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<x-charset iso-8859-1>Hello- I've stumbled a VERY interesting idea, and wanted your guys' ears on it... We all know that a Porsche 911 cooling system sounds different than a VW one, and previously people pointed to the fan. But, awhile ago I discovered this is untrue, as my pancake T4-cooled *aluminum cylindered* engine whines more like a 911 than any other VW I've ever heard. Many others who've driven with me agree. In fact, is the resonating of the noisy aluminum fins vs. the dampening cast iron fins that makes the difference! If you put one of each cylinder next to each other and run your fingernail on the fins of each, you'll see what I mean. Then, a couple weeks ago, I stumbled across part two of the observation. With my engine running, I happened to put my ear up to the vents on the rear fenders, and heard what sounded like an airplane propeller. It had a sort of beating sound to it. I disconnected the intake system from the body bellows to isolate the sound, and it's definately the fan! I can only assume that the rhythm of the beating is related to the pattern of the four posts and the forty fins on on the T4 fan. Most late bus owners would never notice this sound since it is not isolated from the rest of the engine bay noise in the T3-like fashion, and isn't that loud - the sound of the resonating fins would easily drown it out. Since this time, I haven't gotten the chance to be near a T3-powered T3 (they are a scarcity in our shop :-). With the air filter inlet disconnected from the body, what does the fan sound like? Take care, Shad Laws LN Engineering - Aircooled Precision Performance http://www.LNengineering.com ------------------------------------------------ To unsubscribe, E-mail to: <type3-off@vwtype3.org> For more help, see http://vwtype3.org/list/ </x-charset>