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Fast Ford
November 2003
Fast Ford November 2003
Starting Blocks
So, what's Ford's latest engine really capable of? FF dishes the dirt on the Duratec.
Words and photos: Jon Hill
 
As you probably know, there's a brand-new four cylinder Ford engine in town. Currently powering the Mondeo and soon the all-new 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, there's 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 straight 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, efficient. Very.

Still, you can get over 200 bhp from it without touching the engine internals, which sound a bit more like it. But how?

The Engine

So, 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 efficient. 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, you'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 there 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 design to improve it.

Cams

Surprisingly, the method of opening and closing the valves isn't hydraulic but mechanical. Being of overhead cam design, of course, means that the cam is directly acting on the followers - also known 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 because fuel is literally dumped down the ex has ut 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.

Fast Ford November 2003
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 connecting 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 broken 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.

Fast Ford November 2003
Assembly

Like some huge game on your PC, the Duratec is meant for machine assembly aided by computer. Therefore, all the components are made to the most exacting tolerances imaginable. There are no keyways locating the crank to front pulley/crank trigger, and nor are there any to locate the cam and cam wheels. Instead the whole lot relies on friction joints - a good method as far as fast production goes. As a result, every single cam has to be made so it's exactly the same as the next, which you might think would be a nightmare in terms of assembly. The truth is that the valves are all made spot-on too, as are the valve seats. Any variation is taken up in the bucket followers, which also double as spacing shims.

Assembly probably works like this - a CNC machine assembles the valves in the head, then by laser measures the valve height then calculates and drops in the relevant bucket/shim followed by the cam. And it's all done quicker than you could eat a ham sandwich - although by then the machine's assembled umpteen other heads as well. In short, the whole engine is meant as an assemble once-only unit, which kind of highlights the modern dealership/garage thinking. Long gone are the days of greasy overalls and blokes smoking rollies with soft porn calendars up on the wall. Big ends and small ends aren't meant to be touched anymore, and instead you have posh, high-tech showrooms with matching high-tech cappuccino machines and technicians that can change your oil or swap complete units only.

Man-hours in your dealership are incredibly dear things these days, so anything that can ultilise the system is used to full effect. The Duratec drops straight into this with a role of fit and forget. And if it breaks, slot in a new one - true throwaway mentality. The unit has a similar role in motorsport too if you're smart, but we'll examine this in greater detail shortly. In conclusion to this section then, the Duratec is built to be an efficient unit produced in vast numbers. We will be seeing it appear in not just Ford products but related makes and plenty of others too, effectively meaning cheap engines.

Tuning

You'd expect there to be plenty of scope for tuning the Duratec. Well, good news - there is. Up to a point anyway. Put simply, you don't have to do much to wring out the power, as SB Developments has done back-to-back tests all on the same day, after extensive preparation. By junking the standard induction system, which is intended for serious emissions control only, and replacing it with traditional induction methods, you can achieve truly staggering results.

With a pair of 45 DCOE side draught carbs and managed ignition they got 170 bhp - that's 25 bhp over standard. By taking them off and fitting parallel throttle bodies the figure then went to 195 bhp. Then, after replacing them with SBD's own tapered throttle bodies, the power increased to 208 bhp. This, of course, is all on a completely standard engine with no other mods. The Duratec engine we have run has been testing in two forms, parallel throttle bodies which produced an output of approximately 195 bhp and then running the engine on tapered throttle bodies produced 203 bhp (this was used in the American SAE corrections). The implications of this are obvious. The engine is effectively a plug and play unit. If you want to compete in motorsport and are looking for an efficient unit then the Duratec could well be an option. With secondhand low-mileage units retailing at around £700, all you need after that is £1781.90 (plus VAT) of induction. It's kit that's unlikely to break or wear out in a hurry either.

If you're unfortunate enough to blow the engine then all you need do is unbolt it and replace it with another. Compare that to tuning a traditional Ford engine such as a Pinto. To get in excess of 200 bhp you'd need eight grand-plus. And, if all you wanted was a good high powered plant, you could do the dirty and switch to H**nda power - then all you'd need is 'only' around five grand for a basic V-Tech unit. Put in these terms, the Duratec seems like a cheap motorsport unit.

Fast Ford November 2003 More Power

You can obviously go beyond these figures, because until now we've not even taken the cam cover off. Do this and fit higher lift cams, which there's just enough room to squeeze in. That said, pocketing the pistons and much better valve springs is necessary, and this will provide up to 25 bhp more. The standard valve springs are light in both weight and strength , as well as being progressive. This makes for a very svelte, efficient drivetrain but can result in coil bind because of their length. The problem is that space is incredibly tight to get a bigger spring and follower in their place. However , new ones are available from Kent Cams/SBD.

SBD's own cam design is slightly different to comparable aftermarket makes in that duration of the intake valve is deliberately less. Their theory is, you keep the combustion ratio up slightly higher and produce more torque if you compress the gas you've got more, rather than try and cram a greater amount in. If you examine cams like for like, SBD's may not produce any more horsepower, but it will give more torque. And that, as we know, is where the oomph comes from.

Another area that can do with a bit of attention is the flywheel, which in standard form is a whopper, weighing in at around 12kg. Again this is for emissions-friendly purposed. SBD's own purpose-made unit weighs in at around half this, contributing to a freer-revving engine.

The Limit

There's still more you can do. But, as you'll have gathered by now, the Duratec is primarily intended as a production unit. It certainly isn't a Cos YB, which is really a race unit in seriously detuned form for production. In this case you have a cast-iron block, made virtually bullet proof in the 200 motorsport version - something you'd never get with any alloy type. On top of this, everything's made with race in mind from the steel crank and semi-steel rods to the head, which can be hogged out as much as you like to produce the power.

In truth, the Duratec is great up to a point and the limit is around 245 bhp, although we would suggest that the 2.0 litre should be rated 230-235 on standard rods and pistons. Yes, you can tune it further but this breakpoint is significant because if you go beyond it the unit's cost-effectiveness goes out of the window. Those spindly rods, cast pistons and acceptable bearing won't take any more power than this safely. Consequently, the amount of components that will need replacing beyond this point is huge. You take the choice - parts are available but the unit becomes as costly as any other race engine if you want to produce power beyond this point. And that applies to turbocharging too - and no, we're not talking RS Fucus either. It might say Duratec on the rocker cover but in truth this motor is the final derivative of the Zetec. It isn't an I4 Duratec. So retrofitting a blower and you would get gains from a very mild amount of boost on an otherwise standard engine. Go beyond that 245 bhp figure, however, and you're virtually guaranteed to get huge failures.

So in conclusion, your best bet is the plug and play route, along with induction changes. That isn't forgetting that you can upgrade the existing ECU in, say your Mondeo - but don't expect wild bhp gains beyond the few you'll get with a standard chip, filter and exhaust. The ECU in this case is a central computer which is as much likely to control how long the interior light's left on as the injector timing. The motorsport route on the other hand, as we've discussed, is to bin the lot and start again with a purpose-built unit controlling throttle bodies/carbs. This route is currently the favourite in terms of Caterham/kit car applications but as far as uprating your Mondeo - or new Focus - goes, controlling the rest of the car remains open for now.

 
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