Fabio Posted September 4 Report Share Posted September 4 Hy everyone, I am looking for help from expert tuners My car is Impreza v3 with vf35 turbo Lately turbo is spooling slow and suddenly Tune is the same No boost or exhaust leak Tried to put spring on wg and remove b.c. hose No shaft play ,no weird noise, engine pulls hard when boost is reached What can cause a boost risechange like this? I upload two pictures that show the spoolup area, where youcan see a wide difference Thank you to everyone Fabio Quote Link to comment Share on other sites More sharing options...
K4Tuning Posted September 4 Report Share Posted September 4 What kind of wastegate is it? Is there any chance the valve seat came out when you removed the gate and either fell off or got left on the table? If the valve seat isnt there it will not build boost properly. It will essentially leak exhaust pressure until it becomes a restriction and then rocket your boost to its target. Thats a possibility. Other possibilities are vacuum related, make sure the boost control system is installed and routed correctly. Other than that double check everything.. Hope you get it figured out. Another reason is the actuator arm may have been adjusted incorrectly and the gate flapper isnt fully shut. Same thing would happen, it would be an exhaust pressure leak. Quote Link to comment Share on other sites More sharing options...
Fabio Posted September 4 Author Report Share Posted September 4 Thank you for your response, wg is ok I removed downpipe, it seating as the seat area is clean and metal shape, i removed the hose to the wg and put a spring on the arm to make sure was not boost control related is there any chance could be compression related? Timing is ok A big exhaust like to cause something like this should be easily audible I have no idea what else to check I ve got an lpg system installed dual map and it does the same exact thing on both fuels Thank you Fabio Quote Link to comment Share on other sites More sharing options...
K4Tuning Posted September 4 Report Share Posted September 4 If nothing has changed with the engine and it was working as should before you removed the wastegate, then there shouldnt be a random loss of compression but that is a possibility. I think a loss of compression would be more noticed before a late spooling turbo. Ignition timing and VVT play a big part as well but if the tune wasnt changed then that is unlikely. Make sure the plugs on the avcs/vvt solenoids are plugged in if your car has it. Possible chance engine could have jumped time, but again not likely if the engine was running well before you removed the wastegate. Im not familiar with a spring method to check boost control system, I would do a boost leak test if you can. Subarus are difficult to do properly. Hope you find something! Quote Link to comment Share on other sites More sharing options...
Fabio Posted September 5 Author Report Share Posted September 5 I believe a compression loss would show up even on idle kpa that was and is now around 35 850rpm Do you think it could be an exhaust manifold crack somewhere? Wouldn t be a leak like that noticeable even when on full boost? I do not have avcs,I have no idea what else could cause a different boost rise like that Sometimes it does seem the boost pick up earlier as before the boost rise graph does not have the previous shape anymore Have you, in your experience,ever seen a similar behaviour?? Quote Link to comment Share on other sites More sharing options...
dx4picco Posted September 5 Report Share Posted September 5 Timing belt jumped a tooth maybe? Quote Link to comment Share on other sites More sharing options...
Fabio Posted September 5 Author Report Share Posted September 5 One of the first things i checked...all 4 cam wheels are aligned on their marks, I believe anyway that I would feel a rough running engine with even one cam off? Thank you Fabio Quote Link to comment Share on other sites More sharing options...
Vaughan Posted September 5 Report Share Posted September 5 Attach a copy of your tune and a PCLog of the boost not building fast Quote Link to comment Share on other sites More sharing options...
Fabio Posted September 6 Author Report Share Posted September 6 Hy, Here is link of my current tune and a log showing some pulls and the slow spooling compare to the picture loaded https://drive.google.com/drive/folders/1SqfkzWtUQOCQN-KKVlLYMUofSiDlEF-g Thank you Fabio Quote Link to comment Share on other sites More sharing options...
Vaughan Posted September 8 Report Share Posted September 8 That log shows that the boost controller output is commanding maximum boost so you either have an electrical problem (make sure that the Aux 3 PWM Test makes the boost solenoid click), or a boost control plumbing issue or a mechanical issue with boost or wastegate leaks etc. Quote Link to comment Share on other sites More sharing options...
Fabio Posted September 9 Author Report Share Posted September 9 First thing I did was removing downpipe No cracks on turbine housing Wastegate metal shape on contact area ( so sealing properly) Removed hose from wastegate and tried a boost log,same results as you see on log after 3.8k rpm obvioulsy boost peaks without wg hose but spoolup is slow as if you have boost control active Could it be a crack on the exhaust manifold center section? Is it possible that a leak like this is inaudible? I have no idea what else to look for Did you have a look at the tune? Do you see something wrong that maybe I am blind of? Thank you for your help Fabio Quote Link to comment Share on other sites More sharing options...
dx4picco Posted September 9 Report Share Posted September 9 exhaust leak pre turbo will surely spoolup Quote Link to comment Share on other sites More sharing options...
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