Silverstone Preview

Sunday the 6th of May 2018 @ Silverstone International Circuit in Northamptonshire, UK.

To re-cap, our plan for the seasons shakedown day was to run the gearbox in session 1 and then get up to speed, adding boost through session 2, 3 & 4 with session 4 getting close to qualifying benchmark speeds. Session 1 went perfectly with no problems with the re-built box, all gears being selected comfortably and no leaks. Session 2 we piled on the boost and started to get closer to the limit, dialling back in to the cars handling and beginning to trust it once again. It is session 3, with more boost we ran in to trouble. During the session the dash reported low oil pressure and I could see we were running much lower than I would normally expect. We headed in to the pits, broke out the data and confirmed we had a problem which was getting worse.

The red box shows the oil pressure over the duration of the test. Session 1 was typical for last year. Session 2 the pressure dropped progressively. Session 3 the same pattern continued but with a additional sudden drop highlighted with the red arrow.

Back at the workshop the engine was dropped and on taking off the sump we found the main bearings had spun and caused scoring. There was a large amount of metal in the oil so we also took the cylinder head off and found two pistons in the inlet side had valve marks on them and the cam lobe had been rounded by the corresponding valves.

What is easy to understand is the valve / piston issue. This was most likely caused by me over-revving the engine on a up shift, ie instead of going from 4th to 5th, 3rd was selected by mistake and causing the engine to over-rev. This engine has been subjected to my incompetence three times so far, the first took the revs to 8,035, the second was 8,550, both done during a 6-hour race at Silverstone October last year. The valves and cams were checked and looked ok based on a visual inspection prior to this test. The third time it was over-revved was during session 3 and 7,648 revolutions were recorded. I should point out the limiter is programmed at 7,200 and the red line at 6,800. During any one of these times there is a chance that the valve and pistons became ever so slightly out of time and contact was made, bending the valve ever so slightly. As all of the components in the engine are super strong this didn’t cause a catastrophic failure there and then but as the valve never fully closed, caused the wear on the cam. Power wasn’t noticeably down on the engine as boost overcomes all and simply compensated for the lack of compression on the two cylinders.

The main baring issue we believe was caused by the drop-in oil pressure however cause of this is less clear cut. There is a chance the metal being shaved of the cams contaminated the baring, caused the wear and that caused the oil pressure drop. We believe what is more likely is that by adding boost, we increased the oil temperature. The car has an oil cooler fitted but on reflection we could have installed it in a more effective manner with added cowling around the radiator to ensure the air is forced through the airwaves instead of simply spilling below the radiator and underneath the car.

All this means we need a new crank, new cam (inlet only), new valves (inlet only), new shims, oil temperature sensor fitted and cowling around the radiator. With the bank holiday weekend in between the shakedown and race we only had 4 working days to get all this sorted. The whilst the parts were all in stock, building up the head & the valve clearances is not something which should be rushed, and the top end needs some sort of a run in. It was with regret we took the decision to with draw the car from Snetterton.

The good news is that the cylinder head has been re-built complete with valves, shims and cams and the crank is all ready to go back in. Once it is all back together and we are going to try and get a test session done between now and next weekend to make sure it is all ok!

After the disappointment we are looking forward to the second round at Northampton’s Silverstone International circuit. The engine re-build from the season shakedown continue and all fingers are crossed we will be ready in time. We have booked another shakedown at Snetterton again on Wednesday so hopefully things go better this time.

In early May the weather could still be kind to us and spread liberal amounts of water around but looking at the long range forcast it will most likely be dry all day. This year the club has opted for the International layout taking in the newer section as well as the Formula 1 grid complex. With long straights and fast corners, we will be at a slight disadvantage against the competition in the dry, but that is racing and it is the same for everyone else. There is a full grid of 44 cars entered with reserves and cars to note in our class or fighting for overall victory includes a TVR Tuscan Challenge, seemingly hundreds of BMW M3’s and a Z3M, a fellow ex rally car in the form of a Subaru Impreza WRX, Porsches 968 & a 993 911 and the drifters favourite Nissan 200SX. Having raced with most of these competitors over last year the race will prove challenging and we expect the TVR Tuscan Challenge and a super quick Porsche 911 Turbo car to drive off in the distance with their massive power advantages. The BMWs can never be ruled out as their long wheel base, excellent chassis balance sees them carry speed in to and through the apex better than nearly all the cars on the grid. A good result in the dry would see us finish in the top 8 and we are dreaming about matching or improving on our best dry result at Donnington of forth overall. Clearly in the wet with four-wheel drive, nothing short of a win will do!

We had some success at Snetterton in a Renault Clio 182 a few seasons ago and managed a second in class, watch the video here: http://www.youtube.com/watch?v=ICQ2DkAOyJ4  and other races here (with crashes): http://www.youtube.com/watch?v=gOLkWghQIR8

Stay up to date with live timing here: http://www.tsl-timing.com/event/181864 We will also be trying out broadcasting live during qualifying and the race. Stay up to date on Facebook and YouTube for the latest announcements.

rthurbin

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