Do you plan on getting a tune for the ko4?
I'll assume this is not a brand-new-from-Borg-Warner-turbo as they don't sell "hybrid" K04s. If this is an aftermarket or eBay creation it's entirely possible the WG was either not set properly or was set to open at a higher manifold pressure on purpose.
The K04 turbine is larger than the K03 so for correct control via sofltware (i.e. N75) you need a tune calibrated to work with that turbo.
Could possibly be a bad N75. That same exact thing happend on my brothers GTI , would build boost and it would bleed off and open the dv between the rpm range. But he has the stock K03s and is chipped with an APR tune. We reoplaced the N75 and the problem was fixed.
I would say dont drive the car , until you get the right tune for the Turbo, but if you have to drive it ..... baby it and try not to build boost. Get your tune , then see what happens. If the surging problem is still their, replace the N75 and see what happens.
An easy way to confirm of the N75 is the issue, as i said before... bypass it, you should see the 10PSI you where at before.
If you're not, the ECU is protecting the motor and closing the throttle body and using the N249 to Divert the boost.
To fix the later "issue" you'll need software...
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If you had the time and wanted to do this right, I'd bypass the n249 and n75, put in a DV and run a line from your intake mani to your dv. Add an mbc and set that to a low boost level. Eventually, get an upgraded maf, possible rods, injectors and indefinitely a tune.
Speaking of which, what "brand" of a hybrid ko4 is this again?
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how is that an issue, the gate on my k03s would move by hand too. they are supposed to be able to move. its only a 5 pound spring. you should be able to move it. im going to disconnect the waste gate completely and see if it builds and holds boost. im not going wot because if my wastegate does work it would build boost beyond belief. but atleast thats one thing to check off my list. ill just cap off the line from the n75 to the wastegate so i dont go into limp from a leak. ill report tomorrow when i do it. its getting late. atleast then i will know that its either my n75 my wastegate or a major boost leak i cant seem to find.
thanks for all the input it has given me a lot of ideas of what it could be and how to check. the true test will be one by one so i find the actual culprit. i just hope ots something easy and cheap like a boost leak. then ill be really happy.
and to clarify, i broke a clamp yesterday and before i did break it, it was holding boost fine at 10psi. after i disconnected everything and put the new clamp back on is when i had problems. i think i may have dropped my n75 on the ground in the process. could very well be the problem and im borrowing a friends known working n75 tomorrow. and doing a tb alignment just in case.
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hmm that could be an issue too. im going to give rp a call on monday when they are open. i hope i dont have to replace the turbo again. it was a bitch the first time.
also probably why when i had the n75 disconnected the waste gate stayed open and boost dropped.
okay i got a hold of a buddys n75. did the same thing. and we know it works, came off of a running car. so we think its either a boost leak or the gate. he also had a k04 (apr one) on his car and his gate moved just as easy as mine so we dont think its that. we either think its the fact that i have no software (i doubt it because it was running fine before i started messing with my top intercooler pipe) or we think its a huge boost leak that we cant find. im pressure and smoking it tomorrow. so we shall see
finally figured it out. we found a kink in the pressure line going to the n75 from the top intercooler pipe and it would block off the pressure until it hit right around 19psi so we ran a new line from the intake manifold and its all good now. boosting right at 11 psi like it should. didnt need to touch the waste gate at all.