Conquering Le Mans: Analysis of the engineering expertise within an LMP2 engine
26 June 2018
The Le Mans 24-hour race is a high endurance, day-long race that puts the world’s best race cars to the test. In 2017, jaws dropped when an LMP2 car was placed second and third overall. But, why was this a poignant moment for this engine type and why is this significant to the design and development of these race car engines? And how does miniature bearing specialist SMB Bearings fit in to this?
Certain design criteria must be fulfilled
A Le Mans Prototype (LMP) is the type of sports prototype race car used in the 24 Hours of Le Mans, FIA World Endurance Championship (WEC), IMSA WeatherTech SportsCar Championship, European Le Mans Series (ELMS) and Asian Le Mans Series. For a car to be compliant for entry in either the LMP1 or LMP2 category, certain design criteria must be fulfilled.
In a previously LMP1 dominated race, the 2017 Le Mans 24-hour race saw two LMP2s on the overall podium. For a race that had never previously seen an LMP2 car lead, let alone take an overall podium place, it does pose the question, what has changed?
High performance powertrain manufacturer Gibson Technology has been chosen by the FIA/ACO as the sole engine supplier for LMP2 class sports cars from 2017 to 2020. Therefore, all race cars in the LMP2 category during this time are equipped with the latest development from Gibson, the GK428 engine.
The GK428 is the current spec engine supplied to all the LMP2 teams competing in the WEC, the 24 Hours of Le Mans, ELMS, IMSA Weathertech Championship and the Asian Le Mans Series (from 2019 onwards).
One of the most technically advanced engines that Gibson has ever produced
It has been specifically developed for endurance racing and is one of the most technically advanced engines that Gibson has ever produced, incorporating the latest design, manufacturing and development techniques available.
When the GK428 made its debut at the 2017 Le Mans, there was a lot at stake as the largest ever number of Gibson engines took to the LMP2 grid. There were a record 25 cars powered by Gibson engines, in total supplying and supporting 19 different teams.
The results spoke for themselves when 12 LMP2 cars were placed in the overall top 16. It really was the year of the LMP2 — even if the LMP1 Porsche did take the lead in the penultimate hour of an incident-filled race.
Given the extreme temperatures and conditions, the performance of the Gibson engines was unprecedented. An impressive 21 out of the 25 Gibson-powered LMP2s finished the 24 hours, with the only four retirements unrelated to engine issues. These reliable, consistently performing engines are a testament to the engine design, manufacturing and validation process.
Producing a race engine that maintains efficiency consistently over 24 hours is no easy task
Producing a race engine that maintains efficiency consistently over 24 hours is no easy task, especially as it is at full throttle for 70 per cent of the lap at Le Mans. Therefore, a great amount of work goes into the design, simulation and material technology to ensure the engine is able to perform at the highest level.
Getting to this milestone had been quite the journey since Gibson Technology was established in 1987 (formerly known as Zytek Engineering). The company has endured business acquisition, rebranding and ongoing engineering refinements across all engine types, including those for LMP1 and LMP2 race cars, over the last 31 years.
However, one thing that has been constant in the last decade is the bearings used across all Gibson Technology racing engines, courtesy of miniature bearing specialist, SMB Bearings.
The engineering department at Gibson had a challenge on their hands 10 years ago — to source thin section bearings for the throttle barrels that would be able to function in the hostile environment of a race engine. The throttle system is an extremely important part of the engine, designed to control the flow of air or fuel mixture into each cylinder of the engine.
Design of the throttle system has been highly developed
The design of the throttle system has been highly developed, to ensure that good driveability and optimum performance are achieved, along with a reduction in the level of friction which is generated during the rapid throttle movements.
This called for thin section bearings that could perform in a race engine environment. The area of the engine where these bearings are located is subjected to extremely high temperatures, and very high levels of vibration creating considerable stress and load on bearings. In such extreme conditions it is no surprise that so many other bearings failed to meet the brief.
After going through several bearing suppliers, all of which were unable to provide a bearing that would function correctly under these conditions, Gibson turned to SMB Bearings in the hope of finding high performance bearings that could last the test of Le Mans.
The bearing specialist supplied EZO thin section ball bearings, suited to applications when weight reduction is required and where space is at a premium, as with the case of the throttle barrel.
Using the interference data sent from SMB bearings, the Gibson engineering departments undertook work to enable the installation of these bearings into the engine. Once this was completed, the bearings were installed and validated without any issues.
“The success of these bearings in Gibson’s engines has been a huge testament to the skilled manufacturing that goes into EZO’s bearings,” said Chris Johnson, managing director of SMB Bearings. “The endurance, as demonstrated out on the Le Mans track, has been amazing to watch.”
The entire engine was evaluated on a test bed
When it came to testing and validating the race car engines, with SMB’s bearings installed, the entire engine was evaluated on a test bed, enduring the equivalent cycles of two races of Le Mans (48 hours). After this test, all parts were stripped and analysed. Satisfied with the performance of these bearings, SMB’s bearings have now been used in the assembly of every single Gibson Technology engine for the last 10 years.
There is an exciting season ahead for Gibson Technology in 2018 to demonstrate the true capabilities of ongoing engine developments. Race teams have now announced their entries for WEC, ELMS and the IMSA Weathertech Championship, as well as confirmation of who will be competing at Le Mans 24 hours this year.
In LMP2 there will be a total of 17 cars in ELMS, seven in WEC and 20 in the 24 Hours of Le Mans and six in the IMSA Weathertech Sportscar Championship, all powered by Gibson GK428 engines. In LMP1, three cars will take to the grid at Le Mans and WEC powered by the new Gibson GL458 engine.http://www.engineersjournal.ie/2018/06/26/conquering-le-mans-analysis-engineering-expertise-within-lmp2-engine/http://www.engineersjournal.ie/wp-content/uploads/2018/06/a-lm3-1024x683.jpghttp://www.engineersjournal.ie/wp-content/uploads/2018/06/a-lm3-300x300.jpgMechdesign,mechanical,transport