Inside the engineering challenge of getting BTCC hybrid-ready

Developing a car for the hybrid era of the British Touring Car Championship has been a challenging but satisfying job.

We introduced the new 3 Series BMW for 2019, and were thinking of changing the cooling package at the end of 2020, ready for 2021, but when the hybrid was announced we thought if we do it then, we’d have to do it again for the hybrid. So, we kept the car as it was, and then hybrid gave us a new project to take to BMW for 2022.

I represent WSR on the BTCC’s Technical Working Group, and we’d already started having meetings about hybrid in early 2020, so started to thrash out positions for hybrid-related components with Cosworth and TOCA for front and rear-wheel-drive cars. We were talking about it for a good year or so before we even started designing parts for the 330e M Sport.

The first thing that had to change was the bellhousing, because unlike front-wheel drive, which have a modified Xtrac casing to take the hybrid motor on the outside of the casing, we were putting it in line with the gearbox, so it was a new Xtrac casing for us, and a new bellhousing because of that.

Battery position between front and rear-wheel drive was down to TOCA, who did C of G calculations to tell us where we were going to put it. Unfortunately for us, this pushed the battery for rear-wheel drive as far forward as it could go. So, I had to do a lot of toing and froing when the initial schemes came out, and eventually we got them to turn the battery around – it was supposed to be facing the other way, but the control unit (MCU) was going to be in our engine bay!

Because that meant some of the weight came backwards, they had to compensate for front-wheel drive, so now front-wheel drive has a maximum rearward and minimum forward position whereas RWD has just one position. But that’s the way it goes!

We didn’t get the hybrid kit until late February, but up until then we had all the drawings from Cosworth, we knew the position the battery had to be, so basically, I just designed all the bracketry to hold it in place in the passenger footwell where it had to go, and all the other stuff that goes with it.

Colin Turkington, Team BMW 330e M Sport

Photo by: JEP / Motorsport Images

We had to move electrical boxes, so had to redesign trays to make the boxes stack – we don’t usually have them stacking, but we were running out of room basically. It was a packaging exercise more than anything. We used EY3 Engineering to assist with the front bumper surfacing that incorporated the ducts for the LTRs, which are situated under each headlight, one for ESS battery cooling and one for the EV motor and MCU.

There was a rear-wheel-drive hybrid test car – the Ciceley Motorsport 1 Series BMW, built and supplied by WSR. But as Cosworth ran the test, you weren’t allowed to look at any data, and they had their own drivers. They didn’t run anywhere near enough kilometres and what running they did do was in winter temperatures, so there have been some problems this season.

Basically, the EV motor was designed to be shared between all the cars like a common part, as TOCA parts are, and the bracketry for it was just holding the motor in line with the gearbox on a transverse engine. For the rear-wheel-drive because we’re in-line, it turns the motor 90 degrees so now that little bracket was trying to stop the motor going backwards and forwards under braking and acceleration. And then coupled with some early tolerancing issues, the whole unit would flex.

These issues became apparent when we started running at the first round and I had to quickly come up with a solution to support the bracket better, to stop everything flexing. The brace I designed was also supplied, in principle, for the Infiniti.

From the first race event it also became apparent the gear teeth that drive the EV motor were not up to the loads being experienced. At Thruxton the gears in RWD cars suffered with cracked idler gear teeth. The drivers had no hybrid deployment during races. Since then, Xtrac responded very quickly and improved the design and material to eliminate any further issues.

There’s also been an issue with heat-soak to the EV motor when the car’s in the garage. So we’ve used the driver fan to duct air into that area on the motor, which seems to have worked out OK so far. The drivers are now cooled via a hose from a NACA duct in the rear window.

We not only did the hybrid this year, but we also repackaged the intercooler, radiator and their cooling ducts for better airflow under the bonnet. We’ve got louvres in the bonnets now; it’s all to do with airflow to keep the charge temperature down because we were suffering in races with it getting hot when we were up behind cars. I think that, plus a little bit of aero work that we’ve done, has been another step forward for the car. It’s been worth all the extra work over the winter.

Now I just wish we could get back the boost we are supposed to have so we can show our true performance this year.