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Realistic HP gains from intake and muffler

Discussion in 'Performance & Fuel' started by theartist, Apr 29, 2010.

  1. theartist

    theartist New Member

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    Hello all. New guy here
    I recently purchased a new 2010 chevy silverado.
    it has the 4.8 v8 2wd. and i looove the power, coming from a 4.3.
    that being said, i'd like MORE. lol isn't that always the case? needing more power.

    Anyway, i DID just buy a new truck and i don't have a lotta money to spend, so i'm thinking an intake and muffler would be the obvious choice.
    So, realistically, what kind of horsepower gains should i expect from...say, a K&N air intake system, and a flow master muffler, or corsa, Single in-Dual out.

    Sorry if this could've been found using the search feature. i DID look, but it's late, and i'm late for bed.
    Thanks for any input!
    #1
  2. vncj96

    vncj96 New Member

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    depending on what you wanna get from what company they actually have dyno tests for some products, but realistacally you arent gonna feel mu if anything, but for sure you will see in your upper RPM band, your RPMs will climb quicker when trying to pass someone. But agin it really comes down to the truck. You could take an identical truck to yours and add the same things you do and you will get different results. Its reallywhat your prefernce and budget are gonna allow
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  3. murdog94

    murdog94 New Member

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    X2. Ive had CAIs and exhaust, and noticed a nominal gain, but i really like the sounds, and the typical mpg increase.
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  4. theartist

    theartist New Member

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    alright, thanks, I see what you're saying about every truck being different. I think that applies to a lot of different things other than trucks also.
    but anyone else? any opinions suggestions or so on?
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  5. ejohnson03

    ejohnson03 New Member

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    In my opinion....

    Just a muffler swap won't give you much of a HP gain.

    You would need to go to a set of Headers, Hi-flow CAT's and then muffler.

    Now your talking some extra ponies....
    #5
  6. Enkeiavalanche

    Enkeiavalanche Moderator

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    A good cat back system like from Corsa or Borla or Billy Boat About $699-$900 A good CAI about $250.00 HP Gains I would say about 15-30 Hp Headers ? Your factory Header and Cats are not as bad as they used to be. They are pretty much open..A good programer will also give you some power..MPG's all depend on your Right foot.. I am now Avg'ing 14 and on the way up with my 08 5.3 Avalanche.

    Good luck and just remember If you have more air coming in (CAI) You have to do the same for the Out put (Exhust system) Also keep your Mass Air Flow Sensor clean.
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  7. Quincy

    Quincy New Member

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    OK now I know I will be in trouble for this buy here goes,,, this is an opinion forum right? I bought a Spectre cai for my 06 Silverado 5.3 and noticed about two mpg increase after about 100 miles of driving until the ecm could figure out what was happening and adjust. This was done with no exhaust mod. The part cost a little over a hundred bucks after I shopped around and it was the same as the high end parts and looked better than some of them.

    Frankly any company that sells a six inch tin tube and air filter for $300 plus should be boycoted. Same for an exhaust system. Exhaust systems are two things, bigger pipes and header tubes the same length which is a poor mans way of saying they are "tuned" You are really buying the space inside the pipe if you know what i mean.

    Also if the vehicle is new I dont understand why someone would tear off good exensive parts that are brand new and they are probably making payments on and throw them away.

    Spend the money on stuuff to make it prettier that you can see like running boards or a tonneau cover or what ever.

    Anyway, no offense meant this is just my humble opinion.

    Good luck with the new ride.

    Q
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  8. theartist

    theartist New Member

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    guys, remember, this is a NEW truck. tearing off the whole exhaust is out of the question. so is a tuner... don't know about the other stuff. I'm up for anything that won't void my warranty.
    I ask about the muffler because any thing behind the cats ie, muffler and new pipe, won't void my warranty. SO, i was just wanting a ballpark hp gain from these two items.
    thanks again.
    #8
  9. c_m_chance

    c_m_chance New Member

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    Realistic gains without a programmer: about 10HP from BOTH at the same time.

    Realistic gains with a programmer: about 10HP from EACH.

    I can understand not wanting to get a programmer due to the fact that it voids your warranty.

    Once thing you could do to pull a little extra HP from the exhaust system though is install a crossover after the cats. An X-Pipe will give you more high end power, and H-Pipe will give you more low end torque. (Personally, I would go with an X-Pipe because of how much it helps with flow compared to the H-Pipe.) But if you throw in a cross over, you can probably pull another 2 or 3 HP as well.

    Also something to note, the newer trucks (I think 08 and newer) have REALLY good air intake systems stock. They really did a pretty good job fixing them to flow better than previously. To save some money, you might just get a better high flow filter first before you actually buy a full intake system.
    #9
  10. theartist

    theartist New Member

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    Good info! thanks a bunch. exactly the kind of answer i was looking for.
    I REALLY want more low end torque, so i think an H pipe is the way to go for me. Is an H pipe something fairly common for an exhaust installer? or is it something i'll have to show them how to do? lol
    I once read that the "H" section isn't ACTUALLY shaped like an H, more like the bar in the middle being angled or something? could someone show me an example of this setup?

    Also, i was planning on adding the filter first anyway, before i went ahead and bought the whole setup.
    #10
  11. c_m_chance

    c_m_chance New Member

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    Here's what an H-Pipe looks like. It's simply a small piece of pipe to connect the pipes that come out from both sides of the engine which helps balance out the exhaust flow on each side of the exhaust system. And yes, it is fairly common. They'll know what you mean when you tell them. And don't let them trick you and tell you it's gonna cost an ungodly amount extra. It's literally just a piece of pipe welded in between the existing pipes. Shouldn't cost too crazy.

    [​IMG]
    Last edited: Apr 30, 2010
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  12. theartist

    theartist New Member

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    out of curiosity, would i get a better hp gain if i set up my exhaust just like that one ? except after the cats of course.
    #12
  13. c_m_chance

    c_m_chance New Member

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    Wellll...I'll leave that one for you to decide, cus it's a close call in my opinion. If you are wanting more low end torque, then you don't want to over flow your exhaust. If you lose too much back-pressure, then you will lose torque.

    With the 4.8L Vortec that you have, it is rated at 300HP stock. Rule of thumb is, for every 1HP, you should have 2.2CFM of exhaust flow. So that means for 300HP, you should have about 660 CFM of exhaust flow. So, if you were to true dual your exhaust similar to this picture, you would be at about 500 to 600CFM per side (about 1000CFM total or more). (Something to note, 2.5" straight pipe flows about 570CFM.) So your limiting factor would be the muffler's you install and what they flow.

    Now, with that said, it would sound like a good idea to true dual your truck if you consider that the average muffler flows about 300 to 400CFM. This would put you somewhere between 600 and 800CFM. Perfect for a 300 horse engine. But something else that should be considered is just the shear size of your engine. It's only 4.8L. True dual might be a bit too much for the 4.8L and you would probably get better numbers and better response out of a dual in/dual out system and just stick with one muffler. The reason I say this is because when you have a smaller size engine, it becomes easy to over flow the exhaust. I think on average, the line where it becomes beneficial to actually true dual is when you start getting around 5.3L or more. The difference is simply because larger engines have more air/fuel mixture that is being combusted that they need to get out of that engine, where smaller engines don't have as much. Unless you have some major mods like forced induction or something, then I would stray away from a true dual on the 4.8.

    Definitely get someone else's opinion though who has the 4.8L and has done a true dual on it. My thinking processes is just from calculations and my own reasoning. But the realistic results that someone has are much more helpful than my thoughts lol.
    #13
  14. theartist

    theartist New Member

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    Wow, thanks for the responses, it appears you have a wealth of knowledge in those opinions of yours. but anyway, you mentioned a dual in dual out. Would that act as an H Pipe? or would i still have to incorporate an h pipe somewhere in there ? Also, how would that sound? i know it's hard to answer that kind of question, but i don't want it to be terribly loud. However, if that's the case, i'd sacrifice a bit of sound for more power.
    #14
  15. c_m_chance

    c_m_chance New Member

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    The dual in/dual out mufflers muffler's wont really act like an H-Pipe because the muffler is slowing the flow down a good bit. Plus, by the time the exhaust gets to your muffler, it's basically considered exited out of the truck. If you look at the point of view of the engine, all it notices is the exhaust up to the point of the muffler. Anything after the muffler is pretty much just for sound (with the exception if you were to reduce to something ridiculous like 1.5" pipe or something lol).

    But the idea of a crossover, be it H-Pipe or X-Pipe, is to balance the flow going into the muffler or mufflers. The way V style engines work, you basically have two engines. In the case of the V8, a 4 cylinder engine on each side. Each side of th engine has it's own set of exhaust valves that are pumping at separate times. And, with all engines being different, one side of your engine might be flowing a little more exhaust than the other. So what the crossover does is balance that exhaust out to both sides of the exhaust system so that you don't have say 60% of your exhaust going through the right side and 40% going through the left side.

    Now, there are two different types of mufflers. There are baffled/chamber mufflers (Flowmaster, Thrush, ect. This is the standard style of muffler) and then there are straight through mufflers which instead of using a system of chambers, all it is is a corrugated piece of pipe running through the muffler from inlet to outlet that has some form of packing material all around it to muffle the sound. Hooker Maximum Flow mufflers are a great example of this style of muffler.

    So, if you think about it, the straight through design of mufflers for dual in/dual out mufflers is ALMOST like doing a true dual. The only difference is really that the dual in/dual out straight though style muffler doesn't quite have the same flow that two completely separate and individual mufflers would.

    Now, to reconnect this to the idea of an H-Pipe, if you were using a chamber style dual in/dual out muffler and you used an H-Pipe, it wouldn't do much because all the exhaust is mixing back together anyway and slowing down in the muffler. But if you used and H-Pipe with a straight through style dual in/dual out muffler, then each inlet of that muffler is keeping the exhaust separate from the other inlet and your balanced flow is still being maintained.

    I guess a simplified version of what I'm trying to say is, when installing crossovers, you want to install them as early on in the exhaust system as you can to get the most efficiency out of them (ideally if you have cats, right after the cats/last O2 sensor). Could a chamber style dual in/dual out muffler act as an H-Pipe? Theoretically, yes I guess so, but its so late in the exhaust system when you get to the engine wouldn't even be recognizing the balanced exhaust flow.

    And, as far as sound goes, crossovers actually help quite down the exhaust system. As far as the mufflers, they really do vary from muffler to muffler. A lot of the straight through style mufflers are typically a bit more muffled than the camber style mufflers because of the different sound dampening techniques that they use. A lot of them are starting to incorporate resonators into the mufflers as well which help out a whole lot too. Here's a couple of charts that you can take a look at of some more popular mufflers to get some ideas. The second chart is loudness of the mufflers in decibles.

    http://www.qsl.net/st0f/mufflers.htm

    Sorry for such long responses too, btw. I'm about to have my exhaust system done on my truck, and I actually did a lot of calculations with my Fluid Mechanics professor at Texas A&M and we figured out some pretty good information about what works best and things like that. So I've got a pretty good grasp on exhaust flow now lol.
    Last edited: May 1, 2010
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  16. theartist

    theartist New Member

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    So, it sounds like an H pipe incorporated with a straight through design muffler would yield the most hp. awesome.
    You know anything about suspension stuff too ? lol i've started another thread over in that sub forum if you do!

    thanks again for all the help. good info.
    #16
  17. c_m_chance

    c_m_chance New Member

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    Haha! I wish I knew more about suspension than I do. I know my old 86 that I had, I got the suspension professionally done and it was absolutely AMAZING how well my truck hooked up after that! Cars that I wasn't able to get off the line before, I was able to completely leave behind all from suspension adjustment and tuning. Whatever that guy did to my truck, it was awesome! lol
    #17

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