My car has always required higher than normal WGDC to reach target boost, and sometimes weird stuff happens. I found (using smoke tester and 5psi pressure on the system) and fixed a minor boost leak on the cold side charge pipe but could never find any more leaks. This log is the most extreme example of the car not making consistent boost. What do you think could be the root cause? My next step is to test the system at higher pressure but think something weird is going on.
2015 535i xdrive for inconsistent boost control
- Thread starter mikesrex
- Start date
I don’t believe this one has a boost solenoid. The wastegate is electronic on the 2015.
I'm not sure what's going on, but yes wgdc is super high - 90's through 3rd gear and 100% in 4th
. Your stft goes very negative, so your DME is pulling out fuel from what it thinks you should need based on MAF value, which suggests you're losing metered air (a boost leak).
As mentioned above, a bad diverter valve could contribute to the high wgdc, and usually wouldn't show up on a boost leak test. But a bad diverter valve usually wouldn't contribute to negative stft, unless it was actually leaking out of the compressor housing vs. just leaking back to the inlet. Doesn't mean you don't have a bad diverter valve, just that if you do it may not be the only thing going on.
What's really strange to me though, is your boost actual actually follows target really well all the way up to shift point in 3rd gear, but then it falls on its face for all of 4th gear. It should be EASIER to hit boost target in 4th gear, because your engine rpm (and therefore airflow demand) is increasing slower than in 3rd. So why is 4th so much worse than 3rd
? It makes me wonder if your issue is also tune related? Is this a custom or OTS tune?
. Your stft goes very negative, so your DME is pulling out fuel from what it thinks you should need based on MAF value, which suggests you're losing metered air (a boost leak).As mentioned above, a bad diverter valve could contribute to the high wgdc, and usually wouldn't show up on a boost leak test. But a bad diverter valve usually wouldn't contribute to negative stft, unless it was actually leaking out of the compressor housing vs. just leaking back to the inlet. Doesn't mean you don't have a bad diverter valve, just that if you do it may not be the only thing going on.
What's really strange to me though, is your boost actual actually follows target really well all the way up to shift point in 3rd gear, but then it falls on its face for all of 4th gear. It should be EASIER to hit boost target in 4th gear, because your engine rpm (and therefore airflow demand) is increasing slower than in 3rd. So why is 4th so much worse than 3rd
? It makes me wonder if your issue is also tune related? Is this a custom or OTS tune?This is the base map of a custom flex fuel tune. Tuner asked me to check for boost leaks. I plan on checking for leaks at a higher pressure level but also think something weird is going on when I compare the 4th gear part of this specific log to third and fifth gear (and other logs). I ordered a GFB DV+, since it appears the factory diverter valve could eventually (if not currently) a weak link on my setup. I wonder what else I should be looking for. I typically log this car when I drive, so I probably have a thousand logs at wide open throttle. If someone can help me know what to look for, I can use JMP software to find it in my logs.
If it's a base map flex fuel tune, the negative stft could be related to getting the fueling dialed in. But I do think a boost leak and/or bad diverter valve is going on. But I still don't understand 4th doing so much worse than 3rd. This is what makes me think something tune related is going on I'm wondering if there is an air flow adder per gear or something similar that's dependent on gear (like boost by gear, or load by gear) but that doesn't impact the boost target?
The car makes near target boost most of the time, even in fourth gear. Every now and then it might be a little bit less than target, but the first log I posted is that only example I have noticed with max wgdc and not even being close to target.
Here is what I would typically expect. This is from a 12,7@108 pass at evadale raceway in Texas, during a no prep event.
Here is what I would typically expect. This is from a 12,7@108 pass at evadale raceway in Texas, during a no prep event.
Thoughts are I could have problems in several categories.
1. Boost leak (why would it be inconsistent at times?)
2. Diverter valve leak (could be inconsistent, especially if it opens up during shifts…. And could stick open or closed… Does it open between shifts???)
3. Boost is not being properly measured (this would most likely be a consistent error, I think)
4. Wastegate is not consistently working to keep air from being diverted around turbo. (This also makes sense, as some of my logs see slightly higher than target boost….. but why they high WGDC?)
5. Any other ideas I haven’t thought of yet
1. Boost leak (why would it be inconsistent at times?)
2. Diverter valve leak (could be inconsistent, especially if it opens up during shifts…. And could stick open or closed… Does it open between shifts???)
3. Boost is not being properly measured (this would most likely be a consistent error, I think)
4. Wastegate is not consistently working to keep air from being diverted around turbo. (This also makes sense, as some of my logs see slightly higher than target boost….. but why they high WGDC?)
5. Any other ideas I haven’t thought of yet
I like your thoughts. Regarding the wastegate, can you log wastegate position target, and actual wastegate position? I beleive the EWG has a wastegate position sensor, so if you can log target and actual wastegate position it should help determine if your wastegate is sticking sometimes. That's also an interesting idea about the DV valve sticking intermittently, IDK if it generally opens briefly during shift, but it seems plausible without knowing more.
I ordered a gin dv+ upgraded diverter valve and plant to install the weekend after next. I also got some logs which include everything MHD can get for wastegate related stuff. Will post a couple logs once I sort through to look for good examples of when the car does and does not make target boost.
Update
1. Stock diverter valve appeared to have a leaky diaphragm. It let air through when I tried to blow air through the diaphragm itself. GFB DV+ installed with the extra spring option.
2. Oring on hot side charge pipe was chewed up a bit, being a potential leak source. I could not detect a leak during smoke and pressure tests, but new oring was installed upon reassembly.
3. I also took the opportunity to install an upgraded inlet and down pipe.
Car feels faster now, according to the ass dyno. Spool appears to be much quicker. Will post some logs when I get a chance to upload. WGDC is definitely lower at the current boost level. Car currently has E70 in tank, running about 13psi boost.
Hopefully this is what I need to convince the tuner to get me a little more boost. Would love to see 11 second ETs. Last night my dragy got me 12.28 with my 200lb friend in passenger seat on a closed course location.
1. Stock diverter valve appeared to have a leaky diaphragm. It let air through when I tried to blow air through the diaphragm itself. GFB DV+ installed with the extra spring option.
2. Oring on hot side charge pipe was chewed up a bit, being a potential leak source. I could not detect a leak during smoke and pressure tests, but new oring was installed upon reassembly.
3. I also took the opportunity to install an upgraded inlet and down pipe.
Car feels faster now, according to the ass dyno. Spool appears to be much quicker. Will post some logs when I get a chance to upload. WGDC is definitely lower at the current boost level. Car currently has E70 in tank, running about 13psi boost.
Hopefully this is what I need to convince the tuner to get me a little more boost. Would love to see 11 second ETs. Last night my dragy got me 12.28 with my 200lb friend in passenger seat on a closed course location.
