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Discussion Starter · #1 ·
Hi all, i have only just registered, i have a friends R33 an L reg according to vin plate an RB25 Det engine is fitted
the problem is that the engine is over boosting to nearly 20 psi and popping and banging,the boost control valve works as i have powered it myself, it appears that there is no signal coming from the E.C.U to the boost control valve on the L/h inner wing by the air filter, this wire is ok as i have checked the continuity
im struggling as the wiring diagram i have is not very good, also im not sure where the map sensor is i have found a sensor on the drivers side by the brake servo that looks like the MAP sensor and that appears to be working but there is no mention of this sensor on the wiring diagram. i have 12v and ground and when it is running it fluctuates from 1.25v idle when revved goes up to nearly 2v then comes down again
Does anyone have the correct diagram,book or pdf on how the system works and what readings i should be getting from the sensors
The E.C.U fitted is the following :
Hitachi A1 3Y16
23710 21u01
Thank you in advance for your help
 

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RB25DET's dont have a boost control valve, they have what you are looking at a boost solenoid.

Boost is controlled usign the actuator spring rating. The boost solenoid only diverts a certain amount of pressure away to allow running second stage boost. The opening of this boost solenoid is controlled by the ecu and comes in play at a specific RPM.
 

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As Blitzer has already said the ECU has very little control over the boost level, all it does is at 4800rpm it opens the solenoid to bleed off some air from the wastegate actuator allowing a slightly higher boost level.

If the car is overboosting the the problem is with the wastegate actuator. Try connecting the wastegate actuator directly to the I/C pipework and see what happens, it shouldn't boost higher than 0.6 bar. If it is still overboosting disconnect the actuator and make sure the arm that opens the wastegate can open and close freely. If you need to replace it you should be able to pick up a replacement quite cheaply.

HTH.
 
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