Compression Ignition Addict
Join Date: Jun 2010
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Yes peak boost is pretty irrelevant like you said, but from my understanding the waste gate is not opening unless peak commanded boost is reached. How could you possible build boost efficiently if the wastegate was constantly opening say at 10 pounds because that is the commanded boost for that given load and rpm? I mean the wastegate isnt even hardly necessary, a lot of diesels don't even have them since diesels are controlled by fueling and not air flow like a gas engine. You dump the fuel to it to make the engine build boost and supply more air to properly burn the mixture. Thats obviously why diesels smoke more on takeoff or pulling stuff, there try to build the boost to get enough air to burn the fuel, the wastegate is only there to control excess drive pressures. If you have a waste gate that is constantly opening it would be like having a cracked uppipe or leaking manifold and would result in poor performance. On top of that why would the gate open when you get out of the throttle? That is when boost is decreasing, it wouldn't stay shut the entire time your giving it then open once you get out of the throttle, thats what a bov does. I could be wrong though, the dualboost turbo is new technology.
Edit: Just read your edited post, I don't have a 6.7 yet so all i can go off of is videos I have heard lol. I didn't know that you can hear the wining noise when your in the throttle, I thought it was only when you get out of it like all the youtube videos show. You may be right then, it could be the wastegate opening to control boost even in a low rpm low load situation. Traditional diesels I always thought just cut fueling, opened the egr valve more, or opened the veins on the turbine to relieve pressure. Maybe they decided on the 6.7 that a proper wastegate was also needed.
Last edited by jordan572; 10-02-2013 at 11:54 AM.