Boost issue.

Jan 22, 2020
9
1
Hi guys, just looking for some advice here. My Leon has a stage 2 map by R-Tech and was pushing about 1550mb of boost (roughly around 22.5psi) however a little while ago it started to plummet and now boosts on average anywhere between 1100-1250mb. I’ve been endlessly reading forums for common issues etc and I’ve replaced the N75 valve for a genuine VAG one, a new Badger 5 oversized TIP as this was leaking at the metal flange that goes onto the turbo inlet when I did a smoke test, and a new forge 008 recirc valve as apparently these can go weak after some time too, it’s also had new spark plugs recently as well. While the boost did pick up slightly in the lower gears, it doesn’t hold the boost in the higher gears. I’ve removed my turbo and checked for play etc and there is none; I’ve also tested the actuator with a mittyvac and the cracking pressure is about 5psi and when the actuator is fully opened, it holds the position so I assume there are no leaks from there and the spring appears to be okay. On my liquid gauge it’s saying the N75 duty is only about 85% but as I mentioned earlier, the n75 is brand new! Has anyone else experienced this or got any ideas of any thing to check that I might not have done? Advice would he greatly appreciated! Thanks!


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Connor H

Active Member
Dec 19, 2019
893
446
Essex
Hi guys, just looking for some advice here. My Leon has a stage 2 map by R-Tech and was pushing about 1550mb of boost (roughly around 22.5psi) however a little while ago it started to plummet and now boosts on average anywhere between 1100-1250mb. I’ve been endlessly reading forums for common issues etc and I’ve replaced the N75 valve for a genuine VAG one, a new Badger 5 oversized TIP as this was leaking at the metal flange that goes onto the turbo inlet when I did a smoke test, and a new forge 008 recirc valve as apparently these can go weak after some time too, it’s also had new spark plugs recently as well. While the boost did pick up slightly in the lower gears, it doesn’t hold the boost in the higher gears. I’ve removed my turbo and checked for play etc and there is none; I’ve also tested the actuator with a mittyvac and the cracking pressure is about 5psi and when the actuator is fully opened, it holds the position so I assume there are no leaks from there and the spring appears to be okay. On my liquid gauge it’s saying the N75 duty is only about 85% but as I mentioned earlier, the n75 is brand new! Has anyone else experienced this or got any ideas of any thing to check that I might not have done? Advice would he greatly appreciated! Thanks!


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4psi drop is quite a lot, if it was a boost leak i imagine you'd be able to hear it in the bay. I'd go over all the little plastic valves, check valves etc. Im not an expert on N75 duty but 85% doesnt sound too bad, do you know what it was at before?
 
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Jan 22, 2020
9
1
Hi guys, thanks for the advice! There doesn’t appear to be any leaks around the N75 pipes. And the N75 duty was reading 100% with my foot planted before the issue occurred.


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Gokiwi64

Geriatric Member
Apr 26, 2014
1,341
685
Hockley, Essex
Possibly the best thing to do is a boost leak test - you can get a half decent kit off of ebay. In my case the seal between the compressor housing and the oil feed part of the turbo was failing and I was loosing boost that way. But it would only start leaking at approx 7 psi , you could quite clearly hear the oil gurgling sort of like running water then when the pressure dropped below 7 psi it stopped.
 
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