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Mills
Dodge Dakota
11/05/2001
21:42:42
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 Subject: exhaust inconsistencies
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Message:
hi everyone...quick question. I recently (August) become a proud owner of a 2000 Dak CC w/ 4.7L V-8. I've been thinking about going to an exhaust upgrade (gibson dual cat-back). I have seen many posts saying that adding a dual actually lowered performance, and I have seen others that say it made it better. So my question is, who is right? Thanks for the help.
Mills
2000 4.7L, Kick @$$ blue Dak
K&N filter, Extang Tonneau, Herculiner
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CW
Dodge Dakota
11/05/2001
22:31:59
|  RE: exhaust inconsistencies
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Message:
Good question. Wish I had a g-tech I will be surprized if it has a noticable difference either way. I am going for the sound plus if there is a noticable diff then I will put the stock system back on. I have the cat back off of my 97' sitting in the corner.
My theory being that if the truck slows down dew to uncorking the exhaust then it is running lean. When the exhaust is lower restriction there is more air going through leaning out at full throttle. Maybe the 4.7 is a delicate balance and the exhaust upsets the balance. Hopefully that I will be able to put a little more fuel in with the IAT adjuster but just a thoery at this point though. They seem to take to the intake mods just do intake then exhaust.
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Dan Gruber
Gen III
11/06/2001
12:34:21
|  RE: exhaust inconsistencies
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Message:
I have the Gibson single side swept. I can't offer any hard data on performance gained or lost in comparison to the stock exhaust. And the answer on gained or lost performance may depend on how you define performance (improvements in low-end vs. improvements at high rpm). But as I understand it, the theory goes something like this. A single larger diameter exhaust (like the Gibson) is supposed to increase mid-high end power by reducing backpressure, but it doesn't reduce backpressure enough to kill low end torque. Good low-end torque requires some backpressure in the exhaust system, except on turbos...turbos tend to like a really open exhaust. A dual setup may increase high end power more by reducing backpressure more than a single, but it might come at a small expense of low end torque.
After installing my Gibson single, I felt that it pulled harder from about 3200 RPM on up. Did I lose torque but gain hp? Did I not lose torque and gain hp? I have no idea. I don't have dyno sheets or even track data showing before and after. All I know is that I like the sound and don't much care if I gained or lost anything.
Dan
2000 CC SLT 4.7 4X4 Auto 3.55 LSD
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Mills
Dodge Dakota
11/06/2001
12:57:42
| RE: exhaust inconsistencies
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Message:
did you happen to notice any change in your gas mileage?
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Dan Gruber
Gen III
11/06/2001
20:05:48
| RE: exhaust inconsistencies
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Message:
Short answer: No, I didn't notice a change in gas mileage.
Long answer: There were several mods that I did within a two-three week period: install the gibson single cat-back, install an airaid, and install a 200 pound topper, all around the 5000-6000 mile mark. If I gained any mileage or performance from the gibson/airaid combo, I lost it with the topper. I did notice a significant improvement in performance with more miles...1/4 mile runs changed from 16.9 @ 79.5 at roughly 6500 miles to 16.4 at 81.5 at roughly 15,000 miles, give or take a couple thousand either way and both under similar weather conditions. But those runs were all after the gibson, airaid, and topper installations, so I don't have a stock baseline to gauge performance improvements. I pulled off the airaid this summer because as the weather got hot, the truck felt really doggy...I think it was sucking hot humid Tampa air really bad because as soon as I put the stock airbox lid and filter back on it seemed to perk up considerably. I have also recently pulled the topper off and installed a soft tonneau cover. That helped the truck feel more lively, and I noticed a small gain in highway mileage, from just under 17 to just over 18. Now that the weather is cooler again, I'm going to re-install the airaid to see if that makes a power and/or mileage difference by itself. But the mileage differences are all relatively minor: new with no mods I got about 13/17-18 city/hwy; with all the mods and the topper I averaged 13/17; now with no topper and just the gibson I'm at 13.5/18. This doesn't account for seasonal differences (running the AC in summer vs not running it in winter) of about 1 mpg.
Dan
2000 CC SLT 4.7 4X4 Auto 3.55 LSD
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Mills
Dodge Dakota
11/06/2001
21:29:11
| RE: exhaust inconsistencies
IP: Logged
Message:
I'll be curious to hear about the difference in installing the airaid made much difference. I still just cannot decide if single or dual is the way to go...it seems very much like a give and take.
p.s. good move on the soft tonneau...putting mine on made a huge dif in my mileage and a slight (but noticeable) dif in higher speed performance.
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