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  1. #51
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    Click here to enlarge Originally Posted by V8Bait Click here to enlarge
    The engine is an air pump and at no point does that ever change, regardless of combustion really. And yes you're right, pressure drop is assumed... but that drop is not related to cooler denser air, it's related to restriction of the core 98%. I was attempting to explain why the density of the air post turbo and post intercooler makes no difference to the pressure drop, as it's related to restriction. And I'm apparently failing miserably to explain how heat and entropy and velocity and such relate in a system with a compressor a pump a heat exchanger and a restriction.
    The problem with your explanation is only this one point which is plain wrong.
    are reducing the heat of the aircharge, you are also reducing it's entropy inside the intercooler, which in a closed system like this results in a loss of engery of motion (which loosely translates to velocity).
    Reducing temperature proportionally reduces entropy (the velocity of the molecules Thad gives rise to temperature and static pressure) but that randomness and molecules pinging about has absolutely nothing to do with flow rates so please don't confuse with that.
    Stop trying to say hotter ~ faster flow, and you're all good. The statement entropy = heat / temperature. is correct but has no place in fluid dynamics. You are quoting one law of thermodymamics that has nothing to do with the fluid dynamics. The velocity of air molecules you mention as temperature increase is random and in all directions so doesn't have any bearing on flow rates.

  2. #52
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    Click here to enlarge Originally Posted by V8Bait Click here to enlarge
    The engine is an air pump and at no point does that ever change, regardless of combustion really. And yes you're right, pressure drop is assumed... but that drop is not related to cooler denser air, it's related to restriction of the core 98%. I was attempting to explain why the density of the air post turbo and post intercooler makes no difference to the pressure drop, as it's related to restriction. And I'm apparently failing miserably to explain how heat and entropy and velocity and such relate in a system with a compressor a pump a heat exchanger and a restriction.
    Its absolutely related to tempature. Granted a majority of the pressure drop after an intercoller is due to restriction but tempature of a gas ie ambient air changes pressure. Think of your tires. Temps go down and your pressures go down temp goes up pressure goes up. I understand what your saying but completely ruling out air temp as its related to pressure loss is wrong.
    Density of the air post intercooler does make a difference in pressure as density is related to tempature.

  3. #53
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    Anyway, back on topic. Does anyone have the dimensions of a large aftermarket aa cooler that's not metric. I wanna do a lil research and see if i can find an aw cooler that would fit in the stock location.

  4. #54
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    The mass flow rate entering the intercooler has to be the same as the mass flow rate exiting the intercooler.

    If the intercooler is cooling the air, the oxygen molecules are going to get closer together and the density is going to increase. More air will be packed into a unit volume post-intercooler than when compared to the same unit volume before the intercooler.

    This means that either the gas after the intercooler has to slow down for the mass flow rate to remain the same, or the static pressure of the gas has to decrease to allow the molecules to grow apart if we assume that the flow velocity remains constant.

    Assuming air velocity remains constant before and after the intercooler, I calculate a pressure differential across the intercooler 2X greater than what was measured on page 1.

    So I believe V8 is right when he says the temperature drop causes the fluid to slow rather than reduce the static pressure. Disclaimer - I'm a subpar ME that does not specialize in fluids lol.

  5. #55
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    Click here to enlarge Originally Posted by Jewber Click here to enlarge
    The mass flow rate entering the intercooler has to be the same as the mass flow rate exiting the intercooler.

    If the intercooler is cooling the air, the oxygen molecules are going to get closer together and the density is going to increase. More air will be packed into a unit volume post-intercooler than when compared to the same unit volume before the intercooler.

    This means that either the gas after the intercooler has to slow down for the mass flow rate to remain the same, or the static pressure of the gas has to decrease to allow the molecules to grow apart if we assume that the flow velocity remains constant.

    Assuming air velocity remains constant before and after the intercooler, I calculate a pressure differential across the intercooler 2X greater than what was measured on page 1.

    So I believe V8 is right when he says the temperature drop causes the fluid to slow rather than reduce the static pressure. Disclaimer - I'm a subpar ME that does not specialize in fluids lol.
    Yes. And this decrease in flow rate cause a decrease in the volumetric efficiency of your engine, meaning that denser air causes no increase in horsepower versus the thinner, faster air that results in higher volumetric efficiency. It's different for naturally aspirated cars because the velocity is set by atmospheric pressure, so air density effects volumetric efficiency, but in a turbo things are all linked to the airmass from the turbo. I'm glad some understand.

    You guys are both spot on in the physics just not applying it 100% correct, but I'm not gonna argue. Hey, maybe I am wrong anyway. But I sincerely doubt it.

  6. #56
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    My last post on this issue... kinda blew up. Maybe I didn't explain well, I didn't ever say the air doesn't get denser. I did it say it plays no part in the cause of the pressure drop. It's largely negated by other factors. The loss of energy in flow is the cause of the pressure drop. If there was no restriction, the air getting denser would have the same pressure on both sides of the intercooler, but there is a restriction, so there is a differential. Thus the pressure drop is caused by resistance to flow. Not density. Does the air become dense? Yes, sorry if I discounted that. It just simply doesn't matter for anything here. The gains from the intercooler are knock headroom only.

  7. #57
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    Ok I lied one more

    Click here to enlarge Originally Posted by crypticc Click here to enlarge
    The problem with your explanation is only this one point which is plain wrong.


    Reducing temperature proportionally reduces entropy (the velocity of the molecules Thad gives rise to temperature and static pressure) but that randomness and molecules pinging about has absolutely nothing to do with flow rates so please don't confuse with that.
    Stop trying to say hotter ~ faster flow, and you're all good. The statement entropy = heat / temperature. is correct but has no place in fluid dynamics. You are quoting one law of thermodymamics that has nothing to do with the fluid dynamics. The velocity of air molecules you mention as temperature increase is random and in all directions so doesn't have any bearing on flow rates.
    You are not reducing temperature proportionally. The air isn't sitting still and losing heat to the environment. You are creating turbulent flow, crashing molecules into cool metal to exchange the heat. So you're losing more than just heat, you are losing entropy, or the velocity of the fluid, or the energy of the fluid, at the same time. I said heat and entropy are related, but absolutely not the same thing. I never once said entropy = heat / temperature. Also, in this case, hotter is faster flow. Not because that's a physics formula but because of how you are cooling the charge. The air is fastest after the turbo, and unless you let the heat bleed off naturally or inject chemicals like meth to cool it, you are absolutely slowing it down by making it cooler, because you're using a restrictive device to cool it. Gotta go study, thanks for the discussion though guys. I enjoy this stuff.

  8. #58
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    I will stay with stock BMW intercooler. Looks like they did a good job.

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    1 out of 1 members liked this post. Yes Reputation No
    I think whats happening here is everyone is comparing different aspects of intercooling. One person is stating why there is a pressure drop minus all other factors while others are stating the actual effects overall in normal operation.

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    Click here to enlarge Originally Posted by vasillalov Click here to enlarge
    HPF is still one of the best intercoolers out there. ..and still the only one that uses the OEM connectors. As for the pressure drop, I am not so certain about that....
    Wagner uses OEM connections or aftermarket depending on model. I have the OEM one.

  11. #61
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    I disagree with a lot of what is being said here. On a fundamental level your colder denser air charge out thru back is going to lead to a larger pressure drop as the denser air required more volume flow of hot air on the inlet side. More volume through the pipe leads to more resistance. This is obviously a simplification, but this the basic premise.

    The tire analogs incorrect because V is constrained there and here it is not. If you conserve mass V and T can scale together. That doesn't mean they will maintain the same ratio exactly, but its not constrained.

  12. #62
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    Click here to enlarge Originally Posted by hakentt Click here to enlarge
    I will stay with stock BMW intercooler. Looks like they did a good job.
    Bad idea, but do as you please. Click here to enlarge
    From all the things I've lost,
    I miss my mind the most!
    Click here to enlarge

  13. #63
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    Click here to enlarge Originally Posted by hakentt Click here to enlarge
    I will stay with stock BMW intercooler. Looks like they did a good job.
    They did a good job for about 300 crank hp inside the turbo's efficiency range. In a moderate climate at sea level. If you limit your runs to spirited driving and not actual racing. And use premium gas.

  14. #64
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    If pressure drop and velocity are more important to performance than intake air temp then the outlaw drag racers must be completely backwards cause they run their intercooler piping inside the car then back out to the intake. Making the piping not only longer but making a 180 degree turn inside the vehicle.
    Pressure drop is not as important in an internal combustion engine as the drop in intake air temp. There are also other variables that come into play such as the efficienty of the turbos, fuel and the engine itself. Just because you have more velocity does not mean you will make more power. Eventually the turbo becomes a hot air pump and timing must be pulled in order to safely run additional boost and negates the point of the additional air.

  15. #65
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    Click here to enlarge Originally Posted by turbodan Click here to enlarge
    If pressure drop and velocity are more important to performance than intake air temp then the outlaw drag racers must be completely backwards cause they run their intercooler piping inside the car then back out to the intake. Making the piping not only longer but making a 180 degree turn inside the vehicle.
    Pressure drop is not as important in an internal combustion engine as the drop in intake air temp. There are also other variables that come into play such as the efficienty of the turbos, fuel and the engine itself. Just because you have more velocity does not mean you will make more power. Eventually the turbo becomes a hot air pump and timing must be pulled in order to safely run additional boost and negates the point of the additional air.
    I was just trying to explain the nature of pressure drop and why it has nothing to do with air density. Of course it's not the most important aspect for a gasoline street car, unless it is in your specific application... it's just one aspect. But it's the one with the most popular misconceptions, even people who professionally race get it wrong here a lot. Luckily it's not a big deal usually. And also there's plenty of racing classes that do not run intercoolers because it's unnecessary restriction.

    All of my posts I've tried to relate to the fact that the intercooler pressure drop is effectively only due to restriction. The denser air after the intercooler is nice, but 99% of the time not responsible for hp gains, and has nothing to do with the source of the pressure drop. Things like velocity change with that density due to core restriction. I've beat this past dead, and I'm not saying anything about how important that aspect is vs others. Just simply trying to explain how that one piece works to try and kill misconceptions.

  16. #66
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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    @ModBargains.com please send me the results.
    You got it!
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    Sean Singh | Sean@modbargains.com | (714) 582-3330 x 8009
    We Specialize In: BMW Parts In Stock | BMW Wheels Experts | BMW Brakes | BMW Suspension | VMR Wheels Experts | Cobb AccessPORT N54 In Stock | Avant Garde Wheels In Stock | BMW Headlights Fast Shipping | BMW Exhaust
    Hours: Monday - Friday 8:00am-6:00pm / Saturday 8:00am - 5:00pm (PST)
    Check out our BLOG for the latest updates and discounts!

  17. #67
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    Good discussion. I have a question. Do turbos actually move air mass (or volume)? In my experience I'd say this is incorrect. Would mean turbo doesn't work off PR.

  18. #68
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    The only real way to understand this is to model it using computational fluid dynamics. Theory and practice are two different things.
    However I appreciate the data posted by Mosselman and Wagner. I know Mosselman they are a good European company that has produced a lot of tuner products mainly Europe only over the years. I have a Wagner FMIC and mine uses stock connections. Whatever produces more power is all that counts to me with my Cobb tuner.
    One company shows one thing in the data another shows another thing. Having done test for 30 years I am certain of one thing, you tell me the results you want and I can assure you my testing will provide them. Independent testing with no company bias is the only honest way to get the data.
    Fun discussion however...

  19. #69
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    Click here to enlarge Originally Posted by fun2drive Click here to enlarge
    ndependent testing with no company bias is the only honest way to get the data.
    Exactly.

    I like seeing the users here test things personally.

    Even then though you have to be able to sort through who got a deal to positively review a product. Wasn't there a guy named formerboostedis known for this?

  20. #70
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    I'm still amazed nobody has made a air to water cooler. For what some of these a/a coolers are expensive enough that you could put together an a/w kit fairly easy with some time spent.

  21. #71
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    Click here to enlarge Originally Posted by turbodan Click here to enlarge
    I'm still amazed nobody has made a air to water cooler. For what some of these a/a coolers are expensive enough that you could put together an a/w kit fairly easy with some time spent.
    Because of complexity, cost, and maintenance. The gains, if any, won't be realized over a quality ATA IC. Would you use the already saturated coolant system? What would cool the coolant, radiator or separate cooler? The whole idea for an N54 isn't feasible IMO.

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    Click here to enlarge Originally Posted by E90Company Click here to enlarge
    Because of complexity, cost, and maintenance. The gains, if any, won't be realized over a quality ATA IC. Would you use the already saturated coolant system? What would cool the coolant, radiator or separate cooler? The whole idea for an N54 isn't feasible IMO.
    But there's so much room in these engine bays for additional rads, dedicated coolers, and plumbing Click here to enlarge
    E88 N54 w stuff
    F30 335 X-Drive EBII....PPK otherwise Stock
    Click here to enlarge

  23. #73
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    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Exactly.

    I like seeing the users here test things personally.

    Even then though you have to be able to sort through who got a deal to positively review a product. Wasn't there a guy named formerboostedis known for this?
    Ya I think FBIS got some sort of favorable deal for certain reviews.

    Good, honest data or GTFO.
    E88 N54 w stuff
    F30 335 X-Drive EBII....PPK otherwise Stock
    Click here to enlarge

  24. #74
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    Click here to enlarge Originally Posted by 135pats Click here to enlarge
    Good, honest data or GTFO.
    A man after my own heart.

  25. #75
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    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    Good discussion. I have a question. Do turbos actually move air mass (or volume)? In my experience I'd say this is incorrect. Would mean turbo doesn't work off PR.
    Yeah they work off a pressure ratio. That pressure ratio is also related to velocity and mass flow rather than plain volume though IIRC, but since the A/R is set on a turbo the pressure ratio can in essence dictate a compressor mass flow rate, and you can calculate the efficiency of that mass flow at certain outlet pressure, again IIRC. A post from Rob Beck or Tony would be cool for turbo theory and pressure ratio's vs mass flow and such, I'm not really an expert, but I did stay at a Holiday Inn express last night.

    How I love some of the questions you bring up.

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