power steering

[johngosnell]

If I going to keep my car I need to improve the power steering, it is far to light. How much of an improvement will it be if I was able to change the steering box to the later varamatic steering box from the original power steering unit that I have.


Regards John

1BW1257BW

[cass3958]

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.

[cass3958]

These are photos of the two systems.

[Glyn Ruck]

We cover the 3 S Type systems here:

https://www.jaguarforums.com/forum/mki- ... in-224005/

I believe you should be able to reduce the PS boost by reducing the pump pressure at the control valve but can't find anybody that has done it.

PS Pump..JPG (81.72 KiB) Viewed 2784 times

PS Flow Control-Pressure Relief.JPG (190.23 KiB) Viewed 2784 times

[johngosnell]

I had thought about using a smaller steering wheel but because of using hand controls which means puting my left hand through the steering wheel to change the auto gearbox. So If I fitted a smaller wheel I may not be able to get my hands through. The picture should give the idea of what I was trying to say. The pump that is fitted is from an early rover discovery of the same design as the original but a lot larger, I could change the relief valve spring to a shorter spring as I do have the original pump and I know that the size is the same but shorter in length than the one now being used .

Regards John
1B1257BW

73388368_458791608074999_4770910179896066048_n (1).jpg (732.39 KiB) Viewed 2758 times