This prototype Jaguar XFR saloon is faster than the Jaguar XJ220 supercar. Inside, as it speeds across the Bonneville Salt Flats in the US state of Utah on November 8, 2008, is Paul Gentilozzi, race-car driver. His son, John, engineer at the family’s Rocketsport Racing company, talks Jaguar magazine through the record attempt.
"We took great pains to keep the car as close to stock as possible. That was our brief from Jaguar and we felt that it would be the only proper way to go at this record. The car arrived as a production prototype without most of the interior finishes. To conform to the Bonneville safety rules we would have needed to remove most of the interior anyway, although the dash and instrument cluster were identical to stock."
Although lots of the interior was removed, no doubt you had to add in a lot of safety equipment?
"The car had a full roll cage installed to meet Bonneville rules. A racing seat and a five-point racing harness were fitted. There were two fire-extinguishing systems on board, totalling nearly seven kilograms of extinguishing material. We also added a radio-communications switch to the steering wheel so that we were able to talk to Paul.
"There were only four additional aero parts added. We did not actually want to make any downforce as that always comes with a drag penalty. At best we hoped to go from the positive lift of the production car (nearly all production cars create lift), to a less positive lift or a slight amount of downforce. This was done mostly for stability. The boot extension and endplates help keep the air flow from the top of the car attached longer. The endplates specifically help prevent air from the sides of the car from curling around the rear of the car into an area of low pressure behind the trunk, which would cause drag. The flat floor was similar in function to the XFR’s stock floor, but we extended the edges to join the rest of the body. The front air dam helped prevent the front of the car from lifting at high speeds, thus improving steering. It was slightly lower than the chin spoiler fitted to the Jaguar R models. There were also two roof rails – one down each side of the roof. These are required by Bonneville rules and are designed to improve aerodynamic performance at high yaw angles. Basically, they help limit the possibility of the car rolling over if it gets sideways at high speed. You will also see them on every NASCAR race car. We also used ballast – about 113kg of the stuff, bolted to a special carrier in the spare tyre bay in the trunk. Sorry… boot. Getting traction on the salt can be very tough and this ballast provided a huge help in sticking the rear of the car to the ground. A few people saw that the car did not have an interior and immediately said that we removed it to increase the speed of the car. This is not true as weight has very little to do with top speed if you’re given enough room to accelerate (at a place like the salt flats). Aerodynamic drag, rolling resistance and horsepower are the most prominent determinants of top speed. Weight does have a place in the rolling resistance calculation, but it is negligible when compared to the aerodynamic loads. On course, the car weighed 2181kg, heavier than the 1891kg the road car weighs. So we may not have had the interior panels, but we sure had the weight."
What components were changed in the engine and gearbox?
"Only an uprated supercharger pulley was installed. The part was manufactured by the Jaguar prototype shop. A more direct air intake path was designed and fabricated by Rocketsports Racing. This created a direct path from the air intake to the throttle body to clean up the flow of air at high speed."
Didn’t you have to change the gearing?
"No. This seems to surprise many people, but if you work out the stock gear ratios, the car is capable of some unsightly speed at the rev limit in sixth gear, so no changes were necessary."
Did the speed runs take place at one of the Bonneville speed trial events or on a closed course?
"Initially, we intended to go to the World Finals, which is an official Southern California Timing Association/Bonneville Nationals Incorporated (SCTA/BNI) event. To prepare for that, we spent four straight 18-hour days to finish the post-test work on the car and get it into our transporter. Two days after the truck left the event was cancelled due to water on the course – if you have hundreds of square miles of hard flat surface and you pour water on it, you will have a wonderful wading pool, but a poor race track. In the end, we arranged a private test organized by the former president of the SCTA/BNI."
Could you describe the course?
"We set up the course – it was five miles long and 36 metres wide – only to have it washed away when high winds moved water over it. So we made another course and achieved a speed of 219.1mph (352.5kph). The next day the water moved again, so we made another course in a different area, this time six miles long."
What are the rules for speed runs at Bonneville?
"We followed the safety rules, but since this was a private test, we did not need to conform to any class rules. This happens at sanctioned events as well, when cars are run in a ‘time-only’ category. The rules for the actual run are quite simple – start at the zero-mile marker and keep your car under control until the last speed trap. Going as fast as possible, of course."
How are the runs timed and adjudicated?
"We had no control over the way that the speed measurement was performed. An independent company called Chronologic organised the timing. It is also the official timer for the sanctioned events as well. The car is timed in two places. The first is the flying mile – this speed trap started at mile marker five and finished at mile marker six on the record run. The second is a speed trap – it is placed at the end of mile number six. This trap is exactly 132-foot long. Light beams are set up at precise distances. When the car breaks the first beam, the clock starts. It stops when the car breaks out the other side. At Bonneville, ‘speed’ is not measured – the time that it takes the car to travel a carefully measured distance is, and this time is used to compute the speed based on known formulas."
How many runs did you make?
"We made nine, with the 225mph (362kph) run coming last."
What speed did you hope to achieve?
"I believed that we would break the Jaguar production-car record. I thought we would do it during the early tests, but the oval simply wasn’t large enough. We didn’t attempt another run at Bonneville since it was fairly late in the day when we broke the record and we had some promotional filming to do with the car. Also, after you make a speed run it takes a long time to cool the car down to optimal operating temperature."
And this is a Jaguar production-car record?
"Absolutely. It’s the fastest Jaguar road car since the XJ220."225mph!
"Well… 225.675mph to be exact."
THE DRIVER – PAUL GENTILOZZIThe Gentilozzi and Rocketsports Racing names have been associated with US motorsport success for many years. The team was formed in 1985 and is based in Lansing, Michigan. Paul is a five-time Trans-Am Series champion, and Rocketsports Racing has won seven manufacturers Trans-Am championships, five with Jaguar XKs. In addition to its success on the track, the team has become a leader in race engine and chassis design and construction. In 1994, Paul won the Daytona 24 Hours race, probably his biggest win as a driver.
BEHIND THE WHEEL
"It was great to be driving a Jaguar again," says Paul Gentilozzi. "It’s always fun to be doing high-performance, racing type activities, but my affection for Jaguar makes this very special."
LESS HASTE, MORE SPEED
"Driving on the salt requires great patience as grip, at low speeds in particular, is at a minimum. It requires very gradual throttle application."
CONTROLLED POWER ON SALT
"As top speed was our focus, we took only casual interest in acceleration, but the car was still fast from 0-60mph. I used the XFR’s steering-wheel-mounted paddles to give me more control over the power application of the engine. Shifting gear at lower revs makes the car easier to control on the salt."
"At 70mph it ran really easy – like pushing a baby carriage!"
THE EXTRA MILE
"I was quite surprised how the car accelerated from 100mph to 180mph. It was so comfortable that, at first, I thought the speed indicator was wrong."
JUST PASSING THROUGH
"The car accelerated so hard to 180mph that 155mph (the speed at which the road-going XFR is limited) was just a passing thought.”
TAKE IT TO THE BANK
“We tested at the Chelsea proving grounds’ 4.7-mile, high-banked oval in Michigan, US. It was very easy to achieve 210mph. I did several runs holding the throttle flat entering the oval turns at 180mph – Sunday ride!"
IN THE ZONE
"At 200mph on the salt, though, you begin to really feel the aerodynamic lift the car is subject to, your focus gets serious and your field of vision narrows. At high speeds, keeping the car in alignment with the track becomes your focus."
THE JAGUAR PURRS AT 6400RPM
"220mph. The engine reaches 6400rpm and the car calms again. It’s as if it is starting to have real fun. But at that speed you soon run out of track. We were prepared with a rules-required parachute, but only used it for a few photos – the XFR’s brakes were great."
"I really didn’t want to stop as the car is so much fun to drive. I was honoured to beat the record and be part of Jaguar’s history; this brand has a unique ability to make you loyal."
[Issue 1, 2009]