VW cooling

Discussion in 'Volkswagen' started by Kmccune, Jun 26, 2010.

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  1. Jun 15, 2011 #41

    bmcj

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    Sadly, It has been nearly 20 years since I last saw him (when I moved to another town). I think he was playing with a supercharger on this engine too, so that may have been where the detonation problems came from.
     
  2. Jun 17, 2011 #42

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    [FONT=&quot]
    Here is the reality check. With a turbo you can make an engine produce whatever power they will stand. How many Type one air cooled VW based engines are currently available with turbo(s) for airplanes? If it worked there would be a lot of them.[/FONT]
     
  3. Jun 17, 2011 #43

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    The small bump in HP is from the evaporative cooling of the charge before the intake valve closes. The down side of water injection is water in the oil. It makes a mess of the bottom end but it will very effectively cool the engine. One source I read said that the amount of heat rejection was even at 169 BMEP and at 240 BMEP with enough water added to prevent detonation, very effective cooling.

    [FONT=&quot](BMEP= Brake mean effective pressure)[/FONT]
     
  4. Jun 17, 2011 #44

    fly2kads

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    I'm sorry, I'm not understanding your line of thinking. Turbos on aircraft engines are a distinct minority, in most cases only added when the mission of the engine/airframe calls for them. Hence, they usually appear as turbo-normalizing configurations on the big six-cylinder engines. There are only a very few small engines with turbos. How many O-200s, O-235s, O-320s are available with turbos? Nil? VW-based aircraft powerplants have been operated with Rayjay turbos before, but they are significantly more expensive and complex than the normally-aspirated configuration. I would venture that the vast majority of VW installs are done by people who select them precisely because they are simple and inexpensive.
     
  5. Jun 17, 2011 #45

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    Too true but back in the day they were offered as a way to make 100 hp. They (the type one vw) aren't up to the task. One thing you can do with a turbo is to take a small displacement engine and make it make outrages amounts of power. One of the best records that has been achieved is 1,000hp out of 1.5L for 50 hrs without a failure in competition by Porsche.

    If you are expecting something like 40hp out of the type one with a stock head then you aren’t going to be disappointed. My comment about the turbo is that you can make whatever power continuously at any altitude. That no one makes them is indicative of the fact that they don’t cool well enough to be reliable. With normally aspirated performance they get flown closer to where they are reliable than where they are not. If your plane will fly well with 40~50 hp you will be happy with a VW type one. There is a point where the engine life goes down fast with a small increase in power. The exact point depends on a number of factors some of which are airplane specific.

    [FONT=&quot]On my too do list is a small turbo charged engine. There are a lot of benefits to having a high power to weight ratio. Supercharging is a very effective way of getting a high hp/lb ratio.

    [/FONT]
     
  6. Jun 17, 2011 #46

    Andy

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    It wouldn't be hard to rig a solenoid that came on at a preset temp based on the cylinder head temp. So I would only be injecting water/alcohol when cooling was really needed. That would limit water in the bottom end. Wouldn't small amounts of water in the crankcase boil off???
     
  7. Jun 17, 2011 #47

    bmcj

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    You get the water in the oil from burning gasoline too. Remember that combustion of a given volume of gasoline (hydrocarbon) produces an equal volume of water. Even if you do water down the oil, most of it burns off (evaporates) when the engine is at operating temperatures. That is why they recommend against making all short trips where the engine and oil never come up to full temperature.

    On the plus side, I used to change the oil in my VW Bug every 2,000 miles... it took all of 2-2.5 quarts. :gig:

    Bruce :)
     
  8. Jun 17, 2011 #48

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    In theory you are correct. Small amounts of water should boil off. With water injection you should be able to use a higher compression ratio that should get you better fuel mileage. In practice running the extra water through the engine reduces the engines life. But it does keep the combustion chamber squeaky clean. That tends to reduce the chances of preignition. Rather than an on off switch with a solenoid valve I’d go with a computer controlled water flow that would add progressively more as the temp went up over a 10 degree spread or so. You could also set up a safety that would not inject water into a shut down engine.
     

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