The home of the UK's greatest sportscar
27/10/2009
The FFF engine from Racing Green TVR is just getting better. The accuracy of new Racing Green semi counterweight billet crankshaft allows the use of a high performance crankshaft scraper to minimise crankshaft drag due to crankshaft windage. Surprisingly enough during normal engine operation a significant amount of oil adheres to or becomes entrained in a cloud surrounding the spinning crankshaft. This oil is not cleared by centrifugal forces but becomes a parasitic drag factor on the crankshaft. Significant amounts of development takes place in both racing engines and modern road engines to mitigate the losses cause by this parasitic drag factor on the rotating crankshaft.
This mass of oil causes a number of problems and no benefits for a performance engine. The extra mass slows down acceleration of the crank due to its increased effective mass and in a dry sumped engine like the TVR Speed 6 deprives the dry sump tank of critical oil to feed the bearings especially at higher RPM. It is extremely important that the oil is controlled and returned to the dry sump tank quickly to allow any air to separate prior to the oil returning to the high pressure lubrication system.
The oil caught up in the windage cloud also becomes unnecessarily aerated and heated which can cause further lubrication problems. The heating effect of the work done by the crankshaft on this mass of oil leads to a requirement to provide extra cooling to remove this unwanted heat!! In effect preventing the oil from spinning around with the crankshaft means the oil remains cooler and the crankshaft has less drag. This means there is a lesser requirement to cool the oil and more power liberated from the engine.
The scraper plate fits above the sump casting and literally due to its proximity to the rotating crankshaft cuts the oil from the shaft and returns it to the directly to the sump preventing the oil spinning around with the crank and hence all the associated problems.
It is very hard to achieve a competent crankshaft scraper with a standard cast TVR crankshaft as the crank is just not accurate enough in its overall dimensions to allow a scraper plate to be designed that runs within 1.00mm of the rotating surfaces. However with a CNC billet crankshaft where all dimensions are known the scraper plate is a far more realistic proposition. This is now available from Racing Green TVR with the billet crankshaft.