by cass3958 » Thu Jan 16, 2020 5:00 pm
I read that the old pumps worked at 800 PSI and the newer pumps on the Variomatic worked at 1200 PSI. The older Burman PAS system also worked with 3 1/4 turns from lock to lock where as the Variomatic fitted to the later 1967/68 S Types as well as the 420 was only 2 7/8. The Manual as you can read below had 4 1/4 turns because it was so heavy without the PAS.
The major benefit of the Variomatic system is the reduction in the amount of "arm twirling" and effort required when steering, particularly when a lot of cornering is involved. For example, the Variomatic system fitted as an option to the Jaguar 420 required only 2-7/8 turns of the steering wheel from lock to lock, which compares favourably with 4-1/4 turns between locks for the manual Burman F.3 recirculating ball system that was standard fitment on the 420, and 3-1/4[4] turns for the constant ratio Burman power steering system optional on the 420's predecessor, the Jaguar S-Type.
Whilst advanced for its time, the Variomatic system did have certain drawbacks. It was more complicated and expensive than a constant ratio power assisted system. The Variomatic system was also criticised for feeling too light at high speed, when greater weighting tends to give the driver more confidence in making fine steering adjustments. Later systems by other manufacturers would adjust the behaviour of the steering in reaction to road speed.
So the drawback of the Variomatic was it was very light at high speeds. My car is supposedly fitted with the Variomatic and I have got used to this now but I have also fitted a 16 inch steering wheel rather than the standard 17 inch which gives me a bit more feedback. The 17 inch wheel was possibly a necessity when driving an S Type without PAS but with the variomatic you could even drop to a 15 inch steering wheel to get even more feel but it might look too small. I have been told the difference visually between the two systems is if you look at the top cover the variomatic is square shaped with four bolts where as the older Burman is more round in shape and has six bolts. This is a link to the archives with photos of each system for identification.
http://www.jagstyperegister.com/forum/v ... rles#p1502
I do not know how easy it would be to fit a pressure relief valve in the system somewhere that would reduce the PSI reading whilst driving but have the ability to turn it up when you are stationary so you still have the full power steering to park and maneuver at slow speeds.
I read that the old pumps worked at 800 PSI and the newer pumps on the Variomatic worked at 1200 PSI. The older Burman PAS system also worked with 3 1/4 turns from lock to lock where as the Variomatic fitted to the later 1967/68 S Types as well as the 420 was only 2 7/8. The Manual as you can read below had 4 1/4 turns because it was so heavy without the PAS.
[quote][i][b]The major benefit of the Variomatic system is the reduction in the amount of "arm twirling" and effort required when steering, particularly when a lot of cornering is involved. For example, the Variomatic system fitted as an option to the Jaguar 420 required only 2-7/8 turns of the steering wheel from lock to lock, which compares favourably with 4-1/4 turns between locks for the manual Burman F.3 recirculating ball system that was standard fitment on the 420, and 3-1/4[4] turns for the constant ratio Burman power steering system optional on the 420's predecessor, the Jaguar S-Type.
Whilst advanced for its time, the Variomatic system did have certain drawbacks. It was more complicated and expensive than a constant ratio power assisted system. The Variomatic system was also criticised for feeling too light at high speed, when greater weighting tends to give the driver more confidence in making fine steering adjustments. Later systems by other manufacturers would adjust the behaviour of the steering in reaction to road speed.[/b][/i][/quote]
So the drawback of the Variomatic was it was very light at high speeds. My car is supposedly fitted with the Variomatic and I have got used to this now but I have also fitted a 16 inch steering wheel rather than the standard 17 inch which gives me a bit more feedback. The 17 inch wheel was possibly a necessity when driving an S Type without PAS but with the variomatic you could even drop to a 15 inch steering wheel to get even more feel but it might look too small. I have been told the difference visually between the two systems is if you look at the top cover the variomatic is square shaped with four bolts where as the older Burman is more round in shape and has six bolts. This is a link to the archives with photos of each system for identification.
http://www.jagstyperegister.com/forum/viewtopic.php?f=16&t=132&p=1502&hilit=marles#p1502
I do not know how easy it would be to fit a pressure relief valve in the system somewhere that would reduce the PSI reading whilst driving but have the ability to turn it up when you are stationary so you still have the full power steering to park and maneuver at slow speeds.