I have cross referenced my speedometer, ECU speed, and GPS phone app speed at constant speeds . At GPS 100, ECU reads about 96-97, and dashboard speedo reads 103-104
Allowing for this, I tried some acceleration times with the traction control turned off today. It was 26’C, air con turned off, Andy’s reprogrammed EPROMs, and Powerhouse 10% overdriven supercharger drive pulley, standard air box and filter, new Bosch intercooler water pump, manual gearbox.
First run, too much wheel spin and axle tramp
Second run, no wheel spin, fairly quick take-off, but could do better with practice. However I don’t like hard standing starts as they are harsh on the drivetrain.
Anyway, graph from second run is shown below. It took me about 0.6 secs to change from 1st to 2nd gear. Despite this, my 0-60mph time is about 5.5 to 6 seconds.
I might try again on a cooler day, and not change from 2nd to 3rd great just before 100 !

 

Hats off to you for trying to attain best performance of the XJR with the manual set-up. I think 5.5 seconds or anywhere near is difficult to beat as the primary obstacle of the XJR is its weight. So it would help with the timing by reducing the weight of the car such as by removing the spare wheel, tool kit as well as running with a fuel tank with just enough fuel for the test? Other factors are tires, tire pressure and the most challenging one is how to start off at an rpm optimal for the XJR without spinning the wheels or burning the clutch and changing gear at the best time. I find the following video quite useful. .

Wish you better luck in your upcoming attempts!

 

Hi Al,
0-100km/h in 5.5 secs is an excellent result. The original manual press cars took 5.9secs to do 0-60mph (0-96km/h) . The bigger crank pulley and my reprogrammed ECU have shaved over 7% off the time. The 3.27:1 final drive ratio of the XJR was specifically chosen so that 60mph can be achieved in 2nd gear. I'm not sure if you can achieve 100km/h in second, but if you can, then your time will be even shorter if the 5.9ssecs result includes a 2-3rd gear change.