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Thread: RevTalk and Radiators...

  1. #46
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    Quote Originally Posted by KnifeEdge_2K1
    bhp/l is one of the best measures of efficiency

    gasoline has a set amount of energy per litre, the engine is designed to harness this, if it cant harness as much energy per litre of engine displacement it means one of or both these things, 1 it is loosing more energy (comparitavely speaking) during combustion, or it isnt getting as high volumetric efficiency

    however you look at it, the lower bhp/liter the less efficient the engine

    you're just trying to find random arguments now, so off topic you it's not funny. the whole point was american engines are inefficient, and that given the same engine a european company would easily be able to tune it to give more performance. you then brought up the fact the cars those engines are placed in cost 10x as much as the base cars, i merely stated that the price difference is not attributed to the extra tuning of the engine, but rather set by demand and supply forces.

    next time you decide to voice your opinion, straiten out your facts and argument

    Unfortunately you are wrong yourself.

    HP/L is a very iffy number that actually has little value on it's own. Take for example the rating of one of the worlds most efficient engines. it can achieve over 50% thermal efficiency but only has a HP/L rating of 4.27HP/L that is really low and would suggest a low efficiency engine to you. A much more usefull measurement that will tell you exactly what the efficiency is brake specific fuel consumption (rated in lbs/hp/hr or pounds of fuel used per horsepower per hour) the same engine I have been talking about gets a surprising 0.260lbs/hp/hr whereas car engines get between 0.385-0.600lbs/hp/hr.

    When you look at america V8s and their BSFC then you see that they are infact pretty efficient and surpass many european and japanese engines. You see you forgot a few reasons that could lower HP/L ratings without decreasing efficiency (Like peak rpm, whether the engine was tuned for power or economy ect.)

    High HP/L ratings normally indicate a lower efficiency engine, think about it if you make more power in a smaller space more waste heat is generated and to get higher peak HP you normally need to rev quite high which leads to increased friction and other mechanical losses.

    In the end HP/L is a useless rating for anything other than specific power.

    In the end americans don't make bad engines they just use displacement instead of technological advancement...
    Last edited by hightower99; 06-27-2006 at 01:29 AM.
    Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
    Engine torque is an illusion.

  2. #47
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    Quote Originally Posted by hightower99
    Unfortunately you are wrong yourself.

    HP/L is a very iffy number that actually has little value on it's own. Take for example the rating of one of the worlds most efficient engines. it can achieve over 50% thermal efficiency but only has a HP/L rating of 4.27HP/L that is really low and would suggest a low efficiency engine to you. A much more usefull measurement that will tell you exactly what the efficiency is brake specific fuel consumption (rated in lbs/hp/hr or pounds of fuel used per horsepower per hour) the same engine I have been talking about gets a surprising 0.260lbs/hp/hr whereas car engines get between 0.385-0.600lbs/hp/hr.

    When you look at america V8s and their BSFC then you see that they are infact pretty efficient and surpass many european and japanese engines. You see you forgot a few reasons that could lower HP/L ratings without decreasing efficiency (Like peak rpm, whether the engine was tuned for power or economy ect.)

    High HP/L ratings normally indicate a lower efficiency engine, think about it if you make more power in a smaller space more waste heat is generated and to get higher peak HP you normally need to rev quite high which leads to increased friction and other mechanical losses.

    In the end HP/L is a useless rating for anything other than specific power.

    In the end americans don't make bad engines they just use displacement instead of technological advancement...

    in some other context you would be right, but we are looking at the engines from a performance perspective, that means power, fuel/thermal/volumetric efficiency aside, whichever engine with equal displacement outputs more net power is the better one

    you said it urself, they use displacement instead of technological advancements, how is this NOT inefficient ??
    surely the super efficient engine you noted was not relying on displacement alone, as something as spectacular as 50% thermal efficiency must rely on some other means of technological assistance
    if you could get the same results by tweaking a low displacement engine vs increasing the dispalcement why wouldnt you ??

  3. #48
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    Quote Originally Posted by QBridge
    American car makers don't keep it real because they fit those V8s in big ugly heavy cars with automatic trannys making 50bhp/liter. Europeans keep it real because they can take a small block Chevy V8 and put it in a supercar and make twice the power out of that engine.
    You are surprisingly ignorant of the equipment available to American cars considering your location. Most american cars that are fitted with a V8 can also be fitted with a manual. The fact that your fellow Americans prefer autos has nothing to do with the car.

    There are no European supercars powered by the SBC, the Ultima GTR is the closest but that falls short of the supercar mark by lacking the style, presence, price and exclusivity of REAL supercars.

  4. #49
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    Quote Originally Posted by KnifeEdge_2K1
    bhp/l is one of the best measures of efficiency

    gasoline has a set amount of energy per litre, the engine is designed to harness this, if it cant harness as much energy per litre of engine displacement it means one of or both these things, 1 it is loosing more energy (comparitavely speaking) during combustion, or it isnt getting as high volumetric efficiency

    however you look at it, the lower bhp/liter the less efficient the engine
    So you are telling me that if I have a car that makes 50 hp/l and I add supercharging to get 100 hp/l, the engine is twice as efficient at converting fuel to work?

    Quote Originally Posted by KnifeEdge_2K1
    in some other context you would be right, but we are looking at the engines from a performance perspective, that means power, fuel/thermal/volumetric efficiency aside, whichever engine with equal displacement outputs more net power is the better one
    Net power is how you define the engine performance. I highly doubt that is the single design goal for a high production application, or even a low production application.

    Quote Originally Posted by KnifeEdge_2K1
    you're just trying to find random arguments now, so off topic you it's not funny.
    So the bhp/liter = efficiency was neither random nor off topic because it was a) your post or b) funny?

    Quote Originally Posted by KnifeEdge_2K1
    the whole point was american engines are inefficient, and that given the same engine a european company would easily be able to tune it to give more performance. you then brought up the fact the cars those engines are placed in cost 10x as much as the base cars, i merely stated that the price difference is not attributed to the extra tuning of the engine, but rather set by demand and supply forces.
    I am not arguing that a European company could not easily get more performance. I bet there is America company that could get more out the engine as well, even the original manufacture.

    My point was that if the design goals change anything can be done, but that doesn’t necessary make it better than the original. The post I was replying to was an ‘apple and oranges’ comparison, with zero effort being made to make it a fair comparison.

    Quote Originally Posted by KnifeEdge_2K1
    next time you decide to voice your opinion, straiten out your facts and argument
    I guess I should be flattered that you hold my posts to a higher standard than you hold your own.
    "In theory, theory and practice are the same. In practice, they are not."

  5. #50
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    Quote Originally Posted by Alastor
    So you are telling me that if I have a car that makes 50 hp/l and I add supercharging to get 100 hp/l, the engine is twice as efficient at converting fuel to work?



    Net power is how you define the engine performance. I highly doubt that is the single design goal for a high production application, or even a low production application.



    So the bhp/liter = efficiency was neither random nor off topic because it was a) your post or b) funny?



    I am not arguing that a European company could not easily get more performance. I bet there is America company that could get more out the engine as well, even the original manufacture.

    My point was that if the design goals change anything can be done, but that doesn’t necessary make it better than the original. The post I was replying to was an ‘apple and oranges’ comparison, with zero effort being made to make it a fair comparison.



    I guess I should be flattered that you hold my posts to a higher standard than you hold your own.
    no because a supercharger is forced induction, you're effectively increasing displacement in that case, even so forced induction when done correctly IS more efficient then just upping the displacement

    regardless of whether it's a main design goal or not, it is important, experically when we're talking about performance

    "So the bhp/liter = efficiency was neither random nor off topic because it was a) your post or b) funny?" i dont even know what you're talking about for this one
    we're comparing american tuned engines and euro tuned engines

    i'm not doubting that they can get more power out of it, but the point is they dont. what possible reason could they have to keep using pushrods and 2 valves per cylinder ??

  6. #51
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    Quote Originally Posted by KnifeEdge_2K1
    no because a supercharger is forced induction, you're effectively increasing displacement in that case
    No, the displacement of the engine does stay the same. It is the amount of air in the cylinders that is changing. For bhp/l , the denominator is the physical volume swept by the pistons and it does not change.

    This is why bhp/l is not a valid form of efficiency. The numerator is a measure of output, but the denominator is not a measure of input.

    Quote Originally Posted by KnifeEdge_2K1
    even so forced induction when done correctly IS more efficient then just upping the displacement
    I did not ask if it was more efficient, I asked it was “twice as efficient”. Which all know is not the case.
    "In theory, theory and practice are the same. In practice, they are not."

  7. #52
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    Quote Originally Posted by Alastor
    No, the displacement of the engine does stay the same. It is the amount of air in the cylinders that is changing. For bhp/l , the denominator is the physical volume swept by the pistons and it does not change.

    This is why bhp/l is not a valid form of efficiency. The numerator is a measure of output, but the denominator is not a measure of input.



    I did not ask if it was more efficient, I asked it was “twice as efficient”. Which all know is not the case.
    you're increasing the amount of air in the cylinders per stroke, thats increasing effective displacement, boosting at 1 bar has the same effect as doubling the displacement

    we're talking about N/A engines here, so bhp/l IS a valid measure of efficiency, even if we were to add forced induction it wouldnt be a huge problem if the boost figures were given

  8. #53
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    Quote Originally Posted by KnifeEdge_2K1
    i'm not doubting that they can get more power out of it, but the point is they dont. what possible reason could they have to keep using pushrods and 2 valves per cylinder ??
    Because its cheap. The SBC is quite compact however, this allows you to squeeze it into absurdly small cars (Lotus 7 replicas)

  9. #54
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    Keeping it pushrod/OHV is what makes it compact. The LS6 is a smaller and lighter than the BOSS 290 despite having more capacity and more power.
    Faster, faster, faster, until the thrill of speed overcomes the fear of death...
    – Hunter Thompson

  10. #55
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    Quote Originally Posted by h00t_h00t
    Because its cheap. The SBC is quite compact however, this allows you to squeeze it into absurdly small cars (Lotus 7 replicas)
    you're right, it IS cheap, but it's not significantly cheaper then it's competitors, which is why we're complaining about it, the europeans and japanese give alot more bang for the buck

  11. #56
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    Quote Originally Posted by 2ndclasscitizen
    Keeping it pushrod/OHV is what makes it compact. The LS6 is a smaller and lighter than the BOSS 290 despite having more capacity and more power.
    but for the cars they're putting it in, space isn't an issue, expecially with american cars

    with your reasoning it should be the americans adopting dohcs and the europeans sticking with the older pushrods

    so the small package excuse isnt valid at all, which leads back to the original question, why dont they change ??

  12. #57
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    Quote Originally Posted by KnifeEdge_2K1
    in some other context you would be right, but we are looking at the engines from a performance perspective, that means power, fuel/thermal/volumetric efficiency aside, whichever engine with equal displacement outputs more net power is the better one
    You are not making much sense at all HP/L is not under any circumstances a measure of efficiency it is a measure of specific output, so call it that instead of efficiency and you won't confuse everyone. Also having a higher specific output does not make one engine "Better" than another.

    Quote Originally Posted by KnifeEdge_2K1
    you said it urself, they use displacement instead of technological advancements, how is this NOT inefficient ??
    You started your post saying "fuel/thermal/volumetric efficiency aside" then you make a statement that A) shows you misunderstood what I said and B) doesn't make much sense. To make things clear, American car companies use displacement to increase total output instead of using a smaller engine and trying to make it have a higher total output. This allows them to make pretty efficient engines that have relatively low specific power.

    Quote Originally Posted by KnifeEdge_2K1
    surely the super efficient engine you noted was not relying on displacement alone, as something as spectacular as 50% thermal efficiency must rely on some other means of technological assistance
    Next about the super efficient engine I was talking about was a immense turbocharged 2 stroke diesel. The reason for it's good efficiency is A) it is massive and frictional and heat losses are smaller relative to it's size. B) it runs at very very low rpm (102rpm) and for it's size it's parts (like piston and conrod) are very lightweight. C) it's a diesel. It actually uses displacement in the same manner as americans (to gain higher total output) The engine it's self is infact very low tech. No special materials are used, it has very basic computer control, it is SOHC and the cams are totally normal, the turbo is just large nothing technologically special about it.

    Quote Originally Posted by KnifeEdge_2K1
    if you could get the same results by tweaking a low displacement engine vs increasing the dispalcement why wouldnt you ??
    To answer your last question: It is easier to make a lower specific output engine efficient and it is cheaper to make a larger engine instead of using new technologies.
    Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
    Engine torque is an illusion.

  13. #58
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    so if you make the same horsepower with more displacement which naturally means more fuel, how is this efficient ??

    if you increased the displacement of an engine which has vvt and lift, ohcs, direct injection, 4 valves per cylinder, etc
    the benefits from those systems remain
    you can only increase displacement so much before it becomes unfeasible, and at that point you'd rather have vvt and lift, ohcs, direct injection, 4valves per cylinder, then not

    assume i'm wrong about this efficiency thing, what in your definition is efficiency then ? mpg ? emmissions ? thermal efficiency ? volumetric efficiency ? what then
    in most if not all of these areas american tuned engines fail to compare with euro or jap standards

  14. #59
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    When hightower talks about anything its been misinterperated directly from a textbook that is at a higher level than whatever he is learning at.

  15. #60
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    Quote Originally Posted by h00t_h00t
    When hightower talks about anything its been misinterperated directly from a textbook that is at a higher level than whatever he is learning at.
    I myself, and I know other members as well, have taken issue with some of his posts in other threads.

    However, that has absolutely nothing do with this thread.

    If you take issue with his posts in this thread, then respond to them accordingly. If he can take the time to create an intelligent comment, then someone of an equal if not higher aptitude should be able to create a comparable technical response.
    "In theory, theory and practice are the same. In practice, they are not."

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