Head Flow - Boost- Dynamic Comression
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Head Flow - Boost- Dynamic Comression

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    Senior Member Hass828's Avatar
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    Default Head Flow - Boost- Dynamic Compression

    I've been thinking about this for a while and I didnt want to cloud up EdonShanno's blown 588 thread. Its winter, I'm bored, so here we go.
    For this discusion lets leave compressor efficiency & intake temps out of the equasion for the time being.
    Lets use EdonShanno's blown 588 for a starting example here. He made 1100hp on pump gas at 7psi of boost. You have to get X-amount of fuel & air into that engine to accomplish this, that fuel & air is converted to a dynamic cylinder pressure to achieve the resulting 1000ftlb & 1100hp. A fuel can only stand so much dynamic compression ratio- cylinder pressure before it will detonate. Here comes the big question, you ready for it
    If you were to put a very small set of heads on that same engine and crank up the boost till you had the exact same tq & hp numbers, wouldnt that indicate the same dynamic comp - cylinder pressure and wouldnt you be able to still get away with the same fuel no matter what the boost guage in the manifold ended up reading?

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    Last edited by Hass828; 01-12-2013 at 10:02 AM.
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    Senior Member Hass828's Avatar
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    Next question,
    An engine with great cylinder head flow actually gets more -boost- into the cylinder which is why they make great power at a low boost number. For this reason do you think that an engine with great heads will find detonation at a lower boost number than the same engine with small heads that would actually get less into the cylinder for compression? Talking about pump gas here.
    Last edited by Hass828; 01-12-2013 at 08:28 AM.
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    Senior Member motor head's Avatar
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    I think this makes perfect since.
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    Distinguished Member David 519's Avatar
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    This could get good. If you get the same HP/Tq, in a basic sense, you're reacting the same amount of fuel. The problem I see is by cranking up the boost, you're also increasing the heat into the charge, so it will be more prone to detonation. Better heads with the proper cam, should fill the cylinder at lower boost. Better heads are never a bad idea, but a blower can definitely make power with "wrong" heads.
    Quote Originally Posted by gn7 View Post
    ....... David 519 is 100% correct........

    Quote Originally Posted by fuelinmyveins82 View Post
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    Quote Originally Posted by David 519 View Post
    This could get good. If you get the same HP/Tq, in a basic sense, you're reacting the same amount of fuel. The problem I see is by cranking up the boost, you're also increasing the heat into the charge, so it will be more prone to detonation. Better heads with the proper cam, should fill the cylinder at lower boost. Better heads are never a bad idea, but a blower can definitely make power with "wrong" heads.
    Thats why I wanted to leave the intake temp and compressor efficiency out of the equasion, because there are certainly more efficient ways of aquiring boost than what they used. And I know that his big billet blower was pretty efficient at those #'s.
    Last edited by Hass828; 01-12-2013 at 08:58 AM.
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    Senior Member Hass828's Avatar
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    Quote Originally Posted by David 519 View Post
    This could get good. If you get the same HP/Tq, in a basic sense, you're reacting the same amount of fuel. The problem I see is by cranking up the boost, you're also increasing the heat into the charge, so it will be more prone to detonation. Better heads with the proper cam, should fill the cylinder at lower boost. Better heads are never a bad idea, but a blower can definitely make power with "wrong" heads.
    What if you put a set of peanut port heads on there and ended up at 21psi in the manifold to make the same 1000ftlb & 1100hp? Could you still use pump gas "if" the intake temps remained the same ? Wouldnt that indicate the same amount of fuel/air being burned as well as the same cylinder pressures?
    Last edited by Hass828; 01-12-2013 at 09:18 AM.
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    Distinguished Member David 519's Avatar
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    Quote Originally Posted by Hass828 View Post
    Thats why I wanted to leave the intake temp and compressor efficiency out of the equasion, because there are certainly more efficient ways of aquiring boost than what they used.
    At first I thought "how can you leave intake temp and efficiency out of the equasion (sic)....." until I realized this is a clever attempt at another "turbos are better" thread. You guys have fun, I'm out
    Quote Originally Posted by gn7 View Post
    ....... David 519 is 100% correct........

    Quote Originally Posted by fuelinmyveins82 View Post
    .....I think people forget that racing is supposed to fun. Losing shouldn't be discouraging it should motivate you work on your pile to make it faster.....

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    Senior Member Hass828's Avatar
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    Quote Originally Posted by David 519 View Post
    At first I thought "how can you leave intake temp and efficiency out of the equasion (sic)....." until I realized this is a clever attempt at another "turbos are better" thread. You guys have fun, I'm out
    Once again, NO. thats why I wanted to leave that out. I'm just talking Head Flow-Boost- Dynamic compression here. I dont give a damn were the boost comes from. I'm just talking about what ends up in the cylinder.

    Here is a neat little dynamic comp. calculator to play with. It doesnt figure cylinder head flow into the equasion at all.
    Wallace Racing: Dynamic Compression Ratio Calculator
    Last edited by Hass828; 01-12-2013 at 09:53 AM.
    "if we keep doing it the same way we always do..we will always get the same results"
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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by Hass828 View Post
    I've been thinking about this for a while and I didnt want to cloud up EdonShanno's blown 588 thread. Its winter, I'm bored, so here we go.
    For this discusion lets leave compressor efficiency & intake temps out of the equasion for the time being.
    Lets use EdonShanno's blown 588 for a starting example here. He made 1100hp on pump gas at 7psi of boost. You have to get X-amount of fuel & air into that engine to accomplish this, that fuel & air is converted to a dynamic cylinder pressure to achieve the resulting 1000ftlb & 1100hp. A fuel can only stand so much dynamic compression ratio- cylinder pressure before it will detonate. Here comes the big question, you ready for it
    If you were to put a very small set of heads on that same engine and crank up the boost till you had the exact same tq & hp numbers, wouldnt that indicate the same dynamic comp - cylinder pressure and wouldnt you be able to still get away with the same fuel no matter what the boost guage in the manifold ended up reading?

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    Quote Originally Posted by Hass828 View Post
    Next question,
    An engine with great cylinder head flow actually gets more -boost- into the cylinder which is why they make great power at a low boost number. For this reason do you think that an engine with great heads will find detonation at a lower boost number than the same engine with small heads that would actually get less into the cylinder for compression? Talking about pump gas here.
    It's difficult to speak of detonation and ignore inlet temp. I get the basis of your scenario, and on the whole you're accurate that if the same amount of air/fuel is burned, the same dynamic cylinder pressure will be achieved, identical torque.

    Taking the theory a step further... If an intercooler is used in both scenarios, and if we don't ignore inlet temps and look at what may occur if we run smaller ports and higher boost to get the number, the restriction may allow more dynamic cylinder pressure/torque to be made overall without detonation.

    I know, makes very little sense. Hold on a sec, let me explain.

    Without going into all the science of why/how, because I'm pretty sure all/most of us ore up to speed in that... As air is compressed it gets hot. Compress it more it gets hotter, more, hotter, and so on. That's what causes detonation, it's compressed to a point which the air is hot enough to ignite the fuel.

    So, anyway... Let's say, hypothetically, you put small port heads on and due to the restriction you had to create twice the boost to get the same number. The intake air temp will roughly double (not taking into account any mechanically added by turbo/blower) before the intercooler. The hotter the charge, the more heat energy the intercooler is able to remove.

    Similar to the way refrigeration works, if the ports were a restriction the air entering the cylinder would contain less heat energy with higher boost and could therefore create more dynamic compression without detonation... More dynamic cylinder pressure... More torque... More Power.

    Anyway, I'm bored too. Just a theory that's been rolling around in my head for a few days.

    Whacha think? Make any sense at all?
    Last edited by Budweiser; 01-12-2013 at 10:36 AM.

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    Or Seth, either one Budweiser's Avatar
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    Another way to look at it:

    What if you put a restriction in-line post intercooler and pre throttle body/carburetor? Say a plate with a hole drilled in it... And raised the boost (measured at compressor/ outlet) until performance was identical...

    In my theory, manifold boost pressure that would previously cause detonation should be able to be met without detonation, as more heat has been removed by the intercooler.
    Last edited by Budweiser; 01-12-2013 at 10:45 AM.

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    Quote Originally Posted by Budweiser View Post
    It's difficult to speak of detonation and ignore inlet temp. I get the basis of your scenario, and on the whole you're accurate that if the same amount of air/fuel is burned, the same dynamic cylinder pressure will be achieved, identical torque.

    Taking the theory a step further... If an intercooler is used in both scenarios, and if we don't ignore inlet temps and look at what may occur if we run smaller ports and higher boost to get the number, the restriction may allow more dynamic cylinder pressure/torque to be made overall without detonation.

    I know, makes very little sense. Hold on a sec, let me explain.

    Without going into all the science of why/how, because I'm pretty sure all/most of us ore up to speed in that... As air is compressed it gets hot. Compress it more it gets hotter, more, hotter, and so on. That's what causes detonation, it's compressed to a point which the air is hot enough to ignite the fuel.

    So, anyway... Let's say, hypothetically, you put small port heads on and due to the restriction you had to create twice the boost to get the same number. The intake air temp will roughly double (not taking into account any mechanically added by turbo/blower) before the intercooler. The hotter the charge, the more heat energy the intercooler is able to remove.

    Similar to the way refrigeration works, if the ports were a restriction the air entering the cylinder would contain less heat energy with higher boost and could therefore create more dynamic compression without detonation... More dynamic cylinder pressure... More torque... More Power.

    Anyway, I'm bored too. Just a theory that's been rolling around in my head for a few days.

    Whacha think? Make any sense at all?
    I'm trying very hard to leave that part out of the equasion. It is possible to reach a relatively high boost number and keep the intake temps very low if the correct components are used. But once again, lets just say that its possible (because it is) and figure that the intake temp remains constant.
    Kind of wanting to take the direction of comparing boost numbers on pump gas with Big-expensive heads compared to stock low performance heads. Is the boost # in the manifold really that important? Or should we actually have some form of pressure transducer to log actual dynamic cylinder pressures so we would be able to walk right out to the edge on pump gas? Could you get very close to the same pump gas results with both sets of heads if we did this?
    Last edited by Hass828; 01-12-2013 at 02:08 PM.
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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by Hass828 View Post
    I'm trying very hard to leave that part out of the equasion. It is possible to reach a relatively high boost number and keep the intake temps very low if the correct components are used. But once again, lets just say that its possible (because it is) and figure that the intake temp remains constant.
    Kind of wanting to take the direction of comparing boost numbers on pump gas with Big-expensive heads compared to stock low performance heads. Is the boost # really that important? Should we actually have some form of pressure transducer to log actual dynamic cylinder pressures so we would be able to walk right out to the edge on pump gas? Could you get very close to the same pump gas results with both sets of heads if we did this?
    Even without intercooling, higher boost will still contain the same heat as lower boost per given volume... and in this case volume in the cylinder is identical. Even if the air temp in the manifold is significantly higher. Interesting thought pattern.

    Good thread. Interesting.
    Last edited by Budweiser; 01-12-2013 at 11:23 AM.

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    Senior Member motor head's Avatar
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    Y'all are making me want to put a blower on my $hitty heads instead trying to make hp na with big $$ heads!
    [SIGPIC]

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    Senior Member Hass828's Avatar
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    Quote Originally Posted by Budweiser View Post
    Even without intercooling, higher boost will still contain the same heat as lower boost per given volume... and in this case volume in the cylinder is identical. Even if the air temp in the manifold is significantly higher. Interesting thought pattern.

    Good thread. Interesting.
    Thanks. Some of the Diesel guys are running over 55psi and well below ambient intake temps with w/a intercoolers using ice.
    With us boat guys having the water to use, and its almost always below the ambient outside temp, we should be able to get some great results with the w/a intercooling.
    "if we keep doing it the same way we always do..we will always get the same results"
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