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All About Exhaust Systems



  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,422
    So it's a 6 cylinder?

    Well that's what the book says:

    "Remove the 6 nuts, crossover pipe and 2 gaskets."

    Have you removed the intake manifold and stripped everything else off the top that you need to? Maybe that's how you gain access.


  • srs_49srs_49 Posts: 1,394
    Sorry for the untimely reply, but...

    I never had to touch any of the exhaust components (pipes, muffler, cat, hangars) on my '94 Dodge Caravan. That was in something like 174,00o miles of driving over 11 years (got rid of it back in 2005).
  • 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
  • obyoneobyone Posts: 8,065
    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.
  • 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.
  • 2000exped2000exped Posts: 1
    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?
  • all exhaust has a database and how tos if you run into a problem with installation they have every single exhaust, header, and muffler. Yoiu can also try searching youtube for your year make and model and the exhaust part you want for install videos.
  • kiawahkiawah Posts: 3,666
    Well you need a mechanic to look at it, could be a number of things.

    If you heard a loud metal hitting metal sound prior to the pop, it could have been internal engine parts (like from the valves or piston/crankshaft), and then a 'pop', which could have been a backfire/explosion from unburned gas which got dumped into the exhaust pipe where it ignited and exploded.

    Shouldn't have been driving it with making a loud noise like that.
  • mg45mg45 Posts: 8
    Hello, i am new to this forum and this is my first post. I have a 1999 saturn SL2 that is getting miserable gas mileage, 12 mpg! I have been calculating the gas mileage by setting the trip ODO and driving miles driven by gallons used, as well as by the gauge and using a few iphone apps. Im getting a max of 150 miles per tank.

    I noticed today that when i rev the car, it sounds very "ricey". I am thinking maybe the catalytic converter is falling apart, like some pieces of the "honey comb" inside the converter. Maybe this is causing my bad mileage? I would love to replace it in a heartbeat, but as you know it's not the cheapest thing to replace. But if the cat is the problem, it will be replaced ASAP. Below is a link to a video i made tonight with the exhaust sound on my 99' SL2. Below the link is a list of all the things i have done/replaced on the car in trying to fix this issue.

    If you like, give it a watch, or listen and tell me what you think it could be. Also the exhaust pipe and muffler from behind the cat has been replaced back in april when i bought the car, due to a nice rust hole at the first bend behind after the cat. The car doesn't have any loss of power, just the ricey noise and bad gas mileage. Here is the link:

    Here what i have done:

    Transmission was rebuilt at 78,000k due to reverse slam and burnt fluid, current mileage is 84,200k

    Exhaust pipe after the Cat has been replaced.
    ECTS and connector
    AIT and connector
    Thermostat, and radiator flush
    Fuel filter
    Injectors have been cleaned
    Spark plugs replaced with NGK coppers and wires
    Map sensor
    PCV Valve
    Front Oxygen Sensor, OEM not spliced.
    Cold air intake

    The car doesn't burn a drop of oil and is always up to date on oil changes. Any help would be great!
  • srs_49srs_49 Posts: 1,394
    Is your check engine light (CEL) on? If so, did you have the OBD-II codes read? That's the first step in diagnosing anything on a post 1996 vehicle.

    Without any codes to go by, I would replace the front O2 sensor (though I see that you already did that), though if that were bad it should set the CEL. It could also be a vacuum leak which lets more air into the intake. That might causes the ECU to dump more fuel into the engine in order to keep the air-fuel ratio without bounds. These are just guesses.
  • mg45mg45 Posts: 8
    Thanks for the reply. There are no engine or service lights lit on the dash.I had the car car scanned for codes at auto zone a few times but no codes are coming up.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,422
    Okay, so then we sit down and play Sherlock.

    What throws no codes on an engine that sounds like it is running well, but could result in awful gas mileage?

    (I'm thinkin' I'm thinkin' :confuse: )

    Excessive fuel pressure from the FP regulator?

    Leaking injectors?

    Not shifting into high gear?


  • kiawahkiawah Posts: 3,666
    - Dragging brake pistons, or mis-adjusted parking brake.
    - underinflated tires
    - my first thought when I heard that whinning, was a bearing going bad on air compressor, waterpump, or alternator
    - and that is a really throaty exhaust any back pressure?

    What is the color on the interior of the tail pipe? Is it a really rich black substance, showing as running too rich?
  • mg45mg45 Posts: 8
    I jacked up each wheel today and the brakes are not sticking. The tires also have 32psi listed on the tag in the door jam. I removed the front o2 sensor and the car drove the same if not worse, so i don't think the cat is clogged. I also put my hand over the tailpipe, but it kept getting pushed off from the pressure, so once again i don't think thats clogged.

    The inside of the taipipe does have a good amount of black substance, that it actually left a black line going down the exhaust pipe and onto the muffler, but the car is not blowing black smoke. I also removed the spark plugs and took some photos of each, as well as the exhaust pipe. Here are the photos:">
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,422
    You're running rich all right.


  • mg45mg45 Posts: 8
    Ok, as you can see from my first post those are all the things ive replaced. What should i do next? The only sensor i haven't replaced is the cat o2 sensor, but there are no engine lights on. Im thinking injectors? Should i pay the 65 bucks to have them professionally removed and cleaned, or could it be something else as well?
  • watkinstwatkinst Posts: 122
    It's a saturn!

    Any chance its leaking gas when its rolling down the road? I worked for saturn in the early years. Only saturns that didn't burn oil were the ones in the shop getting the fuel pumps replaced or the one's at the scrap yard being scrapped. Hence not running.

    Later years the Honda motors were nice but the rest was well what can I say GM parts.

    Its a fuel system issue not an exhaust issue or break issue or tire issue. Given your car has no engine lights on would indicate that the car has more than just a fuel system issue given the GOV mandated engine management systems are failing to pick up an obvious fuel issue. When was the last time you had it smoged? Did it pass?

    The fuel goes some place :-)

    Is your kid or neighbor syphoning your tank? I'd consider that a very big possibility given its nearly impossible for that car to burn that much fuel without very obvious problems.

    Get a locking gas cap! See if your milege improves - they cost like $8 :-)
  • mg45mg45 Posts: 8
    I tried that before except with a clear piece of tape on the gas tank cover at night to see if anyone was siphoning my gas. As for leaks, i looked under the car while it was running and after a drive but i don't see anything leaking, (one of the first things i suspected. I also revved it while looking underneath but once again, i didn't see any leaks. Are there any special places i should look for leaks at that are most likely going to leak? What about the pictures i posted, does it look like it's running rich? Also I've been getting this gas mileage since day one when i got the car in April 2009. It was inspected then and passed. I live in New York and its due for inspection in April.

    Don't they just hook something up to the OBDII and scan for codes? And if nothing comes up then they pass the car? Thats what all the mechanics i talked to over here said, unless the car is older and doesn't have OBDII. Here are the pics again:
  • watkinstwatkinst Posts: 122
    No engine lights - would mean essentially no codes to pull if NY inspection is only doing a non run - check the codes inspection. I'm not familiar with NY inspections.

    Do you live in the city? I didn't know people owned cars there? HA HA Wife lived in NY for 7 yrs.
  • srs_49srs_49 Posts: 1,394
    The cat O2 sensor (in back of the cat) has nothing to do with how the car runs. It's just there to monitor the efficiency of the catalytic converter. It's there to make sure the cat is doing its emissions thing.

    Shifty/anyone else - Don't you think if he's running that much excessive fuel through the engine, it would fry the cat in short order, and so set the CEL? Cat's are not tolerant of fuel-rich exhausts, IIRC.
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