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Hey Jim- > > 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.......... > > At least Gene wrote up his testing (in his own, very unique, style.) > You've offered us a lot of rather unique thinking of your own, but > backed it up with very little. I'm just starting out... so far, I have some articles on ignition timing out there and, as soon as VWT gets their act together, I'll be sending off a set of articles on A/C systems for the aircooled VW. The problem I have with Gene Berg is this: too much preaching, not enough engineering. He came about at the right time and spoke loudly to kids that didn't know anything about how to hot rod these things. Some things he said were quite accurate, but many are quite wrong. I'm an engineer, but have no desire to preach. I'll only talk about what I actually know and shutup otherwise :-) It may not make as many people take interest in hi-po products that I produce for a lot of money that still break, but oh well. Hell, I've got my hands tied up trying to produce ONE product for the VW aftermarket. (I'm finishing development on a piston/cylinder/stud set for the T4 at a 101.6mm bore - the cylinders are nikasil-plated aluminum and the studs prevent compression leaks :-) > Can you offer anything that can back > up some of your claims? I learned all about the VW cooling systems by taking them apart and analyzing them myself. The reason that I don't know about specific 25-36hp details (although from what little I've seen I'm *pretty* sure they're all very similar in design to the non-fresh air 40hp) is because I haven't taken them apart myself :-). As for the 356 one, I've just seen them and read about them - they look just like the non-fresh air T1 style. I've never taken apart a 911 cooling system myself, but know their basic design second-hand from other engineers I know who like to toy with these things. > While I can't compete with you on your > apparent knowledge of the various VW and Porsche cooling > systems, I'm skeptical about SOME of your claims, particularly > that the air flow to the type 4 oil cooler is shut off as the engine > warms up. I'll have to look thru my manuals to see if I can find any > evidence of that. Forget the manuals, take apart an engine. On that specific point regarding the T4, I am 100% absolutely positive that I'm correct. I can describe the differences between the T3 (with which everyone here is pretty familiar) and T4 setups it in more detail if you like: First off, one correction to what I stated earlier: all T4 used the 80-85C (or is it 85-90C? I really don't remember offhand... I'll check next time I'm near my parts and I'll check one). Until 1974, the T1 used 65-70C, but afterward they went to 80-85C. I *think* that the T3 came with the 65-70C variety from the factory, but on this point I could be wrong. Anyway, the bellows thermostat for the T3 and T4 are of identical dimensions except that the T3 is vertical and is threaded on top whereas the the T4 is mostly horizontal (slightly angled) with a cable coming out of the top instead of threads. This cable goes backward (toward the shroud) and turns to become vertical by way of a ~2" wheel bolted to the case between the shroud and the #2 cylinder. This is how the thermostat expansion motion is transmitted to the flaps, as opposed to the solid linkages attached to the right-hand head on the T3 engine. The T3 has two similar flaps: one on each side of the engine. They pivot on a rod attached to the tops of the flaps. When nearly vertical, they almost block the air (the hole in the right-hand flaps lets a bit go by... whether or not this is by design to allow a little air to facilitate the thermostat or by economics to make the linkage easier to attach is debatable). As the bellows thermostat expands, the solid linkage pulls the right-hand flap toward the front (i.e. toward the cylinders) of the engine, which then turns the rod between the two flaps and moves the left-hand flap in a identical fashion. The T4 has two dissimilar flaps. They are still attached by a rod similar in design to the T3 rod, but instead of the fancy (and hard to adjust!) linkage like the T3, the simple cable connects to its own small arm. The adjustment of the cable on this small arm is easily adjustable from the engine compartment without removing much at all (maybe a hose at most is in the way... clearly an upgrade from the T3 :-). The rod's position is spring-loaded into an "open" position and is pulled back by a cold thermostat, kinda like the rest of the flap-based cooling systems. The right-hand flap moves just like the right-hand flap of the T3 engine: hinged at the top and it moves toward the front of the engine to open (although it doesn't have any holes in it - the only hole is designed to be plugged by a rubber stopper, hinting that the T3 hole is more likely by economics and not design :-). The left-hand flap is a hole 'nuther ball game. First off, the oil cooler is located between the fan shroud and the #4 cylinder horizontally with the mounting surface on a vertical plane, NOT above the #3 and #4 cylinders horizontally with the mounting surface on a horizontal plane like the T3. The left flap is hinged at the bottom, but is not hinged on the rod. The rod connects via an arm on the end of the rod to the flap to move it dissimilarly from the right-hand side. When mostly vertical (again, actually on an angle), it blocks the air. Then, as it opens, the flap again pivots toward the front of the engine. Partially open, it lets a bit of air into the ductwork, allowing air to go to the cyls/heads and the oil cooler. When fully open, the left-hand flap is nearly horizontal and completely blocks the oil cooler cooling air inlet. The flap and the ductwork around the oil cooler fit together like puzzle pieces, blocking it completely. > > 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.] > > If you actually check your numbers I think you'll find that the actual > coefficients of expansion of different alum alloys don't differ by any > significant amount. Of course we can debate what constitutes a > "significant" difference, but we have to agree that the difference > between iron alloys and alum alloys is something like a factor of 3. > So I'm gonna claim tha a 10% difference in alum alloys is > insignificant; calculate what difference this will make in cylinder > wall clearance and we'll see that we can't even measure it. Sorry Jim, but that is entirely untrue. The big difference is that 390 Aluminum is a hypereutectic alloy. I'm not sure what you know about material science, but please forgive me (and skip down a bit...) if I insult your intelligence with the following explanation. The eutectic composition of an alloy of two materials is defined by the point when as much of the minor constituent is totally dissolved in the major constituent as possible. An analog is salt in water. When you put in a little bit of salt, it gets dissolved. That is like a hypoeutectic alloy. When you put in lots of salt, pretty soon it can't all dissolve and some falls to the bottom of the glass as salt crystals. That is like a hypereutectic alloy. The point when the maximum amount of salt as possible was in there and fully dissolved is like the eutectic composition. In the case of aluminum, many times the main alloying agent is silicon. It's the analog of carbon in iron for steel. Generally, the eutectic composition of silicon in aluminum (it depends slightly on other minor constitents, but not much) is about 12% by weight. So, if you have 12% of silicon in your alloy, it's all dissolved in the aluminum matrix. However, 390 aluminum has 16% silicon. So, primary silicon crystals appear in the material matrix. This DRASTICALLY changes the properties of the metal. It becomes much stronger and resilient to wear, and pretty brittle (<1% elongation at room temperature). Additionally, its thermal expansion is greatly reduced. Modern technology is replacing the old technology forged aluminum 2618 pistons with cast aluminum 390 pistons both at racing and OEM levels. First of all, the tooling used for casting 390 along with the different properties allows less metal to be used than for forging 2618 without any degredation in strength, so the pistons weigh less. Second of all, the reduced thermal expansion means that there can be a smaller piston to cylinder clearance, resulting in less piston and ring wear when cold (less banging around). Groovy, eh? > > 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! > > Here I'm confused. I thought there was agreement among all of us, > Berg included, that too hot was bad. I thought that the post I responded to said the opposite... I thought it said that too long a warmup period made cylinders crack more easily. Perhaps it was a misunderstanding my either myself (sorry!) or the poster, I dunno. > > 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! > > This surprised me, but I have verified that this is basically the way > that magnesium is produced in the US. We should not confuse this > to mean that it is cheap. It's an electrolytic process, much like the > production of aluminum and uses huge amounts of electricity. I > think you will find that magnesium is more expensive than > aluminum and that aluminum is more expensive than iron or steel. Per pound, that pricing is true. Then again, the magnesium case weighs much less. > So perhaps we should ask ourselves why they choose such an > expensive material. Interestingly enough, in the very beginning (1930s), one of the reasons that the engine and transaxle cases were magnesium alloys was political. The KDF was the pride of Nazi technology of the era and they wanted to boast it and use it as a propaganda piece to glorify Nazi Germany. The hubcaps bore Nazi symbols. Heck, even the name was an acronym for a propaganda phrase. Anyway, getting metals from sea water was new technology during this time and Germany was one of the countries that really pushed it. Hitler claimed that metals from magnesium to gold could be extracted from sea water in pretty good quantities. While the gold claim brought about nothing more than the Nazis building fake gold "factories" to interest foreigners and investors (that, for the most part, believed him!), the magnesium claim was true. The KDF was to showcase this new Nazi technology... :-) Why they stuck with it could be due to many reasons. One is simple: the equipment to extract the metal from sea water is already made and the tooling was already set up. Why change? Bauxite is primarily in places like Australia, Russia, Brazil, Guinea, and Jamaica. Especially with large amounts in Brazil, one must wonder why they didn't convert to aluminum eventually. Well, the reason is simple: the vast majority of the equipment to actually refine bauxite into aluminum is in the US :-) In the early 1960's when they went to the 40hp-style case, they probably kept the same metal because a cost-benefit analysis showed that it was cheapest to keep using it. Why establish new tooling? Plus, although the metal is pricier per pound, it also weighs much less. I have a T1 and T4 case around here... perhaps I should weigh them for fun to see the difference. But, although weight might have been a concern in the beginning, I doubt they cared much about adding 20lb to the bug once they started adding safety features like heavy bumpers and supports and the like... But all that is speculation. I am curious to know exactly what their reasoning is... Take care, Shad > > - > ******************************* > Jim Adney, jadney@vwtype3.org > Madison, Wisconsin, USA > ******************************* > > ------------------------------------------------------------------- > List info at http://www.vwtype3.org/list or mailto:help@vwtype3.org > >