Shortshift

The only comment I'd make about your choice there (above), James, is that the initial failures (from 2008 through to around 2010, when the conical VS60 spring was introduced) all occurred with straight Kent springs that are otherwise unidentified.

Just make sure you're not leaping out of the pan into the fire...  Maybe better to move away from Kent altogether, perhaps to the Cosworth, SBD or one of the Piper alternatives, unless you can be sure that your chosen Kent spring isn't the spec that caused the very-first failures? 

I know I'd not re-fit a Kent spring to my car because I'd always be worried.

James

Good work, James.  This is really rather fascinating. 

The R500 has a soft-cut at 8,500rpm and a hard-cut at 8,600rpm (well above the R400 rev limit) so enthusiastic track driving will likely result in regular operation in the 8,000 to 8,500rpm band.  It seems your thoughts on resonance fit well with this, with your R400 having failed inlet springs only whereas my R500, operating at higher engine speeds, has failed both inlet and exhaust springs.

I've been digging a bit too, including looking-up valve spring rate data which I table below.  In some cases, the figures are as-quoted by the manufacturer/supplier; in other instances I have had to do some rough estimation from data that I have been able to access.  However, even if not 100% accurate, I think the figures are good enough for comparative purposes.

James

Kent VS60 single                                       35 N/mm
Kent VS59 double                                     37 N/mm
Piper VSSDUR single                                42 N/mm (242 lb/inch)
Piper VDSDUR double                             52 N/mm (297 lb/inch)
Cosworth YD0093 single                         tbc
Ultimate Power single                             tbc
SBD VLSK-DUR-01K double                     44 N/mm

Just measured one of my now-removed springs and, as near as I can measure with my digital calipers, all dimensions are identical to the figures you have provided, James, apart from coil count where I'd say my spring comes in at 6.5 turns, end-to-end.

If these are Kent VS60 springs (and I suspect they are) then I haven't been able to find a quoted rate for them but, working from the Kent Cams spec sheet (using known free and installed lengths with their quoted installed load) then I calculate the rate to be around 36N/mm.  Very close to your 40N/mm measured figure.

I'll get the actual rate measured when I can but these two springs (your R400/420 and my R500) look spookily similar.

James

Thanks James.  So, different cams in the 400/420 compared to the 500 (as you'd expect, really) but I have a sneaky feeling that these conical Kent springs from circa 2012 might be common across both car types.

I'll see if I can get mine measured and rated when I am next round at Premier Power. Stuart works fast so it won't be long till my R500 is fully fixed and ready to go.

James

Replying to #4:

I wonder if the R400/420 valve springs are the same as those fitted (in the corresponding period) to the R500?  I know that 400s/420s were built with an uprated (Kent?) cam and uprated (maybe also Kent?) springs, so perhaps the cam and springs are common across these two model types? 

Your springs certainly look similar to mine, James - conical, mostly open and even winding of coils, etc.  And your car and mine are both 2012 builds.  Do you have any information on the make/brand and even part number of these springs?  And, for completeness, do you know the type/model of cam fitted?

James

No - none of the alternatives mentioned above are standard Ford parts.  All are third-party upgraded springs, intended for use in high-lift (11.5mm with the Kent Dtec 35 cam used in the R500) and high rpm applications.  Some way away from standard Ford Duratec fitment!

James

A cautionary tale...

My 2012 factory build, 10,000 mile car has just fallen victim to the dreaded valve spring failure issue though, almost unbelievably and thanks to great fortune, my engine has escaped from being subjected to any further damage.  In fact, on strip-down (thank you Stuart at Premier Power) we found that no fewer than four springs had failed - two inlets and two exhausts, and that on one valve, half of a valve collet had come out of its retaining groove!  And yet somehow, despite all of this, none of the valves had dropped into the cylinders...

To summarise what I think I know about valve spring history here:

• It seems that early R500s (let's say from 2008 until 2010/2011) were build using a 'straight Kent spring' and it is these items that are widely known to be prone to failure.  There's no shortage of reported failures and tales of (mostly) expensive engine rebuilds as a consequence.
   
• Because of these failures, it seems that Caterham Cars changed the valve springs around the 2010/2011 timeframe and moved to a 'conical Kent spring' but these were fitted for only a short period, possibly until 2012 or thereabouts.  Maybe these springs were also found to be failure prone which prompted their replacement in factory build engines after such a short time; it certainly appears that my car was fitted with this type of spring which adds credence to the view that these, too, should be regarded as suspect for the R500 application. For reference, I believe these are likely to be Kent VS60 springs.
   
• Finally, around 2012 or 2013, Caterham Cars changed the spec again and moved to a 'conical Cosworth spring'.  I understand that these have been fitted to all 400/420s, 500s and 620s since that time (not sure about 360s?) without any known issues and I believe they are still fitted to these engines as of today. For reference, I believe these springs are Cosworth part number: YD0093 (and Caterham Cars reference 30E365B).

If anyone can add to the potted history above, that would be great.  Though I think it's pretty accurate, I'm very happy to be corrected if anyone has better information.

Back to my car, my engine.  I had thought that, being a 2012 build, my car was likely fitted with the final Cosworth spec springs but on stripping-down it's clear that this isn't the case.  I gambled and lost, though in losing I have been very lucky indeed.  However, I hope this tale encourages all R500 owners in particular (and anyone with a 2-litre Duratec that was built before, say, 2013 and which revs beyond 8,000 rpm) to really find out what springs are fitted and, if in doubt, change them all before a costly bill is incurred.

To finish my story, I have followed Stuart's advice and the cylinder head on my car is now being rebuilt with Piper twin-springs.  This arrangement is Stuart's preference and he has built many performance Duratecs this way without issue over recent years.  Whilst I would have been equally as happy to have had the conical Cosworth springs fitted, as Caterham Cars have done for around ten years or so, I do like the idea of the second spring being there to save the day in the event of a main spring failure.   Very, very unlikely to happen now, I know, but once bitten...

Once again; not a call to check your nuts but, rather, CHECK THOSE SPRINGS!

James

All sorted now!

James

I've posted before but I'm still looking!

Anyone??

James

Hi Finlay

PM sent!

James

As this thread continues, it becomes increasingly clear that the design appears to be poor in so many respects, including that it can be assembled with the through-bolt, collets and washers in the wrong order without any indication that this is incorrect.  Assuming that this is a critcal assembly process then it should have been made error-proof.

From what I've read on here, the specified alloy is also an incorrect choice (prone to failure at low strain, effectively insufficiently ductile and correspondingly too brittle), there could be some dimensional issues (for instance, possibly allowing the damper body to contact the upright and act as a leverage-increasing fulcrum on full rebound and) and the general concept of the expanding collect and washer arrangement (promoting high levels of hoop stress in the lugs) are all also points of concern.

Furthermore, it has to be recognised that the probable failure mode can be far more serious than the usually benign failure of a coil spring in a 'normal' road car - which often goes undetected by the driver until the failure is spotted on inspection or during a service.  From posts above it looks likely that a failure of one lug (it seems that it's usually the cap-head and collet end that fails first) may go completely undetected, with the remaining lug carrying all loads until it, too, fails without warning.  The consequences of a sudden failure along these lines could well be serious indeed - the yellow car in Scotland that ended up in a field below the road reinforces the point.

Having kept quiet on this for quite some time, I do hope there's a resolution underway that will be made available for all factory-spec CSRs to reflect the magnitude of problem, concern and possible consequences.  And I don't just mean fitting Luke's brackets without an appropriate degree of engineering assessment and validation work having first been carried out on that design; the offered solution has to be fit for purpose in all respects.

James

Replying to #178:

So, would the incorrect assembly of the clevis pin and through-bolt arrangement have been a contributory factor in the failure on Steve Marsh's car?

And can Steve shed any light on whether the car might have been assembled in that incorrect condition from new (assuming his car is a factory build) or whether that corner might have been subject to 'servicing' at some time after initial build?

James

Err - so am I having a bad day or is the bolt reversed in one picture, relative to the other?

James

Does the photo at #167 represent the correct assembly of the through-bolt, spacers and collets?  I ask as it is different from images posted earlier (in the 'other' thread, by Hanns Per):

 

I know that the CSR build instructions are quite clear but I can't find those at the moment.

Anyone able to clarify?

James

Ref #8:

You mean: Pins 5, 23 and 24, James??

James

Replying to #5:

Yup - and as you've mentioned before James (Aerobod), these programmable pins are features of the more recent 9Ax architectures, and are not present on the older 992 spec ECUs.

Replying to #6:

Yes - if you cross-refer the diagram I have posted with the pin-out table that James (Aerobod) has reposted (that's the more commonly published chart), you'll see a number of pins which offer 0V, including #5, #23 and #24.

James

Chris - it's not a Caterham-specific diagram but, as is the case with the more normally published ECU pin-out tables, it depicts a generic MBE 992/9A4 configuration (including, for instance, other features that are not normally found on a Seven, such as power shift, traction control and so on). 

So you may have to overlay your own individual power-supply circuitry (cut-off switch, ignition switch, starter button, etc) but as far as ECU inputs and outputs are concerned it's 100% - and complements the usual pin-out tables perfectly.

James

PS: Are you sure that your ECUs are permanently powered, even when the car is keyed-off?  I'd find that rather surprising; are you sure that 'permanently powered' doesn't mean 'through the ignition switch'?

Came across MBE9A4 4Cyl COP-1342.pdf and thought it worth sharing as a diagram to complement the usual pin-out table that is often seen online for use with MBE 992/9A4 ECUs.

I found this chart useful for a number of reasons, including that it helps to show a numpty like me the 'switch to earth' functionality of the ECU for injector and coil firing.  Somehow, this diagram makes it all so much easier to visualise and understand.

A small, additional point that I have commented on elsewhere; the diagram shows that the cam sensor return should be connected to 0V at pin #23 (which is how they are wired, ex factory) and not to pin #31 as has been mentioned previously on Blatchat.

James

Well, this probably gets some sort of prize for dredging-up an old thread (7.5 years and counting) but I've found something that I think is relevant here and worth sharing, relating to 992/9A4 ECU pin-outs and wiring.

James (Aerobod) made the recommendation back in 2015 that the cam return should go to pin # 31 ('cam sensor return') and not to pin # 23 ('0V') as our cars all seem to be wired ex-factory from Caterham Cars.  I followed his advice and rewired the pin-out accordingly - oh, how I love working on that 36-pin connector...

However, I've just come across some further information from MBE which shows that the wiring of the cam sensor return to 0V (and not to ground) is very deliberate. 

The pdf is attached MBE9A4 4Cyl COP-1342.pdf and I'll load a lower-resolution image in this post as well.  Food for thought?

I'll also make a separate post in TechTalk to make the diagram more readily available.

James

Replying to #164

Oh - did it ask for VIN?  Sorry - I must have forgotten that!  (I was thinking that many of us use personal plates on these cars, so age - of car! - wouldn't be clear).

Thanks, Sam.

James

Me too.  Slightly surprised that, in neither this latest questionnaire nor in the earlier one, has a question been asked about the age of the car.  I would have expected both age (or build year) of the CSR, as well as mileage covered to date, to be parameters worth capturing.

James

Hi Paul

Any update on the length of your hoodbag?

James

The alternative solution, that I went with, was to purchase a replacement detachable swan-neck towing hitch.  In other words, not the hitch specifically intended for my car but one for a different car, but made and supplied by the same tow-bar manufacturer. 

From memory, the tow ball I am using on my Macan is from a Volvo of some sort.  I recall that I viewed the alternative hitches online, where I could see the different drop-heights, to decide which one I needed,

James

Hi Paul

Apologies for the delay - I had to go hunting for the S3 bag I have which turns out to be 90cm long.  So an SV/CSR bag would be longer than that - around 100cm or thereabouts? 

Hopefully yours will fit the bill...

James

I'm looking for a hood bag for an SV/CSR if anyone has one available.

James