TwinTurbo.NET: Nissan 300ZX forum - Well given that post is nearly six years old
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Subject Well given that post is nearly six years old
     
Posted by Broke_as_**** on September 21, 2018 at 6:21 PM
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In Reply To Don't think this has been shared here before... posted by Barry (NJ) on September 20, 2018 at 05:36 PM
     
Message and Dieseldave only had 13 posts we'll probably never know anything more about it. But this is the internet so let us speculate. A piston going from stopped at top dead center to full speed in a quarter turn of the crank and subsequently to another stop at bottom dead center in just another quarter turn generates some big g-force numbers rather quickly. Those forces go up at the square of the engine rpm multiplied by the stroke so how fast the piston has to move up and down in the bore quickly becomes a limiting factor. Average piston speeds in the high four thousand feet per minute area are about the limit for road going cars, the pistons in a LFA were moving 4924 fpm at 9500 rpm for example. Even F1 cars aren't too much above that, I think the V8s topped out at 5200 fpm.
So to keep the piston speed under 5000 fpm at a 10500 rpm redline the stroke would have to be under 72mm or there abouts. This would imply a 97mm bore at 3.2L displacement, up from 87mm bore and 83mm stroke on a stock VG. 107mm stands out in the mind as VG bore spacing so 97mm would require a sleeved block but should be doable. Darton does out to 4.185" (106mm) sleeves on LS blocks with 4.4" (111) bore spacing.

     
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