There are a number of different types of turbocharger used within the automotive industry:
Variable Geometry Turbo
Variable Twin Scroll Turbo
Single turbochargers are what most people think of as turbos. By differing the size of the elements within the turbo, completely different torque characteristics can be achieved. Large turbos provide higher levels of top end power, whilst smaller turbos can spool faster and provide better low-end power. They are a cost-effective way of increasing engine power and efficiency, and as such have become increasingly popular, allowing smaller engines to increase efficiency by producing the same power as larger naturally-aspirated engines, but with a lower weight. They do however tend to work best within a narrow RPM range, and drivers will often experience ‘turbo-lag’ until the turbo starts to operate within its peak rev band.
As the name implies twin-turbos mean adding a second turbocharger to an engine. In the case of V6 or V8 engines, this can be done by assigning a single turbo to work with each cylinder bank. Alternatively, one smaller turbo could be used at low RPMs with a larger turbo for higher RPMs. This second configuration (known as twin sequential turbocharging) allows for a wider operating RPM range, and provides better torque at low revs (reducing turbo lag), but also gives power at high RPMs. Unsurprisingly, having two turbos, significantly increases the complexity and associated costs.
Twin-scroll turbochargers require a divided-inlet turbine housing and exhaust manifold that pairs the correct engine cylinders with each scroll. independently. For example, in a four-cylinder engine (with a firing order 1-3-4-2), cylinders 1 and 4 might feed to one scroll of the turbo, while cylinders 2 and 3 feed to a separate scroll. This layout provides more efficient delivery of exhaust gas energy to the turbo, and results and helps provide denser, purer air into each cylinder. More energy is sent to the exhaust turbine, meaning more power. Again, there is a cost penalty for addressing the complexity of a system requiring complicated turbine housings, exhaust manifolds and turbos.
Variable Geometry Turbocharger (VGT)
Typically, VGTs include a ring of aerodynamically-shaped vanes in the turbine housing at the turbine inlet. In turbos for passenger cars and light commercial vehicles, these vanes rotate to vary the gas swirl angle and the cross-sectional area. These internal vanes alter the turbos area-to-radius (A/R) ratio to match the engines RPM, and so give peak performance. At low RPM, a low A/R ratio allows the turbo to quickly spool up by increasing exhaust gas velocity and. At higher revs the A/R ratio increases, ther4eby allowing increased airflow. This results in a low boost threshold reducing turbo lag, and provides a wide and smooth torque band.
Whilst VGTs are more typically used in diesel engines where exhaust gases are lower temperature, until now VGTs have been limited in petrol engine applications due to their cost and the requirement for components to be made from exotic materials. The high temperature of the exhaust gases means that the vanes must be made from exotic heat-resistant materials to prevent damage. This has restricted their use to applications within luxury, high performance engines.
Variable Twin-Scroll Turbocharger (VTS)
As the name suggests a VTS turbocharger combines the advantages of a twin-scroll turbo and a variable geometry turbo. It does this by the use of a valve which can redirect the exhaust airflow to just a single scroll, or by varying the amount the valve opens can allow for the exhaust gases to split to both scrolls. The VTS turbocharger design provides a cheaper and more robust alternative to VGT turbos, meaning it is a viable option for petrol engine applications
An electric turbocharger is used to eliminate turbo lag and assist a normal turbocharger at lower engine speeds where a conventional turbo is not most efficient. This is achieved by adding an electric motor that spins up the turbo’s compressor from start and through the lower revs, until the power from the exhaust volume is high enough to work the turbocharger. This approach makes turbo lag a thing of the past, and significantly increases the RPM band within which the turbo will efficiently operate. So far, so good. It appears that electronic turbos are the answer to all the negative characteristics of conventional turbochargers, however there are some disadvantages. Most are around cost and complexity, as the electric motor must be accommodated and powered, plus also cooled to prevent reliability issues.
Melett UK will close for the Jubilee bank holiday at 17:00 on Wednesday 01 June and reopen at 08:00 on Monday 06 June. Any orders that are not picked or dispatched before we close will resume preparation when we reopen. If you would like any more information or guidance on the above, please contact our customer care team on +44 (0)1226 320939.
Memorial Day 2022
Melett North America will be closed for Memorial Day on Monday May 30th and will reopen at 8.00 am on Tuesday May 31st.
Melett Polska will be closed for a public holiday on Thursday 16th June and will reopen on Friday 17th June. Any orders that are not picked or dispatched before we close will resume preparation when we reopen. If you would like any more information or guidance on the above, please contact our customer care team on +44 (0)1226 320939.
May Bank Holiday opening hours
Will close 5.00 pm Friday 29th April and reopen 8.00 am Tuesday 3rd May
Will close 4.30 pm Friday 29th April and reopen 8.00 am Wednesday 4th May
PLEASE NOTE -THE ABILITY TO SUBMIT YOUR ORDERS THROUGH THE MELETT WEBSITE HAS BEEN RESTORED
We are delighted to advise full website functionality has now been restored, meaning you can view stock and pricing, add parts to your basket and submit your order via the website. In addition, all turbo/part number searches are fully working.
Until further notice please place your orders by 2.30 pm and we will endeavour to dispatch the same day dispatch.
We will keep you updated as we navigate through the remaining internal connectivity issues, we have dedicated teams working round the clock to resolve any remaining issues as quickly as possible.
We, at Melett, would like to stress our gratitude for your continued patience and support throughout this difficult time.
Please note you can now view your pricing on the Melett website.
We appreciate this is not a complete solution at this stage, however, please be assured our internal website and IT teams remain focused on reinstating the stock availability function.
We cannot stress enough that we are doing everything we can to reconnect our internal system, and we will restore full website functionality as soon as possible.
If you experience any problems whilst ordering online, please do not hesitate to contact:
W związku z awarią sieci telefonicznej prosimy o kontakt na telefon komórkowy: Damian 512 372 612; Kasia 511 372 612
Melett UK will be closed on Monday 29th August and will reopen at 8.00am on Tuesday 30th August.
Any orders that are not picked or dispatched before we close on Friday 26th August will resume preparation when we reopen. If you would like any more information or guidance on the above, please contact our customer care team on +44 (0)1226 320939.
Melett Polska will be closed for a public holiday on Friday 11th November and will reopen on Monday 14th November.
Any orders that are not picked or dispatched before we close on Thursday 10th November will resume preparation when we reopen. If you would like any more information or guidance on the above, please contact our customer care team on +44 (0)1226 320939.
Queen Elizabeth II state funeral - Monday 19th September
Melett UK will be closed on Monday 19th September for the state funeral of Queen Elizabeth II . Melett will be joining people and businesses across the country in reflecting on Her Majesty's incredible contribution and enduring legacy.
Melett North America and Melett Polska will remain open as normal.
Easter opening hours
Melett UK - will close 17:00 Thursday 14 April and reopen 08:00 Tuesday 19 April Melett Polska - will close 16:30 Thursday 14 April and reopen 08:00 Tuesday 19 April Due to essential maintenance, the Melett website will be temporarily unavailable on Thursday 14 April from 17:30 to 19:30. We apologise for any inconvenience caused.
Due to essential maintenance, the Melett website will be temporarily unavailable on Friday 25 February from 18:00 to 20:00 (GMT). We apologise for any inconvenience caused.
Planned maintenance – Thursday 24 March 2022
We will be undertaking planned maintenance on our internal systems this evening between 17:00 and 20:00 GMT, which will affect some website functionality.
We aim to keep disruption to a minimum and the website will remain online. However, we will need to temporarily disable online ordering during this time.
Thank you for your understanding.
We are undertaking essential maintenance this weekend (February 19-20) and some of our website services may be unavailable at times. We apologise for any inconvenience this may cause.
- Due to essential maintenance, the Melett website will be temporarily unavailable on Friday 28 January from 18:00 to 20:00 (CET). We apologise for any inconvenience caused.
Festive opening hours
- Melett UK Will close 5:00pm Thursday 23rd December and reopen 8:00am Tuesday 4th January
- Melett Polska Will close 4:30pm Thursday 23rd December and reopen 8:00am Monday 3rd January
- Melett North America Will close 5:00pm Thursday 23rd December and reopen 8:00am Monday 3rd January
Please note: Due to essential maintenance the Melett website will be temporarily unavailable on Friday 10 December from 5:00PM (CET) to 11:00PM (CET). Apologies for any inconvenience caused.
Please note; Unfortunately, we are experiencing processing delays for all orders which may result in delays in shipping. If possible, please confirm orders at your earliest opportunity to help minimise disruption to our normal high standards. Please accept our apologies and rest assured that we are working hard to resolve the issue.
Melett Poland will be closed for a Public Holiday on Thursday 11th November. Any orders that are not picked or despatched on Wednesday 10th November will resume preparation when we return on Friday 12th November.
Melett Poland will be closed for a Public Holiday on Thursday 6th November. Any orders that are not picked or despatched on Wednesday 5th November will resume preparation when we return on Friday 7th November.
Melett will be closed for a Public Holiday on Thursday 11th November. Any orders that are not picked or despatched on Wednesday 10th November will resume preparation when we return on Friday 12th November.
Melett will be closed from 5 pm on Wednesday 24th November until 8 am on Monday 29th November for the Thanksgiving holiday
Online ordering now available
In addition to viewing inventory levels and pricing, you can now place orders directly from our website. Download our user guide below to help you get started.