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Wanted to share some turbo info

This is a discussion on Wanted to share some turbo info within the Forced Induction forums, part of the LSx Technical Help Section category; Hello, I'm not exactly an expert on turbo systems.. but everyone who has talked to me about charging my engine... ...

  1. #1
    DisCrete
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    Wanted to share some turbo info

    Hello,

    I'm not exactly an expert on turbo systems.. but everyone who has talked to me about charging my engine... always seems to point me to turbo chargers... the classic response "Free power"

    I just read this article about how turbo's work.. and I found out... using a turbo charger is infact not free power.

    You lose power in other cylinders when using a turbo charger... more so than if you did not have it at all. The issue then becomes a displacement issue.

    Here's a quote about the article as well as the URL.

    "Turbochargers allow an engine to burn more fuel and air by packing more into the existing cylinders. The typical boost provided by a turbocharger is 6 to 8 pounds per square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see that you are getting about 50 percent more air into the engine. Therefore, you would expect to get 50 percent more power. It's not perfectly efficient, so you might get a 30- to 40-percent improvement instead.

    One cause of the inefficiency comes from the fact that the power to spin the turbine is not free. Having a turbine in the exhaust flow increases the restriction in the exhaust. This means that on the exhaust stroke, the engine has to push against a higher back-pressure. This subtracts a little bit of power from the cylinders that are firing at the same time."

    http://auto.howstuffworks.com/turbo2.htm
    Last edited by DisCrete; 08-31-2005 at 07:22 AM.

  2. #2
    quicky06
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    yes they do give more back pressure. thats expected when you put a turbine in the wayits like a super charger it takes power to turn it but it makes much more

  3. #3
    Awaiting Activation Liquifire's Avatar
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    there is no such thing as free power..........but turbos are one of the most efficient ways to increase horsepower for the money. All FI that I know of take some power to make power(whether it be from backpressure in the case of a turbo or rob it directly off the crank in the case of a supercharger. I guess it just depends exactly what characteristics you are looking for out of the power you want and how much you want to spend on it

  4. #4
    Senior Member ss~zoso~ss's Avatar
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    no such thing as free power, thus no perpetual motion

  5. #5
    DisCrete
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    I've always been told.. hp equates to how efficient you can move air in and out of the engine... while you increase air into the engine.. you are also decreasing it flowing out of the engine.

    Hypothetical question: What if.. you were to install a supercharger... then put in a reverse turbo in the exhaust.. blowing the exhaust out at accelerated speeds...

    matching the intake velocity with the exhaust velocity... for obvious reasons.

    so say you are moving 200CFM intake and 200 CFM exhaust.

    would there be an advantage to this setup?

    what would be the disadvantage of this setup?

  6. #6
    Awaiting Activation Liquifire's Avatar
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    Quote Originally Posted by DisCrete
    I've always been told.. hp equates to how efficient you can move air in and out of the engine... while you increase air into the engine.. you are also decreasing it flowing out of the engine.

    Hypothetical question: What if.. you were to install a supercharger... then put in a reverse turbo in the exhaust.. blowing the exhaust out at accelerated speeds...

    matching the intake velocity with the exhaust velocity... for obvious reasons.

    so say you are moving 200CFM intake and 200 CFM exhaust.

    would there be an advantage to this setup?

    what would be the disadvantage of this setup?
    there was a post like this.........what if you turboed a supercharger engine......on the old site. Anyway......you would have somewhat minimal gains because what you are trying to do( I think anyways........I am not an engineer) when you have a FI system is pack as much air and gas on the inlet side. It will automatically dissapate on the outlet end faster just due to pressure that was created on the inlet side.....It would help out a very little bit to just "suck" out the exhaust faster. It would be a huge waste of money for a very small( less than 5-10%) gain. Advantage.....small gains Disadvantage......waste of money. Question.....why did you say reverse turbo? If my thinking is correct you would just route the outlet out the exhaust instead of back through the motor...... my .02

  7. #7
    DisCrete
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    I guess was a stupid idea.

    Just figured based on the idea above

    "Move air in and out of the engine as fast as possible.. is how you gain horsepower."

  8. #8
    quicky06
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    Quote Originally Posted by Liquifire
    there was a post like this.........what if you turboed a supercharger engine......on the old site. Anyway......you would have somewhat minimal gains because what you are trying to do( I think anyways........I am not an engineer) when you have a FI system is pack as much air and gas on the inlet side. It will automatically dissapate on the outlet end faster just due to pressure that was created on the inlet side.....It would help out a very little bit to just "suck" out the exhaust faster. It would be a huge waste of money for a very small( less than 5-10%) gain. Advantage.....small gains Disadvantage......waste of money. Question.....why did you say reverse turbo? If my thinking is correct you would just route the outlet out the exhaust instead of back through the motor...... my .02
    that was my post i ment putting them booth for the exauhst so you wouold have around 15 psi going into the super

    but you dont want yor exausht leaving to fast or youll fry your valves epesially if your using nitrous

    and if you do how will you tirn the turbine?

  9. #9
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    Quote Originally Posted by DisCrete
    The typical boost provided by a turbocharger is 6 to 8 pounds per square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see that you are getting about 50 percent more air into the engine. Therefore, you would expect to get 50 percent more power. It's not perfectly efficient, so you might get a 30- to 40-percent improvement instead.
    Not sure how much I agree with that. My car stock makes about 190whp (taurus SHO). With 13psi I make 390whp, or 105% more power. At 7psi, I am sure I would see more than a 50% gain in power (which would equate to about 290whp). ANd with my new setup, I am probably going to see close to a 150% gain (from 190whp to 475whp) at only 15psi. According to 'how stuff works', I should only be making 380whp. Take that for what its worth.

  10. #10
    DisCrete
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    I don't know much about turbo's so I've been researching reading about them etc.

    I know people gain alot more than what was said there.

    Just was curious about everyones imput.
    Last edited by DisCrete; 09-05-2005 at 09:05 PM.

  11. #11
    DisCrete
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    At the same token Tool,

    I have heard from a turbo technican who designs turbo chargers that I have talked to recently he said for every 14psi of boost you double your hp.

    so you running 13 psi and doubling your hp is not unheard of.

    Now run 6 or 7 psi boost.. see what your hp is at.

    I dunno... not arguing or anything... just stating some info is all.

  12. #12
    Yeah, That's right CaptainCaveMan's Avatar
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    Mexican killed my car

    The common theory is 1 pound of boost = 10hp.

    That of course if very very very genaric. Every engine and car is different. Some will gain more, some will gain less. Lots of varibles.

    Edit: That equation is for turbos, i'm not sure if that same rule applies to superchargers or not.

  13. #13
    DisCrete
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    I'm not sure cap..

    Everything I read about super chargers... unless twin setups.. you do not gain as much as you do with turbo's or twin turbo's

  14. #14
    Awaiting Activation Liquifire's Avatar
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    Quote Originally Posted by CaptainCaveMan
    The common theory is 1 pound of boost = 10hp.

    That of course if very very very genaric. Every engine and car is different. Some will gain more, some will gain less. Lots of varibles.

    Edit: That equation is for turbos, i'm not sure if that same rule applies to superchargers or not.
    so you are saying that if I take my John Deere lawnmower, put a ten pound blower on it that I will have a 122 HP mowing machine

    Grass=

    j/k

  15. #15
    DisCrete
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  16. #16
    Azhigher
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    eeww, too much misleading information here.

    Yes, 14.7 psi should equate to somewhere near double hp, because atmospheric pressure is 14.7psi, therefore you'd be double'ing the air in the cylinders, however, with that kind of PSI, you'd be pushing hot air, so you'd have to aftercool it, which would drop pressure a bit, and you'd have to have some decent supporting mods to accomadate pushing that much extra air in... blah blah blah and a bunch of variables.

    As for the reverse turbocharger spitting the exhaust out faster, it'd be a restriction in the intake, as the air comming in would have to spin it, even if it was being pushed by a supercharger, the gains would be minimal, if even at all.

    The 1psi = 10hp really depends on the size of the engine, supporting mods, and how big the turbo is pushing it. I.e. my old Talon didn't gain 30 hp from me pushing 3 more psi through it, course that was a 2 liter engine, on a stock T25 turbo.

    Psi to horsepower conversion is really more of a percentage difference. As pushing 10 psi through an LS1 is going to get you a bigger increase in power than pushing 10 psi through a honda B16.

    Anyone feel free to correct me if I misstated something, I'm no expert in turbo systems either, but I do have a bit of experience with them.

  17. #17
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    Quote Originally Posted by CaptainCaveMan
    The common theory is 1 pound of boost = 10hp.
    The common theory is actually this, 1 pound of air in actual weight equates to 10 hp, turbochargers are rated in pounds per minute of mass air flow (at least that's how Garrett has always measured mass air flow) so you really need to know the amount of mass air flow Vs the pressure ratio/boost in psi, hope that helps.

    Peter

  18. #18
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    Boost is resistance to flow so dont believe that the higher the pressure the more hp you will make, its not true.

    You can run 30 psi and make 600 hp or you can take a bigger compressor that runs up to 20 psi and make the same amount of hp. What's the difference? The amount of air you will flow ( cfm ) through the motor and the compressor wheels are only capable of flowing so much air and that is it no matter what psi level you push it to.

    Dont forget, air is only half of the equation. You must have a fuel system that can support the amount of air the turbo can flow. That means a fuel pump, injectors and a good way to tune the motor to get the fuel map right. Its not like learning quantum physics, its just a different way of making lots of torque and hp and you have to approach it with a " systems " mindset. If it I turn this up I will need to do this, and this and this.

    Hope that helps

  19. #19
    IROC-ZTT
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    Nothing is "free". However, how could anyone ever argue with a reliable 30% to 40% increase in power? And yes, turbochargers can be just as reliable as any system when setup with the correct equipment and tuned by qualified professionals, or at least by someone who lucks into doing it right.

    Now, in the boost world, 6psi is very low. Try 30psi. Run those numbers through, then come back and try talking about inefficiency. Take the blinders off and you'll realize that turbocharers have much more potential than superchargers do.

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