I feel the need to point out some aspects over this topic for which I would like our ECU experts (Mihnea, Paul N. and others) to give theyr contribution.
Given the system works in the following way (please confirm or belie statements):
1) ECU reads intake absolute pressure at plenum;
2) ECU reads athmospherical pressure by its "altitude" sensor (?);
3) With previous two parameters it compuetes it's predefined boost curves;
4) Turbocharger provides pressurized charge by flowing charge and compressing it at a value given by it's specific compression ratio (P2/P1) depending on impeller speed and total flow);
5) P1 is absolute pressure at cold side inlet (less than athmospherical and dependent on "pre-cold side" intake system efficiency);
6) P2 is absolute pressure at cold side outlet (presumibly different than pressure at intake manifold because of pressure drop in plumbing, intercooler, and eventual pressure variations inside plenum).
THEN
If we upgrade intake duct BEFORE turbo cold side, from a theorethical point of view P2 should increase because P1 will be higher (while P2/P1 remains constant), which means higher pressure all the way through intake up to the plenum (lets call it Pp).
BUT
Since ECU has a setted Pp map it will just reduce pressure P2 accordingly to have same Pp as before. If no change is made in ECU boost map, therefore, no gain can be achived other than a slightly more reactive turbo and pressure build up while reducing P2/P1 which means letting cold side give same flow at lower CR (compresson ratio).
Same thing if we upgrade intake duct "after" cold side, including IC and IM.
In this case we would rise Pp just reducing pressure drop after turbine leaving the P2/P1 the same. ECU again would reduce P2 accordingly to have same Pp as before.
All this unfortunatly, doesn't give unlimited benefits. Turbocharger operational limit is given by two parameters CR (P2/P1) and flow.
So gains can be obtained only in the engine's rpm range where CR of cold side is at its top limit but not flow capability, which are more likely to happen at mid rpms:
increasing intake efficiency (up to IM) means that at same CR of cold side you get higher boost at IM. Of course with more flow from the turbine, proportional to the gain in the intake efficiency.
At high rpms, where cold side is already operating near it's maximum flowing capability (choke line), increased flow efficiency of intake doesn't provide gains because cold side cannot provide higher flow (without going in the "danger" area of working) thus not giving higher Pp.
Marco
Given the system works in the following way (please confirm or belie statements):
1) ECU reads intake absolute pressure at plenum;
2) ECU reads athmospherical pressure by its "altitude" sensor (?);
3) With previous two parameters it compuetes it's predefined boost curves;
4) Turbocharger provides pressurized charge by flowing charge and compressing it at a value given by it's specific compression ratio (P2/P1) depending on impeller speed and total flow);
5) P1 is absolute pressure at cold side inlet (less than athmospherical and dependent on "pre-cold side" intake system efficiency);
6) P2 is absolute pressure at cold side outlet (presumibly different than pressure at intake manifold because of pressure drop in plumbing, intercooler, and eventual pressure variations inside plenum).
THEN
If we upgrade intake duct BEFORE turbo cold side, from a theorethical point of view P2 should increase because P1 will be higher (while P2/P1 remains constant), which means higher pressure all the way through intake up to the plenum (lets call it Pp).
BUT
Since ECU has a setted Pp map it will just reduce pressure P2 accordingly to have same Pp as before. If no change is made in ECU boost map, therefore, no gain can be achived other than a slightly more reactive turbo and pressure build up while reducing P2/P1 which means letting cold side give same flow at lower CR (compresson ratio).
Same thing if we upgrade intake duct "after" cold side, including IC and IM.
In this case we would rise Pp just reducing pressure drop after turbine leaving the P2/P1 the same. ECU again would reduce P2 accordingly to have same Pp as before.
All this unfortunatly, doesn't give unlimited benefits. Turbocharger operational limit is given by two parameters CR (P2/P1) and flow.
So gains can be obtained only in the engine's rpm range where CR of cold side is at its top limit but not flow capability, which are more likely to happen at mid rpms:
increasing intake efficiency (up to IM) means that at same CR of cold side you get higher boost at IM. Of course with more flow from the turbine, proportional to the gain in the intake efficiency.
At high rpms, where cold side is already operating near it's maximum flowing capability (choke line), increased flow efficiency of intake doesn't provide gains because cold side cannot provide higher flow (without going in the "danger" area of working) thus not giving higher Pp.
Marco
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