There is a purity to land speed racing – in any one its myriad classes there are entrants striving only to be the fastest ever. There are landmark speed records, of course, but for every land speed record worthy of a news item around the world, there are hundreds of successful attempts to raise the bar. Even if a new record is not set, there is competition to be the fastest at a meeting.
The Speed Demon about to embark on a run along the 5-mile course at Bonneville. Capable of almost 500 mph with a turbocharged methanol-burning V8, this is the fastest wheel-driven car ever (photos courtesy of Speed Demon Racing/ARP)
For many years the land speed record has not been wheel-driven. Every successful attempt on the outright land speed record over the past 50 years or so has featured a rolling chassis propelled by jet reaction, with the high-velocity stream of exhaust gas usually provided by a gas turbine engine or rocket, although in the case of the (currently stalled) Bloodhound project for example, a gas turbine and a rocket will be used. The last time a wheel-driven car held the absolute land speed record was 1964.
However, there is still significant competition for hundreds of other classifications of land speed racing, either on two or four wheels and using a wide variety of propulsion methods. Most entrants rely on an IC engine using pistons, and most land speed competition classes are classified according to engine displacement, fuel type, boosting and so on.
At the very highest speeds for wheel-driven competition though, gas turbines with a shaft output also compete for the wheel-driven record. A British team is aiming to be the fastest with a new wheel-driven car powered by a gas turbine but the record is currently held by a piston-engined car called the Speed Demon, driven by George Poteet.
The Speed Demon, with its single V8 engine which we investigated in RET 99 (December/January 2017) is the standard against which others need to measure themselves.
The Speed Demon is a type of racer known as a blown fuel streamliner, which means it is a streamlined car with a boosted engine burning alcohol. The boosting element can come from a turbocharger or a supercharger. It is a very effective vehicle because, when fitted with different engines, it holds multiple records in classes with very different engine capacities.
The engines are all built by Duttweiler Performance, in California. A long-term engineer on the project, Chris Raschke, also works as an engineer for ARP, one of the Speed Demon’s suppliers, provides some unique insight into the project. Raschke has driven the Speed Demon in anger, and has the unusual role of having to put his personal faith in his company’s products at speeds far in excess of those almost everyone reading this will ever travel on land.
Cooling
Land speed racing is all about top speed, and two of the main aims of producing a vehicle to achieve that are abundant, reliable power and low drag. Clearly, the power comes from the engine, while the low drag aspect imposes conditions on the engine installation in terms of cooling.
The energy input to a typical engine is converted into three main energy ‘streams’. The one we want the most of is motive power, and about a third of the energy going into an engine in the form of fuel comes out as kinetic energy. Another third comes out of the exhaust as heat and the rest is rejected as heat to atmosphere, commonly via a coolant.
The usual heat exchange in a passenger car is through radiators or oil coolers. These impose a significant aerodynamic penalty that is simply not realistic for the very fastest land speed cars to carry.
Cars with several thousand horsepower require many times the cooling capacity of the average roadcar. We don’t see huge radiator ducts on the fastest wheel-driven land-speed cars, and the cooling systems have no coolers; they rely on phase change and specific heat capacity to absorb energy.
Iced water is used where engines require cooling. In the case of a typical naturally aspirated engine, this is heat rejection from combustion, and for a boosted engine there may be an extra cooling requirement arising from an intercooler. The flow of cool water to the heads is of paramount importance to avoid end-gas detonation.
There are many challenges involved in land speed racing, some which are particular to the Speed Demon and its multi-class approach to competition. The aim is of course is to achieve the highest speed possible, and that naturally involves driving from a standstill to the top speed and slowing down in the available space.
Full-throttle time
Duttweiler described this as “a 5-mile drag race”, because it is effectively going full throttle and holding it there through the measured mile or kilometre, the start of which might be 4 miles from the start of the course. Most entrants, whose vehicles can reach their competitive speed and enter their measured mile 2 miles from the start run on a 3-mile course, but the Speed Demon needs a 5-mile course. Even with its impressive acceleration, it requires the long track to get close to its maximum speed.
From zero to the end of the course at 5 miles takes around 60 seconds of full throttle. It is interesting to note that the car is still accelerating through the end of the course and exit speeds can be a few percent higher than the average over the measured mile. Duttweiler notes that the time during the run which seems to pose the greatest danger to the engines is around 40 seconds into the run. There is little to lose in going flat out and accelerating all the way through the measured mile. Other than the short breaks in transmission through the gear changes, the whole run is constant full-throttle time.
A lesson for the apprentice. Long-term engineer and new driver Chris Raschke (in the red hat) takes instruction from record-holder, long-term driver and car owner George Poteet (in the orange shirt). Engine expert Ken Duttweiler looks on
Where land speed racing involves very high speeds, as with the Speed Demon, there simply aren’t tarmac courses that are long enough. The Bonneville Salt Flats therefore offer a perfect venue for a large event such as the annual Speed Week.
Traction and track surface
The salt itself represents a difficulty not found in many other kinds of motorsport, owing to what Duttweiler describes as “a total lack of traction”. In low-traction situations, we might ordinarily turn to reducing tyre pressures and using deep tyre treads. For land speed racing though, the tyres are of a specific construction and are still pneumatic.
However, they have no tread and have to be used at 100 psi (6.9 bar) pressure and, when coupled with the low coefficient of friction, traction is a real problem when engines are built with torque and power in mind. In this case, traction control is used to good effect, well beyond the speeds at which any circuit racers operate.
Wheelspin can still occur at speeds of 400 mph (643 kph), depending on salt conditions, and traction control plays a significant part, even at 3 miles from the start line. The aim, according to Duttweiler, is to limit wheelspin to 7%.
The salt itself is variable in terms of surface quality and consistency owing to the climate and the weather preceding the event. There is a known ‘wet patch’, where there is thought to be a subterranean water course. Duttweiler says the “wet salt feels like sloppy snow”, but when conditions are good “the salt is like concrete”. And when good conditions prevail, there is a crust of around 3 in of hard salt.
The track also degrades over the Speed Week. The condition of the salt is best at the start of the week, when everyone is there. Getting a run on the course involves queuing, and as competitors begin to leave later in the week, there is an opportunity to run more often but on salt of poorer condition.
Sometimes a new parallel course has to be prepared, if or when the salt condition degrades, by moving the course slightly to one side, and that involves a lot of work in clearing, smoothing and marking it out. The word ‘smooth’ is comparative though – Raschke describes the salt as being “rippled”.
Weather plays a part too. Bad weather, particularly rain, can affect and even ruin the whole event. The course is very flat and is undrained, so any rain creates standing water. Wind direction and strength can change very quickly as well, and that can affect competition and damage the temporary working areas.
Heat is also a factor, both for cars and drivers. Some teams prefer to run early in the day, when it is still cool, for performance reasons, but Duttweiler notes that the Speed Demon seems less sensitive to this and continues to perform well throughout the day with the hotter, thinner air later in the day being an advantage for aerodynamics.
With new driver Raschke seated in the cockpit, he and Ken Duttweiler discuss engine matters
Raschke has a different perspective though, based on him recently working from the driver’s seat in a break from his usual engineering role. When installed in a cramped, enclosed cockpit in fireproofs, he notes that driver comfort is, “much better at 78 F [26 C] than 100 F”.
Team activity
The team arrives at Bonneville a few days before the event to set up their camp and working area. Bonneville is not a permanent course and there are no garages for teams to operate from, so the team is self-sufficient.
On competition days, track running starts at 6.30. The plan for the next day’s running is finalised and the car is prepared the day before. “We don’t change anything on the morning,” says Duttweiler. Early-morning snap decisions aren’t always good, and team activity before starting the car for warm-up involves preparation, checking sensors and reviewing the car set-up, the plan for the day and any relevant car data.
From the point of view of the car, engine and driver, the run seems uneventful. The car is ‘charged’ with fresh chilled water in the coolant system, around 30 lb of ice is added and the engine is warmed up.
Coolant temperatures are kept low. Without having to consider radiator performance and cooling drag, high water temperatures are not advantageous, and the water temperature at the start of a run is around 80-90 F, which is exceptionally low when compared with top-level single-seater cars such Formula One, where coolant temperatures are limited by system pressure but where a figure of 275 F or so is common. The rise in coolant temperature from the run is around 40-50 F.
The team does something surprising with the coolant at the end of a run. There are spray nozzles in the water pipes surrounding the engine and the water is pumped out over the external surfaces of the engine to cool it. The coolant needs to be drained and replaced anyway, so why not use it to good effect?
The team’s recovery vehicles are based at 4, 5 and 7 miles out from the start line. If the team looks like setting a new record, the car is ‘impounded’ and must run again within 4 hours of its return to the impound area. The team has an hour in which to get the car back from the end of the course to the impound, and effectively has to decamp to the impound area around a quarter of a mile away from its base to prepare the car.
Ken Duttweiler tends to one of his engines. The Speed Demon is unusual in that it has several engine options of different capacities to compete in different classes. It holds records in six categories (Courtesy of Marc Gewertz)
During that hour, decisions are made about what set-up changes are required. The team can work on the car but not fundamentally alter it – it can check hardware, borescope the engine, change plugs and so on. The sort of activity that we might do during the gap between races at a short circuit is allowed, but not changing engines, which would be a fundamental change to the car.
FIA-ratified world records are a different matter. The FIA requires a return run, in the opposite direction within an hour. That gives only enough time only to pump out the coolants, refill and re-ice the cooling system, check the tyres and repack the braking parachutes.
Multiple engines and classes
One rather unique aspect to the Speed Demon’s efforts is the use of a single car in multiple classes. Driver and team owner George Poteet holds records in the AA, A, B, C, D and F classes in the car, each fitted with a different engine complying to specific class rules. To give this some context, the AA class is effectively the unlimited class for engine capacities of more than 501 cu in (8.21 litres or over).
The classes from A downwards are for ever- smaller engines. The F class, the record for which is also held by this same car, is for 123-184 cu in capacity. At very high speed, low aerodynamic drag is clearly very important, and the effort put into reducing drag coefficient and frontal area to an absolute minimum for the AA and A class records also pays off in the less powerful classes.
Given that the Speed Demon often competes in different classes at the same meeting, that means having change engines. The team has some simple rules that make this as easy as possible. There is no robbing one engine of parts for another; each has its own ancillaries, fuel system, inlet wiring looms, mounting plates and so on.
The engines all have the same connections though, so they can be removed and replaced with the minimum of effort and time. The only engine-related car changes are the installation of the correct map for the engine. The team runs all week, from Saturday to Saturday. “We keep going until we run out of engines!” says Duttweiler.
As the team is chasing records in a number of classes, engine changes are often through choice, whereas most other teams compete in a single class and change engines only out of necessity. The ability to change engines as fast as possible is important. Each engine is well-integrated into the car, so changes are not a trivial matter. However, the team has managed to change them and be ready to go in just over 80 minutes.
Ken Duttweiler leans on the structure of the rear fin to examine something on the car. One of the twin turbochargers is visible in the foreground
Given the consequences of loose bodywork at such high speeds, the team does not have the luxury of using quick-release latching or dzus-type fasteners. There are many threaded fasteners holding down the engine cover, and removing and replacing this piece of bodywork can take 5 to 10 minutes.
Engine longevity is a real unknown. Those in a low state of tune have been known to last for 10-15 runs without maintenance. Some of the more highly-strung engines run three times, others run once and have a problem.
Experience counts
Land speed racing is gloriously amateur in many respects – it is an engineering and innovation competition, not a spending contest. Good engineering counts, and good engineers working on the car makes the week run smoothly. The Speed Demon’s aerodynamics have been designed by someone working in Formula One. There are also current highly experienced NASCAR and Indy engineers on the team.
I am not being insulting by saying that engine specialist Ken Duttweiler and team owner (and current driver) George Poteet are not in the first flushes of youth. Long-term experience of land speed racing abounds in the team. They have a calm, measured approach, learned through many years of returning to the Salt Flats with a car that they know well.
Duttweiler and Raschke both praise driver George Poteet and his feedback to them. Of course, the engineers examine the data from each run, but if Poteet comes back from a run and mentions something unusual at the end of mile 4, say, the engineers are likely to find something in the data that matches this.
One might think that driving at such incredible speed would overload the senses, but onboard footage shows that the driver is very cool and calm. The constant feedback given over radio transmissions from Andy Green when driving the Thrust SSC to the outright record reveal that the people at the top of this discipline of racing show none of the excitability and petulance we see from some of their circuit-racing colleagues.
This calm approach from Poteet, and the quality of his feedback, takes some of the burden from the engineers, who have to assess the large amount of engine data generated during a run; this can be important in situations where the car requires a quick turnaround to complete another run. There is a degree of mutual trust in a long-standing team comprising highly experienced individuals that makes such a team run well.
Engine specifics
When describing his engines, Duttweiler says they are very much akin to a drag engine but with heavier components (especially rods and pistons) for longevity. He notes that some elements of the pistons are similar to those in diesel engines in terms of weight and proportions.
He adds that the cams are much ‘softer’ than for drag engines, saying he prefers to run big lift and big duration and uses this to limit cylinder pressures to help with durability. In terms of dealing with high cylinder pressures, Duttweiler uses a soft copper gasket to maintain a seal between head and block that is aided by a ‘bite ring’ which protrudes 0.035 in (0.89 mm) to provide a very high pressure area on the gasket close to the cylinder bore.
The power potential is really based on the turbochargers. The current engines have a potential power output of 3400 bhp, but the next Big Block engine has a potential 4000 bhp available. The turbocharger speeds are relatively low, at around 77,000,rpm, and so are very safe.
The Big Block engine, which is used for the AA class record attempts, is a new development; the Speed Demon is designed around the Small Block Chevrolet LS engine. The car originally ran with the 8.2 in deck Small Block engine, but longer rod ratios were possible and the engine would still fit with higher deck variants.
It was realised by Duttweiler that with narrower, siamesed-port cylinder heads suitable for Big Block engines, it would be possible to fit a relatively low-deck Big Block between the frame rails in the car. The aim here is not to build the biggest engine possible, but to get the smallest possible capacity engine with a good durable specification which works well and which is big enough to get into the AA class.
Duttweiler thinks that, with currently available components of proven durability, something around 520 cu in is the realistic minimum engine capacity that he would build for the AA class, but he has run with a 555 cu in. The stroke of the Big Block is 4.25 in, and at 9,000 rpm that equates to a mean piston speed of 32.4 m/s, which is very high for anyone used to dealing with circuit race engines.
Across the range of the Speed Demon’s engines, irrespective of capacity, Duttweiler uses very similar combustion chambers that give consistent spark timing over the operating speed range. In squeezing larger engines into a very limited space, he has to compromise on his preferred high rod ratios. His smallest ratio of rod length to crank stroke is 3.04, but his shorter stroke engines have ratios as high as 2.6 (multiply these figures by two if you measure rod ratio using crank throw rather than stroke).
Many land speed cars competing with piston engines are equipped with two engines. The 501 cu in minimum engine capacity requirement of the AA class could easily be met with two smaller engines, and this has been a common approach by those competing in the fastest classes. Some other competitors also use the two-engine set-up to provide drive to all four wheels, which aids traction.
Air supply
There have been two Speed Demon cars. The first had the engine air intake in a wide, flat scoop above the roofline. This was felt to be restrictive though, so the new car breathes through a pair of oversized ducts in the side of the bodywork. These cause less disturbance to the airflow over the car and make the stabilising fin more effective, as they no longer block the flow to this important piece of the car aero package.
The new intake ‘holes’ are also less restrictive. They are placed on an area of the bodywork which, owing to its shape, has a slightly higher pressure on the surface compared with any alternative location near the engine.
One feature that Duttweiler wants to investigate is active knock control. The engines are currently mapped pretty conservatively in order to account for changes in air temperature so that the margin to knock is generally very large. Duttweiler notes that the large engines all have “more power than we can use”, so it’s not a big deal to sacrifice a bit of power for mechanical safety.
On average, the trend in performance of the car, engine and driver combination has improved every year. There was no sense, when speaking to Duttweiler or Raschke, that they feel that they have reached a plateau of performance. There is a real belief that records in all the classes they compete in can be improved upon, or in some cases comprehensively beaten. There is much more to come from new features in terms of engine control and from developments in improving the distribution of air in the intake system and fuelling the cylinders accordingly.
Future records?
I hope the decision to give Raschke a competitive run in the car is an indication that, should team owner and driver George Poteet decide to step back from driving, the car is not retired from competition. There is clearly more to come from the car, and the team is closing on the 500 mph mile-5 exit speed that foreshadows a 500 mph average speed through the measured mile.
The record for the measured mile stands at 470.733 mph, with a 481.576 mph exit speed. The car is clearly still accelerating pretty hard during the 7.6 seconds it takes to complete the measured mile. It is an over-simplification of the situation, but if there were a ‘mile 6’ with an entry speed of 481.576 mph, a 500 mph exit speed might be possible.
According to Duttweiler, the driver has an excess margin in terms of performance available, so there is clearly more to come even with no improvement in engine performance. 500 mph from a piston-driven car is within reach, and nobody other than Poteet’s Speed Demon team seem close to beating this. On 10 occasions, they have left Bonneville with the fastest speed during the week, and have the current record according to the SCTA (Southern California Timing Association) rules. This long run of success for more than a decade though has not dimmed their enthusiasm for competition and pushing the records further.
DATASHEET
Speed Demon 2 land speed racer
V8
4.17 x 3.55 in = 388 cu in
Twin turbo
Methanol
Aluminium block and heads
Linerless
Five main bearings
Steel crankshaft
Steel con rods
Light alloy pistons, three rings
Pushrod, single camshaft
Two valves per cylinder
22° valve angle
2.23 in (57 mm) intake valve,
1.55 in (39 mm) exhaust
Electronic fuel injection
Engine management system
9.5:1 compression ratio
Maximum rpm, 9800
KEY SUPPLIERS
Block: Dart
Heads: Dart
Sump machining: Kenny Duttweiler
Crankshaft: Crower
Camshaft: Comp Cams
Drive belt: Jesel
Pushrods: Trend
Tappets: Jesel Belt Drive
Rockers: Jesel Belt Drive
Pistons: Diamond
Rings: Total Seal
Piston pins: Trend
Circlips: Diamond
Con rods: Crower
Big-end and main bearing: Mahle/Clevite
Bearing coating: Clevite
Camshaft bearing: Durabond
Studs: ARP
Other fasteners: ARP
Valves: Ferrera
Valve springs: PAC
Gasket: SCE-Dart-FelPro
Ignition system: M&W
Spark plugs: Champain
Coils: MSD
Injectors: Siemens and Enderle
Engine management: Motec
Sensors: Motec
Data acquisition: Motec
Throttle: Wilson Manifolds
Water pump: Meziere
Oil pump: Aviaid
Oil filter: Baldwin
Exhaust: Maxwell Industries
Induction: Hogans
Fluid lines: Brown and Miller
Wiring loom: Gregg Pyles
Fuel pump: Waterman
Fuel: VP Racing
Oil: Lucas
Dynos: Froude with AVL controls
Turbos: Precision Turbo