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copbait73 copbait73 is offline
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Join Date: Nov 2003
Location: Chesterfield IN
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I don’t think the original poster was asking for advice, he was making an observation and everyone else including me was responding accordingly. I didn’t say use this turbo or that one. But since you often seem to take issue with almost everything I post, I’ll take you on, no problem.

The wastegate is a necessary evil and a cost effective compromise to attain boost response. The variable nozzle turbine (VNT) is a better compromise because they use the energy instead of dumping it overboard. VNT was not an option during the days of F1 however they are used on Porsches top of the line modern TURBO and on millions of diesel engines. The VNT uses the exhaust energy more efficiency and oh by the way can also be matched with a larger turbine and still provide better response.

Responding to your map, that is all good but what happens when the wastegate opens and dumps energy overboard? Your effective turbine efficiency is now poo-poo. Here’s Porsche own published data, P2 is intake pressure and P3 exhaust pressure. When you open the W/G you begin generating pumping losses in the engine system.



Everything about turbos and matching is a compromise. Relating to rotor inertia, what would you rather have? 1) a small turbine wheel that comes up to pressure a split second quicker but is restrictive and has poor efficiency from there on, 2) A larger turbine with less restriction and higher efficiency that can offset opening of the W/G to a higher engine speed. There is no set answer it’s a compromise for the conditions and intended use.

Manifold pressure does not = power. Positive pressure differential between the intake and exhaust manifold at a set manifold pressure = power. Yes, Eddy is out there making big power using known turbocharger principles
Oh, regarding your F1 motor. Marvelous piece of engineering those motors. I would consider those turbos to be quite large. I have an F1 turbocharger and it has a 65MM turbine that was fed by only 750CC.

Last edited by copbait73; 03-21-2010 at 10:50 AM..
Old 03-21-2010, 10:03 AM
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