05-05-2014, 11:39 AM | #23 |
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Liquid to air is awesome and provides a fantastic amount of cooling for short bursts. It's even better if you ice it. This is why it's preferred for drag racing. The problem is that the water temps can go up very very quickly and once they do, you are done. The air to air is universally preffered for track usage, yes it can heatsoak but as someone already mentioned it will dissipate quickly. As far as lag, size an IC properly with low bend, low travel pipes and you can bring it down tremendously. The non M cars having air to air is one of the reasons I spoke about differentiation.
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05-05-2014, 11:54 AM | #24 |
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With all the testing on the Ring I think they would have gotten the air to liquid ratio correct and these cars should not heat soak unless air flow is reduced somehow.
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05-05-2014, 12:59 PM | #25 |
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LTA is supposed to be awesome for short sprint drag runs and not so hot for the track or street vs ata.
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05-05-2014, 01:07 PM | #26 | |
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And, Ferrari are using a liquid to air intercooler in their 2014 F1 car BTW... Talks about the Ferrari system from 7:30 onwards: |
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05-05-2014, 01:07 PM | #27 |
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Sounds like a pretty amazing system then. It all comes down to how much heat it can radiate out vs. how fast it's taking it in, and that's a design function. It's not like Liquid to air (LTA) is inherently inferior in some way, it's all about how quickly it was designed to drop stored heat. It's just more challenged in that regard.
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05-05-2014, 03:37 PM | #28 | |
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Naturally, it has to be properly designed and sized to avoid heat soak; the same applies to an air to air system. There are drawbacks from an air to water system, such as added weight and complexity, but performance is not one of them. |
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05-05-2014, 03:43 PM | #29 | ||
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05-05-2014, 03:49 PM | #30 |
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The latter being a significant reason for an liquid-to-air system.
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05-05-2014, 03:59 PM | #31 | |
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Nor the 2014 Ferrari F1 car... Lag is not a "potentially" issue here. You have substantially less volume of air pipes and less distance the compressed air has to travel from compressor to intake with the S55 design. A huge air to air intercooler has a much larger volume that the turbo has to fill than a water to air cooler. Turbo lag is definitely one of the reasons. Cooling capability of a water to air intercooler is far better than a air to air cooler. There is no argument there. Heat soak is the water to air intercoolers main issue. If the water that cools the intercooler becomes hot, then it also takes more energy to cool it Down than a air to air intercooler that has heat soaked. So, heat soak is the thing engineers need to worry about. If they have failed there, then it's a possible bad choice. If they have that under control, water to air is the superior coolant Method And, Ferrari relies on water to air intercoolers in their current F1 car, so it's doable for racing as well. |
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05-05-2014, 04:15 PM | #32 | |
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Why do you think Underground Racing Twin Turbo Lambos producing 1750HP have been engineered with an air-to-water cooling system... With air-to-air there are less moving parts to circulate the heat rejection medium which makes it more reliable, but less efficient in pre-cooling intake air. |
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05-16-2014, 01:04 PM | #33 |
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The beauty of the M5 system (and others like it is) is that the radiator fans and intercooler/turbo (they're water cooled) cooling pumps (x2) can remain on when you turn the car off removing heat... Something that you cannot easily do in an Air to Air environment. Thus preventing heat soak when parking in hot environments after spirited driving.
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05-23-2014, 09:23 AM | #34 | ||
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Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."
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05-23-2014, 09:24 AM | #35 | |
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Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."
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05-24-2014, 05:40 AM | #36 |
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Like 431hp for a 20-30min session?
Water has a good ability to absorb heat. The problem is that's once it has absorbed too much heat it's equally hard to dissipate. If you spend much time at the track you know that an air/air system is easier to manage. BMW chose air/water for throttle response bad choice. |
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05-24-2014, 05:42 AM | #37 | |
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It's all the same to keep the electric fans running to pull air through an air/air heat exchanger. The fact that the M5 needs this system is telling. |
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05-24-2014, 06:46 AM | #38 | |
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And yes, throttle response is a big reason for going liquid-to-air. Heat exchange is dependent on 4 important parameters, specific heat, mass, temperature difference and time. To produce more power, a greater mass of air is needed for the engine. To produce more power with a given displacement, more boost is needed, hence more temperature in the intake charge. So relative to an N55 engine, the S55 needs ~40% more air mass flow that is also hotter due the higher boost; a massive air-to-air intercooler would have been needed on the S55 to slow down the greater and hotter air flow to cool it down sufficiently. The huge volume of air stored in that big intercooler would have killed throttle response. An air-to-air intercooler performance is totally dependant on the ambient air temperature and the speed of the vehicle (mass flow), so it is not possible to have a good control over the intake charge temperature. With a liquid-to-air system, it is possible to control the intake charge temperature by varying the water flow (with the speed of the water pump or through a thermostat) in the system depending on operating conditions. Last edited by CanAutM3; 05-24-2014 at 11:33 AM.. |
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05-24-2014, 03:51 PM | #39 | |
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The choice to go with liquid to air in the new M cars is probably influenced by the need to keep engine's modular since BMW is getting pretty engine swap happy between different models. Same reason DMEs are not bolted on to the engine and not tucked away somewhere else in the engine bay. It saves a ton of wiring and allows engines to drop in easily from one model to another without much complication. Going with Liquid to air intercoolers in the M cars also do a fair share to improve boost response. BMW went to great lengths to make the new turbo M engines feel as close to NA as possible. Not requiring a big front mounted IC in the noise of the car also pays dividends when it comes to weight distribution and polar moment. They are trying to keep as much weight between the wheels instead of hanging on either end of the car. Liquid-to-air ICs do have better cooling characteristics than air-to-air since water does a much better job of cooling the air than air. Assuming BMW sized the water reservoir generously and is running a beefy enough water pump, it should remain very heat-soak resistant. If not, that is all easy stuff to rectify in the aftermarket Cheers, shiv |
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05-25-2014, 11:29 AM | #40 | |||
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Last edited by CanAutM3; 05-25-2014 at 12:15 PM.. |
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05-25-2014, 01:09 PM | #41 | |
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At the end of the day, a good liquid/air IC design is a balancing act between the heat exchanger, pump and intercooler core. BMW tends to engineer these things very well. So who knows? I'm eager to see what design decisions they made |
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05-25-2014, 01:50 PM | #42 | |
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Agreed . I can't wait to try it out a the track . |
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05-25-2014, 06:15 PM | #43 | |
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"control over intake charge temp" is not really necessary. The goal is to get as close as possible to ambient in all cases. You might save a little juice by decreasing electric pump speed in an air/water system when demand is reduced but that's more minimizing the downside than it is upside. |
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05-25-2014, 06:19 PM | #44 | |
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