Optimal operation of internal combustion engines requires careful regulation of the fuel and air in the combustion chamber. Engine valves are the vital component of this regulation as they adjust the flow across the inlet and exhaust ports. The conventional approach is to use mechanically driven camshafts to actuate the intake and exhaust valves. The motion of the valve is controlled by a fixed cam profile to ensure the soft landing of valves, minimal noise and long life. As every engine with a camshaft uses a single profile, the timing of the valve with respect to piston motion is fixed for all speed and load conditions. Thus, the selection of cam profile today involves a restrictive trade-off between fuel economy, engine performance, emissions and noise.

This restriction can be overcome if fully variable electronically controlled valve timings are deployed that depend on engine demand conditions. Fully variable valve timing is sometimes referred to as camless engines, Lotus Engineering’s patented Active Valve Train (AVT) system being a specific example.

ParOS, with the support of the UK Department of Trade and Industry Global Watch Secondment Scheme, developed a model-based controller for the electronic regulation of the research (AVT) system at Lotus Engineering. The scheme is an output feedback predictive optimizing controller that was derived off-line using parametric programming techniques. The controller was tuned for a range of given valve profiles and tested experimentally.

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We are a Subaru performance engine and parts supplier but also an engine reconditioner who also specialise in Subaru performance engines for road or race application and work closely with Roger Clark Motorsport.

We have a retail/trade shop and engineering workshop situated on the Bristol A420 main road and have a fully equipped engine workshop. The company has been established for over 40 years supplying local companies with engineering and parts but have over the past five years concentrated on Ford and Subaru as the main interest. We have gained a vast knowledge of Subaru engine modifications due to the nature of our early business in performance engine building and machining, mainly gained from the Cosworth YB era and we have applied this to our now prominent Subaru field. We have a well equipped engine workshop and can carry out many engineering services which include:- Reboring and precision honing Surface grinding to a very smooth um finish Valve guide fitting and honing to size 3 angle valve seat cutting and valve facing Crank case and cylinder head pressure testing (hot) Conrod straightness checking and measuring Ultra violet magnetic crack testing All our engines are custom built to order using our own RD to ensure a reliable product with repeatable results.

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