Fueling Issue

[Simisimi]

I am going to do my best to describe an issue I am having with lean fuel condition in the midrange, roughly between 3000 and 5000 RPMs in hopes someone can provide some insights.

First, my 2013 BRZ has the AVO turbo kit with an 8PSI spring and Overpipe back exhaust replacement (Hi flow CAT).

The turbo has been on the car for about 3000 miles and has worked great.
It was tuned by Paul at ECS in Connecticut and his Mustang Dyno pegs it at 274 RWHP.

Several weeks ago I attended the Subaru Wiked Big Track Meet at Thompson Speedway and while there I put 5 gallons of 112 octane fuel in to top off my tank before running laps on the road coarse. The car ran beautifully. I then drove it mostly at highway speeds another 150 or so miles on that same tank before I began to notice hesitation on hard acceleration mostly in 6th gear but also in 5th. I brought it to Paul at ECS where he confirmed a lean fuel condition in the 3000-5000 RPM band. He confirmed that the ECU is telling both port and direct fuel systems to push injection fuel volumes and the data log correlates that the injectors believe they are doing what they are being told.

I learned later that the fuel I used was leaded. So we immediately replaced the O2 sensor with no result. It is my understanding that any issues leaded fuel might cause with a catalytic would take more than 5 gallons of blended fuel to occur.

Paul thinks this is either a mechanical problem with the fuel system or could be some sensor (example oil temp) that is reading outside safe operating conditions and cutting fuel to cut power and thus heat. But we don't know for sure and he is planning to work on this next week by tuning the car to run on just Port injection and then just Direct injection in the effected RPM range to determine which fuel system is causing the issue.

Anyone following this and have any thoughts?

Thanks in advance.

[Sony]

Originally Posted by Simisimi

I am going to do my best to describe an issue I am having with lean fuel condition in the midrange, roughly between 3000 and 5000 RPMs in hopes someone can provide some insights.

First, my 2013 BRZ has the AVO turbo kit with an 8PSI spring and Overpipe back exhaust replacement (Hi flow CAT).

The turbo has been on the car for about 3000 miles and has worked great.
It was tuned by Paul at ECS in Connecticut and his Mustang Dyno pegs it at 274 RWHP.

Several weeks ago I attended the Subaru Wiked Big Track Meet at Thompson Speedway and while there I put 5 gallons of 112 octane fuel in to top off my tank before running laps on the road coarse. The car ran beautifully. I then drove it mostly at highway speeds another 150 or so miles on that same tank before I began to notice hesitation on hard acceleration mostly in 6th gear but also in 5th. I brought it to Paul at ECS where he confirmed a lean fuel condition in the 3000-5000 RPM band. He confirmed that the ECU is telling both port and direct fuel systems to push injection fuel volumes and the data log correlates that the injectors believe they are doing what they are being told.

I learned later that the fuel I used was leaded. So we immediately replaced the O2 sensor with no result. It is my understanding that any issues leaded fuel might cause with a catalytic would take more than 5 gallons of blended fuel to occur.

Paul thinks this is either a mechanical problem with the fuel system or could be some sensor (example oil temp) that is reading outside safe operating conditions and cutting fuel to cut power and thus heat. But we don't know for sure and he is planning to work on this next week by tuning the car to run on just Port injection and then just Direct injection in the effected RPM range to determine which fuel system is causing the issue.

Anyone following this and have any thoughts?

Thanks in advance.

Leaded fuel can do many things in a car that is not meant for it. Including fouling the spark plugs and pluging up injectors on top of the things you mentioned.

It could be any number of things.

I was at WBTD as well, I hope you had fun and I hope you fix your car! Hopefully I'll see you as some meets in the near future.

[Simisimi]

So far we have determined the issue is with the Port Injection. Direct Injection only works find until high RPMs when it can't supply enough fuel. Replaced the Port Injection fuel pump with a larger one but that did not help. The prospect of plugged injectors which seemed unlikely is starting to look possible.

[Simisimi]

Current theory is that this is the Active Valve Control System described in TSB #02-132-12 and is not related to forced induction or leaded fuel.

[Simisimi]

Unfortunately this does not appear to be the AVCS issue. We know a great deal about what this problem isn't but have yet to figure out what it is. Port injection just isn't' providing fuel in the midrange and we don't know why.

[Simisimi]

Chalk this issue up to the well documented TSB earning high pressure fuel pump. Chirping isn't all of it...lean fuel and on a turbo charged motor it's more pronounced. Subaru did know I had put a turbo on the car and did warranty it because...well it's got nothing to do with the turbo. Sure I am asking the fuel pump to work harder but that's no reason for it to fail at 5,000 miles and clearly that has happened to many other owners that did not modify their cars.

The car was gone 2 months and it cost me a few thousand dollars to remove and reinstall the AVO turbo. I can't wait for an aftermarket high pressure fuel pump replacement to arrive.