Quarter Jr.
Serious Racing Tool?
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The Ultimate Automotive Dreamers Toy?
Quarter Jr. Has been around for a long time, at least as long as the Commodore 64 and Apple II for which it was originally written. It is also well thought of by serious drag racers who will vouch for its accuracy.
Quarter Jr. is available from Racing Systems Analysis, Glendale AZ. It is a Windows application and costs $95, shipping included. The Windows version is a recent develpment; until recently (version 3.0) it was MS-DOS only. The current version as of 10/2000 is 3.1.2.
Using Quarter Jr. is simple. At the opening screen the basic parameters are entered. All factors that affect performance are covered, including environmental variables.
Street racers will have a ball with Quarter Jr. For a test drive, we'll use the '99 Mustang Cobra. We'll start by inputting the standard specifications for the Mustang.
Hit the TS (Time Slip) button and the results pop up on the right. The Cobra covers the quarter mile in 13.51 seconds, traveling 105.1 MPH at the end. Road & Track tests resulted in a quarter mile acceleration of 14.1 seconds at 101.5 MPH, only .59 seconds and 3.6 mph off from what Quarter Jr. preidcted. Very impressive! Pressing the Detailed Parameters button produces a listing of what was happening when. The RPM ° MPH vs Time button produces a graphical representation of the speed and engine RPMs vs. time over the run. The shifts, and how they affect engine RPMs id clearly evident. In this case the Mustang never used fifth gear; maybe a closer ratio transmission would keep the engine RPMs inside of the big horsepower portion of the power band? The RPM ° MPH vs Distance button produces a graphical representation of engine RPMs and MPH vs. time. The high acceleration rates at the beginning of the run and the lower rate at the end when speed accumulates is a testimony to the aerodynamic factors involved. Maybe some aero trim items and a spoiler (the real stuff, not the tacky stylish junk) might pay off. You can start to see where Quarter Jr. is useful.
Let's have some fun with Quarter Jr. Assume we have Bill Gates pay scale and we spend a few seconds of his hourly rate and buy a big horsepower motor. Quarter Jr. kind of lives in the real world and the most it will allow us to input is 560 hp. The 3.0 MS DOS version did not have this restriction, which is probably a good thing. We hit the TS button and the results are a 14.37 ET with a terminal speed of 121.4 MPH. This is actually not as quick as the 320 hp motor, and the reason can be seen by looking at the Detailed Parameters. We are slipping (as indicated by the "(s)") through the important beginning portion of the run. Looking at the RPM ° MPH vs Time and the RPM ° MPH vs Distance information shows a flat and downright pathetic acceleration curve. On top of everything else Quarter Jr. is honest and will reinforce the point that many aspects of the car affect performance. In this case we do not have enough tire on the road, hence the slippage. Quarter Jr. allows us a maximum 18 inches of tire (that real world thing again) and while we are at it, lets up the motor hp to 1100. The results are awesome, with a 9.02 second ET and a speed of 151.1 MPH. Looking at the Detailed Parameters reveals some slippage, although we are using fifth gear because of the high speed at the end of the run. the RPM ° MPH vs Time graph reveals a big RPM drop, from 6000 rpm to just over 4000 RPM. Maybe that fifth gear is a little too tall?
Quarter Jr. is not only a serious drag race engineering tool, it is a lot of fun. Just add imagination.
Also available from Racing Systems Analysis: Quarter Pro, ($295) which takes in engine dyno results as well as clutch data, transmission and rear gear efficiencies, and polar moments of inertia for a more thorough analysis. A variety of other software packages, all aimed at the serious racer, is available.
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