Inside the 800-hp Olsbergs Fiestas – update 1



Nope, no Fiesta in here! A Fiesta engine bay is below for your consideration. Not only is the engine oriented the wrong way, but it's not even the right engine. Oh, but the engine is so very right. The Ford Duratec (aka Mazda MZR) is an amazingly popular engine both in production (everything from the Mazdaspeed3 to the new Ford Transit Connect bakery van) and in motorsports (everything from Formula Atlantic, to half the Caterham 7s on the planet to, well, this monster). Given the orientation and the front differential I spotted under the intake manifold, I'd guess the drivetrain is based on the rally proven Escort/Sierra Cosworth.


Stock Fiesta Engine



X-Games rallycross olsbergs Fiesta exhaust side


There's a lot going on over here on the exhaust side. First, note the long-tube header. No shortie log manifold is going to support this kind of power, you need a smooth-flowing shape and proper pulse tuning on top of raw boost. Unfortunately, the heat wrap obscured a lot of details, like how the weight of that turbo is supported. This is no small detail when the turbo is this far from the engine (the long lever arm means a lot of torque on the manifold flange) and has to deal with the g-forces of a massive, 50-foot crossover jump.

It also isn't clear if its a single-scroll or twin-scroll turbo. Although a twin-scroll should give better boost response and a wider powerband, the single tube running up to the wastegate (sticking up behind the turbo) suggests its a single-scroll. A twin-scroll turbo would have separate collectors for cylinders 1 & 4 and for 2 & 3, with a wastegate tube coming off each collector. Before pencil pecker ran me out of town, Ericsson did let me know it was a Garett turbo, and that they ran a smaller turbo for X-games than they did for Pike's Peak. No surprise there, since the hillclimb is completely unrestricted, while X-games requires a 40 mm intake restrictor (you can see it just behind the lower blue turbo hose) allowing a little more power than the 37mm restrictor all Rally America open-class cars must run in normal stage rallies.

The two small stainless tubes running across the manifold are part of the anti-lag system. The valve at the front of these tubes (with the aluminum cap and blue banjo fitting on top) functions like a blow-off valve. Boost comes in from the hot side of the intercooler. When the driver lifts off the throttle, the valve opens, dumping that hot boost into the exhaust manifold. At the same time, the ECU goes stink rich and ignition timing goes extremely retarded, sending raw fuel and belching flame into the manifold That raw fuel mixes with the air that was just introduced, goes kablooey, and spins the turbo, keeping it spooled up and ready for when foot hits firewall again. Of course, with the throttle closed, and no actual blow-off-valve venting boost, the spinning turbo has nowhere to pump air to. Some goes through that anti-lag valve, but a lot of it just stalls and falls back through the compressor – a.k.a. compressor surge. That horrendous chirping you heard on that Pike's Peak video? That's the resulting compressor surge.


olsbergs fiesta duratec R coolant manifold


Its easy to be distracted by all the turbos and plumbing over here, but there's a big, very important detail hiding in plain sight. Notice that conical, cast-aluminum manifold right over the exhaust manifold flange? Its a water manifold, collecting coolant as it exits the four individual coolant outlets over each combustion chamber. Look closely at your Ford Focus, Mazda MX-5, or Mercury Mariner, all of which have this same engine, and you won't see these coolant outlets. Ericsson said his early efforts with the Duratec resulted in a series of mechanical failures of the cylinder head itself, so he had Motor Design Sweden make a stronger one. The MDS head has a 15mm thicker deck and more material around the combustion chambers, plus the improved coolant flow form the four outlets which helps keep the hottest parts of the head from reaching structurally critical temperatures.

Naturally, if you're going to build a race head, you do more than make it stronger. The head also features ports that are larger, straighter, and higher in the head (Duratec/MZR heads are known to have very good ports from the factory, so this probably wouldn't have been enough to motivate a new casting all by itself), and leaves room for bigger valves (as big as 37mm intake/33mm exhaust, up from 35/30 on the stock head). Around the camshafts, there is additional clearance for high-lift cams, and the lifter buckets are substantially larger (36mm on the intake, 35 on the exhaust side, both up from the stock 31mm), allowing more aggressive opening and closing ramps without the cam lobe wiping off the end of the bucket.

While we're noticing things in this picture, notice which way that coolant manifold points. It goes backward, down the transmission tunnel..


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