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Competition Basics - Basic Training

How-to: Drag Race, Sled Pull, and Dyno

Jason Sands
Nov 20, 2013
Photographers: Jason Sands, Mike McGlothlin
We’ve all heard the question by curious onlookers: “Hey man, what’ll she do?” With diesels, that can mean a variety of things, as modern pickups use sled pulling, dynoing, and drag racing as measuring tools for performance.
A Little History
Back in the 1940s, “what’ll she do” usually meant top speed. Roads were gravel, and a lack of traction meant top speed was the most often quoted performance benchmark. Then came drag racers, named because they raced on the main roads of a town (called “the main drag,” a term coined in the 1850s), when horses could be seen dragging carts and buggies down the street. Drag racing upped the ante on performance, as it required traction, driving skill, shifting prowess, and not just horsepower and aerodynamics like top speed.
Sled pulling has been around since the early 1900s, when strong farm horses were attached to a flat barn door, and the door would be pulled through a crowd. Every few feet, another person would jump on, until the weight became too much for the horses to bear. Thus, the idea of a moveable weight for an ultimate test of strength was born, and when tractors came along, they pulled a “sled,” too. In 1929, tractor pulling was officially a sport and was a new way for farmers to test the might of their machines.
Although dynamometers have been around since the 1700s, modern chassis dynos really didn’t get their start until the 1930s. Even then, they were heavy, often overheated, took up a lot of space, and usually weren’t rated to handle much horsepower. They were also very expensive. That all changed when Mark Dobeck developed the DynoJet, an inexpensive (compared to others) inertia-based dyno that measured horsepower by simply accelerating a large, heavy roller. While it wasn’t a load dyno that measured actual resistance, its numbers were repeatable. From the mid-’90s on, dynoing became an accepted way to measure horsepower.
Drag Racing for Beginners
With drag racing, even in the eighth-mile, you’ll be going between 70 and 100 mph right next to a concrete wall, so safety is a big issue. Make sure your truck isn’t leaking anything and that the suspension is in good shape. The windshield shouldn’t have any cracks in it, and any batteries should be secured with hold-downs. If you think you’re going to run quicker than 13.99 seconds (quarter-mile), you’ll need a helmet, and if you have an aftermarket turbo or nitrous (most people) you’ll need a $70 fire jacket you can buy from places like Summit or JEGS.
Photo 2/7   |   One of the perks of drag racing your diesel is the chance to beat up on old muscle cars. Is there anything better? We don’t think so.
Once you’ve got all the proper safety equipment, it’s time to go check out the track. Familiarize yourself with all the turnouts and return roads, and where the staging lights are. Rolling through the starting line (and lights) is probably the most common mistake. Fortunately, there’s no harm done. The track official at the starting line will just wave you back to the proper starting place.
For the actual run, your strategy may depend on how highly modified your truck is. Vehicles such as Dodges with stock flexplates, or GMs with stock tie-rod sleeves, should go easy on the boosted launches as power goes up, if they are four-wheel drive. Having four-wheel drive and doing a boosted launch helps immensely and is worth nearly half a second in the quarter-mile—even on stock trucks. Another common mistake is launching too hard; most trucks won’t need more than 10 to 20 psi of boost at the line to get a quick 60-foot time. Tire pressure is also important, and racers should start at 30 psi and work their way down from there, depending on traction.
Photo 3/7   |   Stripping weight is like adding horsepower. Every time we take our ’97 F-350 to the dragstrip, we pull the tailgate, ditch the rubber bedliner, empty the toolbox, and show up with roughly a quarter tank of fuel. By doing this, we drop nearly 500 pounds off the truck’s curb weight!
Once you’ve gotten off the line, there’s still more driving to do. If your truck bounces, let off. If it spins, try and pedal it. Staying in the throttle in a spinning, bouncing truck is a good way to either hit the wall or break parts. Also, if it doesn’t shift or the torque converter doesn’t lock right, let off—don’t just let the engine scream. Hopefully, everything goes right: The truck shifts appropriately, and you go screaming through the end timing lights in record time. If that’s the case, then it’s just time to drive down the return road and collect your timeslip.
Sled Pulling 101
In many ways, the basics of sled pulling mirror participating in a drag race. Make sure your truck is in good shape, familiarize yourself with the track, listen to the officials, lower your tire pressure, and let off if you start bouncing. With sled pulling, we’d recommend trailering your vehicle to the track if possible, because driveline breakage is very common. Before your first pull, get used to your vehicle and find a gear that allows your truck to run 30 to 40 mph at the top of its rpm peak. Any more wheel speed will just result in tire spin or bogging, and any less will risk over-revving the engine, or a short pull.
Photo 4/7   |   Feature Editor Mike McGlothlin took Brian Randall’s 2.8 Class puller for a ride, launching at 4,800 rpm. Mike said the experience made him realize why sled pullers travel hundreds of miles for just 15 seconds of seat time.
Safety regulations and classes vary greatly from pull to pull, but at the very least it’s a good idea to have driveshaft loops and a helmet when competing. Once you’re ready to pull, make sure the truck is in four-wheel drive and, for most pullers, low range. You’ll also need your own pulling hitch, which you can either buy, borrow, or make. A broken hitch can be potentially dangerous and will result in a disqualification. So, either way, make sure it’s a quality piece. When you’re ready to go, the starter will wave you to the front of the sled, and then help you back up. Once you’re hooked to the sled, you’ll slowly ease forward to take up the slack on the chain, and then stop when you feel the weight of the sled. Next, watch for the flagman to give the green flag, at which point you should start spooling the turbo (with your foot on the brakes). Try to leave the line with at least 10 psi of boost (or more, depending on track conditions), and roll into the throttle for the first 20 to 50 feet. After that, you should be wide open, and it’s pretty much hammer down the whole way until the truck stops. Again, it’s time to look at the flagman for instructions on unhooking, then it’s back to the pits.
Photo 5/7   |   We’ve seen multiple hitches break over the years, so make sure you have a quality hitch when you hook to the sled.
Dos and Don’ts of Dynoing
Separate from drag racing and sled pulling, dynoing is an activity that is variable; as in, a truck can make many different power numbers based on the type of dyno, whether or not a correction factor is used, and how much of a load is placed on the truck. Since we’ve had the most experience with Superflow, Mustang, and Dynojet dynamometers, we can give some good advice on how to run on those. On a Superflow, a 20 percent load seems to work well for stock to slightly modified trucks; on a Mustang, an 8-second timed sweep gets the job done; and on a Dynojet, it’s best to run on a large roller dyno and brake boost to keep the turbo lit. Dynocom also makes a good portable dyno, but the rollers are very light, and it’s hard to get big-turbo trucks to load correctly.
Photo 6/7   |   If there’s anything we have a bunch of experience with, it’s the dyno. Collectively, the staff has made hundreds of dyno pulls, and we’ve run everything from the aforementioned Sleepermax to our ’82 Chevette, which registered an Earth-shattering 37.5 rwhp.
Unlike drag racing and sled pulling, dynoing very rarely results in any type of driveline breakage. If there is some sort of damage, it’s usually engine related and involves spraying nitrous. The other type of mishaps we’ve seen were on a load dyno where the person controlling the dyno placed the truck under an insane amount of load, resulting in 15- to 20-second pulls. This type of load simply isn’t needed for 99.9 percent of trucks and usually doesn’t help power any—it just makes EGT go sky-high.
In most cases, the dyno operator will load the truck onto the rollers and even make the runs, leaving the owner with very little to do. Most of the work in dynoing a truck involves doing research and finding both a dyno and operator you’re familiar with, so you can be satisfied with the results.
Photo 7/7   |   The Dynojet 248 is perhaps one of the best dynos we have run across for back-to-back testing. We’ve run everything on it from our 854-rwhp ’89 Dodge to this stock Duramax-powered GMC, which laid down a whopping 258 hp. The best results, even in lower horsepower trucks, are usually achieved in an Overdrive gear.
Don’t Take it Too Hard
If we have one universal truth to give about all this stuff, it’s that you shouldn’t take it to heart. Many people will run well at the dragstrip but not on the dyno, and they’ll spend countless hours trying to figure out why. A sled puller, on the other hand, may not dyno like it’s supposed to for load reasons. Finally, a big-power-number vehicle may be ill suited for either track. Don’t worry if your truck can’t do it all—this stuff is supposed to be fun! The fact that you’re out there competing can give you insight into your truck and yourself, and you can make some great friends. And that’s what counts.



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