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All About Exhaust Systems

90 messages,  Last post on Jun 17, 2009 at 1:11 PM

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What is this discussion about? Exhaust, Diesel, Fuel Efficiency (MPG), Car Warranties, Coupe, Convertible, Hatchback, Truck, Sedan, Wagon, SUV, Van

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#87 of 90 Sierra exhaust: less is more? by gabrieltelling Nov 06, 2008 (10:07 am)
I have an 02 GMC sierra 4x4 with a 5.3. It has two catalytics, one per pipe, then the pipes Y together into the muffler. I, being a carpenter, took my sawzall and cut the muffler off and replaced it with a 30" section of straight pipe. The truck sounds fantastic, and of course it feels like it has more horsepower. But I'm getting 16.5 mpg on the interstate. My neighbor has a 99 silverado all factory and he gets 20.    So, I am trying to sort this exhaust business out. I do not need more horsepower than the truck comes with from the factory. What I am interested in is sound and mpg.    What is a 'tuned' exhaust? Does it do something that I can't by merely buying 2 mufflers and having my mechanic make true dual exhaust?    Am I gaining anything other than sound with true duals vs. single muffler? Does one flowmaster perform better than one factory muffler, or is it just the sound factor?    What if I bought a chip and left the exhaust as is? Would the chip compensate for the loss of back-pressure and re-tune the engine in a way that recovers mpg?       There are so many options and variables, I don't even know what to base a decision on. Again, what I want is best mpg, best setup for the longevity of the engine, and some sound. Oh yeah, and I don't want to spend more $ than I'm going to get back over the life of the truck. Simple right?      Thanks, Gabriel Replies to this message: obyone (Nov 06, 2008 2:47 pm)
#88 of 90 Re: Sierra exhaust: less is more? [gabrieltelling] by obyone Nov 06, 2008 (2:47 pm)
Replying to: gabrieltelling (Nov 06, 2008 10:07 am) Sawzall eh?   You don't state what your mileage was before hacking the exhaust. Plus your neighbor's version of the 5.3 produces less hp than the '02. One thing I can pretty much guarantee is that there is virtually no hp gain nor significant mileage increase over stock with a catback "tuned" for your truck. Forget the flowmasters. They will crap out within 4-5 years forcing you do buy another. Plus they will get you less mpg than you're getting now.   Corsa and Borla make the best exhaust systems. They will outlive your truck. Install one of those and forget about it if what you're looking for is a loud but no resonance exhaust.   Am I gaining anything other than sound with true duals vs. single muffler? Does one flowmaster perform better than one factory muffler, or is it just the sound factor?   True duals will lose low end torque and lower mpg. Flowmasters will create more problems than you would want.   What if I bought a chip and left the exhaust as is? Would the chip compensate for the loss of back-pressure and re-tune the engine in a way that recovers mpg?   A chip may give you an increase in HP depending on which one you get. It will not increase mpg nor compensate for your sawzall job.   Oh yeah, and I don't want to spend more $ than I'm going to get back over the life of the truck. Simple right?   Yes and no. The cheapest route and perhaps the most effective at this point would be to install a Borla or Corsa muffler. Might not be tuned specifically for your truck but some of them will make your truck sound like it has a big block. Assuming that's what you want. Check out some of the online sellers for the muffler and if you have a mig welder you can do the install yourself. Wait. Sorry you're a carpenter not a welder. Well take it to a muffler shop and they can weld it on for you.   I'm surprised that your truck doesn't give you any problems since it lacks a muffler.
#89 of 90 Re: 1994 4Runner Exhaust Corssover Manifold [jspiro] by allenjackson Nov 10, 2008 (9:48 pm)
Replying to: jspiro (Sep 24, 2008 2:38 pm) There are two types of manifold restriction. With manifolds in-hand, look inside one of the two "T" junction ports. You will see the slots in the main tube. That slot material is one type of restriction. The 2nd type is present in all 3 ports. Put your finger inside any of the three ports, and feel for a raised welded bead at the opening where the tube itself is welded to the flange. If you measure the holes in the engine head, and compare that dimension to the inside diameter of a clean manifold tube, you will note them to be about the same.
#90 of 90 Exhaust by 2000exped Jun 17, 2009 (1:11 pm)
I have a 2000 Ford Expedition 4.6L with about 150,000 miles on it. I was driving and I'm not positive but I think I heard a pop, kinda like a cork from a wine bottle, then I heard what sounds like a belt flapping or as I read on another post, sounds like a chopper. I pulled over and looked under the hood. A usual DIYer co-worker says it sounds like the exhaust, but can't tell for sure. It starts up fine, but the chopper sound is noticeable and loud (not like metal hitting metal). For a while before this happened I was hearing a ticking sound when it is idleing, not really noticable when driving just mostly when idleing and sometimes the truck rattled, but not all the time. Not sure if all these are tied together with the chopper sound. I've never had work done on the exhaust other than installing an aftermarket exhaust. I managed to drive it into a parking lot, but afraid it would do more harm driving it to a repair shop and until I can figure out what the problem could possibly be and have it towed. Do you have any suggestions as to what the cause of the sound could be? Could it be the exhaust manifold?

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