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Fords Duratec Engine.
As you probably know, there's a brand-new four cylinder Ford engine in town. Currently powering the Mondeo and Focus, the Duratec is the engine of the moment, as far as Ford's top bods are concerned. But just how good is it? How does it compare to the Zetec it's replacing, and will it be a match for the mighty Cosworth YB? Even more importantly, how much power can you squeeze out of it on a shoestring? To really nail these questions (and plenty more besides), we've visited SB Developments- the company which is currently investigating the release from Ford's latest.
This new engine is referred to as a Duratec, which stands to reason really - that's the name on the rocker cover. That said, its other official title is an I4. Now, theres the first bit of confusion we're faced with, because of course Ford already has an I4 - the twin-cam jobbie that used to power the last of the Sierras, remember? As we know, this went on to spin the tyres on the RS2000 MkV Escort in 16-valve form. This I4 has nothing to do with the old one, which is why it's called Duratec and will be from now on. The only real thing it has in common is its chain-driven cams. In fact, it isn't really a Ford engine at all; it's a Mazda. Which, of course, Ford owns - quite handy really.
The point of the motor is that it's going to be produced in simply vast numbers. Yep, they said that about the Zetec - that was supposed to be the first Ford 'world' engine - but this one really is. And the word production is the key to the whole thing, although it owes a lot to race track tricks too. The only downside is that it isn't of the Ford family, and therefore won't fit where a traditional Ford engine will. Look at it and you'll see it breaks with years of Ford family bellhousing tradition in that the pattern is completely different. As a result, no rear-wheel-drive box will bolt staight on like virtually all past Ford engines; you now need a purpose-made one to do the job instead. The engine mounts are like nothing we've seen before and the whole thing is, well, efficeient. Very.
Still, you can get over 220 bhp from it without touching the engine internals, which sound a bit more like it.
The Engine
What have we got then? First off, all alloy engine - alloy block and head, four cylinders, twin cams and 16-valves. All fairly normal, modern, great stuff. But the motor is designed entirely with production in mind, to the extent that it'll pass emissions without even trying - it's that good. Everything has been designed to be a light and svelte as possible, which can't be anything but effieient. Consequently, many of the components within the engine bear a striking resemblance to race parts.
Take the pistons, for example. If you didn't know they were cast, yu'd think they were the very latest slipper pistons with Teflon inserts. Yet, although they will produce more horsepower that the standard Mondeo-rated 145 bhp, they simply aren't up to the standard of monster power. True, they are being used fairly conservatively and will take a touch more- but literally only a touch. And ther lies the key to this engine. Everything is designed to produce the power of a smooth, reliable, moderately high performing rep-mobile/family car that's totally cost-effective and nothing else. Arece car weiting to happen - like the Cosworth - it ain't. But don't despair - you can get a fair old whack out of it. As Clint Eastwood famously growled: "A man has to know his limitations" - and this applies in engine terms too. For the right application, the Duratec's a cracker. We'll show you why.
The Components
The key to producing horsepower is excellent breathing, with big valves, huge part and good induction all contributing to the process of getting lots of air/fuel mix and gas in and out respectively. The downside of an engine like the Zetec was that it was designed to be as compact as possible, especially in bore size. Consequently, everything was crammed in; the valves were too small with no real scope for a size increase, and the ports weren't much better either.
In the name of great emissions, the Duratec has whopping valves - 35mm inlets and 29.90mm exhaust, plus huge, well-designed ports. Both of these contribute to producing horsepower. The valves have nice , thin stems- meaning the guide bosses don't have to be massive and therefore obstruct flow thought the ports. The valves are also stainless although they're of two-piece construction and have lovely thin valve seats, again, optimising gas flow. Physically there really isn't anything you need to do to the head desing to improve it.
Cams
Surprisingly, the method of opening and closing the valves isn't hydaulic like the old CVH but mechanical. Being of overhead cam design, of course, means that the cam is directly acting on the followers - alsoknown as buckets, as upturned they assume that configuration and carry the springs. Modern cam thinking is different to that of old, where loads of duration was used along with low lift, producing lots of overlap. This is a real baddie as far as emissions go becasue fuel is literally dumped down the exhasut valves, resulting in horrendous backfires and sky-high lambda readings.
Consequently, cams are dialled in the direct opposite way, with large lift and small degrees of duration. The Duratec's dimensions therefore are inlet 257 degrees, with 9.87 mm of lift, and exhaust is 252 degrees and 8.45 mm of lift. Not huge in terms of lift, but they don't need to be - the valves and ports are whopping, so why do they really need to open by huge amounts if they can get the gases in without doing so? True to the emissions-friendly ethos, just enough is about right and consequently there is room for improvement.
Cranks & Rods
Again, the crank is cast to be svelte; to do its job and no more. The bearings are of a tin aluminium construction and though capable of plenty of miles in a cruiser, high revs and bhp will see 'em fail. Like the pistons, the connectiong rods are also pretty feeble and, compared to more traditional rods, look like on good burst would knacker them. like everything else, they designed for low-mass reciprocation, basically meaning that it's all about the efficiency.
Interestingly, like many modern engines, they're also of boken big end cap design. This means that the rod is cast as a one-piece unit, machined to tolerance then broken in a totally controlled way across the bid end journal hole to form the big end cap. The cap can therefore only fit one rod and one rod only.
Block
Like a Vauxhall XE engine - which SB Developments is most famous for developing - the bore/stroke ratio is pretty much square on the Duratec. You have an 87.6mm bore which is actually slightly bigger than an XE and a 83mm stroke. America, as usual, is blessed with something of larger girth - 2.3 litre version of the Duratec. This has a slightly larger bore size but in comparison a far greater stroke . It stands to reason that these engines will produce more power, but it comes at a price. The Duratec version is harsher and less able to rev - ideal for turbo applications, you would think.
All Duratec blocks have some great design features built in, although it could be argued that they don't look too hot. Most guilty culprit are the exterior oil-carrying gullies cast into the block, but obviously there's a reason for this. See it's no secret that oil dropping onto the crank, whilst returning to the sump, produces drag. This, in an engine where efficiency is everything, robs bhp. So by directing the oil down the outside of the block in purpose-built channels, the oil returns to the sump completely independent of the crank, therefore having no effect on it in terms of hindrance. There's more too. The crank is mounted high up in the block away from the sump, and is braced by a cast girdle housing all the main bearing carriers. Thus, several components are incorporated in one, cutting costs. The downside may well be the need for precision machining and assembly - but we'll discuss this later because it's significant.