Drivetrain Blow off valve
1st Gear
Joined: Dec 2016
Posts: 29
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From: Wichita Kansas
OK it looks like I was mistaken about the vent to atmosphere (VTA) valve on the N18. It is about 50/50 on the N14 though based on posts from people who have installed one.
The reason for either a VTA or recirculating valve is to prevent turbo "flutter", which is the impeller blades of the turbo stalling when the air stops moving because the throttle closed. This can damage the turbo bearings. N14 and N18 engines differ in that the N14 uses the throttle plate to regulate airflow into the intake manifold, the N18 uses variable valve lift. I'm not sure how this affects the overall issue but since there is a longer path in the N18 vs. the N14 (the N18 air path is all the way through the throttle body and intake runners up to the intake valves) there's likely more of a spring or cushion effect when you suddenly lift in the N18 vs. the N14. In either case there is be a boost spike as moving air hits closed throttle plate or intake valves.
With sustained full throttle, the turbo will be at maximum RPM so lifting suddenly and closing the throttle plate (N14) or reducing intake valve lift (N18) will stop the airflow out of the turbo. That airflow either has to get vented or recirculated. Venting it makes noise, which some people like, but it also means that the pressure the turbo has been working hard to build is lost and the turbo starts to slow down. Recirculating the output of the turbo back to the input keeps the turbo from slowing down which means that boost will build faster once you're back on the throttle again, so it minimizes turbo lag.
I get it that some people like to hear the noise of the turbo boost being released. I'm an engineer and tend to over analyze things, I think the recirculating valve is an elegant solution to minimizing turbo lag, and will always make my decision based on performance and efficiency. The original reciculation valve is well known for failures, there is an updated part available. But it's your MINI, you get to do what you want with it.
The reason for either a VTA or recirculating valve is to prevent turbo "flutter", which is the impeller blades of the turbo stalling when the air stops moving because the throttle closed. This can damage the turbo bearings. N14 and N18 engines differ in that the N14 uses the throttle plate to regulate airflow into the intake manifold, the N18 uses variable valve lift. I'm not sure how this affects the overall issue but since there is a longer path in the N18 vs. the N14 (the N18 air path is all the way through the throttle body and intake runners up to the intake valves) there's likely more of a spring or cushion effect when you suddenly lift in the N18 vs. the N14. In either case there is be a boost spike as moving air hits closed throttle plate or intake valves.
With sustained full throttle, the turbo will be at maximum RPM so lifting suddenly and closing the throttle plate (N14) or reducing intake valve lift (N18) will stop the airflow out of the turbo. That airflow either has to get vented or recirculated. Venting it makes noise, which some people like, but it also means that the pressure the turbo has been working hard to build is lost and the turbo starts to slow down. Recirculating the output of the turbo back to the input keeps the turbo from slowing down which means that boost will build faster once you're back on the throttle again, so it minimizes turbo lag.
I get it that some people like to hear the noise of the turbo boost being released. I'm an engineer and tend to over analyze things, I think the recirculating valve is an elegant solution to minimizing turbo lag, and will always make my decision based on performance and efficiency. The original reciculation valve is well known for failures, there is an updated part available. But it's your MINI, you get to do what you want with it.
1st Gear
Joined: Dec 2016
Posts: 29
Likes: 0
From: Wichita Kansas
did you swap the coils? spark plug gap also could be a possibility. funny story, mini replaced my turbo with a jmtc s42 and I has having a loss of power and cylinder misfire. took off the stock heat shield and they had tightened it binding up the waste gate actuator.
Since someone brought this back, I have upgraded my DV with Alta boost spring and knock off forge adapter with no issues. Holds boost all the way through rpm range, no fluctuations. This was more for the psss sound. Clubman’s are too quiet.
1st Gear
Joined: Dec 2016
Posts: 29
Likes: 0
From: Wichita Kansas
N18? I'm thinking of doing the same thing. Chinese adapter (eek) and spring.
https://www.ebay.com/itm/Blow-Off-Va...a-f4d370addf6d
this cost me 9 bucks and change shipped.
1st Gear
Joined: Dec 2016
Posts: 29
Likes: 0
From: Wichita Kansas
N14, yes Chinese, Alta spring from Amazon.
https://www.ebay.com/itm/Blow-Off-Va...a-f4d370addf6d
this cost me 9 bucks and change shipped.
https://www.ebay.com/itm/Blow-Off-Va...a-f4d370addf6d
this cost me 9 bucks and change shipped.
that is what I have heard, I think it’s the bottom left bolt, I honestly can’t for sure say. I’m sure you tube has a video on it.
Alliance Member
Joined: Jul 2016
Posts: 7,509
Likes: 2,480
From: WNY
I also have one of those installed to my N18. The plate just needs to be filed down next to the waste gate actuator. It is a very minor modification.
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