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so a friend told me i should just cut the muffler off my 05 dakota and replace it with a pice of pipe so will i lose any hp or torque or gain any ?
 

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not too sure, but the muffler does create some bit of back pressure so removing it can increase HP a bit, but i wouldn't think it would be enough to notice. it will be louder
 

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I know straight piping is very popular with cars (ricers) so theres gotta be a better reason then it sounds good as to why they do it. I would get a flowmaster muffler instead of cutting it out completely. I have a 30 series and i like it.
 

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You may lose a bit of torque in the lower RPM band but gain a bit of HP in the upper RPM band. Torque is what gets you moving, so for a truck I would go with a more free flowing muffler that will still keep a tad of the backpressure needed to make torque.
 

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I just cut my muffller on my 2000 sounds wicked goin to run a small glasspack just to tune the noise a littlle and have it come out just in front of rear wheal
 

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so a friend told me i should just cut the muffler off my 05 dakota and replace it with a pice of pipe so will i lose any hp or torque or gain any ?
You mean just the muffler and not the cat?, because if you remove the
cat, (which is illegal) as well, it will probably fail emissions test and the 02 sensors pre/post cat won't function correctly and the PCM will post a Check engine light.


Probably an increase in peak engine horsepower can be achieved
but only at higher rpms and that isn't going to happen very often
if you have an automatic on your truck.

The huge disadvantage of running a straight pipe after the cat is
that there won't be any back pressure from the muffler to scavenge
the exhaust at low speed and without some kind of muffler behind the
cat, those loose and expensive platinum catalyst beads will get blown
out over time and the truck could very well fail the next emissions test.

Here's some more disadvantages:
-Engine sound may be more noticeable to both driver and pedestrians, resulting in increased noise pollution. Cops may be targetting you for excessive noise.
An incorrectly designed exhaust can cause loss of low-RPM torque, and a possible decrease in fuel economy.

Also, some modifications can also void factory warranties, although a 2005
is 6 years old and probably well out of warranty.

From your truck's "bio" you live in Ontario with the scheduled emissions tests done every second year. If it were mine, I would NOT take a chance on it.
It might pass the next emissions test and it may not..and at that point to get it to pass, you will need to install an aftermarket muffler of some kind, and repeat the emissions test over again.
 

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Hi everybody, my truck actually ran a lot better after I had some generic turbo mufflers installed. When I got it someone had removed the cats and muffler and installed to pipes out to the rear. I think this caused it to run lean because it would pop out the exhaust going downhill, strangely enough I get better gas mileage now.
 

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Hi everybody, my truck actually ran a lot better after I had some generic turbo mufflers installed. When I got it someone had removed the cats and muffler and installed to pipes out to the rear. I think this caused it to run lean because it would pop out the exhaust going downhill, strangely enough I get better gas mileage now.
What was done with the two O2 sensors?
Running straight pipes on a modern V8 doesn't make a lot of sense,
unless you modify it for the racing strip only.

You lose the scavenging effect due to eliminating any backpressure
in the exhaust caused by the cat and the muffler and the pCM
will ignore the sensor data..because it probably doesn't make much
sense to it at this point.

Popping out the exhaust means some unburned fuel gets re-ignited
inside the exhaust pipes and that creates a little pop when you
go downhill because you are coasting/backing off on the throttle.

Unless you have modified the injector/O2 sensor curves in the
PCM you are probably burning a richer mixture...but I don't
know what else was done in the process of modifying the exhaust
system on your truck.
 

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I agree with caverman on the merits (demerits actually) of removing the cats. Without the O sensor input, the ECU/PCM will stay in open look mode which will be rich, so any efficiencies that took years to engineer into these new motors have now just gone down the toilet. The straight pipes with no cross-over will actually give you less power than you had with a single exhaust and all the other stuff hanging on. If you were able to design some simple circuitry, you could make a "fake O sensor box" which would allow the PCM to close the loop, (I'd just change to a high-flow cat on each side - this way I could still add the sensors and have the ECU work as it was intended to) and then add an X cross-over which would assist in the exhaust scavenging. The cross over (either X or H) is a good idea for any dual exhaust, especially with a V8, whether you use mufflers or not.
 

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Sorry guys I should have given a little more details. The truck I was referring to was my 1987 Dak. 3.9 with carb, 02 sensors in exhaust manifold. The fuel injected truck is my wifes and she would skin me alive for messing with her exhaust, she likes her Dakota just the way it is. On my 87 I just couldn't stand the noise from the straight pipes, maybe in my younger days but not now.
 

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Sorry guys I should have given a little more details. The truck I was referring to was my 1987 Dak. 3.9 with carb, 02 sensors in exhaust manifold. The fuel injected truck is my wifes and she would skin me alive for messing with her exhaust, she likes her Dakota just the way it is. On my 87 I just couldn't stand the noise from the straight pipes, maybe in my younger days but not now.
Adding dual exhausts to that vintage 3.9 V6 should be relatively simple - you can weld in the O sensor threaded fittings & you don't need a cross-over (the firing order of the V6 is more "balanced" than you get on a V8). Once you install your custom bent (I'd select mandrel bending instead of the cheaper ripple bending) pipes and mufflers of choice, you should have a truck with good sound & response.
 

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I prefer a good sound that is not very loud. I usually do a "cat-Back" exhaust whenever I replace one. On my '06 3.7 liter I am going to replace with a Flowmaster exhaust. Who knows if I will gain anything on hp, but I will lose about 100 lbs in the weight department... lol. The stock exhaust has two small "cats", a resonator, a mufller as long as I am tall, and another resonator before it exits behind the right rear wheel. DANG!!!!
 
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