Had to replace the engine but now I have no boost from the turbos. The mechanic has had it for 4 days and still cant find a cause. He's taken it to an auto electrician who cant find any electrical faults.
The second turbo simply follows the first when the system activates it by bringing it in parallel with the first. The first turbo is only designed for a 1200cc motor so it can not deliver enough compressed air at revs for a bigger motor so they arrange to bring in a second turbo of the same size when the first one runs out of puff. The first turbo is a semi-mechanical device. The ecm raises the boost level at which it operates but it should be producing some boost regardless. So concentrate on the first turbo. Isolate it from the ecm control system (There is a misleading tip on youtube involving pulling hoses but it is misguided, the comment is ignorant, and I do not recommend it) Instead, as per the manual, on the first turbo remove the system pressure lines from exhaust and wastegate. Loop a short piece of vacuum hose from the primary turbo output to its own wastegate. Blank off the system hoses you disconnected. Fit a boost gauge, drive it and observe the boost gauge readings (manifold pressure). If the primary turbo is OK this will make it operate at a lower boost level (5-7psi ?) than the system control (10-17psi) but it will be a purely mechanical operation which will isolate where the fault is. If there is no boost and the pressure stays zero down then the turbo is not working. Check for the wastegate being stuck or maladjusted. If that is working then you bave a faulty turbo for whatever reason. Maybe there is a loose bolt stuck in it from the engine rebuild?
If the turbo is working OK then it points to an electrical issue with the the boost control solenoid which is inside the wing near the vacuum tank beside the battery compartment. The control voltage from the ecm usually pulses it on/off at a fast rate to give a measured control and it may be stuck. Maybe it is the ecm or maybe the valve. But before you go dig it out, first check the pressure lines such as 10 and 23 are connected or not reversed at their connectors where they go through the wing (just behind the battery) Good luck
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fit a boost gauge to the manifold to see if the turbo is actually producing boost. Fit temporarily by running the hose from the engine compartment to the cabin where you or a passenger can read the results. Turbos only produce boost under load as they need heat from the fuel to spin the turbine . If you cannot get a boost gauge then take it to a speed shop that has a chassis dyno and have it tested there . This will also test the pump for correct calibration and timing
In your case the turbocharger is responsible for engine losing power. The car goes in "limp home" mode!!! After scan the EDC-15P engine control unit with a VAS, VAG or KTS -BOSCH diagnosis tool you will find this: Fault code: P1557-Turbo Boost pressure control exceeded 1. Engine stopped and ignition switch off. Check all pneumatic connections and hoses between turbocharger actuator = pressure unit for boost-pressure control, boost-pressure control solenoid valve, vacuum reservoir, EGR control solenoid valve, intake-manifold flap solenoid valve, EGR valve with throttle - part of intake manifold. Also the vacuum connection between tandem pump and brake booster. If you find something wrong replace parts. If not go to step 2. 2. Extract the hose of the turbocharger actuator = pressure unit for boost-pressure control part of turbocharger. Instead of the original hose you must place another 1 meter long hose with the same inside diameter, and then you check to inspire yourself the air from the other one extremity of this hose. The mechanical connecting rod of the turbocharger actuator must have a smooth and whole motion. If you can do that with your mouth, then you must replace the boost-pressure control solenoid valve. If you can not reach this with your mouth, then you go to step 3. 3. This is the most difficult work. The problem is that the soot particles deposits inside the turbocharger plugging the variable nozzle geometry mechanism = adjustable vanes of the turbine. If the turbocharger actuator is not able to adjust the turbine vanes the charge air pressure increase too much and ECU (engine control unit) go in "limp mode" = engine protection software. As a result the "limp home" mode engine still running until you turn the engine off (ignition switch off) and back on when the "limp mode" is deactivated, but the fault still remain in ECU memory! 4. You must be able to extract the turbo out from the engine. Then disassemble the turbocharger, clean inside adjustable vanes mechanism, and refit all in reverse order. Good Luck!
Hello, that is a puzzler, but the blow off valve opening up at an idle is making me think exhaust/catalytic converter restriction causing to much back pressure. Like it can't get the air through fast enough so it's backing up in the intake. I would start my chase there... Let me know if you find any thing...(subyguru)...
all turbo vehicles can only make boost if induction system is sealed,at this stage rather than looking for a fault with actuator controls,i would check to see if all ducting(piping) is secure.from airfilter,intercooler,turbo etc to engine,just check that there are no leaks,if there are any loose,revving it on the spot to cut in turbo should cause a loud rushing of air.if this is all ok then we need to further.
This can be caused by many different things, it could be the transmisson or it could be the engine, if the oil level is low that could cause it, also if the oil is dirty or the oil filter is bypassing, So it really needs to be checked by a mechanic becasue it has to do withthe engine control system there is no way except to hook up a diagnostic tool and read all codes and read boost and driveability problems. It could be something simple but pay the $75.00 for the hook up fee and they can tell you whats wrong. And if the check engine light is a red check engine do not drive it to it to a shop.
I don't know much about Subaru but I expect the turbo wastegate is controlled by vacuum which is switched by the engine management system.
In the old days the turbo wastegate was normally closed and the manifold pressure was fed into a servo which opened the gate at the predetermined pressure.
The new way of doing things is to have the wastegate normally open and the turbo producing no pressure until the engine management decides the time is right and it switches a vacuum supply to a vacuum servo which then closes the wastegate. With this system the wastegate is constantly moving and so is unlikely to give trouble though the vacuum servo sometimes leaks and vacuum lines give trouble.
A fellow I know had a similar problem where the engine check light would light up and he would lose performance. In theory this was because of an overboost condition but the repair shop after fiddling around with it for a week fitted a new EGR valve to produce a cure.