danc Posted November 25, 2004 Share Posted November 25, 2004 Guys: I'm trying to decide what rear end ratio to use with my 700R4 (seperate post) and found out about a software package called "Quarter Jr." ($95.) that is supposed pretty accurate. Anyone know anything about it, and if it worth the price?? Thanx Dan Quote Link to comment Share on other sites More sharing options...
Guest Phil1934 Posted November 25, 2004 Share Posted November 25, 2004 Here you go FREE and agrees well with my Desktop Drag http://www.maxracesoftware.com/prod03.htm Also has a nice feature that shows weight on front wheels. Nope, my blown street rod still won't wheelstand when done. Biggest item on all these is picking realistic traction. Pick one that gives you 1.7 or so 60' with Drag radials or 2.1 with good street tires. Some other numbers you'll need are 19.7 SF of frontal area with a drag coefficient of .45, 2700# with 45% on the rear wheels and a 90" wheelbase, and 700R4 ratios of 3.06, 1.63, 1.00, and 0.7. Going back to the 60' times, take some HP out and see if they improve. I've got a dial back MSD retard box and a digital timer so I hope to make a cheap traction control. Quote Link to comment Share on other sites More sharing options...
DaleMX Posted November 25, 2004 Share Posted November 25, 2004 Here is an Excel program I wrote a while back to help me determine my ideal ratio. http://www.circuitflex.com/Rpm3.xls Right click and save target as please. It's set up for a T56 tranny 195 70 14 tires and a 3.54 rearend, but just click on the transmissions tab and get the ratios for yours and enter them in by hand. Enter the tire and rearend stuff by hand also. Quote Link to comment Share on other sites More sharing options...
Guest Phil1934 Posted November 25, 2004 Share Posted November 25, 2004 The program I posted will tell you 1/4 mile ET and MPH but not how to optimize. rear ratio=peak HP RPM x tire dia./(310 x MPH). MPH is at finish of 1/4 mile. If using a non lockup convertor pick the next lower numerical rear ratio as there is a few percent slippage. This puts the finish line RPM about 8% higher than peak HP RPM. For an auto trans low gear = tread width x MPH/(1.8 x HP) For a stick shift lose the 1.8 as that is torque convertor multiplication. For treaded tires take the tread width as 60% of overall due to grooves. You'll see that big 1st in a 700 is too much. Maybe a 200 would be better or a PG with a GV OD. If you street drive you need the OD as RPM at cruise=rear ratio x 336 x cruise MPH/tire dia. Quote Link to comment Share on other sites More sharing options...
danc Posted November 29, 2004 Author Share Posted November 29, 2004 Thanks a bunch guys. I need to get busy and plug in the numbers.. Appreciate the hep!!! Quote Link to comment Share on other sites More sharing options...
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