Please Discuss
12-04-2007, 07:35 PM
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Please Discuss
Right my cossie engine has had the pistons (4x4 in 200 block) machined down but there is a load took off.....for instance when the engine is at top dead center the piston is about 2-3mm down the bore....
i am driving the car now with a t34.63, grays and 32psi of boost but with the comp been so low when it comes on boost it takes of but does not come in with the big f*ck me while holding on like they normaly do but it will rev to 8000rpm for fun in every gear....
what are the pro's and cons of having comp this low apart from i would be able to run more boost safer....what about getting it live mapped would the engine be able to run more advance because of this and what affects would this have......
next winter i am wanting to gt30 it but in 2 minds wether to leave the comp like this as it is a fresh engine or rip it apart in the winter again and put some new pistons in.....
lets here your views.....
i am driving the car now with a t34.63, grays and 32psi of boost but with the comp been so low when it comes on boost it takes of but does not come in with the big f*ck me while holding on like they normaly do but it will rev to 8000rpm for fun in every gear....
what are the pro's and cons of having comp this low apart from i would be able to run more boost safer....what about getting it live mapped would the engine be able to run more advance because of this and what affects would this have......
next winter i am wanting to gt30 it but in 2 minds wether to leave the comp like this as it is a fresh engine or rip it apart in the winter again and put some new pistons in.....
lets here your views.....
12-04-2007, 07:53 PM
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my engine is same spec as yours (+ cams and some head work) and has flat top pistons and they also sit about that distance down the bore. the head was 137.6mm and the pistons are pa1079 (old spec low comp). the block was also skimmed 3/4mm with the end result of a cr of 7.2 iirc. the car was live mapped by stu and when the boost comes in it does really go well (mind it only weighs 800kg 
). should also say that stu set the max rev at 7200 and max boost at 30psi
). should also say that stu set the max rev at 7200 and max boost at 30psi
12-04-2007, 07:57 PM
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yip but your block been skimmed to compensate.....my pistons like yours but with out the block been skimmed so i dare say the comp ratio is in the 6's... 
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13-04-2007, 06:56 AM
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Originally Posted by puddy
Mine is old skool btcc spec,6.8:1,t04 etc,comes in with a fooookin big bang!
Get a bigger turbo?
puddy
Get a bigger turbo?
puddy
13-04-2007, 07:01 AM
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think a live map would be good for now......cause the chip is just for a t34.63 with lowcomp and grays......and i bet the low comp is no were near my low comp....
14-04-2007, 08:17 AM
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tell me about it....going to put a gotech pro ecu on it with new engine bay harness and live map.......
should sort it out for now........
should sort it out for now........
14-04-2007, 08:23 AM
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Originally Posted by PGT
but ive also lost about 2mm of the head thickness
are you sure!EDIT: or are you talking about the comination of skimming head and block?
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