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spare time toys |
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hooked on grilling food. ![]() ![]() ![]() ![]() Group: Members Posts: 4,059 Joined: 3-April 04 From: West Plano Tx Member No.: 1,884 Region Association: Southwest Region ![]() |
Check www.ststurbo.com they put it away from the engine. I would think it would have a big turbo lag. (IMG:style_emoticons/default/huh.gif)
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Brett W |
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Advanced Member ![]() ![]() ![]() ![]() Group: Members Posts: 2,856 Joined: 17-September 03 From: huntsville, al Member No.: 1,169 Region Association: None ![]() ![]() |
QUOTE Hmmm, I guess you've been reading different books than I have. According to Bob Tomlinson in turbomania (a book about turbocharging air cooled flat 4 engines) he states that long duration is a negative because it allows some of the charge to go out the exhaust with no benefit. He says anything over 270 degrees is too much. Corky Bell agrees with that statement in principle. I can't say much more except I've BTDT with good results. Can you provide some information to what you used to make the statements on the cam? Particularly higher duration and lobe centers as it applies to air cooled flat 4 engines. I'd be interested in reading that. Have you driven a turbocharged 914 with a type 4 engine? Others have done it with great sucess, they used the stock cams and had very boost happy motors. If it works it works. I'm a little confused at your statement that it takes too much to make a type 4 boost happy. Can you provide more details of what you think it takes? Granted you can't make a type 4 like a twin turbo supra engine or nissan skyline, that isn't the point and only a fool would even contemplate such a concept. I have read Tomlinson and Bell. Both are good authorities, too bad Tomlinson beleives heavily in that Draw through crap. Duration is based on pressure ratio. IF you have a higher pressure in the exhaust than the intake then running long duration can cause intake charge dilution. In most cases the stock T4 engines when run with 4-6 psi will have a much higher exhaust pressure thus to much duration can be a bad thing but "too much" duration is realtive. The stock cam is cut on a 108 centerline, where most turbo cams will run 112-120+. Excessive overlap can result in poor running. The stock cam has something in the neighborhood of .242 lift with 192-210 deg @.020. Not enough duration for a good turbo cam, nor lift. Yes you can boost with the stock cam, that is not what I am saying. I am saying it is far from "optimized" for the boost situation. ON an aircooled motor running wide lobe centers tends to make the exhaust valves run very hot, not good on a motor that already has problems. Never driven a turbo 914. A type four is not an engine that is good for boost. The stock cooling system is pretty taxed in stock form, the heads are way to weak, thus the need for 5-6 stud arrangements, in addition to the shitty ports. In order to make it acceptable for boost it would take a major chunk of cash. It can be made into a really good NA motor. If you want to boost your 914 go ahead. I have yet to see one that was done "right". I mean intercooled, standalone or programmable fuel injection , proper cooling system (not having the turbo up in the engine bay where all of the heat is preheating intake and cooling air), proper oil cooling to cope with the extra heat generated. Ed's car was the closest but most people won't go to the trouble to do it all out. They want to throw a junkyard turbo kit on there and call it good. |
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