Less good was the chargecooler pre-rad which showed up how undersized it was. Further investigation is required but it looks like a doubling in efficiency of the pre-rad is required. A change to a proper rad, rather than the oil cooler may resolve it, as might a change to a normal style radiator.
Pretty much all the time I was out I had passengers, all of whom seemed to be converts to the joys of sevens and turbocharged ones in particular. The instructor I had with me for a session is now desperate to take the car out himself. The car behaved impeccably throughout and I managed to get some interesting data from the temperature probes that I'd added to the plenum, air filter and chargecooler reservoir. Plenum air temperature peaked at just over 60deg;C which is consistent with expectations after my experience at Snetterton. The suprise was quite how hot the air was at the filter at 53°C at times. Granted there is some hot air coming from the oil cooler etc but I wasn't expecting that sort of level. This wilk obviously cause the chargecooler to work harder than it should have to so some ducting will be added to keep the air taken in as cool as possible. There was also a little surprise at how cool the oil cooler was actually keeping the chargecooler water, peaking at around 40C but averaging in the mid 30s when being driven fairly hard. It's worth noting that the car never really cooled down between sessions so the water was hot from the word go.
All the data from the temperature probes seems to indicate that the chargecooler itself will keep inlet temperatures withing 15-20C of the water temperature and thus the water temperature is critical. Although this isn't really that surprising it's now obvious that to work as effectively as a large intercooler the water temperature needs to be kept very close to ambient temperatures. Now because the rate of heat transfer is proportional to the temperature difference between the coolant and the airflow the job gets much harder as you get closer to ambient. With the current setup we had water temp of 40C and air temp of 20C, giving a difference of 20C. To get down to 30C I need to double the size of the pre-rad, to get down to 25C I'd need to double the size again!
The upshot is that I've now got a 41 row oil cooler on order to experiment with although I have a suspicion that it will restrict airflow to the radiator too much. If that's the case then a low core density water rad from Pace will be the (costly) answer.
I managed to do about 150 track miles and would probably ended up nearer 200 but decided to call it a day when one of the cycle wing supports sheared on me. It looks to have gone at one of the welds so hopefully a phone call to westfield on Monday should sort that out.
As the day went on I grew in confidence and started to get a few corners right. By the look of the datalogs I've improved an awful lot since last year. Unfortunately during what was to be my last session of the afternoon I suddenly lost all power as I passed the pits. Coasting to a stop on the grass it was apparent that something had gone very wrong, the tattered remains of the cambelt were the giveaway clue.
Back at base the root cause was traced to a loose temperature sensor that had been ingested by the belt and the valves had then made repeated contact with the pistons. The plan now is to drop a temporary replacement in to get me back on the road and then rebuild this engine over winter, fitting in the odd upgrade here and there.
A new engine has been sourced and it became apparent that more of my install was more non-standard than I'd anticipated which led to a great deal of faffing to transfer parts over. When I rebuild the old engine I'll be duplicating all the changes. Whilst the engine was out I made a few changes to the car; a new pre-rad, some modifications to the chargecooler and a lightened flywheel. I had bad experiences with the flywheel in the Tiger that I used to own but I'm now convinced that in that case it was the progression on the carbs rather than the flywheel. A lightened flywheel on a YB, is absolutely driveable and indeed a joyous thing.
The new engine was finally installed and running with just 72 hours before we had to leave for the tour so the car was relatively untested. Catherine was a very reluctant tourer but in the end she was converted. The tour took in 1100 miles of excellent roads with 40 or 50 other cars including a 1959 series 1 lotus 7 and a bike engined 1960 lotus! Apart from a sticky throttle cable the car behaved impeccably.
In terms of runs it was a bit disappointing, it was heaving so I only managed to get 2 runs in. The first seemed to be technically pretty good, I got off the line well, timed the changes well but as soon as I changed into third the car seemed utterly gutless.
The AP22 had that down as a 13.9@99.2 mph, official timing had it at 13.5@99.9. All the AP22 times for 60,330ft and 1/8 mile are all .35s slower so I think the AP22 is picking up the initial twitch as I dump the clutch whereas the track timer only starts ticking as your wheels roll off the line. Still the speeds at each of the checkpoints are all within 1mph of the track timings and once that "twitch" constant is factored out it's impressively consistent with the track timings.
Once I got back into the queue and had the bonnet off the cause of the power loss was obvious - a boost hose had come off. Once everything had cooled down it was just a case of groping blind underneath the car to loosen, adjust and refasten the jubilee clip. AP22 analysis is saying that it never saw more than 205bhp on that run which coincides with the bottom end of 3rd gear.
The second run was a bit of a mess really, I hit the limiter in 1st and 2nd, short shifted third but ended up with a 13.1@114mph (13.3@118 on the AP22). I think the main lesson is that drag racing isn't easy and I *really* need some practice, at least now that I know that the AP22 is accurate I can get some in. Despite the way things went it was still good enough to place me 13th in the Castrol Challenge which isn't too shabby really.
Bloomin brilliant day. They were running a twin circuit format, so for the morning we were running on the combined South and West circuits, then in the afternoon they added in the North and East to make up the full GT circuit.
There were about 65 cars in total and they were letting 40 cars out on the 3 mile SW circuit and 50 on the 3.6 mile GT so there was loads of space and never any queueing. People always moan about how boring airfield circuits are but Bedford is completely unlike any other airfield. The surface is silky smooth like a proper race track and it has real character with proper corners and curbs rather than coned off bits of runway and access road.
Facilities were good too, pits with a compressor, free drinks and biscuits, decent rest areas, good restaurant and cheap super unleaded. For next year they're adding tyre changing facilities which will be handy.
The mix of cars in attendance was intersting as well, there was only one racer there using it as a test day, a formula 750 that seemed to crawl around but stayed out of everyones way and there was a total absence of chavved up motors. As a result driving standards were exceptionally good, better than the last couple of BaT days that I'd done in fact. The only slight discourtesy that I saw on the day was an M3 that was reluctant to lift on the straight to let people past. Apart from that everyone kept a good eye on their mirrors and was only too eager to get out of the way.
The car behaved brilliantly and apart from a complete loon in a 911 the only things that could keep up were a Caterham CSR260 and an elise with a 350bhp audi turbo conversion. Chatting to the CSR guy we worked out that to all intents our power to weight ratios were identical and if I was following him I felt he was holding me up and when he followed me he thought the reverse was true so we were pretty evenly matched. The odd thing about the elise is that he was a little quicker through the corners but despite his far superior aerodynamics I could reel him in on the straights - most odd.
The only slight glitch was a brake balance bar locknut that wouldn't lock and an inside rear that kept locking up under heavy braking. The two are unrelated but annoying teething problems in the new braking system that I need to sort out over winter.
Looking at the GPS logs since I got home it appears that on the SW circuit I was doing 141s laps whilst on the Gran Turismo circuit it was around 185s.
The plan for next year though will be Bedford, Rockingham, Donnington and possibly the 'ring. Snetterton I'll probably skip until they've finished the circuit redevelopment.
A long time since the last update and a lot of events that I've been too busy to write up.
An event organised by Javelin at Waterbeach, just down the road from us was too good an opportunity to miss. The event was unusual in that it was timed and also that they were running a sprint lane in parallel with a 1/4 mile drag lane.
Since the queue was generally shorter for the drag lane and I had a set of tyres that needed using up I spent most of my time burning up the drag strip refining my technique. I got 15 or so runs on the drag strip in and it was instantly apparent that starting in first was a waste of time as second gear worked so well, it was just a case of controlling the wheel spin. The critical aspect was keeping the wheels spinning for long enough that you could ease off for a nanosecond to regain traction without bogging down.
I was finding it relatively easy to get consistently in the 12.1s and 12.2s but either missing a shiftpoint or wasting time bouncing off the limiter with the tyres lit up as I fishtailed away from the line. On the second run after lunch though things came together and I posted a time of 11.760s @120.65 mph. My previous attempt on a dismal day at Santa Pod had only yielded a time of 13.1s so I was somewhat pleased with myself. After the next run I checked the tyres for wear and noticed canvas showing through so called it a day on the 1/4 mile satisfied that I'd achieved my dual aims of killing the tyres and learning how to do a drag run.
Having spent most of the day on the drag strip there was only time for seven or eight runs on the sprint course once I had swapped to some "wooden" road tyres. The course was a very tight and technical course that ill suits the car but it meant plenty of opportunity for sliding the car around and indeed sliding the car seemed to be the best approach. The slightly depressing aspect is that although I kept getting faster I realised towards the end of the day that accelerating out of corners although my brain said "faster please" my right foot decided that in fact it knew best and that half throttle was plenty fast enough really.
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