About the N75 Wastegate Bypass Regulator Valve. (m)
05-04-2009, 04:36 AM
#13
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03-13-2011, 09:43 AM
#14
AudiWorld Senior Member
So the height of the N75 piston controls the amount of bleed off.
Someone scoped the N75 and mentioned 300Hz, and duty cycle (for example 95% shown with ECU on and engine off, 40% at idle, 25% when revving).
What does the duty cycle of the signal mean?
Does this mean a 300Hz signal (12V) from the ECU is switched on for a certain percentage of time? I was expecting to see a variable frequency signal from the ECU.
BTW: does anyone know what Amps the N75 draws?
Also with respect to the modified 'racing' N75: are they changing the set up (the screw) or putting a different spring in (changing the natural frequency of the valve maybe)?
Someone scoped the N75 and mentioned 300Hz, and duty cycle (for example 95% shown with ECU on and engine off, 40% at idle, 25% when revving).
What does the duty cycle of the signal mean?
Does this mean a 300Hz signal (12V) from the ECU is switched on for a certain percentage of time? I was expecting to see a variable frequency signal from the ECU.
BTW: does anyone know what Amps the N75 draws?
Also with respect to the modified 'racing' N75: are they changing the set up (the screw) or putting a different spring in (changing the natural frequency of the valve maybe)?
03-30-2013, 04:56 AM
#16
AudiWorld Senior Member
N75 tuning, N75 versions
I experience large boost swings (4-5 psi) around 2800-3200 rpm, maybe 1-3 Hz ('swings' per second). I have larger, RS4/RS6 type turbos.
(Note: I see this on 3 (Three) pretty identical 1.8T AEB, but for the purpose of this discussion disregard the engine type)
When disconnecting the WG actuator hose from the N75, boost goes through the roof (as expected), NO boost swing.
Conclusion: it is NOT caused by the 'hardware' (turbo, high flow manifold, downpipe, etc.) but by the combination/interaction of N75/wastegate/Giac PC16 tune.
With the N75 electrical disconnected (no energy state), the boost goes to 4-5 psi (on 2 of the cars) and 7-8 psi (on the other); as expected (boost set by spring pressure of WG actuator; difference between the 3 cars is caused by stiffer spring used in one car).
Now reading about the 'adjustment' screw: could 'playing' with the potentially get my swinging system out of its 'resonance'?
In this context: does anyone know the physical difference between the N75 used in the 2.7T Allroad and the 1.8T AEB?
(I have a few 2.7T around I could 'borrow' N75 from for testing in the AEB). Same connector? Different orifice (flow restrictor)?
(Note: I see this on 3 (Three) pretty identical 1.8T AEB, but for the purpose of this discussion disregard the engine type)
When disconnecting the WG actuator hose from the N75, boost goes through the roof (as expected), NO boost swing.
Conclusion: it is NOT caused by the 'hardware' (turbo, high flow manifold, downpipe, etc.) but by the combination/interaction of N75/wastegate/Giac PC16 tune.
With the N75 electrical disconnected (no energy state), the boost goes to 4-5 psi (on 2 of the cars) and 7-8 psi (on the other); as expected (boost set by spring pressure of WG actuator; difference between the 3 cars is caused by stiffer spring used in one car).
Now reading about the 'adjustment' screw: could 'playing' with the potentially get my swinging system out of its 'resonance'?
In this context: does anyone know the physical difference between the N75 used in the 2.7T Allroad and the 1.8T AEB?
(I have a few 2.7T around I could 'borrow' N75 from for testing in the AEB). Same connector? Different orifice (flow restrictor)?
Due to surging in factory configuration, so a blatant, don't screw with it, is in accurate.
I agree 100% this is not to be used to increase boost, but this is a nice tuning mechanism to dial out unwanted spikes in your boost delivery.
Before spikes of 1.4, now a constant 1.23 on **** gas and a bit less on great gas!
I think with the proper checks in place, one can absolutely tune the N75 to function properly if not set by factory properly (in most cases)
I agree 100% this is not to be used to increase boost, but this is a nice tuning mechanism to dial out unwanted spikes in your boost delivery.
Before spikes of 1.4, now a constant 1.23 on **** gas and a bit less on great gas!
I think with the proper checks in place, one can absolutely tune the N75 to function properly if not set by factory properly (in most cases)
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