The problems...

Following the Rockingham track day, the car definitely felt like it was missing something at the top end of the rev range and the stuffing was once again blown out of the exhaust in its entirely.

Managed to get on to Surrey Rolling Road for a back to back session with 2 Caterham Super Graduate cars and a Mega Graduate.

the results weren't that encouraging.  In contrast with the lasst rolling road session, it appears that the car was running on the lean side of things, especially at motorway mileage and was recording only 163.4bhp @ 7200rpm.

What's more, the torque figure was under 125lbft which is even worse than the last session.  Setting the fuelling correctly gained 5lbft of torque across the whole range, but the car was still dropping very rich at 6250rpm.

On getting home, we then discovered that the alternator lower mounting bolt had sheared off in the block, allowing the alternator to swing down and the belt to come loose.

What next?

Well, it looks like a compression test and a leakdown teste, followed by a borescope down the bores to take a look.  We'll inspect the top of the pistoins to see if there has been any damage from running lean and work froom there.  The plug gaps have grown by nearly 10% sincne the engine was put back in the car, which is a worrying sign that there's been some detonation.

The plugs were nice and clean however, so the run home looks to have been at the correct fuelling.

Updates will be poosted here as i make more progress.

Update 1 (26/09/2009)

Compression test shows 210,210,210 and 220 across the cylinders and a leakdown test shows nothing amiss.  To ensure that everything was ok, I ran the tests back to back with a Caterham Super Graduate that had a brand new engine in it (only 200 miles old) for comparison purposes.

To eliminate any possible problems on the exhaust front, I have taken the car over to Powerspeed to check that the manifold and collector are OK and to investigate anything on the outlet side of the engine that might restrict flow or cause a dip in the torque curve.

Once that's back, I'll then be checking the operation of the VVC mechanism with Ronnie and possibly whipping the cam cover off and checking the mehcnicals on the mechanism.

Final task will be to whip the head off, do a skim to raise the CR to 10.1, make sure that the inlet ports are properly matched and then re-fit with cam timing set correctly.

Update 2 (03/01/2010)

Well, we have found the problem.  Having gone through yet more tests with Ronnie Gibson and Dave Fender (both caterham 21 owners and both ex rover engineers), it appears that the VVC mechanism is not functioning fully.  I have included the report from Ronnie below....

"Upon closer inspection of the VVC mechanism (cam cover removed), it was confirmed using pegs in the alignment holes that the VVC mechanisms (front and rear) were mechanically synchronized correctly. However, it also became apparent that the control mechanism had excessive friction/stiction and did not move freely as expected. The Hydraulic Control Unit (HCU) body was also removed for inspection during this process, and the force required to move the Piston/Rack Assy was excessive and indeed sometimes it would stick completely. Note, as demonstrated on the bench with another cylinder head, the piston/rack assy should move smoothly in and out of the cam carrier bore when a ‘reasonable’ force is applied, but this force should not be excessive.

It was also observed that the rack teeth were impacted, resulting in a slight spreading of the teeth at the edges. This has resulted in the rack machining the bore in the cam carrier, which was evident from swarf in the bore and in the rack teeth themselves, together with corresponding marking in the bore and on the rack shaft.

The HCU was cleaned, refitted and the engine was run up to fully warm temperature, then the VVC Target Periods were checked using the laptop. Up to 250 deg (approx) the system was achieving the target. However, anything over this target value could not be achieved, which is consistent with the mechanism sticking. In addition, when the target value then dropped below 250 deg, the mechanism remained stuck for a short time, but then regained control and returned to the idle value at 225 deg. Clearly if the target period is not achieved at the desired speed/load site, the operating conditions will deviate from those used to calibrate the basic air mass calculation, fuelling and ignition values of the engine. It is difficult to predict the precise behaviour, but clearly this would cause significant engine running symptoms at mid/high revs and then upon return to low/idle rev conditions.
Although our investigation did find the final root cause, it is clear that the VVC mechanism has excessive friction/stiction and consequently the HCU piston/rack assy has experienced abnormal loading. The head should be removed, disassembled and the root cause of the failure in the mechanism should be identified. It is also our recommendation that the engine should not be run in its current state. The head should be replaced or rebuild with known good/new parts and the complete mechanism should mechanically operate freely as demonstrated"