Tech Talk - Race Course Simulation Dynamometer* |
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(603) 226-DYNO |
Read
about some of the important requirements for performing high power race track
simulations on a chassis dynamometer.
"*This article
first appeared in Circle Track magazine."
Dyno Tech Talk is a compilation or
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Can I simulate a race course with the dyno? Many Circle Track racers have explored the idea of using chassis dynamometers to help them develop faster and more reliable combinations (without chewing up valuable track test time). The idea is certainly alluring. Simply drive your car onto some high inertia rolls, hit the gas to get a power reading, and start making changes to see what works. Alas, like most things in life, it’s a bit more complicated when you really get into it! First, you’re probably already making big power – at least a lot more than most street guys really make. Therefore, getting traction between the tires and rollers is more involved than it is for testing grocery haulers. High power requires high traction, and unfortunately, small rolls require lots of strap down pressure to reliably transmit 400+ wheel horsepower. Excess pressure deforms tires around the small roll contact area. Besides robbing power, this overheats and damages the tires during lengthy race simulations. So, to provide most of the traction from gravity alone, you need large diameter rolls (at least two or more feet in diameter) with grooved contact surfaces.
Next, if your dynamometer is going to be suitable for anything other than “carnival smoke shows,” it requires a computer-controlled absorber equipped with a torque measuring load cell. This allows capturing much more than just flash inertial acceleration data. While some drag cars might get at least tidbits of useful information from a few seconds of inertia-only spin-up, circle track engines must run longer (under real-world loads) to return meaningful test results. You want to be able to see what happens to the power as water jacket and oil temperatures stabilize, etc. That’s why Land & Sea builds large diameter roll chassis dynos with computer-controlled absorbers that handle over 2000 Hp.
However, mating a chassis dyno that can handle long duration
race speeds and a computer-controlled absorber that simulates on-track drag
loads is only part of the equation. Ultimately the dynamometer’s data
acquisition and control software makes or breaks your system’s usefulness (Imagine
if the latest 1+ gigahertz PC only ran DOS!). Fortunately, these systems utilize
DYNO-MAX 2000 “Pro” software. Besides handling user
programmed racecourse
simulations, DYNO-MAX can also automatically and “intelligently” simulate**
appropriate loads (real-time) based on the driver’s throttle movements. With
optional electronic throttle control, the driver doesn’t even need to provide
that! As Land & Sea reminds us, powerful and flexible control software soon
becomes the dyno, whereas a weak program just becomes a straight jacket!
**DYNO-MAX 2000's "Simulate Road
Load" is a special load control formula. Instead of adjusting the absorber to
hold a fixed velocity, it continuously calculates the total Hp delivered against
the theoretical vehicle drag (using both wind drag and road friction data) to
determine how fast the vehicle should be going. It constantly readjusts the
dynamometer load to hold that calculated road speed (even simulating vehicle
inertia). Drag is calculated based on user entered Run Information parameters
like Coast Down G’s and Vehicle Weight. |
