 3" pipe from the y-pipe to the cat. That picked it up a lot. It's been like that until last Friday.
Then I got 2.5" true duals run. No cat, x-pipe, short magnaflows, and turn-downs. It picked up from running consistent 14.4's to a best of 14.14 on Saturday night at the track. I backed that up with a 14.17 and a 14.23 and a 14.22..... I also picked up 1.6 mph in the 1/4 mile.
Take it from a guy who's almost in the 13's with an all-motor club cab (with a 3.55 rear end)... If you have a large TB & HO cams, or if you have forced induction, the true duals are worth it. Go. Now. Get it done. Seriously.
Dyno results in a week or two.... I promise.
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j
GenIII
10/27/2003
18:19:00
| RE: 4.7 Exhaust Drama
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I agree, the true duals were a big improvement over my catback. My problem is the engine runs lean and there is no way to tune this thing. So I don't feel I'm getting the full benefit of my exhaust or the s/c either.
2000 4.7 CC auto, clear corners, Spintech true duals, Kenne Bell s/c, Aquamist water injection.
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Demon Dakota
DakotaEnthusiast
10/27/2003
22:51:49
| RE: 4.7 Exhaust Drama
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Message:
Tell me about running lean...I'm going to have to go to larger injectors ASAP.
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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Demon Dakota
DakotaEnthusiast
10/27/2003
22:54:53
| RE: 4.7 Exhaust Drama
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Message:
Alex, that's the same setup I had before the header adventures. I might have to go back to a "semi-stock" exhaust setup until I can figure out what to do with running lean. I'm running exceptionally lean right now, and the only thing saving my a$$ is the colder weather right now (I think)...
Oh well, exploring the possibilities of 4.7L power is turning out to be more of a challenge than I thought...
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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.alex.
Dodge Dakota
JOIN HERE
10/28/2003
09:20:48
| RE: 4.7 Exhaust Drama
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Message:
Demon,
Check out the Roe Fuel Controller for sale in this same section..... Plays with the MAP sensor and allows rich/lean adjustment. See if that helps. I've got one on my truck, but just havne't had the patience & dyno time to dial it in.....
E-mail me about your heads!! What shop did them for you? truck_nut@hotmail.com
Thanks dude.
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.alex.
Dodge Dakota
JOIN HERE
10/28/2003
09:28:34
| RE: 4.7 Exhaust Drama
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Message:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2439223323
ROe Fuel Controller. Buy it now for $225. They sell at KRC for $450 and Roe Racing sells them For $425. I got mine for $250 from (formerly) CadetDak. They work pretty good, but I just can't find the dead on tune.
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Demon Dakota
DakotaEnthusiast
10/28/2003
20:43:02
| RE: 4.7 Exhaust Drama
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Message:
Alex, I'll give you the folks that did mine, but I would in no way reccommend anyone else using them. They really tried to rip me off (twice). I don't screw around when it comes to money and my stuff, and they royally pissed me off...
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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.alex.
Dodge Dakota
JOIN HERE
10/29/2003
08:46:47
| RE: 4.7 Exhaust Drama
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Message:
I'll shoot you an e-mail & you can tell me what happened. I guess I really want to know prices & what you asked for them to do....
Doesn't sound like it turned out very well....
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buy cheap oem
Dodge Dakota
JOIN HERE
2/12/2012
04:06:00
| GNBQBCGoDSq
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Message:
ow5Hhv Thank you, a very interesting note!!...
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