Variable Nozzle Turbines explained
Posted on October 11, 2014
There are many turbocharger reconditioners who are using inferior parts when repairing turbos. This is obviously to cut down on cost which we believe is not the best way to provide a good quality product and give customer satisfaction which has always been our ultimate aim.
Approximately 10 years ago several turbocharger manufacturers were of the opinion that the new higher speed turbos now being manufactured could not be repaired satisfactorily as the specialist balancing equipment needed for this type of turbo did not meet the required standard. Here at Turbo Clinic UK the first test machine we bought was the very latest High speed balancer (VSR) capable of speeds upto 250,000 RPM.
The setting and control of VARIABLE NOZZLES are vital in order for the turbo to operate efficiently and this procedure needs a VNT AIR FLOW RIG.
Variable Nozzle performance explained
The Variable Nozzle Turbo (VNT) allows changes to the exhaust gas inlet area to match the different boost requirements of the engine. For example; at the initial low speed response the nozzle vanes move to the closed position to reduce the nozzle area which gives increased gas speed through the turbo. Then as the engine speed increases the nozzle vanes move to fully open position to maximise the exhaust gas flow.
Vane setting accuracy is so important and can only be achieved by using accurate air flow equipment. If the vanes are too close this can cause choking of the engine and over speeding of the turbines. If it is set too large the turbo will have too much lag and will not respond sufficiently.
In the past, Turbo reconditioners did not use a VNT FLOW RIG to set the air flow which resulted in air flow inaccuracies. however, because the engine would accept quite a large tolerance of air flow, the repaired turbo would give a marked improvement prior to its repair, making the customer believe the problem was sorted. In reality, the VANE NOZZLE assembly could be a long way out before performance is affected which, in our opinion, is not acceptable, either to the customer or ourselves; hence the need for accurate air flow equipment. (VNT FLOW RIG).
When improvements were made to meet Euro emission regulations the air/fuel improved dramatically. As these newer vehickles are now widely used, it is essential for a Turbo Reconditioner to have the correct and most up to date equipment available. This in turn will mean that repairs on older turbos will also be improved.
Although there are quite a few VNT FLOW RIGS available to the aftermarket these days here at TURBO CLINIC UK LTD we have the very best on the market as it has been developed by 3 ex Garrett employees and we were the first company in the WORLD to own such a machine, so you can be confident that the turbo will perform and match the accuracy as a genuine OEM part.