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If you’ve been building sport compact engines and...
Rally consists of a mix of production vehicles an...
Rally engines must handle varying conditions such...
Rally and Off-Road Racing Engines
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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.”
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