Family Software Newsletter #30 - April 17, 2006

Drag Racing Computers and Software -


1. High MPH Throttle Stop Setup

-- High MPH Throttle Stop Setup --
There are two types of Super racers, The Dialer and The Wheel Racer. The Dialer is confident in his equipment and ET Prediction program. He sets his car up honestly to run the number and can run it out the back door when necessary without much fear of breaking out. The Wheel Racer always sets up quick to get their first, and tries to "nose out" his opponent by taking the least possible finish line margin. The Wheel Racer must have the better reaction time because his ET is going to be based on his opponents performance rather than his own. Any good dialer will tell you that he has the advantage. Most wheel racers believe that they have the advantage. Go figure!

The Dialer wants a car that is consistent and predictable rather than run a high mph. The Wheel Racer must have the higher MPH car. The only problem is, with the high MPH comes inconsistency and therefore an unpredictable race car. The reasons are simple. Today, the high MPH car is an extremely high horsepower car. Traction and throttle stop problems are big issues for high horsepower. Throttle stop factors are effected by engine RPM (Coast RPM) but more importantly by launch MPH which is not necessary equal to a specific Coast RPM! Better traction, or "getting up on the tire" will increase the MPH at launch, then when the car coasts on the throttle stop, the vehicle speed is different than the base run. Multiply the amount of MPH difference by the throttle stop timer duration and the effect on ET can be huge. The best way to try and eliminate this problem is too launch the car softly and as consistently as possible in order to leave the starting line at the exact same MPH each time. Then the throttle stop duration must be limited to the least amount of time as possible. This means you can't cruise at 5000 engine RPM. A car with 3 to 4 seconds in the timer duration can only be consistent if the throttle stop RPM stays exactly the same on each run.

If you are not using a Family Software DataMaster computer, you will never know if your throttle stop repeats or not. NO other data recorder can see the minute changes in throttle stop RPM that the DataMaster can see. Looking at graphs from a RacePak or other data recorder, you would tend to believe that you have a consistent throttle stop, yet you can't run the number and your 60 to 330 foot times, and/or 330 to 660 foot times vary even with the same timer duration setting. It's because your Coast RPM is varying and your data recorder cannot see it happening. This is due to poor programming and low sampling rates.

The best way to increase your consistency is to reduce your timer duration. An under the carb throttle stop cannot be used in most cases because the Coast RPM will have to be set below the point of main booster flow. Therefore, accelerator pumps are necessary when the throttle stop comes off. Because of traction problems, and again to limit timer duration, the car should be in high gear almost immediately into the run. This will remove .3 from the ET and reduce timer duration dramatically. It will also help to eliminate any traction problems coming off the stop. The best throttle plate and timer duration setting would be one where the throttle is returned to idle, but the timer duration never allows the engine RPM to reach idle. In other words, a short, controlled hesitation or cough. The amount of ET you need to reduce may limit you from having the perfect throttle stop setup.

Here is a recommendation for a starting point. Use a linkage type throttle stop. Set your launch RPM to 4200 to 4600 RPM for consistent reaction times. (The DataMaster is also the only computer that can accurately monitor Vehicle Reaction Time.) The throttle stop goes on immediately. If your timer allows it to start at .000 use that, otherwise use .001. Set your shift timer to two tenths (.2) into the run. Set your Cruise RPM as low as possible and begin testing. Adjust for the shortest timer duration where the throttle response is good coming off the stop. If you don't have a DataMaster computer, make several runs with the same timer duration setting. If the car will run the same STP ET (corrected ET) three times in a row with the same timer duration, you have it right. Otherwise, you still have work to do.

-- REAL World Technical Support --
With Family Software, you'll get better technical support than anywhere on the planet. Why? Because, we design and/or use all of the products that we sell. All of my 35+ years of racing experience and knowledge is available to you and our other customers. Try to find that kind of information at any one of our competitors. You won't be able to, I guarantee it! Family Software cares about the racer and his/her success as a racer. We also want you to get the most value for your hard earned dollars.

-- Secure Ordering --
You can safely order directly from our web site. All of your information is handled on our Secure Server. We have established a privacy policy and it is posted on the web site. Our company is registered with the Public Eye for safe, secure ordering.

If you have questions or topics that you would like to see covered in this newsletter, please Email them to me.

Bob Kodadek
SC 1596
Family Software - Drag Racing Computers and Software - 610.497.5561(Voice/Fax)

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