Rally and Off-Road Racing Engines - Engine Builder Magazine

Rally and Off-Road Racing Engines

Early automobile races were held on horse tracks or dirt covered roads, but then came pavement and over the decades, many racers forgot about dirt. Today, racers who like to kick dirt will tell you there’s a whole other world of racing in the off-road market. Cleanliness may be next to godliness, but getting dirty can be devilishly profitable.

Just like most forms of motorsports, off-road racing is not quite cut and dry. There are several different forms of off-road racing that include trucks, cars, ATVs and purpose built race buggies. Off-road racing generally consists of trucks and cars racing around a predetermined course or a closed circuit where track conditions are not usually measured by how hot it is but how much mud and dirt you have to plow through.

Engines for these dirt-eating beasts range from big singles to domestic iron V8s pumping out almost as much power as a sprint car. The engines that operate in this environment are abused as much by the  surface conditions as they are by the drivers themselves, and must have durability to withstand whatever Mother Nature blows through the intake manifold.

The Motorsports Industry Association estimates that the off-road market makes up about four percent of the total racing market, but that four percent, like most racing disciplines, comprises a loyal bunch of enthusiasts. Off-road races may include rock crawling, desert racing, rallying, hill climb, short course stadium racing and more. If it runs on dirt, there are people who will build and race it.

Engine builders who like dirt can climb into their favorite form of dirt sport by doing their homework and getting involved with one of their local off road racing events. It may take a little bit of research to find what events are closest and what forms of off-road racing make the most sense to your brand of engine building. If you are already building sprint car engines, for example, you may find it’s not a difficult stretch to build a dirt motor for a trophy truck racer.  

Another popular form of off-road racing is rallying, which has become increasingly more popular in the last decade thanks to media attention and even video games. A big part of its popularity is because manufacturers have been successful selling their homologated rally cars like the Subaru STi and Mitsubishi EVO. Both were designed with rallying in mind.

Ironically, while their factory rally teams are no longer involved in the World Rally Championship (WRC), the car companies still support the grassroots racers and have made many performance parts available for these vehicles. There are also a number of aftermarket companies producing components for these vehicles.

If you’ve been building sport compact engines and really know what makes them tick, getting into rallying may be a logical step, as many of the cars and engines are the same or similar. The major differences are making adjustments to run on dirt and the people who are your customers. Experts say there’s a little more involved than knowing the engines but it is a good place to start.

Jim Justice of Justice Racing Engines in Winchester, VA, started building engines for rally racing after successfully competing in SCCA for more than 20 years at Quicksilver engines. Quicksilver has built race-winning engines for several SCCA open-wheel classes, but Justice had a desire to branch out on his own. Now, while he is still building road racing engines, he also has had success building winning rally engines.  

“If you look at Rally America (SCCA) or National Auto Sport Association’s (NASA) rally website you’ll see that the majority of the races are in the Northeast or North Central part of the country. There are two or three NASA events in New York and some in West Virginia, for example,” says Justice. “Our rally customers are mostly concentrated where the races are.  Some people cross over between the two sanctioning bodies because the rules are very similar.”

Rally consists of a mix of production vehicles and open class vehicles, which is the top tier class in both NASA and SCCA. The turbocharged open class is fairly free engine-wise but does have a turbo restrictor, says Justice. Other than that, they are full-on race cars. The production class is much more restricted, running virtually stock engines. These are basically street cars modified for rally use. You’re allowed to balance and blueprint engines in production class and replace some of the OE parts with aftermarket components, but there are restrictors, which is how the sanctioning bodies control the ultimate horsepower.  Both classes must be street legal, because they do run on open roads.

The open class is very similar to the World Rally Championship (WRC) cars but Group N cars are all-out (Group N is a modified version of a production car that is homologated by the FIA). “We’ve had customers go down to Mexico to run with the World Rally Championship drivers down there. It’s very competitive in the WRC so most of the guys who show up to run the one event are excited to compete and see where they stand against these multi-million dollar teams.”  

Rally teams build their open class cars basically the same way many of the top WRC teams do – from production-based vehicles such as the Subaru Impreza STi and Mitsubishi Lancer EVO. There are a lot of aftermarket parts available for these cars so the teams don’t have to fabricate many parts. The engines and drivetrains are controlled by electronics, so knowing how to tune is an important factor in building a successful rally engine.

Tuning is so important that Justice says he leases space to rally tuner Franz Diebold, of Diebold Autosport, who does ECU tuning on most of his rally customers’ cars. “He was up in Canada for a few years and then came into my shop. We got to talking and worked out a deal to have him come into my place and work out of here,” Justice says. “He does all the tuning on my EFI engines. We have an engine dyno and chassis dyno for him to use and he brought along a lot of his rallying customers. One of his customers who came to us is Seamus Burke, winner of the 2007 US Rally Championship and another is Bill Bacon, who’s currently second in the championship. We also have Josh and Jeremy Wimpey who run the production class in the Max Attack series (a 2wd rally series). Our business spread by word of mouth: when one person is happy with your services he’ll tell his other racing friends. So we were fortunate to meet with Franz. Now he attends the events so he can help tune the engines for the varying weather conditions.”  

Justice says he also does some tuning so his customers can choose either one of them to do the work. “I am familiar with tuning and can do it but Franz is better at the whole package and at recognizing how a rally car works during the event. There are programmable differential controllers and he understands all that too. Rally is a little bit different than other forms of motorsports like road racing or drag racing, so the approach to building engines is also a bit different. We can work together on designing them for their intended use.”

The most important aspect of a rally engine is torque and drivability, Justice says. “The open class engines have a restrictor on the turbo inlets that limit horsepower to the 300-plus range. This limits the speed but, due to the varying conditions, these engines could run in gravel, mud, pavement and various other weather conditions. The driver must be able to put his foot down on the throttle and still have instant response from around 2,000 rpm. Drivers want as much torque as possible until they get into the restrictor. And, the engine needs the durability to handle the varying conditions throughout the entire event with no failure. With a rally engine, it’s always seeing 400-500 ft.lbs. of torque for extended periods of time. So the parts and everything have to live up to that.

If you took the restrictor off of these engines they would be making about 600 or more horsepower with the right turbo on it. Below the restrictor the engine is still a “full-horsepower” race engine.

The biggest issues Justice says he has with these engines are probably dealing with temperature variations. These engines are run extremely hard without a break in conditions where mud or dirt can clog a radiator very quickly. Snow and other adverse conditions are also challenging, because it might block off air inlets or coolers and cause the vehicle to overheat.

“We run racing oil coolers and try to place them in the best location to be out of the way of  debris getting into them, but it’s very tight in the engine compartments of these vehicles,” Justice says. “Especially in an EVO or STi, because you still need to maintain a lot of the street car items like power steering and the alternator.  As such, trying to place other components in the engine bay is a challenge. Most of these engines use a modified wet sump system. We do use heat exchangers to help control the oil temps. As long as you can control the conditions and maintain good water temp and oil temp, the wet sump has proven extremely durable and cost effective. There are fewer things attached that might break with the wet sump.”

According to Justice, the basic recipe for a rally engine is an OE block, crank and cylinder heads. “You could replace the crank with an aftermarket unit, but unless you’re building a big stroker motor the stock crank is very good in these engines,” he explains. “We replace rods, pistons and the valvetrain, so as far as the basic long block we’re using the main OE components and replacing everything else.”  

One of the reasons Justice likes doing rally engines is because they are still open to some degree. He feels it hurts the engine builders when sanctioning bodies close the hoods.  

Even though there’s a restrictor on the rally engines, Justice says it’s still an exciting challenge to build an engine up against that restriction. “It’s just as hard as a NASCAR Cup engine builder trying to get all that he can get out of a restrictor plate engine,” he says. “You still have to get all the characteristics you want and aim for 100 percent efficiency as much as possible.”

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