Lotus Elise – Race Rebuild

For any of you who follow us on Facebook you will of seen increasing mentions of our stunning Lotus Elise S2, we are planning to run the car in the MSVT Track Day Trophy series this year. Whilst the changes on the exterior are easy to see and have made a noticeable difference to the aesthetic of the car we all know it’s what’s on the inside that counts right? It would be fair to say we’ve carried out a pretty extensive overhaul of the car since she last hit the track. It’s been keeping us busy throughout the winter so given we’re less than a week away from her debut, it’s only right that we fill you in on all the details!

We last raced the Lotus in 2017 in the 750MC Club Enduro round at Silverstone, where we managed to take the Class C Win, with drivers Louis Wall and myself, James Tucker. The beauty with a two-hour race is it gives you a lot of time to evaluate the car, particularly the weak areas to be addressed! You can view onboard footage from the race here.

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Since that sunny and successful August race its been a long road back to the race track, although we do accept that’s partly down to not knowing when to stop on car development! The Lotus has definitely proved a fun, if not at times trying project for the Tucker Motorsport Team!

Where to begin? Well, there was one very apparent issue with using the Lotus in an endurance racing format, and before you all jump to it, no, not the badge – Lots Of Trouble Usually Serious – but actually the fuel tank capacity. Or more to point the lack of capacity. The Series 2 Elise left the factory with a 36-litre fuel tank capacity. This meant that even with refuelling in the mandatory pit stops and employing fuel saving techniques made famous by F1 Drivers (Lifting and coasting before hitting the brakes), we still finished the race on fumes. Luckily, despite the compact construction of the Elise there is still room around the fuel tank, allowing a larger version to be fitted in it’s place. So, the first job was decided, it was out with the original 36-litre tank and in with a new Pro Alloy 60-litre fuel tank. This simple change should help us to run at full speed all race long without the worry of fuel preservation.

From this initial endurance race it was apparent that we were down on power, even considering that the classes were derived on a power to weight ratio (180bhp per ton, measured at the fly wheel without a driver). Following that first race we took the car to a rolling road to see exactly what we were starting with. This showed the car to be producing 123bhp, therefore a power to weight ration of 159bhp, it was clear why the Lotus felt a bit sluggish on the straights! With the start point now clear we decided the best way forward was to entirely rebuild the engine, with a target power of 135bhp. It quickly became clear this is the one place where we didn’t quite know when to stop…

We replaced pretty much the entire engine, even fabricating several of our own parts, namely our own VVC Blanking Plates which would in turn allow us to use a later head which allowed better air flow and as such more power. As you can see the list went on!

  • Westwood Ductile Liners
  • Omega Pistons
  • Max Speeding H Rods
  • Race Spec main bearings and big ends
  • High flow oil pump
  • Land Rover oil ladder
  • Later spec VVC Head 
  • VVC Blanking Plates (made in house)
  • 270 Piper Cams

With all this work carried out on the engine, we quickly found that the original ECU wasn’t up to the take of running the uprated engine. We managed to get the original ECU to power the engine, following many hours spent modifying sensors. In order to ensure reliability and efficiency the decision was made to replace the original ECU with a standalone, after-market alternative, which also allowed unique programming to keep the engine running safely and to adjust power output. So you can add an Emerald ECU to the above list of additions!

When we look back now this might have been a slight over kill for the extra 10bhp we were looking for! Following all of the modifications it may not be a surprise that we ended up slightly over our target power.

When we returned to the rolling road the Elise was now putting out 132bhp at the rear wheel, so, an estimated 155bhp at the flywheel, nearly 20bhp over target!

This year we are looking to enter the Elise in the MSVT Track Day Trophy, where power to weight and as such the classes are calculated differently. This is perfect for our Lotus, fitting into Class C/175bhp per ton (bhp at the hub, weight with driver). However, if we do decided to go back to the Club Enduro series we will be able to de-tune the engine using the uprated ECU. It’s always better to have too much to reign in than not enough in the first place!

With this extra power we needed to look into our cooling system, as with 122bhp at the flywheel the car was running at a whopping 102-105 degrees! Anyone familiar with the Rover K-Series Engine will know this isn’t ideal, not only for performance but importantly for reliability. With this in mind we ordered a new aluminium radiator from RadTec, with a 50mm core. This proved to be a wise move, as during the replacement we found the original radiator had deteriorated and was likely to start to break up and leak. The recent test days completed with the Lotus have proved the radiators worth, bringing the coolant temperature down to a consistent 92 degrees. These test days have proved incredibly insightful and we are planning to further improve this area to help with reliability and performance over a race distance.

The test days were also invaluable in the development of the engine. The initial runs shows the engine to be ‘breathing’ quite heavily, which only served to increase the crank case pressure. This ultimately cause a cam-seal to pop out, quickly followed dramatically, by the sharp exit of most of the engines oil! Following this we had a quick engine rebuild and enlarged our oil breathers, plumbing them into an external catch tank. This has not only cured the issue but is an incredible addition to the engine bay. At the same point we introduced a cold air intake, as the heat in the engine bay ramps up considerably under revving. This is an inevitable side effect of the flat floor and mid-engine design, resulting in very little airflow to dissipate the heat. To further reduce the engine bay temperature we cut the boot compartment bulk head out of the rear clam shell and created five 2inch holes in the rear of the body work, to encourage greater airflow throughout.

 We weren’t done there! The suspension underwent a huge overhaul, the Elise has spent of 20,000 of its 45,000 miles on a race track, so as you can imagine many of the bushes, bearings and ball joints were showing signs of wear. Many of you will of experienced suspension bush wear causing suspension geometry to move in an uncontrolled and unpredictable manner. We chose to replace all joints and uprated the original wishbone rubber bushes with spherical bearings. This removes all ‘slop’ from the suspension, meaning it only rotates in the way it was designed to, whilst this would prove too harsh on badly surfaced roads, but on track it really connects the driver to the feel of the car and the track.

Despite the Lotus having great feel and balance, during the 2017 Club Enduro race both Louis and myself struggled to get the car to stop and efficiently turn into the infamously tight Silverstone corners. This was a result of the amount of weight transfer during braking, the car was nose diving, overloading the front tyres, which made the front want to lock up and understeer on entry. It was therefore decided that we needed to dramatically increase our spring rates all round, which in turn led to a few other changes. The higher spring rates meant that our dampers needed to be modified to cope with damping the new springs. We sent these to Protech Shocks, where they were serviced and re-valved to compliment the new spring rates. The final piece in the jigsaw was an uprated anti-roll bar, with such high spring rates it was clear the original was not going to be up to the task. We ordered a new 28mm anti-roll bar from eliseparts.com and manufactured our own adjustable rose jointed drop links. This is not only to cope with the extra strength of the new anti-roll bar, but also to have a more direct response than the original (less slop) whilst aiding effective car set up.

So whilst the outside is looking race ready don’t forget we’ve back this up with a lengthy overhaul of every aspect of the car. We can’t wait to see it all come together for the first MSVT Track Day Trophy round at Donington Park, this weekend.

James Tucker

 

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