odaen Posted August 3, 2007 Report Posted August 3, 2007 Maybe I just do not understand what you are saying but moving the cylinder up or down will not have a linear change in duration. I thought you were referring to a stroker in which you would just adjust the ports up 2mm to "match" the -2mm deck. That would not yield the same durations as a stock motor. That is about all I was saying. Brandon Yeah, you misunderstood what I was saying. I was comparing same stroke/rod length motors, not a 4mm vs a stock stroke. And, yes, I agree, that you can't just add 2 mm to your port heights to make up for the 4mm crank and expect to have the same durations as you had with a stock motor. If that's what you were getting at with the term linear. :beer: Quote
racer Posted August 3, 2007 Report Posted August 3, 2007 The stealth factor is out the window, unfortunately........the cylinders are polished. media blast them, good bye shine! Quote
370banshee Posted August 4, 2007 Report Posted August 4, 2007 odaens on teh right track.. and... i know a little program that can help you out... Quote
370banshee Posted August 4, 2007 Report Posted August 4, 2007 and.. with a 4mm crank and a measurement from the top of ex port to deack hieght of 33mm you'd have an exhaust port duration of 179... thats lower than stock.. thats IF i entered the info correctly and with a measure ment on teh transfers form deck heifght to top of port of 33mm you'd be at a 132.. again if i entered this right into the portmapper program Quote
blowit Posted August 4, 2007 Report Posted August 4, 2007 and.. with a 4mm crank and a measurement from the top of ex port to deack hieght of 33mm you'd have an exhaust port duration of 179... thats lower than stock.. thats IF i entered the info correctlyand with a measure ment on teh transfers form deck heifght to top of port of 33mm you'd be at a 132.. again if i entered this right into the portmapper program I have never seen a stock cylinder with a 33mm exhaust. Your 179 sounds like you might be referencing a zero deck and not a -2mm deck which is what you would have in a non-plate 4mm motor. Quote
blowit Posted August 5, 2007 Report Posted August 5, 2007 I have never seen a stock cylinder with a 33mm exhaust. Your 179 sounds like you might be referencing a zero deck and not a -2mm deck which is what you would have in a non-plate 4mm motor. Ah, you have me wondering now if you are just using the new piston TDC as your deck for reference instead of a negative deck. That might explain that. So many ways to looks at these things I guess.... Quote
370banshee Posted August 5, 2007 Report Posted August 5, 2007 thats why i said "if i entered it right" i might be using this incorreectly.. i do ahve it adjusted for a 58mm stroke.. i figure rod length for this purpose wont; affect it.. i tried it with -2 deck height... maybe i need +2 deck height. i'll try it again.. i know that 179deg is way wrong.. but it was mentioned that 33mm was a wrong mesuerment Quote
370banshee Posted August 5, 2007 Report Posted August 5, 2007 ok... i'm not trying to fuck up this guys thread but... here what i got.. with the measurement of 33mm deck-top of ex port... with the portmapper on 58mm stroke and std deck height i got 179.6 adn the trasfers at 132 now.. with +2 deck height... i get 187.5 ex..and 141 trans.. and a blow down of 23.25.. which i'm thinking that the first figure is right.. judging by the 132deg transfer duration.. which with a 33 blow down would give a 198 exhaust port duration and a deck-ex top measurement of 132... these figures are from the deck height and not top of piston.. Quote
370banshee Posted August 5, 2007 Report Posted August 5, 2007 i' doing the figures for a PLATE motor.. i guess thats why we aren't seeing the same numbers. i would say with the tranfer duration he has posted that it's got to be a plate motor.. Quote
blowit Posted August 5, 2007 Report Posted August 5, 2007 i' doing the figures for a PLATE motor.. i guess thats why we aren't seeing the same numbers. i would say with the tranfer duration he has posted that it's got to be a plate motor.. If you are looking at a plate motor, the deck height reference should be zero. You might check your software and see if pos or neg deck refers to the piston above the deck. We always refer to neg deck as having the piston above the deck but that is not really an industry standard. Brandon Quote
370banshee Posted August 5, 2007 Report Posted August 5, 2007 (edited) i am making these figures with 0 deck height for a plate motor.. so my figures must be right then? i'm tto saying i'm right.... i'm asking IF i'm right.. Edited August 5, 2007 by 370banshee Quote
blowit Posted August 5, 2007 Report Posted August 5, 2007 i am making these figures with 0 deck height for a plate motor.. so my figures must be right then? i'm tto saying i'm right.... i'm asking IF i'm right.. It would seem your numbers are pretty close. The only thing I am baffled about is that 33mm exhaust. And you can really see why the plate is not a good option unless for drag racing. Those transfer numbers are too aggressive for a smooth, linear response. We wrote our own porting programs just because we need to "know" how these numbers are derived. We used one and did the numbers on it and found several degrees error because of rod angle issues. We just found it easier to know what we have. That is not saying all software if crap though, it would just be nice to see the equations. Brandon Quote
370banshee Posted August 5, 2007 Report Posted August 5, 2007 yeah his 33mm measurement is way off.. but he did say something about going up thorugh the exhaust port to get that measurment.. Quote
J-Madd Posted August 6, 2007 Author Report Posted August 6, 2007 Well, I went ahead and ordered a spacer plate. I haven't gotten around to re-measuring. Port heights and durations are over my head. When we put the motor together, we'll find out!! Quote
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