Air Filter and Intercooler Temperature Guide for OM606 Diesel Builds

Air filter and intercooler temperature management are two topics that directly affect how much power your OM606 build can make reliably. Today we cover filter selection, charge temperature limits and the most effective intercooler setup for serious diesel builds.

Air Filter Selection – What Actually Works

The stock air box with a panel filter is an excellent option if you can use it. The caveat is that stock air boxes are designed for stock turbos with small inlets and outlets. If you are running a larger turbo or a different exhaust manifold that has moved the turbo location the stock air box may not fit or may be too restrictive. If you can make it work without restricting airflow it is a good solution.

For aftermarket conical filters K&N is the most versatile option – available in an enormous range of sizes and shapes making it easy to find the correct fit for any installation. However K&N quality control has a consistent problem. Every K&N filter purchased should be inspected inside before installation. Run fingers around the inside of the filter and check for long metal threads – 15 to 20 centimetre strands of metal that can be sucked directly into the turbo compressor wheel and destroy it. This happens regularly. Check every filter before fitting.

Foam filters from quality manufacturers with a rigid internal plastic cage are also good. The cage prevents the filter from collapsing and being sucked into the turbo – which has happened to multiple people with cheap foam filters that had inadequate internal structure. Buy a quality foam filter with a solid plastic cage and it works well.

The bottom line on air filters: any quality filter works. Check for loose internal material before installation regardless of brand.

Intercooler Temperature – The Physics Limit

There is no temperature target for intake air that is colder than better. Colder is always better. Race applications use ice tanks, nitrous injection and water injection specifically to get charge air as cold as possible. There is no lower limit.

For normal performance builds the limiting factor is simple physics: you cannot cool the intake air below the ambient temperature using an air to air intercooler. If outside temperature is 30 degrees Celsius your charge air will never reach below 30 degrees Celsius through an air to air system. That is the absolute minimum regardless of driving speed or intercooler size.

This is important to understand because it sets realistic expectations. On a hot summer day you will always be working with warm charge air regardless of how good your intercooler is.

How Hot Is the Charge Air Before the Intercooler

When running three bar of boost on an OM606 the charge air exiting the turbo is over 100 degrees Celsius. A brief test with a charge pipe in place of a destroyed intercooler showed 90 degrees intake air temperature even at light throttle at low speed. At full boost on three bar the temperature is higher.

So the intercooler must cool air from over 100 degrees down to as close to ambient as possible. With a front mounted air to air intercooler on a summer day that means cooling from 100+ degrees down to 30 degrees. A temperature drop of 70 degrees or more. This requires a properly sized, efficient intercooler.

The Most Effective Intercooler Setup

The dual stage setup consistently produces the best results in real world testing including dyno sessions in 40 degree ambient temperature:

Stage 1 – water to air intercooler mounted directly at the turbo outlet. The charge air is cooled immediately as it exits the turbo before it has time to heat the charge pipes. This unit can be small because it only needs to handle the initial temperature drop.

Stage 2 – air to air intercooler at the front of the car. This handles the remaining cooling and maintains charge temperature under sustained load.

The result is rock solid intake air temperature through multiple back to back dyno pulls in extreme ambient heat. Neither cooler alone achieves this – the combination does.

The additional complexity of water lines, a pump and reservoir is manageable and the performance gain justifies it on serious builds.

Charge Pipe Sizing Reminder

Keep charge pipes at two and a half inches. The turbo outlet is typically no larger than this and matching it maintains air velocity. On the cold side of the intercooler – after the cooler – the air is denser and cooler so it occupies less volume. Two and a half inch piping on both sides is correct.

Do not run four inch charge piping. The volume of air needed to fill large diameter piping before boost builds adds measurable lag. Keep it small and efficient.

Summary

• Air filter intercooler temperature management is critical for reliable power delivery
• Stock air box with panel filter is excellent if it fits your turbo and manifold combination
• K&N filters: check inside for loose metal threads before every installation
• Foam filters: buy quality brands with rigid internal plastic cage
• Intercooler temperature cannot go below ambient – 30 degree day means 30 degree minimum charge temperature
• Charge air exits turbo at over 100 degrees at three bar boost
• Dual stage intercooler: water to air at turbo outlet plus air to air at front produces rock solid temperatures
• Charge pipes: two and a half inch both sides of intercooler

Go buy a pump and a turbo. Bye!