► New Horse 1.3-litre turbo 4cyl
► Replaces outgoing Sigma 1.6-litre
► Will debut in 2026 Academy car
Did you ever think you’d see the day when a Caterham is powered by an engine shared with a Mercedes-Benz (among others)? No, me neither. And yet here we are, with the 2026 variant of the Caterham Academy racing car using the HR13DDT unit out of the Renault Kadjar, Nissan Qashqai and Mercedes-Benz A-Class to name but a few.
Why? Well, there’s an element of necessity in it, of course. Caterham Sevens have recently run 1.6-litre naturally aspirated Sigma engines but with production now well-and-truly over (it actually ended a few years back) the company has had to look for a new engine to power their cars.
Why this particular engine?
The Horse HR13DDT fitted the bill for a number of reasons, but two stand out as especially important. A) Horse Technologies (a collaboration of Aramco, Geely and Renault) has committed to building the engines for at least ten years and B) it fits into the Caterham’s tiny body. Sort of.
You’ll notice in the pics that the camo’d car we’re driving has a noticeable lump on the bonnet. That’s because the high-pressure fuel delivery lines that sit on top of the engine are just a little too tall for the Caterham’s slender dimensions despite the block sitting as low as possible within the chassis.
George Campbell, Head of Engineering at Caterham, explains why having the ‘lump’ (the car in the pics is a prototype, it will look much neater on the final car) is necessary. ‘We could look at changing it (the layout of the high-pressure fuel lines), but when the manufacturer has put time and investment into it, plus has a build procedure for it, we’re just trying to leave it where it is.’
He also reckons it won’t impact the unique feeling of driving a Caterham. ‘We’re very aware of that. When you’re looking down as a driver, you can still see through this space (to the wheel). So you know when you’re aiming for the apex, you can still line it up.’
What are the specs?
The Horse engine is a 1.3-litre four-cylinder turbocharged unit built in Valladolid, Spain. It uses an aluminium block and delivers 130bhp @ 5,700rpm and 130lb ft of torque @ 5,150rpm, however much of the latter is available from far lower down in the rev range.
The overall weight is around 80kg (all in, there’s no overall increase in the kerb weight of the car), with Caterham fitting a flywheel that’s 30% lighter and a new exhaust system (without modification it would have been a choice between exhaust system or steering column). Caterham also elected to design its own ECU given the specific demands of the Seven.
However, it’s not just the engine that’s new. Caterham has upgraded the old five-speed MX-5 gearbox and got hold of a six-speed unit off the latest version, plus a new custom-built aluminium diff (the old one was from cast iron and from a BMW) that’s now limited-slip – a first for an Academy car.
But let’s get back to the elephant in the room. A turbo? In a Caterham?! George admits it’s something that the company is a little anxious about in terms of the response from customers.
‘I won’t lie, we’re nervous about it. Because, as you know, the whole characteristic of a Caterham is that continual rev. The more you drive it, the more you get feedback, rather than this sort of traditional turbo, where it all comes in early and flat lines. So we’ve done a lot of work to try and retain as much of that linearity in the characteristics possible.’
Have they succeeded?
We got the opportunity to try the Caterham Academy Horse prototype car during an open track day at Brands Hatch. Sounds low-key, but it’s the perfect environment for seeing what the car is like in the real world.
Straight out of the pit-lane, I clip the rev limiter, and then again coming down from Druids. Far from the end of the world, but this engine absolutely feels boosty on first impressions. The initial climb through the revs is as you’d expect, yet reach around 4/4.5k and the boost comes in quickly with the optimum time to change gear not long after.
It really does take some getting used to – as do the deliberately low-grip Toyo tyres. The Caterham Academy is a popular series and it’s open to anyone who hasn’t raced before, the idea being that you learn control and technique like you would in few other modern racing cars.
There’s certainly a lot to learn here and the sound isn’t what you’d called sonorous. It is purposeful and mechanical-sounding, mind, so it fits with the rest of the car well. After a few laps I come back into the pits to talk with Alex Read, Caterham’s Head of Motorsport and a man that’s done many miles of testing in the Horse-engined Academy car.
He recommends taking a higher gear than I would expect pretty much everywhere but the main straight where it’s better to hold 5th then grab 6th. He also suggests getting on the accelerator earlier, just to give the turbo a chance to do its work (so that when I do actually need the power, everything is spooled up and ready to go).
The difference is huge. Using a higher gear, the engine no longer feels anywhere near as boosty. It’s a smooth build-up with only a moderate feeling of forced induction as I transition to the upper third of the rev range. Getting on the accelerator earlier also makes a huge difference. Momentum is key and getting on the power at the right time (and using the new LSD) is the perfect way to stave off mid-corner understeer.
The difference should show in the times, too. Caterham reckon the Horse engine car could be a second or so quicker around Brands Hatch Indy (a big chunk on such a short circuit) and indeed the little car is overtaking pretty much everything on track.
I speak to one of the Caterham techs who also reckons that the racecraft may change as a result of the new engine. Previously, drivers would stop the car on the apex in an attempt to back their competitor up and drop them out of the power band. Such a tactic is likely to be far less effective in the new car.
Whatever happens, Caterham hasn’t got long to get the cars ready. The Horse engine is so far only confirmed for the 2026 Academy cars with the championship starting in Spring, yet the expectation is that the new powertrain will be introduced – year-by-year – in other Caterham series going up the pyramid. No word yet on road-focused models taking the engine, but it’s highly likely.
As is often the case, the best way to get over any concerns about a turbocharged engine in a Caterham is to experience it first-hand. We’ll miss the old naturally aspirated units – they did a brilliant job over the years and were great fun to drive.
Yet the Horse motor gives away very little of the magic and, crucially, it continues to allow drivers to focus on the steering, brakes, weight transfer and everything else that matters when driving a Caterham Academy car. That, after all, is surely the point.