Guest 73Turbo240z Posted September 29, 2005 Share Posted September 29, 2005 Alright... built into a turbo application MSnS... a motorola 2.5 bar map sensor... that being said, w/ 1 bar = 14.7psi... what is the max measurable boost for the map sensor on board? 36.75psi w/ no correction for the worlds ambient pressure? or 22.05 w/ correction of 14.7psi for "ambient" pressure? I can't figure it out since an engine see's the world as a status of vacuum or boost, not ambient like a human body... anyone care to clarify? i'm trying to figure out if i need to upgrade my MAP sensor or not, cause if 22psi is the true limit on a 2.5bar sensor, i need to go higher... Quote Link to comment Share on other sites More sharing options...
mobythevan Posted September 30, 2005 Share Posted September 30, 2005 MAP sensor measures absolute pressure. That means atmosphere pressure wherever you car is plus boost. at sea level = 14.7 + boost (2.5bar * 14.7psi) - (14.7psi if your at sea level) = 22.05psi now you see why you can raise the boost when you go up in altitude, but absolute pressure in the intake manifold remains the same for all practical purposes. At 6500' altitude where I am, atmospheric pressure is closer to 11psi. so (2.5bar * 14.7psi) - (11psi at 6500' above sea level) = 25.75psi I can run 25psi boost on the same sensor while someone at sea level can only run 22psi boost. If you run 22.05psi at sea level and I run 25.75psi at 6500 feet we both run 36.75psi in the intake manifold. Or, if we both run 22.05psi then my intake pressure is only 33.05 while yours is 36.75, so I loose that much pressure and horsepower from high altitude. The most fun thing from all of this is that I can run 18psi boost here on my L28et with stock headgsket and then sell it to Nelson at sea level and forget to turn it down. Now he will run more abosulte pressure and blow the head gasket (ha ha Nelson, just kidding, that is why we turned his boost down). I still think this is one of the best basic things to understand with boost so you don't read on the forum that joe blo runs x amount of boost and not realize he lives at 9000' altitude. Then you run out and crank your boost up like his thinking he is running all stock components and blow stuff up. The same for the reverse situation is that at high altitude you run sea level boost settings and wonder why your car doesn't perform. Hope that helps. Quote Link to comment Share on other sites More sharing options...
Guest 73Turbo240z Posted September 30, 2005 Share Posted September 30, 2005 MAP sensor measures absolute pressure. That means atmosphere pressure wherever you car is plus boost. at sea level = 14.7 + boost (2.5bar * 14.7psi) - (14.7psi if your at sea level) = 22.05psi now you see why you can raise the boost when you go up in altitude' date=' but absolute pressure in the intake manifold remains the same for all practical purposes. At 6500' altitude where I am, atmospheric pressure is closer to 11psi. so (2.5bar * 14.7psi) - (11psi at 6500' above sea level) = 25.75psi [b']I can run 25psi boost on the same sensor while someone at sea level can only run 22psi boost.[/b] If you run 22.05psi at sea level and I run 25.75psi at 6500 feet we both run 36.75psi in the intake manifold. Or, if we both run 22.05psi then my intake pressure is only 33.05 while yours is 36.75, so I loose that much pressure and horsepower from high altitude. The most fun thing from all of this is that I can run 18psi boost here on my L28et with stock headgsket and then sell it to Nelson at sea level and forget to turn it down. Now he will run more abosulte pressure and blow the head gasket (ha ha Nelson, just kidding, that is why we turned his boost down). I still think this is one of the best basic things to understand with boost so you don't read on the forum that joe blo runs x amount of boost and not realize he lives at 9000' altitude. Then you run out and crank your boost up like his thinking he is running all stock components and blow stuff up. The same for the reverse situation is that at high altitude you run sea level boost settings and wonder why your car doesn't perform. Hope that helps. definately moby, thanks! Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 2, 2005 Share Posted October 2, 2005 There is source code available and directions for several on-board MAP sensors that can be used in the MS that allow maps for higher boost levels. Rick Yaoccuci uses one in his Bonneville Streamliner---I think he is running 30+ or 45 psi on his Busa Motor to make over 619HP at 10,500rpm.... Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted October 17, 2005 Share Posted October 17, 2005 ok so what MAP sensor is required for N/A applications. the MPX4250AP MAP sensor from what i understand is a 2.5bar sensor... so this SHOULD work from nothing up to 2.5 bar correct? -Ed Quote Link to comment Share on other sites More sharing options...
mobythevan Posted October 17, 2005 Share Posted October 17, 2005 2.5bar sensor will work fine for NA applications. And then when you put a turbo on it you won't need to buy a new one for up to 1.5bar boost. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted October 18, 2005 Share Posted October 18, 2005 ok thanx Quote Link to comment Share on other sites More sharing options...
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