Report on the annual Shell Economy Marathon, July 11th-13th 2006
After the Goodwood Festival of Speed, with attendant camping, late nights and early starts it was all a bit tight getting everything ready for our departure to the annual Shell Economy Marathon, held again at the excellent Rockingham Raceway, near Corby. Matters were complicated when Shell asked us if we could lend them our diesel powered ’Mouse’ for press use at the event. We were unable to get our hands on a suitable trailer so although the loan was not a problem, we were not planning on taking it. After various vehicle juggling involving TSR-1, TSR-2, our non-running Ford Sierra and a donated but nearly stripped Granada (350,000 miles on the original engine!) we got TSR-3 on the Land Rover roof rack (no spare minibus due to a big Biology department field trip), tools, spares, baggage etc in the back and my own petrol/LPG ’Mouse’ loaded onto my small purpose built trailer we were ready to go around 2.30. We usually take the unusual but normally fast route M25, M11, A14 but the Dartford tunnel, it say ’NO’ even though it was early afternoon and midweek. After that hold-up, around 3/4’s of an hour, we were away and drove non-stop to Rockingham, getting there a shade before 6 pm. Our cars were unloaded, polished, dusted, charged, driven briefly up and down the pit lane (useful driver training) and then it was back to the nearest Travel Inn (Kettering) where we usually stay and a nice big feed, followed by an early night. Next morning greeted us with a power cut, so no cooked breakfast for us, instead a visit to the petrol station for bacon and egg sandwiches. At least we got to the track in good time and as usual got in the queue for scruitineering, which we passed no problems....nothing like reading the regulations on the journey up, just checking we had not missed anything.....since last year!!!
With scruitineering over and drivers briefing attended the track opened for practice and away we went, briefly...TSR-3 threw the starter chain off and my Mouse had a front wheel puncture! Having fixed these early traumas it was the turn of the drive chain on TSR-3 to drop off. Closer inspection revealed that is was indeed out of line so an additional spacer was added, alignment and tension carefully checked and away we went....for a while. Although clearly quicker to accelerate, economy was not at this point looking good and as the day warmed up, the driver reported engine ‘stuttering’. Inspection concluded that in our attempts to streamline the carburettor we had removed vital cooling air and the Walbro ’pump’ type carburettor, normally allowed to circulate fuel back to the tank (and blanked off in the SMM application) had found that it could not pump vapour and so we had the starvation problem. Simply removing the gaffa tape fairing solved that one and from then on all went well, apart from our first attempted run failing on the second lap as the hydraulic brakes warmed up and decided to apply themselves. By bleeding out some fluid running clearance was once again restored and Joshua, our technical director and most senior driver was, after a lot of wriggling and squeezing, sent out to get the car ’on the board’. 40 minutes later we eagerly awaited the fuel consumption figure - 1,150 mpg - at last, we had cracked the 1,000 mpg ’barrier’ and by a good margin too. Next out was our new driver Daniel, fresh from making a good start in TSR-1 and then TSR-2. He managed 1050 mpg and was clearly overjoyed. We had a ratio in hand, so we decided to make the change up a tooth and see if it helped. Sure enough, it did, with Joshua managing 1175 mpg. With just one run remaining it all hung on young Daniel, could he beat the current leader on 1224? With nothing to loose other than the day getting hotter, out he went. Clearly learning fast, he delivered laps with increasing consistency until the 7 were up and it was fuel measuring time. The message came over the radio (comms worked faultlessly again) that it looked like a really good run and sure enough, once it was filled, an miserly 31.2cc had been consumed to cover the 10 miles at an average speed of 15 mph. This equated to 1426.3 mpg and put us over 200 miles into first place. Our nearest competitor still had one run in progress but by ear-wigging their fuel measurement were knew we had done it - first in the Autocar sponsored schools class! Pretty much since I first entered this competition way back in 1990 (I think) I have been trying to ’break’ 1,000 mpg, and now after fifteen years trying on a variety of budgets, initially one of nil, we have done it. So what now? Well, first place comes with some prize money so in conjunction with some hardware acquired over the years we will probably be going for fuel injection (see http://www.megasquirt.info/) and if there is enough budget a wide-band oxygen sensor (see http://www.techedge.com.au/). To test this and to fine tune the engine we need to get on and make a load for our rolling road (we already have a pair of rollers for drive-train testing) and an old exercise bike with a fairly huge cast iron ’load’ wheel. Quite how we calculate how it relates to the ’real thing’ will be something for my mathematicians/physicists to work out. True to form the electronics nearly worked most of the time but it did work long enough to capture a whole run (actually Joshuas 1175 mpg) so we have GPS based speed readings every second for the whole 39 minute run. Although there is no need for a gps to derive the speed (which could be done in a much simpler way) it does offer the advantage of inherently accurate timing, also something else that could be done in a simpler way! The altitude resolution is not much help as unlike my personal (for hiking) GPS, the cheapo gps ’engine’ we are using is only a 12 satellite receiver....but it was cheap! What the graph shows with wonderful clarity is the way the run progressed with a fair degree of consistency, given the somewhat cramped conditions Joshua had to endure! We are able to see the entry speeds to the pit straits which we aim to coast along, as once you reach the end, you literally ’drop off’ and coast up to around 22 mph. Then follows a long climb back up around the other side. Clearly a case for data logging especially in terms of looking at differences between different drivers. So, despite the event starting off with a few disasters, we ended up with five valid runs to our credit and an excellent result. Even my ’Mouse’ did well, beating it’s previous best on LPG by over 50 mpg, netting 410 at the hands of Reuben. For a very crude gas delivery system, that isn’t bad as the best it managed on petrol this year was 503, itself not bad for a road legal car. For information, my ’Mouse’ is powered by an internally standard Honda C90 motorbike engine (3 speed semi-automatic) with the addition of an air-bleed tap that the driver can use and an anti-run-on valve that opens when the ignition is switched off. One day this engine is due fuel injection which will sort out a few more mpgs.
