Going lean in boost.

[ohno06gt]

Yesterday I did a few data logs on a base map for my tuner. Sent them off but haven't heard back yet. Today after work I learned how to look at them and the car was going very lean when in boost. At idle the AFR is jumpy as well, getting down into the 13's and up into the high 15's. The car was building boost fine so I don't think there is a leak there.

 

02 sensor is denso and was replaced 5k miles ago. Also cleaned the MAF but the problem persists. I checked all the clamps from turbo to throttle body and they all seem tight. Downpipe to turbo connection and up pipe are tight. Also checked all the vacuum lines that I know about. Fuel pump is aem 320lph and injectors are DW 740cc.

 

Anyone have ideas? I'm not super knowledgeable when it comes to this stuff.

 

Here are the logs if anyone wants to take a look.

 

Cruising around 60mph

https://docs.google.com/spreadsheets/d/1cNSpg9tZ1LairVq2gLXyLdGGpdxM4wDtNYJgRh3MDMQ/edit#gid=28542170

 

WOT 3rd gear (So lean it's terrifying)

https://docs.google.com/spreadsheets/d/e/2PACX-1vRtAgcj2yg9W14S0OEDyHRAhjaBXUpTa0eNq1UJp04b-kkb88btIWCHu-sVVmdaoNWMjtrnmVoP8jjH/pubhtml

Edited December 10, 2021 by ohno06gt

[Pleides]

Maybe keep out of boost until your tuner gets back to you? They’ll be able to offer better advice than anybody here.

 

A boost leak test would be my next move.

[ohno06gt]

Maybe keep out of boost until your tuner gets back to you? They’ll be able to offer better advice than anybody here.

 

A boost leak test would be my next move.

 

Yea I'm not even driving the car right now, just took it out for some logs. I did a low pressure boost test (blocking intake hose and blowing into bpv vac line) and it held pressure but thinking about making a leak tester with pvc and a shraeder valve to up the pressure.

[lagwagon]

From my experience with previous turbo cars with proper wideband O2 sensors, your car shouldn’t even be building boost at that afr. That also looks like the free air calibration O2 measurement so I don’t see how that can be correct with any combustion actually occurring.

 

There is also a spot where your throttle and boost are more or less constant but your rpm drops by about 1000 rpm in two time steps/samples. The only way I can see that happen is if you hit the brakes at wot. Even if that was a shift, boost would’ve dropped somewhat, even with flatfoot shifting, but I can’t imagine that a shift can be done in 0.3 of a second. In short, your rpms don’t look realistic either.

 

I would wait to hear from your tuner but it looks like there is something majorly wrong with the data. I would think something in your harness is shorting out. The only time that I’ve seen something like this was when an O2 signal wire was mistakenly wired to the heater circuit.

 

I’m super interested to hear what others say, and what your tuner says, as I am far from an expert in tuning, and none of my experience is with Subarus.

[ohno06gt]

Looking like it is the MAF sensor. Switched it out and the afr readings are acting accordingly so far. Peg the throttle and it's dropping into the 11's.

[cryo]

great to hear you got it figured out, based on how lean it was going I was going to suggest the same thing.

 

Dave