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Monday, 10 October 2011

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Xtra Flatshift Performance

This report shows the XoomSpeed Westfield's performance with an Elite IL200 gearbox and Xtra Flatshift system compared with the same car a year earlier with a Caterham 6spd manual gearbox.

The runs were recorded at Golspie, in June '09 with the Caterham 'box, and then June '10 with the Elite.

 

Comparison of speeds of the start line at Golspie.

The top strip shows the vehicle speed - measured as the average of the front wheel speeds. Also shown is the gear indicator from the sequential box. On the speed traces you can clearly see the pause in acceleration with the H-pattern box, whilst with the sequential, you really have to look at the gear indicator to see when the shifts occurred.

The lower strip shows the engine speeds.

 

Next we have details of one 2nd to 3rd up shift.

On the top strip, you can see the engine speed, vehicle speed and gear, with the shift taking place at around 5.4 seconds into the run.

On the 2nd strip, you can see the 'Upshift Command' signal. This is the output to the pneumatic valve that starts the cylinder moving to perform the shift. In this case the shift has been triggered by the engine speed reaching the up shift point for 2nd gear - just under 9000rpm. On the same strip, you can see the value of 'Engine Power'. Normally this shows the activity of the traction control system which is working hard between 3s and 4s to stop wheel spin. At 5.4s, it goes to 0% to cut the engine and allow the gear change to take place. It is slightly delayed compared to 'Upshift Command' to allow some time for the pneumatic control valves to move and air to start flowing into the cylinder before cutting the engine. This delay is programmable via XoomCentre and it allows the engine to be cut for the minimum possible time. The short pulse on 'Downshift Command' is used to bring the pneumatic cylinder back to its central position, ready for the next gear change.

The 3rd strip shows the 'Upshift Complete' signal. This is the signal coming from the magnetic sensor mounted on the pneumatic cylinder. It turns on to confirm that the gear shift mechanism has reached full travel and the next gear has been engaged. When this signal appears, the 'Engine Power' goes back to 100% and the 'Upshift Command' turns off. This also triggers the pulse on 'Downshift Command' which returns the cylinder to the centre of its travel.

In this case, the total time the engine was cut was 0.09s.

Traction control activity resumes at 5.6s - wheelspin at 70mph!  As with all the log files we record, the logfile has been cropped 1s before the run started, thus in this case, the car reached 90mph in just 6.5s

 

Similar to the up shift case, this graph shows the sequence of events during a down shift.

In this case, the shift is initiated by the driver pulling the down shift paddle. This is recorded by the XoomBox as 'Downshift Request' and is visible as the small pulse on the top strip at 53.8s

In response the the request, the Xtra Flatshift controller turns on 'Downshift Command' (2nd strip) and 'Throttle Blip' (3rd strip) which starts the downshift process.

On the 3rd strip, you can see 'Downshift Complete' turning on a short while later. This is the signal from the magnetic switch mounted on the gear change actuator and it confirms that the actuator has reached the end of its travel and the new gear is engaged. At that point, the 'Downshift Command' and 'Throttle Blip' outputs turn off and a short pulse is applied to 'Upshift Command' to move the cylinder back to its centre position.

In this case, the time from the driver requesting the gear change ('Downshift Request' turned on) until the shift was complete ('Downshift Complete' turned on) was just 0.08s.

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This site was last updated 10/10/11