Duratec in detail

[Mikie711]

Will watch this thread with interest as the Duratec will be at the heart of my Mk1 Escort build though not in such extreme state of tune

[robin]

Hi David,

It would be nice to know what they think the CFM equivalents of those numbers are. For your 2L duratec, 330BHP is going to need either forced air intake or insane spin speeds (I guess around 11,000 RPM?) - so I agree that's pretty pointless. One common number that's bandied about is BHP = CFM-flow * .257 * number cylinders. That would mean they were achieving flow rates of pretty much 320CFM at 15mm lift. Or am I misunderstanding their graph?

Also ignoring BHP to CFM conversion I am surprised by the shape of their curves which all seem to rise pretty linearly with valve lift; I think you'll see diminishing returns from increased valve lift beyond around the 10mm mark - indeed if you look at Rog's site (sabre-heads.co.uk) you'll see pretty much all the heads he's flow benched tail off by the time they get to 10mm.

Not sure if you've selected cams already but I would think that you'll not go beyond 12mm lift anyway? (I know nothing about Duratec engines, so perhaps 15mm is common there?).

From Rog's site - the CFM flow figures are at 1, 2, 3, ... 10mm of inlet lift - I've only copied the inlet as I suspect the exhaust doesn't feature in your curve.

"FORD DURATEC 2- 2.3 Litre(06 casting) Inlet- 35mm valves. All std parts. My flowbench.

23.93 50.74 74.46 97.39 115.27 126.38 131.94 134.05 134.17 134.86

As above, modded. All std parts.

24.08 50.15 73.92 97.65 119.22 135.95 142.57 146.82 148.65 151.4"

What sort of power output are you hoping for?

Cheers,
Robin

[David]

I've spent many hours reading all the data I can find. Probably the most interesting flow testing was done by one well know developer (now retired from building engines) who concluded the Duratec does not conform well to the 'classic' head model and many of assumptions and formulas associated with it. In particular he found that it is not possible to make the throttle bodies 'invisible' i.e. make them so big they do not impact the flow rates. The significance here is that many of the flow figures quoted are not achievable, whereas on other heads they might be.

I have chosen cams, they give a lift of 12.5 mm. That's about as far as I can go on single (up-rated) springs and standard followers. Certainly 13+mm is not uncommon on the Duratec using modified followers and dual springs. Again, the rule of thumb used on other engines don't seem to apply here. The cam profile is by ultimate (Simon Armstong) and should deliver about 260BHP at 8500rpm. He offers three cams which are roughly 220, 260, 300 BHP (and yes, there have been 300 BHP engines that do rev to 11000 rpm). In my case I thinking around 250BHP, probably at 8250 rpm, but it could be less as exhaust and roller barrels are on the small side. Simon has quite an impressive CV, I kind of trust was he recommends as he does all the R500 and FF heads.

At the end of the day, it'll be as good as the weakest link. I'm just hope I can spot and remove as many of them as I can.

[robin]

Ah good - maybe part of the reason that flow commonly levels off with increasing valve lift is because the tuners assume a certain maximum cam lift and shape accordingly; maybe if you chuck that assumption out of the window and start off with 15mm of lift then you end up somewhere else! Whatever, there are real engines that do this and that's what counts!

I remember seeing a Duratec install into an Elise; the installers removed a big balancer/counterweight thingmy that was driven by the crank via some gears - do they remove that for the R400/...?

What sort of balancing do you need for 8,250RPM - is it a job for VibrationFree-style balancing?

Cheers,
Robin

[David]

I remember seeing a Duratec install into an Elise; the installers removed a big balancer/counterweight thingmy that was driven by the crank via some gears - do they remove that for the R400/...?

What sort of balancing do you need for 8,250RPM - is it a job for VibrationFree-style balancing?

Cheers,
Robin

You're kind of pre-emptying my posts, but the Duratec 'Ranger' engine doesn't have a balance shaft and most people use this as a basis for tuning (Caterham included). The reason being was to cut costs on the less refined cars. In practice, it proved not to need a balance shaft and is considered the engine of choice - and, thankfully, the only one still being made.

Balancing: there's a lot to be said here, so here's a quote from me on another forum.

The Duratec is a modern engine that depends on delivering high efficiency by using extremely small tolerances. As it is not possible to mass produce the parts to the required tolerance, each part is graded so that it can be assembled with a matching set of parts. The block for example comes as grade 1, 2, or 3 and is matched to pistons of the same grade. Big end bearings also have 5 possible std sizes , and the main bearings a whopping 13 std options.


The selection chart for main bearings!

This put the fear of God into me when I first started working on the engine. It was only when I realised it was about reducing emissions that I relaxed a little. Tolerances can revert to normal engineering practices without any loss of reliability or power.

It may be controversial to say it, but unlike many engines, the Duratec is very well balance out of the factory and [edit: the crank] does not need balancing, at least below 9000 rpm. I've weighed my new rods and pistons and although within a gram of each other may investigate balancing dynamically.

David

[robin]

Cool

Do you have the tools to measure +/- 0.001mm? Would guess that temperature changes alone would swamp that measurement! Feel free not to answer until the natural point in your build comes along ... I am just being nosy!

Cheers,
Robin

[David]

No! As you say, without an environmental control, it is not possible. The good news is that this is the factory spec, and it is generally accepted that 'normal' tolerances are acceptable on rebuilds. In fact you can only purchase a single size of std bearing. Ultimately these fine tolerances are to reduce bearing size and friction. But, if you use good quality oils, a bit of extra clearance aids cooling and is no bad thing on a higher performance engine.

[David]

Time for a quick update . . .

Having thought about the risks involved with upgrading my existing engine, I decided there was a high possibility that I was going to end up with a non serviceable car for some time and putting myself under pressure to complete it prior to the start of the season. So, while the Duratecs are still cheap and available, I decided to buy a new engine and go for an all new build. The bonus of course is that I'll have a spare engine, should I ever need it.



So a nice shinny engine is sitting on my garage floor completely unaware of its fate.

[philthy]

I have an engine stand sitting doing nothing in my store in glasgow if you need one?

[David]

I have an engine stand sitting doing nothing in my store in glasgow if you need one?

Thanks for the offer - unfortunately I've been tooling up and just bought one from SGS http://www.sgs-engineering.com/garage-e ... gine-stand. excellent quality, and that price can't really go wrong.

[David]

Work has now begun on stripping the new engine down. I'll update this thread from time to time but for a blow by blow account I've started a FB page here: https://www.facebook.com/Duratec.in.detail

[David]

Just for fun . . .

This was the first day of stripping down the new engine

Watch on YouTube

[Kinger]

Brilliant video clip, keep them coming.

Cheers

[pete]

Brilliant

[David]

Finished the strip down this afternoon.

Watch on YouTube

Pleased with the donor bits and hope to post some more details over the next day or two.