So i got a question ! my golf is a mk4 1.8T the ECU was upgraded ( prev Owner ) so it cranks out 22 lbs of boost qwick lil bugger but what is happining is it would spool up to 22 but it cant hold it anymore and it falls flat back down to 8lbs the motor itself is great no probs besides the turbo issue any ideas ? i really dont want to replace the whole kit if its just a piece i need to buy .... im thinking maybe a pipe is cracked ? but witch one?
bonus question lol saw a Red mk4 the other day was turbo but his BOV sounded like the evo's all loud and **** and it didnt sound like air was being recycled is this possible ? i have a Iforge Bovbut its not loud any help as to how i can make it louder or witch bov to buy ? id like to stay german made if possible ...
the mk4 section is probably the place to be asking a question such as this, however ill try to help answer your question. I am no expert by any means, but have basic knowledge of these cars.
Did the car hold higher psi before and has recently started to drop off to 8lbs, or has it always peaked at 22lbs and dropped to 8lbs?
If its just recently started doing this i would check your diverter valve, it may be going out especially if its stock. It is not designed to hold that much pressure and will wear out quickly.
In response to your other question, some people use BOV's but i would recommend against it. The will make the car run poorly and possibly destroy other components. If you want more sound you can get an intake, or for maximum sound i believe forge (maybe someone else) makes a splitter valve that vents some pressure but also recycles some.
I'd try the 1.8t tech forum before the mk4 forum. The mk4 forum is about the worst forum on Vortex. If you don't have a thread title that has nothing to do with your post, your car is not on bags, and you don't have sick baller wheels then you'll just be told to search. Sadly I don't know much about turbos even though I own one.
There are a lot of parts to check, like someone else said, check/ replace your diverter valves. Also if the turbo is on its way out you could hear it. Find a steep hill, roll the windows down and listen to the turbo as it is pulling in first or second gear, if it sounds like a high pitched drill, then the journal bearing is going out and the turbo needs replace (google dentist drill).
However it is more likely you have a boost leak. A hos may be loose which lets you hit 22psi but then lets the air escape, so you meter more air through your MAF but the engine doesn't see it and goes into a "limp" mode and limits to 8psi. You could also have a bad/ worn N75 valve (stock electronic boost controller)
Finally you may have and old coolant temp sensor that needs replaced, the new ones are green (cheap and easy to replace, do this first, just because you can't go wrong)
Thank u ill have to check that out as far as i know its always peaked at 21-22 ive had the car for maybe about 5 years ? i cnt remember lol but its been doing this for quite a while i just havent had $$ or time to check and im not to motor / tech savy like i wish i was //// and thnk u ill have to look into forge's website and see about thatr splitter hopefully i can get all this done before levenworth lol
Also i was in seattle yesterday while it was hot out and had all windows down i havent heard any unusual noises coming from the engine im willing to bank some $$ on it being a boost leak in one of the pipes also i bet it wouldnt hurt to find a shop around the sound that can do a good full tune up just for preventive purposes
Cheap way to "smoke" test a car and check for boost leaks is get a can of starting fluid and a nozzle with a fog pattern, and spray around the boost pipes, intercooler etc.. letting the car run at idle, if the rpm increases while you are spraying, you have found a boost leak.
If the diverter valve failed then you would only notice it when under boost/ load, so just sac up the $50 and replace it with a 710N, Vastperformance or ECS tuning should still have them (they aren't being made anymore). Vast also has a boost leak checker device for $30.