Duratec in detail

[David]

Some may remember the 'Drying out the Duratec' thread ( http://www.scottishelises.com/phpbb/vie ... =5&t=23877 ) following the dry sump and roller barrel upgrade to my R400. Well that was three years ago and the engine held together and has endured many trackdays and sprint events. In fact, reliability has been excellent with no issues relating to the engine. But sooner or later that was bound to change so I'm going in with a preemptive strike this winter to completely rebuild the engine and carry out a few more upgrades. The 'upgrade program' is long term so all the potential will not be released in this rebuild but will include bits that will help prevent major work as the quest for power continues.

So the project got officially underway with the arrival of a CNC phase 2 head, forged rods, and pistons.



But be warned, this is a six month project, so post may not be that frequent!

[Gourlay83]

More power's cheating !

So, some head work and raise compression ?

I've got mine back now, still having a few issues after the rebuild... Hopefully just minor teething problems.

Look forward to seeing progress.

Alan

[David]

More power's cheating !


Alan

It'll be OK, I' put a secret switch under the dash for the 'quick' map .

The head is CNC ported with bigger valves. It takes it a stage beyond the Caterham R500 head but as I hinted above, the roller barrels and exhaust are not big enough to make full use of it. So I'm only looking at R500 power levels with this rebuild. New rods and pistons to allow some more RPM too.

[r10crw]

New heas looks nice although not sure what to compare to, Looking forward to seeing the old head versus new, when you taking the old one apart?
Keep us updated

[tut]

Not heard anything of Stu's engine build for a while.

tut

[Shug]

Looking forward to an interesting thread - lots of pic content please

[David]

When you start reading engine build blogs, you quickly realise that few, if any, professional engine builders write blogs. Perhaps that is not a surprising as their knowledge and experience has a commercial value.

So most blogs are written by amateurs, and their mistakes are often the entertainment. That’s not to say an amateurs can’t build good engines, it’s just that we are naturally distrusting of ‘anonymous’ individuals. Of course, if you happen to know them, you are much more open to what they are doing.

So, before I start this build, a quick résumé of my engine building experiences in the hope that you will see where I am coming from.



Early Days

With links to the motor trade, cars was never a problem so, by the age of 17, I already owned a Mini Jem. It seemed natural to take it to bits and, inspired by David Vizard’s book ‘How to modify your Mini’, I rebuilt the engine. After many hours grinding at the head, I almost doubled the factory power. The car was briefly hill climbed and did do trackdays at KH before I moved on.


The Mini Jem at Strathclyde Park hill climb in 1980


In partnership with a good friend, I started rallying. My role was the navigator, but with my engine experience, I tended to end up rebuilding the rather ‘soft’ B-series engine (and gearbox for that matter). It was difficult to get more than a 1000 miles out of it – but it was surprisingly competitive for a Marina!



Life moved on and I found myself as a flying instructor and the engines got bigger. I did some work (under supervision) on Lycoming and Continental aero engines of various sizes. The highlight was, without doubt, the Bristol Mercury of the Strathallen Lysander. The power runs were mind-blowing – but then anything that burns 80 gallons of fuel an hour is bound to be good.


I still messed around building cars, the Marlin Roadster was my daily runner and can be seen under the Lysander wing.

Towards the end of that period I spent some time with the AAIB at Farnbourgh - it was part of a trial CAA ran to increase accident awareness amongst flying instructors. It was probably the most influential period of my life and many of the things I saw there still haunt me today. My views on risk taking changed forever.

Married life and kids brought a quieter spell, but I still built engines, often just for fun. Fiat, Renault, Peugeot, and Volvo are among the different makes I’ve tackled. It was when Gordon showed an interest that we bought the Caterahm and performance tuning once again became appealing.

That's where I find myself today – loads of experience, but very little on modern engines with ECUs. The standard Duratec would have represented a highly tuned engine in my time. Much of the technology I’ll be using in this build was beyond the grasp of what even the top F1 teams had at the time I built my first engine.

So for better or worse, here we go!

[robin]

Cannot wait - enjoyed your history post - the Marina brought back memories of my mate's first car (well, it was his Dad's until we destroyed it)

Good luck with the build. When I was 17 we rebuilt a couple of ford cross flow engines, but I doubt we did a very good job but nothing since then. More recently I have considered rebuilding the bottom end of the K a few times, but always chickened out - I don't have the tools to gauge all the journals and work out which shell sizes to buy - in the end it always seemed easier to just replace the whole bottom end with one that was already built.

Heads are, by comparison, less daunting!

Cheers,
Robin

[tut]

Excellent résumé David, must be a lot of members on here that have a past that we hear nothing about.

tut

[Dominic]

Excellent résumé David, must be a lot of members on here that have a past that we hear nothing about.

tut

Interesting read. Looking forward to the build thread.

[Ferg]

The engine is obviously in good hands, but then your previous build threads have all been very interesting. Working on the Bristol Mercury must have been something special.

[pete]

Excellent - looking forward to it.

[David]

With the SLS dates published this week, the timetable in my head is falling into place. November was to spec and order parts, December will be strip and examine, January purchase consumables and resolve issues, February will be the assembly, March start up and map, and April run-in and test. All a bit tighter than I had hoped - mainly due to my new workshop taking a month longer than planned. But I moved in today and I'm keen to get going, even though a few building jobs still need done.

So lets start with the head!



It's of conventional twin overhead cam and 16 valve design



5 bearings per cam using the casting as the bearing surface.



The Duratec is a free flowing head in standard form, particularly the later high port head. This is a new high port head CNC ported by Ultimate Performance and fitted with +1 mm oversize valves. As this photo shows, it's pretty free flowing with head bolts, oil, and water passages carefully positioned to maximise port cross section.



The CNC porting (computer numerical control) has been developed by Ultimate since 2008. This photo shows the tooling finish.



and the exhaust side




There is debate about whether the finish is an important factor in the power output. I think it is now generally accepted that the shape is more important than the finish. A little bit of surface turbulence on the inlet helps mix fuel and helps prevent wetting of the surface.

This photo shows that the original casting still remains in places - only material that has been shown to help flow rate is removed. Interestingly the valves are 1mm oversize and shows that the original designers may have had this size in mind - possibly revised down after shrouding issues with standard cam lifts. It is possible to fit +2mm but there is little or no gain.



The chamber also indicates that the bigger valves where catered for.



Again there is some debate as to whether the valve seats need to be flared into the chamber. Flow testing suggests that the 'lip' does not interfere with flow - which makes sense as speed and direction of flow would be towards the valve head. But those who spend hours grinding them away may disagree.

The exhaust side is pretty open too. This photo shows no. 4 port with the EGR port casting. It has been blanked off.



I am going to use the original injector positions. This is not ideal as it is known to reduces peak power, but cost considerations mean that I intend to retain the Caterham/Cosworth roller barrels which use this location (probably due to packaging issues on the R500). As my target BHP is limited by SLS class B, this is not an issue short term. Longer term I intend to place the injectors within new (and larger the throttle bodies) The photo shows the injector hole and where it meets the port.



And finally the CNC is used to cut a hole for their label

[robin]

Nice. Roger down at SabreHeads has a flow bench, if you want to find out what your inlet/exhaust flow at various valve lifts actually is, he might be able to help.

Shame they didn't CNC their actual logo, rather than just a recess for a label!

On the EGR valve I see the actual egress is blanked off, but is that breach between the port and the EGR "cavity" going to be blanked off as well? If not I wonder if it might not alter the scavenge effect that you are presumably going to be going for with some sort of tuned exhaust? (Helmholtz resonator) Some rough maffs with guess work dimension based on the photograph suggest it'll probably be OK with a resonant frequency of 30Hz = 1800RPM, though it will obviously also resonate at the harmonics, just not with the same intensity. It looks like to blank it off safely you would need a milled "plug" to fill the cavity and return the port to being circular. Probably more effort than it would ever be worth ....

Cheers,
Robin

[David]

Nice to know someone with a flow bench and, if I had the time, it would be great to check out whether what I have been told is true.

This is Simon's graph . .



My cams give 12.5 mm lift so the theoretical BHP is over 300. In practice it is unlikely to anything like that (for many reasons), but it does show that there's little point spending too much time and money to try and improve what is already very good. Better that the money is spent on weaker areas such as the barrels and exhaust.

Interesting comment on the EGR - I had wondered about what effect the 'chamber' would have. It's a shame you can't order a head without it machined out, but I guess it's not that important.