matty_gti 20 Posted October 30, 2008 Hi all, I know its another CR topic but am finding it a lil bit difficult.... I’m going to be using 1.9 pistons that have been machined to the TT spec which i think have been machined 2mm....someone please correct me if I’m wrong. I’ve measured the cc in my head at the moment and is 33.8cc. It’ll be the standard 83mm bore x 88 stroke however the bit I’m getting stuck on is the head gasket thickness or 'squish', the dish size in the 1.9 TT pistons and there deck height in relation to the tops of the liners to work out the compression ratio. Ive been using this http://www.csgnetwork.com/compcalc.html but cant really get an answer without those figures. If anyone knows or can help me work it out it’ll be most appreciated. Matt Share this post Link to post Share on other sites
welshpug 1,621 Posted October 30, 2008 depends how thick your gasket is, but its straightforward(ish) volume calculations, i.e Bore = 83mm, gasket thickness = say 1.7mm. using the information here http://www.pumaracing.co.uk/CAPACITY.htm Bore area is therefore 8.3 x 8.3 x 3.14159 / 4 = 54.11 square cm. Volume of 1 cylinder is bore area times stroke = 54.11 x 8.8 = 476.168cc gasket CC would be 54.11 sq CM x 0.17 cm = 9.1987 cc. to calculate the disc size and clearance volume you need to fit the pistons and see how much clearance to the deck there is, as well as measure the CC of the piston dish. Share this post Link to post Share on other sites
matty_gti 20 Posted October 30, 2008 (edited) to calculate the disc size and clearance volume you need to fit the pistons and see how much clearance to the deck there is, as well as measure the CC of the piston dish. Yeah thats how far i got but cant get an accurate result without the above figures, just hope someone knows them.... And the head gasket thickness would be the crushed size, so IIRC say there 1.3cm unfitted, how much do they squish by when fitted?. Matt Edited October 30, 2008 by matty_gti Share this post Link to post Share on other sites
welshpug 1,621 Posted October 30, 2008 1.3mm not cm I always thought that the stated figure is the compressed one, not that they compress much. Share this post Link to post Share on other sites
matty_gti 20 Posted October 30, 2008 Its getting on a bit and im tierd,lol. Just hoping someone knows how much the TT pistons are machined by.....Ive done a fair few searches. Share this post Link to post Share on other sites
28CRAIG 2 Posted October 31, 2008 The figures i used to work mine out are. Piston Deck Clearance = 0.3556 Piston Dome Volume In CCs = -15mm std 1.9, not sure of TT spec Then alter the head gasket thickness to see how much skimming the pistons will effect the c/r but 2mm off seems a bit low on the c/r what management are you going to be using. Share this post Link to post Share on other sites
