Duratec in detail

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pete
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Re: Duratec in detail

Post by pete » Wed Aug 17, 2016 2:10 pm

campbell wrote:If you're bored, we've a Soapbox project to finish this week, David ;-)

Fabulous insight and hope you have enjoyed yourself. Such patience and attention to detail.

So. What's next...?

I expected you to have sent a Campbell family snatch squad to enlist David's help...
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Re: Duratec in detail

Post by David » Wed Aug 17, 2016 2:14 pm

campbell wrote:If you're bored, we've a Soapbox project to finish this week, David ;-)


So. What's next...?
Loving that thread :)

Maybe dip my toes in some SMRC racing next year, but definitely the domestic life deserves a bit more time . . .
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Re: Duratec in detail

Post by campbell » Wed Aug 17, 2016 3:05 pm

Quite right.
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David
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Re: Duratec in detail

Post by David » Tue Oct 25, 2016 11:19 am

This year I really felt this project had peaked. Not because there wasn’t more performance available from the 2L Duratec, but because I had become aware how much stress a 2L 8500+ rpm engine was under. Three seasons was asking a lot - it was time to retire the engine to the spares corner in the garage.

Last year I had commissioned a new head with the intention of building a new zero hour engine for 2017, and that arrived a couple of day before the SLS final. Perhaps that was tempting fate, but the engine must have known its time was up . . . and it didn't want to go quietly.

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Picture courtesy of Richard Breakell

During the first hot lap in qualifying, I noticed a misfire going up Duffus (reverse direction). In hindsight, I should have abandoned the session at that point, but, with oil pressure and temps normal, I was keen to get a lap time. The misfire cleared for a while, but returned on the back straight and developed into a mechanical rattle as I approached the chicane. The throttle then would not close and the revving engine spectacularly ground itself to bits in a big cloud of smoke. I finally shut it down as I coasted to halt. I knew it was bad, but I was more upset about not finishing the event - my first time ever in the SLS.

Watch on YouTube

There was a fist size hole in the crank, but I sensed this was not a big end failure. The engine was rotating so freely, and with oil pressure normal throughout, it had to be a dropped valve, and that probably meant a valve spring failure.

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Once home, this was was quickly confirmed . . .
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The spring showing a classic fatigue fracture . . .
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It had logged 85 hours, all on track. That is on the lower end of what you might expect from a spring, but not outside the life expectancy with the cam lift and and RPM I was using. Kent Cams have offered to analyse the spring and I will take them up on that offer, but they initial response is that it was not a combination of cam profile they have tested. They say the spring was intended to be used as a duplex set. Strangely they supply seats and retainers to use it as single spring. The early R500 Duratecs do have a history of valve spring failures, but this one is a different spring. Personally, I suspect resonance played a part in the failure as the position of the break strongly suggest that.

The rest of the engine was essentially a write off, and I don’t intend to reuse any of the stressed parts in my new engine, but I’d be happy to run the crank, cams, drysump, remaining rods, pistons, valves, cams, in a ‘down rated’ engine.

For your entertainment, here’s some photos of the carnage . . .

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The dry sump damage to the windage tray, but otherwise intact
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The gudgeon pin circlip that jammed the throttle open.
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So what’s for next year?

As said, I’ve already got a new head, this time to an even higher spec (bigger valves and seats) with hotter cams - basically as far as you can go with the standard head. But what it will be matted with is still under wraps :) But it is looking like something a little bespoke. I’ll keep you posted.
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Re: Duratec in detail

Post by BigD » Tue Oct 25, 2016 11:33 am

Nice blow up there. Well done for getting everything out of it. Impressive.

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graeme
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Re: Duratec in detail

Post by graeme » Tue Oct 25, 2016 1:32 pm

Commiserations on the spring failure, and the DNF.

I have to say, I am looking forward to more posts on the next build though!
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Re: Duratec in detail

Post by Sanjøy » Tue Oct 25, 2016 1:37 pm

Great attitude, kick their ass sea bass.
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David
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Re: Duratec in detail

Post by David » Thu Mar 16, 2017 12:28 pm

Just a quick up date . . .

The engine was rebuilt to more or less an identical spec to the last one. It went on the rollers yesterday and performed faultlessly and returned an almost identical power graph. A little stronger towards the top due to a slightly different cam and overall a little more responsive. Here's it on the rollers having the transient fueling checked for the blipper - something I wasn't able to do last time as it was before the paddle shift was fitted.

Watch on YouTube

Edit just to say a 2.5L is still the long term plan, but the bespoke crank is taking a little longer (as these things do).
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Re: Duratec in detail

Post by David » Mon Mar 20, 2017 9:51 am

Just to follow up, here's the power curve of the new engine

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I say power curve but it's pretty straight and the the torque is strong and heading back up at the limiter. So I should easily get 270+bhp when it's rev'd to 8500 rpm. In theory, it should now run up to 9000 rpm with the new duplex springs fitted to the head, but I'm not sure I'd want to take the penalty in terms of engine life, so it'll be limited to 8000 for track days and 8500 for SLS.
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Re: Duratec in detail

Post by tut » Mon Mar 20, 2017 10:43 am

Presume that is flywheel David?

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Re: Duratec in detail

Post by David » Mon Mar 20, 2017 10:58 am

tut wrote:Presume that is flywheel David?

tut
Yeah, corrected for the flywheel, it made 227 hp at the wheels.
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Re: Duratec in detail

Post by David » Sat Apr 01, 2017 2:57 pm

After the original engine failed, I was very keen to build a 2.5L. In part to broaden my knowledge of the newer Duratec range, and partly as I wanted to explore a big low revving engine in Caterham. What put me off was that I was unsure how well the Sadev and Geartronics paddle shift would cope with the high inertia of the very heavy 2.5L crank.

However, about 18 months ago, I became aware that Ultimate Performance where developing a light weight 2.5L crank. They had already developed their own ‘long’ rods and slipper pistons for the 2.5L, and the combination was looking to be very promising at overcoming my concerns about the 2.5L. In fact, the rotating mass is similar to that of the standard 2L engine.

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So I’m pleased to say that Ultimate has shown a considerable degree of trust in me and supplied one of the first cranks to be manufactured. These are still to be run and tested in an engine, so I’m feeling a little privileged to be in the position of testing it.

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The parts to complete this build are all on order and the build will start soon with a target date of mid-June for putting it on the dyno.

More posts soon . . .
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Re: Duratec in detail

Post by David » Tue Apr 04, 2017 2:56 pm

The 2.5L is relatively new variation to the Duratec range and it has a slightly larger big-end journal. This meant that the bearings shells are not available in the up-rated materials yet. So with this engine, we have decided to use the Subaru VP2 shells which happen to be identical in journal diameter. These bearings have a notch, or tang, so the rods are bespoke and machined to accommodate them.

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The bespoke rods also gave the opportunity to rethink the factory spec and they have been made slightly longer and the gudgeon size has been reduced. This is to reduce both weight and improve geometry.

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The ARP2000 bolts, although nolonger my first choice in bolts, where the logical option and are well proven.

Pistons next . . .
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Re: Duratec in detail

Post by David » Mon Apr 17, 2017 3:40 pm

An update on the new 2L and how it performed at the SLS (my report posted from elsewhere)

After not feeling too well earlier in the week with some bug, and struggling to finish the car, it was good to get the car up and scrutineered on Saturday and relax the night before. But Sunday was so cold and wet! Struggled to get the car up to temperature all morning, but the new engine seemed to be holding together, albeit limited back for the day. Warm up, and practice, were really just checking and testing stuff, so no hot laps.

Qualifiction payed into my hands a bit and group 3 probably had the best of the drying track conditions. Knowing it was getting better all the time, went for it on the very last lap and got under a minute. That was second in class and fourth overall - really pleased with that! There's plenty more in the car and a few errors from me lost some time too.

Watch on YouTube



The Final was more or less dry, just a few wet patches off line. Did a 56.9 which was about as good as the car would do without a few more revs. The car seemed good and really fun to drive this year, the longer gearing is perhaps a little slower, but much easier to drive - Clarks to top of Duffus is now one gear.

Will miss May but looking forward to July
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Re: Duratec in detail

Post by David » Sun Jun 11, 2017 5:48 pm

It was back to the 2.5L project this week after a month off in the States. The crate engine arrived and I had a fun day stripping it down. A few quality issues on this Mexican built engine, but nothing I can't deal with.

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It gave me my first opportunity to compare the cranks - the standard one being 4 Kg heavier.

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The quality problems were relatively minor in nature but these things are always annoying. The engine seems to have been assembled in a poorly washed state and corrosion had taken place on many of the bolts and casting. Some alloy debris was evident on the head gasket and there were some scratch marks on the deck of the block - but not deep enough to require reworking. The main bearings, the part I was most interested in, was all in good order. Ford are usually spot on in terms of QC, so surprised, but I have since learnt the Mexican factory that build these engine (mainly for use in American commercial vehicle market) can be lacking at times.

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