Aston Martin Engine Development: 1984-2000. Arthur Wilson L.
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Название: Aston Martin Engine Development: 1984-2000
Автор: Arthur Wilson L.
Издательство: Ingram
Жанр: Автомобили и ПДД
isbn: 9781910456354
isbn:
Fuel consumption was improved by almost 2 mpg during the official test cycle, partly by quite a tricky modified ignition system giving part throttle advance and partly due to an improved auto transmission. The ignition system was only tricky to set up in that it used a double acting vacuum capsule for retard at idle and advance during part throttle cruise. The fact that our engine did not make enough vacuum at part throttle to advance the ignition meant that we used the air pump pressure to assist the advance side by pushing from the retard side of the capsule. This required that the advance be switched out at manifold pressure above 1" hg to avoid damage to the engine.
The Motor magazine road test of a Vantage in April 1981 obtained figures of 5.2 seconds to 60 mph and 11.9 seconds to 100 mph; they wrote that it was the fastest production car they had tested up to that date.* Comparisons were made with the Porsche 3.3 Turbo at 12.3 seconds to 100 mph and the Lamborghini Countach at 13.1 seconds to 100 mph. They also rated it as the best handling car.
Figure 3.1 Std V8 Torque Sheet 2
Figure 3.2 Std V8 BHP Sheet 1
Figure 3.3 Vantage Torque Sheet 1.
Figure 3.4 Vantage BHP Sheet 1.
* Ref. Motor Road Test No 21/81.
V12 Engine
DP1080
Another interesting project was the development of the Ford Weslake race engine. In 1979, Aston Martin bought the rights, drawings and all tooling for the Ford Weslake V12 race engine. The thought at the time was that it could be developed as a four-litre engine for a new, smaller Aston Martin.
The engine had originally been designed as a 48-valve, three-litre V12 with 75 mm bore and 56.46 mm stroke, with the potential to stretch to four litres for sports car racing by opening the bore out to 80 mm and increasing the stroke to 66.2 mm. It should not be confused with the earlier Gurney Weslake Formula One engine, although the original engine design was based around the crank and main bearing arrangement for that engine. But the Ford Weslake engine has the benefit of having the five intermediate main bearing caps cross-bolted into the cylinder block for added stiffness.
The first prototype of this engine ran at the end of 1971 and in 1973 it is reputed that two engines were used for evaluation by JW Automotive in the Gulf Mirage endurance race car with favourable results. It was reputed to have been producing about 460 bhp at 10,500 rpm.
The AML development project number given to this engine project was DP1080. There was one complete engine, No. 006, included in our purchase and in April 1979 this was stripped to enable our chief engine designer, Alistair Lyle, to evaluate the design. The engine was then rebuilt in preparation for test bed development work. Our first run was 10 March 1980 and development continued on to the end of June. Initially we limited rpm to 10,000 but towards the end we ran to 11,000 rpm on occasions. We couldn’t equal the claimed output for this engine, at least not as fully stabilised readings. But it was an interesting project working on an out and out racing engine, and created some wonderful noises in the process. But at the end of the day it was decided that the cost of transforming it into a road car engine would be similar if not more expensive than starting from a clean sheet of paper. Also the stretch to four litres would be very questionable for a production road car.
Figure 4.1 Weslake V12 Power Curve.
The main features of the engine were:
• 60 degrees V12.
• Four gear-driven overhead camshafts.
• Lucas Mk II mechanical injection and Lucas RITA ignition.
• Slide throttles.
• Firing order 1-12-5-8-3-10-6-7-2-11-4-9, using the traditional AML method of cylinder numbering.
• 75 mm bore and 56.5 mm stroke giving a swept volume of 2996 cc.
• Crankshaft made from En40B.
• 60.4 mm main bearing.
• 41.24 mm big end journal, 120 degree throw.
• Pent roof combustion chamber.
• Inlet ports were angled at 45 degrees from cylinder axis.
• It was said that a 12/1 compression ratio had been achieved but from memory, the engine that we had was found to be around 11/1.
• The piston crown was extensively machined to provide clearance for valve movement and to maximise the compression ratio.
• Cylinder centres were 93.65 mm apart, allowing for a bore increase to 80mm. This combined with a longer stroke of 66.2 mm would give a swept volume of 3993.6 cc.
• The cylinder block and the cylinder heads were cast in LM25WP, other castings were in Magnesium.
• Dry sump lubrication system was via four oil pumps: two for crankcase scavenge, one for cylinder head scavenge and one for pressure feed to the engine.
• Weight was approximately 385lb: it was just under 32" long, 19" wide and 22" high.
• Maximum safe engine rpm was 11,500 rpm.
Aston Martin Tickford
The creation of Aston Martin Tickford (AMT) in the early 1980s had provided a means to offset vehicle engineering development and certification costs to AML by selling our engineering expertise to other manufacturers as AMT, as Porsche and Lotus had done. It also helped to finance a much larger engineering department, with the top specialist engineers and the high-tech equipment required to compete in the modern engineering age. That arrangement had worked well initially, with a number of high-profile projects for major motor manufacturers, and could so easily have been the solution that AML needed. But unfortunately, after a few good years, it was decided that AMT should be separated off to go it alone, eventually to become Tickford Engineering.
Figure 5.1 Early days at Aston Martin Tickford – the 1982 endurance race СКАЧАТЬ