MAP or MAF ??????????
08-15-2003, 01:07 PM
#61
Race Director
" (Again, a K27 flows more air than a K26 at 15psi! Same boost more air. The MAP generates the same signal for 15psi).. "
Actually this is a common misconception. Review your physics of PV=nRT. The boost level is created by the restrictions of the engine, that is, the restrictions present in the muffler, exhaust, turbo, headers, valves, intake-manifold, head, throttle-body, etc. If you bolt on a different turbo without changing anything in the engine, restrictions remains the same and volume-flowed at the same pressure/boost will be the same. The difference in flow between a K27 and K26 is due to the K26's drop in boost at high-RPM (15psi max -> 12psi). That's where the difference in flow comes from. If you have a turbo that can hold 15psi max-boost to redline, it will definitely register differently than one that goes from 15->12psi and will definitely create different power levels.
Let's keep the turbo constant and change the engine restrictions with the same turbo. Put a 1" throttle-body onto the car and at the same 15psi max-boost as before you will actually only have 12-13psi in the intake manifold due to the restriction of the throttle-body. Or we can do the converse and increase the throttle-body by10mm and end up with 16psi in the manifold (smaller difference because the TB is only a minor restriction; improving it won't gain as much).
Actually this is a common misconception. Review your physics of PV=nRT. The boost level is created by the restrictions of the engine, that is, the restrictions present in the muffler, exhaust, turbo, headers, valves, intake-manifold, head, throttle-body, etc. If you bolt on a different turbo without changing anything in the engine, restrictions remains the same and volume-flowed at the same pressure/boost will be the same. The difference in flow between a K27 and K26 is due to the K26's drop in boost at high-RPM (15psi max -> 12psi). That's where the difference in flow comes from. If you have a turbo that can hold 15psi max-boost to redline, it will definitely register differently than one that goes from 15->12psi and will definitely create different power levels.
Let's keep the turbo constant and change the engine restrictions with the same turbo. Put a 1" throttle-body onto the car and at the same 15psi max-boost as before you will actually only have 12-13psi in the intake manifold due to the restriction of the throttle-body. Or we can do the converse and increase the throttle-body by10mm and end up with 16psi in the manifold (smaller difference because the TB is only a minor restriction; improving it won't gain as much).
08-15-2003, 02:44 PM
#62
Drifting
Wouldn't changing the turbo change the amount of heat generated? And as T is part of this equation thus change n? I' don't really know, but thought it was worth discussing.
Justin
Justin
08-15-2003, 05:27 PM
#63
Pro
Join Date: Jun 2003
Location: Bjärred Sweden
Posts: 600
Likes: 0
Received 0 Likes
on
0 Posts
I agree with Justin. n-flow is what matters. Same volume flow of different density means different mass flow. The difference between a K27 and K26 both at 1.4bar at 4000rpm is dramatic.
Bengt
Bengt
