Pikes Peak is a unique challenge in motorsport. It is an extreme example of the hillclimb discipline but, unlike almost all other such events, it carries a popularity and reputation that mean it draws entries from drivers and automotive companies who want to conquer the hill and emerge victorious.
Below: dry roads and sunshine – Pikes Peak at one extreme of weather conditions; abvove: thick fog, wet roads and snow further up the mountain – Pikes Peak at the other extreme. The variability of the weather makes driving and engine mapping difficult (Courtesy of Robin Shute. Larry Chen Photo)
In recent years, Volkswagen poured a lot of money into a successful attempt at Pikes Peak, in the hands of Romain Dumas. The driver quality – past winners include Mario Andretti and Sebastian Loeb – is mirrored in the technical quality of the best cars.
The event has been running for more than 100 years. The start and end of the course are at altitudes of 9390 ft (2862 m) and 14,115 ft. The event often takes place in very low temperatures and with thick mist enveloping parts of the course. Practice is difficult, and each competitor has only one race a year.
The course carves its way up a mountain course in Colorado, with some frightening drops at one side (it is usually a public road). It is only in recent years that the road has had a permanent hard surface: before the 2012 event, the course was only partly paved and competitors had to cope with a gravel section on the course.
The course is very long, although not unique in terms of length or duration. What is unique though is the altitudeand the very difficult and changeable weather conditions.
Robin Shute is one of the more successful drivers of recent years, and he is well aware of the advantages of an electric powertrain in such conditions, although he uses an IC engine for his Pikes Peak car.
He campaigns a Wolf GB08 powered by a four-cylinder, turbocharged, gasoline Honda engine that produces around 580 bhp (433 kW) at Pikes Peak. It is a high-downforce, open-wheel version of the popular sports racer.
Remote location
Pikes Peak is an isolated venue for a race. Like Bonneville Salt Flats, it is a long way from fixed racing infrastructure, so teams need to be relatively industrious and self-reliant. This is an important consideration for Shute in his choice of engine and engine supplier.
Although his racing effort is relatively well-funded, he describes it as “a passion project for a lot of people”, referring to the team members, adding that “the philosophy is to enjoy it”. This isn’t a full-time team, and the people who work to make the car a success are taking time away from other aspects of their lives.
It is something that Shute considers is “the time and effort to run and maintain the engine; there is a human aspect, and we try to reduce the workload.” An engine that needs constant maintenance at Pikes Peak is going to take its toll on staff, so something that is as close as possible to ‘fit and forget’ is good for everyone.
Wish list
Shute’s engine supplier is Mountune USA, which works closely with Shute to give him the package he wants. He says the first desirable quality of the engine is power-to-weight ratio.
The mass of the total engine package including all supporting ancillaries is the key here. Some engine suppliers quote a low mass for their basic engine, and then the customer finds there is a significant added mass of cooling and boosting hardware to consider.
Visible in this image are inlet plenum, intercooler pipe and radiator feed and return. Large-capacity cooling is required for the thin air at altitude (Courtesy of Robin Shute. Larry Chen Photo)
The engine Shute wants is reliable, consistent and cost-effective, and the Mountune unit is based on the well-proven Honda K20 four-cylinder. It is the same basic unit that underpins race engines we have covered in the past, for example the Bourne Time Attack engine (RET 142, October 2022).
It is widely available and seems very tuneable, and has become a real favourite for many engine tuners and suppliers. It is small and light, and other more exotic, bespoke race engine options that might prove to be competitive for events like Pikes Peak, such as ex-IndyCar engines, are very expensive by comparison.
Of equal or, perhaps greater, importance to Shute is driveability, which he describes as being “good, predictable throttle response and linear torque”. In discussing this, he has a good point of reference in electric powertrains, which he says represent the ideal for an engine to strive to match.
What was interesting to hear is that it is important to lose as little of that driveability as possible when going up the course. The changes in altitude mean it is difficult to provide a good match between the engine and the turbocharger components to suit the whole course. Shute compares the effect to that of using an engine fitted with an air restrictor.
He notes that a common mistake among competitors is to chase “big power” at the expense of everything else. The opportunities to use peak power on the course are extremely limited, and there are a lot of corners where a strong exit will save much more time than a bit more power on a straight. On a typical run Shute notes, “You are very seldom at full boost and full power.”
A flexible, responsive engine is much more useful and faster over the course than one tuned simply for peak power. So keen is Shute to maintain driveability and linear response that a tapering boost curve is used to ensure that the engine responds as he wishes, effectively sacrificing a little performance in order to provide a really driveable, linear response. A predictable and linear response places less demand on any traction control and less stress on the driver.
Even with all the downforce-inducing elements on the car, there are a lot of places on the course where the limit to acceleration is grip. “We are traction-limited up to 60 or 70 mph, so it is important to have the best possible driveability in this range,” Shute says.
The boost target is adjusted in each part of the engine’s speed range in order to keep linear torque at maximum engine load. Where there is a widespread tendency among engine developers to map for maximum torque at every engine speed, Shute is asking for the most useable throttle response. He feels that this is also good for driveshaft and transmission reliability.
While the characteristics of the engine have a major effect on the car’s behaviour, the design of the car and the amount of downforce it can produce has consequences for the engine. In cornering, accelerations reaching 4g are measured and, as many readers know, such lateral accelerations can play havoc with the oil system in the car.
In these times of long-life engines, this engine has a relatively short rebuild interval of 300 miles. However, with a total course length of 12.42 miles and the chance to do perhaps the equivalent of only four or five complete runs during all the practice sessions and race day, this is not a limit that entails engine changes for Pikes Peak.
The parts that are prone to wear are valves and seats, mainly owing to high revs and a focus on anti-lag, and the sleeved cylinder block has a short lifetime, which is not too surprising for a modified production casting. According to Shute, the cylinders themselves also “get tired”.
The pistons can be used over more than one build, but the rings are replaced. Chain tensioners in production-derived engines are a common point of concern, and this engine is no different. The consequences of a chain tensioner failing are serious, so these parts are replaced at rebuild.
Mountune has been Shute’s engine supplier since 2019. It is important to Shute and his team that they can run the engine independently, so there are not necessarily Mountune engineers at the track. However, Shute says, “Mountune are always at the end of the phone and they go above and beyond to support us.” Even so, Shute’s team can do all the required engine work at the track themselves.
Weather
One highly variable aspect of running at Pikes Peak is the weather. “There is a huge range of ambient conditions, so engine calibration is the biggest headache,” Shute says. As there is nowhere that an engine can be mapped to replicate the conditions – temperature, pressure and humidity – at the Pikes Peak mountain course, Shute says, The only place to tune the engine is on the mountain, but the ability to make an accurate tune is very difficult.”
Mountune provides the four-cylinder engine used by multiple Pikes Peak winner Robin Shute. It is based on a Honda K20 (Courtesy of Robin Shute. Larry Chen Photo)
There is an element of trying to chase a moving target, and a feeling that improvements can always be made. Shute says the mapping is adjusted after every run. He notes that they have five VE tables (effectively a map of air consumption at each load and speed site over the operating range), from which fuel injection durations are calculated. Different maps are needed to cover the range of ambient conditions. The behaviour of the wastegate control is also given a lot of attention, given its key role in driveability and engine response.
Practice
In any other form of motorsport, it is possible to run the whole course in practice several times in the days before the event and often also on the day of the competition. At Pikes Peak though, the only occasion when the whole course can be driven is on race day, and each driver is allowed only one run.
A unique aspect of Pikes Peak is that the course is split into three sections for practice, and each test day begins at sunrise and finishes by 8.30 am to allow the road course to resume its ‘day job’ of carrying traffic. The first runs can be so cold (around freezing) that they are effectively “junk” according to Shute, and many entrants therefore opt not to run very early in the day.
In general, that means Shute drives one-third of the course three times on each test day. As each section usually takes 2.5 to 3 minutes to drive, that means something less than 10 minutes of driving per test day.
There are nine tests a year, meaning that the total time spent in practice is less than 90 minutes. Add to that a single timed full run for the race, and the total driving time for Pikes Peak a year is quite a bit below 2 hours, split over 10 days of running.
This lack of running and the very disjointed nature of practice, added to the very variable and unpredictable weather conditions, hampers the usual fine-tuning of the engine’s calibration, hence the requirement to try to improve the engine’s response according to how the engine felt from the driver’s perspective and using data from the last partial run, or based on conditions on race day. Data gained from freezing practice sessions can have limited value on race day, when temperatures can be 20 oC (36 oF) warmer.
Summary
In 2023, Shute will try to win his fourth overall Pikes Peak victory in his Mountune-powered Wolf-Honda. His insight into what makes a good Pikes Peak engine shows that, for entrants to optimise their time from the bottom to the top of the course, there are aspects of powertrain behaviour that require more than simple maximum performance at every point of the engine operating range.
To him, the driveability of the powertrain is of equal importance to engine output. Moreover, it is a target to maintain that driveability as the car ascends to high altitude.
There are a number of real difficulties facing competitors at Pikes Peak, which become more demanding for the top competitors needing to keep engine performance and transient response at the absolute optimum.
For a first timer trying to find their way around the course and to post a respectable time without damaging the car or bike, they probably don’t need to worry too much about wringing every last drop of performance out of the engine on every run. For the seasoned competitor, the challenge is to get the engine performing over the whole course in ambient conditions that are much warmer than any of the practice sessions.