Aftermarket AN flanges often come in sizes that are smaller than what is optimal for proper drainage. This can lead to issues such as oil smoking from the turbo, which is a symptom of oil not draining effectively.
Effect on Turbo Performance
When the oil drain is too small, it can cause oil to back up in the turbo, leading to leaks and smoking. This is often misunderstood, with some suggesting to restrict the oil feed to mitigate the issue, which is not the correct approach.
Correct Sizing
The ideal approach is to match the size of the oil drain port on the turbo itself. This ensures that oil can flow out of the turbo as efficiently as possible with minimal buildup.
Different Turbo Types
Ball bearing turbos generally require less oil flow compared to journal bearing turbos. However, regardless of turbo type, the drain size should not be smaller than the turbo's drain port.
Diagnosing Issues
If smoking issues persist even with a correctly sized oil drain, it could indicate other underlying issues such as excessive blow-by (engine breathing heavy) or inadequately sized breathers. Factory breathers are fine in stock form but when heavily modified these become restrictive and can cause excessive crankcase pressure resulting in smoking issues.
Recommendations
It's crucial for those designing or installing turbo setups to adhere to these guidelines to avoid potential issues with turbo performance and longevity.
In essence, ensuring the oil drain size matches or exceeds the port size of the turbo itself is critical for proper turbo function and to prevent smoking issues. This approach eliminates uncertainty about whether the turbo itself is causing the problem, allowing for more effective troubleshooting if issues persist.
