Wastegate spring weak? Only 0.3 bar boost!

[jimmydanny]

I noticed when I got a boost gauge in my car that I only had 0.3 bar pressure (do the math yourselves, psi is like greek to me).

I disconnected the vac hose for the wastegate, and got up to 0.9 (but I got fuelcut then ofc), but I regulary got up to 0.5 bar, which is what it is supposed to do in normal circumstances.

What can I do to resolve this? Running without wastegate isn\'t the smartest thing to do I guess, so I need to get this fixed somehow.

[Prof]

If it\'s stock plumbing, then the stock boost solenoid - on the oil filler neck, is designed to bleed boost off the wastegate to lift the boost from 5psi (about 0.35 bar) to 8.5 psi (0.6 bar). If you put a peg or clip on the line that comes off the T (right on the front of the compressor housing - you can\'t miss it), and you only get 0.3 bar - then the problem is with the piping or connection to the boost solenoid.
 
I\'d also check the wastegate is mechanically connected - it has been known or the actuator arm to come off the wastegate lever - it\'s held on only by a small circlip - it\'s hard to see under the heatsheild - but a mirror and torch should let you see it.

[jimmydanny]

When the car is stock, nothing done with it, i get 0,3-0,35 bar. When I disconnect the vac line to the wastegate actuator (its not really vac line, but anywho), I get 0,5 bar, up to 0,9 when I run it in high gear so the turbo can spool for a longer time under more pressure.

I guess the wastegate actuator got this vac line, and there is a T connector further down, kinda under the air pump, but it is tricky to see anything down there without taking off the front fender and radiator, which I am in no mood for today

I am running now with no wastegate, and using the gauge to chill out, and I only hit fuel cut once, and afaik, it is the fuel cut that is dangerous, making the engine go really lean, and I might blow the seals.

But it is still peculiar that this happens, I am sure I have an S5 engine, so this shouldn\'t be 0,3 bar. Also, compared to my VW Passat 1.8T with 200hp, it didn\'t have the same acceleration, even with the same weight. But now it does. So I guess this is it, something is wrong, somewhere.

If the wastegate wasn\'t mechanically connected, I should have no upper boost limit except exhaust backpressure, unless it was stuck open, which should give me no pressure. But as the wastegate is now disconnected (vac-line wise), and I get up to 0,9, it can\'t be the connection between the actuator and the wastegate itself.

Sorry for actuator/solenoid mixup, I dunno the difference, I am used to wastegates having actuators?

[m1tch]

Sounds like you have a vac leak somewhere between the OEM solinoid and the actuator, if you can boost up fine then the wastegate and actuator are connected fine, its just a case of the solinoid not bleeding enough boost out the system and the wastegate opening early.

If the ECU isn\'t chipped, anything past 0.6 bar isn\'t advised as it would run lean and you might lose a tip or blow a seal.

Standard boost on a Turbo II is 0.6bar

[Prof]

...
Sorry for actuator/solenoid mixup, I dunno the difference, I am used to wastegates having actuators?

It does have an actuator
 
Normally you\'d run a pipe or hose from the output of the compressor to the actuator, and the boost pressure would be controlled with the spring in the actuator.  This is exactly the case with the FC as well, but with one difference.  The pipe that goes from the compessor to the actuator has a \'T\' in it, and that other pipe that comes off it goes to the boost solenoid on a stock car.  This raises the boost pressure above what the stock wastegate actuator would run at and gives the FC the higher boost it has.
 
The attached piccy should help explain it - you should be able to get to that T hose by taking off the main air pipe between air box and Turbo.

[jimmydanny]

I took the vac line off the actuator, ofc I get unlimited boost so to speak, but it is pretty tight with the air pump on top. But on tuesday, I get the dual alt. pulley and block off kit, so I will take a better look then. I can feel my clutch slipping more now, wonder if it is lack of fluid (I got a leak), or if the clutch is dying faster than I thought...

Also, the buzzer goes off some seconds after start, like when not enough oil or water, but both of those are over half full. What other stuff can make the buzzer go off (continuously)?

[Prof]

It will most likely be coolant level in the radiator that\'s causing the beeper - it needs to be up to the top - even an inch or two low will set the buzzer off.

[jimmydanny]

Yeah I got that sorted, just had to get the engine warm enough for the thermostat to open, so it could suck some water in, as it had filled the engine, but not the rad itself. Stupid car.

Anyways, I will take a closer look @ the solenoid on tuesday. Is there anything obvious, and is this a regular part, or something special Mazda-stuff?

[Prof]

I think it\'s a denso part, but I have spare one if you need it

[jimmydanny]

I got pdtaylor shipping some stuff to me from the UK soon (money -.-), if you can get it to him so we get rid of some taxes and shipping, that would be great

But I have to talk to him first, and figure out what this really is

[jimmydanny]

The solenoid, is this places behind the 45 degree angle before the throttle body? I found a vac line going around there, seems to be the one.

[jimmydanny]

The solenoid is working, I got the S4 NA Pressure Sensor, that is why the car is acting up like it is.

So what I need is the N370 Pressure Sensor.