Joejr915 Posted January 7, 2013 Report Share Posted January 7, 2013 What the biggest motor you can build without being spread bore crank? What size crank or cylinder? Quote Link to comment Share on other sites More sharing options...
BANSHEE HP Posted January 7, 2013 Report Share Posted January 7, 2013 dmx is the largest cylinder 85mm bore, 80- 82mm stroke Quote Link to comment Share on other sites More sharing options...
Josh Z Posted January 7, 2013 Report Share Posted January 7, 2013 I thought the DMX uses a spread bore? Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted January 7, 2013 Report Share Posted January 7, 2013 No, the DMX is a 102 spread Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted January 7, 2013 Report Share Posted January 7, 2013 Just a little over 900cc Quote Link to comment Share on other sites More sharing options...
tedd1 Posted January 7, 2013 Report Share Posted January 7, 2013 A "banshee-based" engine has a distance of 102mm between the center of the right piston and the center of the left piston. Any engine that has a distance wider than 102mm from the center of one piston to the center of the piston closest to it....is considered a "spread-bore" engine.A 102mm center-to-center distance is fine if you have a 68mm bore in the engine' date=' but it "stands to reason" that as the bore of an engine gets larger and the inside walls of the transfer tunnels get moved out and the transfer tunnels get smaller, there will be less fuel/air going up the transfer tunnels because the tunnels are smaller. On the outside walls of the transfers, material can be added to increase the size of the transfer tunnels.....but because the center-to-center, (c2c), is limited to the standard 102mm, (non-spread), you cannot get as much room for fuel/air flow.....ESPECIALLY in the center transfer tunnels.Before we first built the Cheetah-DM cylinders, we went out to a 78mm bore on a few Cheetah cylinders, this left the inside transfer tunnels smaller than we felt they should be in the "side-to-side" direction. What we did was a little "out-of-the-box", but we started testing cylinders with the inside transfer tunnels built longer in the front-to-back direction to get back some of the transfer volume lost in the side-to-side direction. To make a VERY long story as short as I can......as far as I know, the DM cylinders were the first "production cylinders" to be built with unbalanced transfers.....and they seemed to work well.....(I am NOT saying we did anything "new" or "special" here....just out of the ordinary for a production cylinder......"standard disclaimer".....lol)The DMX cylinders are even more "unbalanced" in the transfer tunnel design than the DM was, in part because they can bore out to an 85mm bore.....and still maintain the standard...."non-spread".....102mm c2c of a banshee. It would seem that the transfer flow in the DMX "may" have even improved due to the front-to-back extension of the inside transfer tunnels. As I am writing this...."BOOK"....(lol)...we are testing front to back extension of the outer transfer tunnels on some of our engines.....including engines that are wider than the standard 102mm c2c engines. There is some "debate" as to what size an engine must be to see a benefit from spreading the distance between the bores. In the past, I would have bet money, (and in many ways I did bet on it), that an 825cc engine would run better as a spread-bore, at present, I am not giving odds that the 825cc class is large enough to see that difference!....lol [/quote'] From a Calvin Pollet post on PS. According to the man himself, somewhere around 85mm bore will be the limit because of transfer area? Quote Link to comment Share on other sites More sharing options...
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