Blowers on stock bottom ends

Discussion in 'Forced Induction & Tuning' started by Adam, Feb 23, 2007.

  1. Adam

    Adam Member

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    I just wanted to post this for information purposes. A stock bottom end is designed to handle about 1000psi of cylinder pressure. Lets say your blower car makes 400rwhp, that number is more like 440-60 crank hp, that number is actually more like 500crank hp, due to the heat and friction it takes to operate the blower. This is power you never see on a dyno or anywhere else, but it is a reality of running a blower. Now a blower car produces 2.65psi of cylinder pressure per hp produced. Now take the 500hp x 2.65psi and that equals 1325psi of cylinder pressure on an engine that was designed to handle no more than 1000psi. It is a mathmatical certainty than no tune or no amount of safe tuning will reduce the amount of pressure that cylinder sees. You are exceeding the capabilities of the metallurigic make up of the stock components. I am not trying to scare anyone, just stating fact. Moral of the story, your running on borrowed time. I hope this helps some of you. :)


    Adam
     
  2. Adam

    Adam Member

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    In all actuality this can apply to a blower motor making even just 300rwhp. Even at that power range your making 340 to the crank+ the 60 or 70hp it takes to run the blower so you have 410hp X 2.65 psi = 1086psi. This also doesn't apply to NO2, NO2 increases cylinder pressures during use, but is of no extra stress when it isn't activated. I am not advocating one over the other, just throwing this out for information ;)


    Adam
     
  3. Teal_Beast

    Teal_Beast New Member

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    a) if your running boost your not in boost all the time, my twin turbo daily driver only sees boost when i want it too. . which for me is a lot but still.

    b) the majority of busted shortblocks are due to detonation, detionation kills motors 10x faster then cyl pressure. This is the reason that people advocate that its ok as long as you have a good tune, because if you have a good tune you should detonate thus your motor lives longer.


    Oh, and if your going to talk about stock bottom ends dont pick on boost, N20 has its con's as well. with N20 you get that "hit" which jars not only your motor but your tranny/rearend/driveshaft etc not to mention pooling, leak spikes etc.
     
  4. Adam

    Adam Member

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    Turbos are a little different. This applies mostly to supercharged cars, not turbos. I said I am not advocating one over the other, re-read my post. This was posted for information only. Yes detonation kills motors. I do not know the frequency of detonation failures vs excessive cylinder pressure failure. This post was to inform people with safe tunes and good A/F ratios that does not make their setup safe. You need to not jump to the defensive so easily.
     
  5. Teal_Beast

    Teal_Beast New Member

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    with a supercharger you dont have to be in boost if you dont want to either, generally it is controlled via vacume and you wont get boost unless WOT, i've had both and i have to say that it is prolly easier to NOT get into boost with a s/c then a turbo.

    that being said this IS good information. however, were are you getting it from? and what stock block are you talking about? a stock 4v? a stock 2v 4.6? a stock 5.0? a stock 3.8? i cant immagine them all having the same strengths.
     
  6. Adam

    Adam Member

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    So your saying a supercharger puts zero stress on a motor simply because its not producing boost? A KB is full boost by 2000rpm, thats not WOT. Any motor with hypereutectic pistons and powdered metal rods falls into this category. A 2V, 4v falls into it. I don't know about 3.8's but I am gonna go out on a limb and say they are also(except the 89-95 3.8's out of Thunderbird SC). I know most 5.0 pistons/skirts are junk too. This isn't new information. Don't you wonder why 99% of these cars have junk rods/pistons? ANY poweradder adds stress to the internals, whether under boost or not, it adds heat and friction which both reduce the life of the motor, especially on components not designed for that heat and friction and cylinder pressures when it IS under boost. Does my math not add up? Do you think that these numbers are incorrect? Its not rocket science, its simple math. Thats all I can say...sorry if you don't agree.


    Adam
     
  7. Teal_Beast

    Teal_Beast New Member

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    eek i have to go to class but im going to reply real quick.

    first off, a blower will put stress on an engine at all times, just because it is extra drivetrain loss (parasitic loss via pulley) however, you wont get boost enless you go WOT. go take a ride in a blown car, go cruise down the highway at 2,000rpms in high gear, check the boost gauge, I garontee it will not read any boost. Your manifold will only see boost if you go WOT, expecually at low RPMS.

    second, i was just asking about the magic 1,000 number you've been using, im not saying i dont believe you but it has to be derived from a certain engine. I was simply wondering which one.

    got to go to class! later.
     
  8. 94twinscrew

    94twinscrew Active Member

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    Borrowed time huh? ::)

    In premise,it's somewhat correct....but in reality, it's a completely inaccurate example of what a "seasoned" block's tensile strength is rated at. This has been a time proven thing,especially in the engine building field. Most builders would rather use a "seasoned" or heat cycled block,simply because it's molecular tensile stregth is greater than that of a new casting. The more heat cycling,and liquid cooling....the stronger the block's metal becomes(as long as it's not brought close to it's molten point). Oil and water also aid in this process,an allow the molecular structure to "weave" into itself,over,and over again.

    Now,every engine is different,and some can tolerate higher stactic pressures,and some can't. In part,the prior state(condition) of the block,is what dictates it's longevity.....not the level of static cylinder pressure it endures. In fact,most catastrophic failures(block splitting)or even just piston and rod failure, are due to rotational harmonic vibrations,not cylinder pressure.

    The equation is fun to think about,but not really consistant with real world variables. Hell,I've been running high boost on my motor for over 10 years and 169K miles on the clock,and for the past two years over 18psi.......so if this is borrowed time,I'm loving it >:D
     
  9. scarface

    scarface Guest

    borrowed time? maybe, but its fun for now :)
     
  10. Adam

    Adam Member

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    The 1000psi is a number derived from the materials that the hypereutetic pistons and powdered metal rods are manufactured from. Its just basically asking for metallurgical failures by asking these components to handle stresses they weren't designed for. That all. I am not saying you can't do it, I am just letting people know what they need to understand before they do it. ;)


    No one has ever implied in this post that the BLOCK wouldn't handle it, it is the INTERNALS that can't handle the cylinder pressures. In my original post it even says "stock components" never anywhere does it say the block itself would fail.


    Adam
     
  11. 94twinscrew

    94twinscrew Active Member

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    "Stock components" is a very vague term,so it's often that you'll hear many group the block in as a stock component when talking about component failure on high hp applications. ...when you use the term "stock bottom end"....this is typically the block,and rotational assembly. Also "forging pressure" is not the same as tensile breakpoint pressure,they are typically 20-35% greater....and sometimes more depending on molecular bonding or grain weaving. There are tons of contributing factors that play a huge roll to make this equation precise....that's all.
     
  12. ripper

    ripper Well-Known Member

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    Hmmmm wtf? I guess im glad i put a forged bottom end in my motor :hammer: The clock is ticking :noes:

    :rollinglaugh: :rollinglaugh: :rollinglaugh: :rollinglaugh: :rollinglaugh: :rollinglaugh: :rollinglaugh:


    p.s. scarface tell him how long you been on "borrowed" time ;)
     
  13. scarface

    scarface Guest

    2 years @13-14 psi :)

    Yo stevo, I may be getting low on time...can I borrow some of yours :) ..lol
     
  14. ripper

    ripper Well-Known Member

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    Yea ill give ya 2 runs LOL.
     
  15. scarface

    scarface Guest

    shewwww...thanks bro. I dont want to be the first looser :)
     
  16. Adam

    Adam Member

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    Well for those of us who have moved out of the "5.0...1980's" mentality, we know that the stock 4.6 block is a stout piece, so there is no question as to what I am referring to. I am sorry that I tried to share some information with you. It won't happen again.

    Adam
     
  17. Teal_Beast

    Teal_Beast New Member

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    Dont cry, you have good points but dont think people wont counter/debate them, this is the process that keeps random trash from becoming percieved "fact"


    And i've had boost running through my little v6 for 2 years now, 1 year @ 11psi 1 year @ 15psi w00t
     
  18. Adam

    Adam Member

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    No crying just being honest. I'll just keep my myths to myself. Good luck with your 6'er. And to Scarface...you make 13-14psi and make 385 rwhp and 361rwtq? I don't think I would be bragging about that.
     
  19. Teal_Beast

    Teal_Beast New Member

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    bah whatever dude, nobody said you were wrong or its bullshit, they're just trying to fill in the gaps etc.

    If you cant handle a little counter-arguement / criticisms then i guess you shouldnt post things.

    edit: 380whp @ 14psi is kinda bad. . . . :(
     
  20. 97stanger

    97stanger Legend

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    if you ask me those are awesome #'s...you do know hes doing that through untouched non PI heads right?? Non intercooled as well.