bkuempel Posted January 29, 2008 Report Share Posted January 29, 2008 I've been doing some math....and it may be changing my mind on whether or not we should allow overbores (I was originally against it). Take a look and see what you think. Stock bore = 3.03" Stock stroke = 2.3" Stock cylinder volume = 16.58 cid .010" over cylinder volume = 16.69 cid (7/10th of 1% increase) .020" over cylinder volume = 16.80 cid (1.3% increase) .030" over cylinder volume = 16.91 cid (2% increase) Assuming we are pushing 1hp per cid (I think we should be close to that) there's not much of an increase up to .20 over. .2hp shouldn't keep any of us out of the winner's circle! At last Saturday's meeting, I was premature in stating that a used motor is a viable option to continue with a stock bore. I didn't consider that most of these motors come off of pressure washers, generators, etc that have most likely been run into the ground and not adequately serviced while in use. The cost of a new OEM block alone is $608.00 (a whole motor is not much more than that). In conclusion, due to the expense of an OEM replacement and the virtual lack of a substantial increase in hp, I would be in support of allowing overbores up to .20 over. For the record, I have 3 blocks. One would need the .20 over to seal and the other 2 are fine stock. But one is on the loose side and would need to be overbored next season to seal. What are y'alls thoughts? Link to comment Share on other sites More sharing options...
NickHolt Posted January 29, 2008 Report Share Posted January 29, 2008 I'll take a 2% increase in cylinder volume any day, especially as light as these karts are. If these were 3000 pound stock cars with 350 Cubic Inches of displacement, you're correct. The increase in volume would indeed be insignificant. But we're talking 16 (or so) CID. Try running a CID to Kart weight ratio. That would give you a better indicator of the actual benefit the extra volume would provide. A way to compensate might be to add a weight penalty to obtain the same CID to weight ratio for all your karts. I don't have a dog in this one. Just trying to make a suggestion. Nick Link to comment Share on other sites More sharing options...
CuttingEdgeRacing Posted January 29, 2008 Report Share Posted January 29, 2008 Try running a CID to Kart weight ratio. That would give you a better indicator of the actual benefit the extra volume would provide. A way to compensate might be to add a weight penalty to obtain the same CID to weight ratio for all your karts. I don't have a dog in this one. Just trying to make a suggestion.Nick Brian, can you figure this ratio on 450lbs? The weight penatly is an excellent idea. Thanks for the suggestion Nick! Sometimes unbiased outside opinions are what we need! Link to comment Share on other sites More sharing options...
bkuempel Posted January 29, 2008 Author Report Share Posted January 29, 2008 I agree, 2% is too much. As I stated, .020" over (or 1.3% increase) is my suggested limit. As far as ratios go the 3000# car has a three times higher CID to weight ratio: The 3000# car with 350cid is .116cid for every pound of car. The 450# kart with 16.58cid is only .0368cid per pound. Simply put, the car is 6.6 times heavier than the kart. 6.6 kart motors would still only equal 110cid. Now then, add even 2% hp to the mix: The 3000#, now 357cid car is .119cid per pound (a .003cid per pound increase) The 450#, now 16.91cid kart is .0375cid per pound (a .0007cid per pound increase) If my math (not my best subject) is correct, all you'd have to do is add 2% to the weight of the car to keep the ratios in line. The 3000# car is now 3060# The 450# kart is now 459# Even still, this 2% additional cid doesn't necessarily mean a 2% decrease in lap times........ Link to comment Share on other sites More sharing options...
CuttingEdgeRacing Posted January 30, 2008 Report Share Posted January 30, 2008 Brian, I think you should bring this up next time we're all together add 10lbs for overbores...but no bores exceed .20 Link to comment Share on other sites More sharing options...
bkuempel Posted January 30, 2008 Author Report Share Posted January 30, 2008 I will. I also posted it on the IRR forum to see if any other karters would add any input. I'm not convinced that there needs to be a weight penalty, though. Some of our drivers are already carrying more than the 450# minimum. Plus, I'm not (on paper, at least) convinced that a .020" overbore would be that huge of an advantage. Link to comment Share on other sites More sharing options...
n2racing2 Posted January 30, 2008 Report Share Posted January 30, 2008 WELL...WE DO HAVE PRE-SEASON TO TEST IT OUT ON THE 2 MOTORS WE KNOW THAT ARE THAT WAY. BEFORE WE EVEN CONSIDER IT TO BE A RULE CHANGE....SEVERAL TEST DATES TO SEE. Link to comment Share on other sites More sharing options...
CuttingEdgeRacing Posted January 30, 2008 Report Share Posted January 30, 2008 woah woah....easy there Mr.Capslock we're just talking it out Link to comment Share on other sites More sharing options...
n2racing2 Posted January 31, 2008 Report Share Posted January 31, 2008 ROFLMAO..... i just type in WHATEVER TEXT IS ON at the time...when working...gotta type fast....so IF I AM YELLING RIGHT NOW....i cant hear it...lol Link to comment Share on other sites More sharing options...
bkuempel Posted January 31, 2008 Author Report Share Posted January 31, 2008 THAT'S FUNNY, I DON'T CARE WHO YOU ARE! Link to comment Share on other sites More sharing options...
CuttingEdgeRacing Posted February 1, 2008 Report Share Posted February 1, 2008 WHY IS EVERYBODY YELLING!!! LOL j/k Link to comment Share on other sites More sharing options...
beaner Posted May 8, 2008 Report Share Posted May 8, 2008 I've been doing some math....and it may be changing my mind on whether or not we should allow overbores (I was originally against it). Take a look and see what you think. Stock bore = 3.03" Stock stroke = 2.3" Stock cylinder volume = 16.58 cid .010" over cylinder volume = 16.69 cid (7/10th of 1% increase) .020" over cylinder volume = 16.80 cid (1.3% increase) .030" over cylinder volume = 16.91 cid (2% increase) Assuming we are pushing 1hp per cid (I think we should be close to that) there's not much of an increase up to .20 over. .2hp shouldn't keep any of us out of the winner's circle! At last Saturday's meeting, I was premature in stating that a used motor is a viable option to continue with a stock bore. I didn't consider that most of these motors come off of pressure washers, generators, etc that have most likely been run into the ground and not adequately serviced while in use. The cost of a new OEM block alone is $608.00 (a whole motor is not much more than that). BRIAN, I'm fine with overbore. As long as it is upfront when it is done. I'm afraid we are headed that way for next year anyway. Its cheaper to overbore, cost an all. Is your current motor a .010 overbore???? I know we can't bore,but you can hone for a while. With the weight rule, I think .030 is a good size for next year. If we buy all the pistons an rings at the same time, we could get a better price an we could have more of a control with what is going on. As you know I'm into the building mode now. Lets have some feedbackguys... Beaner (ROY BOY) In conclusion, due to the expense of an OEM replacement and the virtual lack of a substantial increase in hp, I would be in support of allowing overbores up to .20 over. For the record, I have 3 blocks. One would need the .20 over to seal and the other 2 are fine stock. But one is on the loose side and would need to be overbored next season to seal. What are y'alls thoughts? Link to comment Share on other sites More sharing options...
bkuempel Posted May 9, 2008 Author Report Share Posted May 9, 2008 BRIAN, I'm fine with overbore. As long as it is upfront when it is done. I'm afraid we are headed that way for next year anyway. Its cheaper to overbore, cost an all. Is your current motor a .010 overbore???? I know we can't bore,but you can hone for a while. With the weight rule, I think .030 is a good size for next year. If we buy all the pistons an rings at the same time, we could get a better price an we could have more of a control with what is going on. As you know I'm into the building mode now. Lets have some feedbackguys... Beaner (ROY BOY) No, I'm not .10" over now. I stated that in the original post. One rounded out at 3.05" and one at 3.07". So, I can probably freshen up the 3.05" once more and run stock piston, but the 3.07" one will most likely end up at least .10" over to true up for next season. Personally, I wouldn't go staright to the max bore. I would bore as needed to get a good seal. At the current rate, I could run the same block for several seasons before needing a new one. Link to comment Share on other sites More sharing options...
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