Cylinder 4 is the most common to break with the Subaru EJ turbo engines. We believe this to be mostly due to coolant flow problems. The 1/3 side of the engine has coolant exiting the back of the head to cool the turbo while the 2/4 side only exits the top of the head to the crossover. There is a pocket of reduced flow at the back of the head. This balance kit will allow coolant to exit the head and go into the heater core lines to increase flow and reduce chance of knock and ringland failure.
- Makes more power
- Longer lasting engine
- Easy to install - No steering shaft interference!
- No sealant or cure time needed for the fitting
- Quality look you expect in your engine bay
- Allows your head on Cyl 4 to run cooler
- Reduces chance of knock
- High quality MADE IN THE USA components
What it does:
The red arrow is the change. The engine will now expel a small amount of coolant to extract more heat from the back of the drivers side head where the flow is low from the factory. We've optimized the amount to be extracted in order to balance the temperatures on the left and right heads. If too much is pulled from this head the right side heads get hotter, impacting their performance. No need to worry about that with your engine after installing our kit.
Results at idle:
The coolant temps before and after the cooling kit install. As you can see, they are balanced very well now.
Results under load:
Bottom two lines are the coolant temperatures at the back of the left and right head. As you can see, they are within 2deg F through the entire RPM range at full load. This allows your engine to run optimally and reduce chance of knock, especially in Cyl #4. You're going to love the performance gain and piece of mind this small investment will give you. Select your fitment and buy now for quick shipping.
02-07 - Pre-cut and crimped for 02-07 WRX/STI, all years Forester XT
08-14 - Pre-cut and crimped for 08-14 WRX, 08-14 STI, all years LegacyGT
15-19 - Pre-cut and crimped for 15-19 STI
Unassembled - 1ft of hose, fittings, tee, and 4 hose clamps to make it yourself in a custom length
New option! - Many people have asked for fittings only, so we now offer the fitting to go in the head by itself in case you want to use your own 6AN hose or another method.