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Hey Jesse- > I just read an article on this question in the Gene Berg catalog. He > states that there is an decrease in engine life between 13 to 19% by > removing the cooling flaps. Knowing the type of "testing" Gene Berg typically used, I can just about guarantee that those numbers hold no significance. They were probably just pulled out of someone's.......... > When the motor is receiving its full > cooling potential during warm up the motor cannot heat up at the same > rate from the case to the cylinder heads, causing cracked heads, > misadjusted valves and cylinders and pistons heating up unevenly > causing ring and cylinder wear. The only one of these that makes sense is ring and cylinder wear. Think about it. (or read below) > He also states that the longer the > engine runs cool the more wear and tear there is on the bearings. True. But, then again, the bellows thermostat on the VW doesn't do much to help this. Staying away from thick, straightweight oils, having working pressure-relief valves, and running at a conservative RPM until warm does. > Also the air control flaps act as air directors forcing the air > across the oil cooler at just the right direction so the air flows > over it and on to the cylinders at maximum efficient. That's just *slightly* inaccurate :-) Here's the thing: there are six different kinds of cooling systems used on aircooled VW engines (excluding any really archaic 25-36hp stuff... I dunno specifics about these). All of regulate based on the air temperature under the 1 and 2 cylinders. The T1 and T3 are fully open at 65-70C and the T4 at 80-85C (or is it 85-90C? I don't remember offhand). The first is the older T1 style - a big baffle is placed in front of the fan shroud opening. The Porsche 356 copied this. In effect, this regulates the amount of cooling air given to both the oil cooler and the heads/cylinders. However, this is somewhat clunky, is somewhat prone to failure, and is somewhat expensive. The second is the newer non-doghouse T1 style - the infamous flaps. Flaps are placed atop the heads/cylinders that only regulate the air to the heads/cylinders! However, with *most* of the air outlet blocked, it *kinda* keeps the oil cooler from getting cooled off much. This system is a bit more robust and cheap, but that's not the main reason VW changed. They changed because of the simultaneous change to fresh air heaters - if they regulate overall air intake, the heater air is also regulated. Was this done for preferentially cooling the heads over the cylinders? No. That was NOT on the VW engineer's design board at the time. And, the more I think about them and stare at them, the less I believe that they do actually prefer the heads over the cylinders during warm-up, although I do agree that a setup that actually did this would be somewhat useful (see below...). The third is the newer doghouse T1 style. The change from the previous one is that the oil cooler receives full-blast air all of the time - it is NOT regulated. Only the heads/cylinders are regulated. The fourth is the newest doghouse T1/911 style, currently used on the VW in Mexico today and on the 911 for it's entire life from 1964 on. The change from the previous one is that there is NO cooling air regulation: full-blast to everywhere all of the time. The fifth one is the T3 style. There are a pair of flaps that regulate the air going to both the oil cooler and heads/cylinders - hotter = more. Functionally, this is most similar to the earliest T1/356 style air control. The sixth one is the T4 style. This one is very unique. It looks kinda like a T3 setup, but has one very important difference! When fully closed, the system blocks all cooling air. When partially open, the system lets air to both the oil cooler and the heads/cylinders. As they open more and more, the system begins to block cooling air to the oil cooler! When fully open, the oil cooler is COMPLETELY blocked! All cooling air is directed toward the heads/cylinders. Clearly, if left in stock form, simply removing the thermostat and leaving the flaps in place will kill the engine. So, what's to realize from all of this? First of all, VW never cared one bit about regulating air to the oil cooler. Any and all regulation of cooling air to the oil cooler is purely coincidental. In fact, the oil cooler itself was originally an afterthought and it's only purpose is to keep the oil cool, NOT the engine cool. I know that this is exactly contrary to what most people believe, namely that VW intended oil to be a coolant, but oh well. That's the truth. Looking at what they did over the years, especially with the T4, it can clearly be seen that oil was NOT intended to be a coolant - just a lubricant. And, if oil gets too hot, then it gets too thin, so they put in a cooler ONLY to keep the oil cool and thick enough! That's it! In fact, the oil cooler was considered so unimportant to overall engine cooling that it was shut off on the T4 when the thermostat signaled that the engine was running hot. (BTW, this is why I laugh when I ask people what they did to the cooling system to offset their kewl 4- or 6-fin hi-po T1 heads and they answer with a big oil cooler :-) Now, there IS a psuedo-thermostat on the oil flow itself into the cooler - the pressure relief valve. When cold, less oil passes through the cooler than when hot. The ONLY function of the cooling air control system is to limit air to the heads and cylinders (non-preferentially) when the exiting air temperature is low. There is one additional function on the T4 - block cooling air to the oil cooler and send even more to the cylinders and heads when very hot. And, this makes sense - the clearance between the pistons and cylinders is larger when cold than hot. [BTW, this is one downfall of forged (Aluminum 2618... or is it 2816? I don't remember...) pistons as opposed to the new, cast hypereutectic (Aluminum 390) pistons - the new ones run with a considerably smaller clearance due to lower thermal expansion.] So, when colder, the rings and pistons wear more. And, the additional function of the T4 makes sense - if the heads get too hot, the heads will crack! This is contrary to what you said that Berg preached - heats crack when they are too HOT, NOT when too COLD! But, how important is the control of warmup to the cylinders and heads? To cars driven in non-arctic climates, it doesn't matter much at all. In fact, Porsche disregarded it with the 911 and VW with the newer aircooled Beetles. The argument of dissimilar cylinder materials can't be used either: all aircooled 911 engines (cyls of solid cast iron like VW, cast iron sleeves and aluminum fins, and solid aluminum) used the same sort of cooling arrangement. If you've ever used a cylinder head temperature gauge, then you know how quickly the heads heat up even without thermostatic control on a 30F day even when driving conservatively to make the cold oil happy (sorry, I haven't done it in the snow and so don't know about much colder :-). > what i have learned is that vw engineers were a lot smarted than me > and most anything that i do to the engine that was not stock is going > to sacrifice longevity and quality. Vw did not just slap things > together and hope for the best. They spend years researching and > developing little things like how to build an efficient cooling > system. Unfortunately, that is not quite true :-). Designing a system that actually did limit cooling air to the cylinders and not heads during warmup based on actual cylinder (not head or air) temperature would be nice, but expensive. So, VW nor Porsche ever felt it was worth the expense for the gain. Also, adding an oil filter like every other auto manufacturer is a big plus. VW engineers weren't the best - they did only what was needed and for as cheaply as needed, especially when discussing the T1-based engines (T4 got a little more money thrown at it). I mean, c'mon, why did they continue to use the magnesium-alloy case even when they knew that they didn't last? Sim ple - getting magnesium from sea water was dirt cheap! Take care, Shad ------------------------------------------------------------------- Unsubscribe? mailto:type3-request@vwtype3.org, Subject: unsubscribe