Fuel Efficiency Up, Boost Down

Posts specific to the 2.0 litre Turbo engine

Fuel Efficiency Up, Boost Down

Postby tkdbboy » Thu Jan 22, 2015 7:02 am

Hey guys,

I have a stock 06 STi and in the past two weeks I have noticed my L/100km being lower than usual for my daily commute.

Usually I get around 12 - 12.5 but now get 10.5 - 11

I have an ECUDatascan so I had a look at where my boost holds with pedal to the floor in second and its at 13.5Psi
First things the come to mind is either the ECU is playing up or I have a boost leak?

Is there any other data I can look at on the ECUDatascan which can give me a better idea of whats going on?

Thanks!
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Re: Fuel Efficiency Up, Boost Down

Postby Robbks » Thu Jan 22, 2015 8:07 am

Look at the engine bay first.

Do an ECU reset and see what happens
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Re: Fuel Efficiency Up, Boost Down

Postby kikxz » Thu Jan 22, 2015 1:20 pm

wow 12-12.5 p.l/100 is pretty high for a stocker!

I used to get 9.6-10 and that's being generous on the pedal... after my tune with bolt ons it sits 9.8-10.2 p.l/100
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Re: Fuel Efficiency Up, Boost Down

Postby tkdbboy » Thu Jan 22, 2015 5:18 pm

Yeah I have quite the slow stop start commute each day 1.5hrs all up.

What stock boost levels should I be expecting it hold in second?

Here's a video of the bay I just took ... nothing seems out of the ordinary physically but I can hear a ticking coming from both sides.
I notice the ticking does become more noticeable after the car warms up.

https://www.youtube.com/watch?v=V3bNLVT_G38

Haven't done an ecu reset yet.
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Re: Fuel Efficiency Up, Boost Down

Postby dr20t » Thu Jan 22, 2015 6:31 pm

Don't reset ecu. If there is any actual problem then you risk doing more damage by resetting as the ecu has self learned around the faults (as much as possible) which resetting will erase

Stock boost on 06 tbsti is 14.5psi

Check for a vacuum/boost leak somewhere

Common places are:

Intercooler to Throttle body hose
Bov hoses (two of them)
Turbo inlet
Pcv hose to throttle body
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