When the first variable nozzle turbos were launched, it was a step change in turbocharging technology. Air mass sensors and ECU’s were programmed to manage the whole engine system, however relative to the current engines tolerances for acceptable air flow were set quite high. When setting up a new turbo, vane setting positions are set using accurate air flow equipment, which ensures that the ‘minimum vane opening’ position is set to allow a specific mass of air flow through the vanes. If the vanes are too closed, this can cause choking of the engine and overspeeding of the turbine. If it is set too large, the turbo will have too much ‘lag’ and not respond as well as it should.
Traditionally, turbo repair workshops did not use an air flow rigs to correctly set the flow. The actuator position was set based upon an accurate measured position of the actuator arm. This produced acceptable results and allowed the repairers to keep on repairing.
In reality, this method of setting the vanes can produce quite larger inaccuracies in the flow of air. The actuator arm measurement is set against a cast finish on the bearing housing, the position of which is not accurately controlled during manufacture. However, as the engine would accept quite a large tolerance of air flow, the repaired turbo still performed well compared to the broken turbo which it replaced, so the vehicle owner was still happy with the results. On older turbo repairs, the variable nozzle position had to be a long way out before the performance was unacceptably affected or for the ECU to flag a problem. From an OEM perspective, this is not acceptable and is the reason for their lack of support of repairing.
In more recent years, as engines have improved to meet tighter Euro emission regulations, the control over the whole air / fuel system has improved dramatically. Many premium brand vehicles have moved to electronic actuation which gives positional feedback to the ECU. Some more advanced turbo controllers now sit within the CANbus talking directly to the injection system and air mass sensors, to respond more quickly to engine demands. For these turbos, the settings are either correct and accepted by the ECU – or not, which results in warning lights, limp mode or refusal to start.
As more of the Euro 5 compliant vehicles enter the aftermarket, problems will arise and for some turbo models, we have already reached the point where flowing the turbo is a necessity and only possible by workshops who have the correct equipment.
Traditionally, in the turbocharger aftermarket the customer had a choice between a new OE turbocharger and a remanufactured turbo. Over the past 10 years the turbo repair market has changed significantly with the number of new repairers entering the market and the number of suppliers of parts. What we now have is three tiers, a new OE turbo, a high quality remanufactured turbo repaired using quality parts and the correct equipment, and a poor quality repaired turbo, using inferior quality low cost parts. There will always be a market for all three options depending upon the vehicle owner’s requirements.
It is important that customer understand that there are different levels of quality for repaired turbos and therefore a different level of associated cost. When outsourcing turbo repairs it is crucial to consider the real cost of replacing a turbo and to educate your customer about the different options and associated risks for going lowest cost vs paying a little more for quality, so they can make informed decisions. Who pays for the time to fit the second replacement? What if it damages other parts of the engine?
We are proud to have G3 Concepts™ latest model or Air flow bench rig, which allows us to ensure our products match OEM or higher quality.