Airboy tuning

In a few days, my 2006 WRX will be 14 years old. Still ticking after roughly 275,000km and 5 turbo swaps. It has taken me North to Fort Simpson (NWT) and South to Flagstaff (AZ).

What is the longest that you have kept a car, and do you still have it?

Some Winter thoughts...

1) Engine oil take longer to heat up than coolant. Even longer if the under tray is missing.

2) PCV valve can freeze, AOS drain hose can clog, especially with sustained highway driving in extreme cold temps. Subaru with FMIC should block off the hood scoop. Ones with TMIC could block off part of the TMIC above the PCV valve.

3) Boost creep (high boost even with fully open waste gate) will happen at full throttle and mid to high rpm

4) Cold air has higher density (more oxygen per volume). More power? Yes, and also more fuel required. Going from +20C to -30C, air density changes by ~20% so fuel demand will also increase by ~20%. Stock fuel systems in STI/WRX or EvoX will see ~90% max injector duty cycle (IDC) at +20C so, it doesn't have the headroom for high boost at -30C. Boost creep from (3) above adds to the problem. If that doesn't sound bad enough, the 90% IDC number is at Calgary elevation (3500'). Air density increases at lower elevation....

Exercise caution...

Continuing with the Fuel Pressure topic...if you have a Subaru with 32bit ECU (04+STI, 06+WRX) and a Version 3 Accessport, you can add fuel pressure monitoring and more importantly, compensation. While it won't prevent fuel pressure problems, excessive compensation values can serve as an early warning.

Example charts with falling Differential Fuel Pressure (should stay ~45psi) and the resulting compensation to injector pulse width by the ECU.

The additional pressure sensor is wired into the ECU via one of the TGV sensor inputs and custom map changes are made to activate this feature.