Green Shower & Part Number
#21
The valve is preset to 1000psi +/- a few and it is adjustable but the problem with the adjustment is that you can adjust it. As for the unit going out of adjustment I would need to refer it to the manufacture. I would first want to know how long the hose was in the car prior to the install of the pressure relief valve. Like I said in the beginning and is stated on the web page the install of the valve will only delay the failure on an already stressed system.
I am surprised to learn that the top controller system is less integrated than that of other manufacturers of the era. Especially since the convertable model was envisioned at the outset and the XK8 was an important milestone for Jaguar. Must have been a cost issue. Another reason to install the relief valve...
#22
Most vehicles with power tops also have a dedicated convertible top controller. Not so in the XK8/XKR. Our cars have distributed control across the Body Processor module, Security and Locking module and the Driver door module. I think this made the design a siginificant integration challenge that was never truly perfected, particularly under fault conditions.
PWM (pulse width modulation) is often used (I know you know this) to control fuel pump voltage and pressure in fuel injection systems, and I bet the same technique is used in many ragtop ECUs.
The voltage reduction system you and I use is in effect a poor-man's ECU.
Last edited by Dennis07; 07-07-2011 at 10:13 AM. Reason: clarity
#23
Yes, use the hose kit from Gus's link. The quality of the hoses and fittings are impressive. It also installs without any issues. My Jag mechanic had never seen this kit, was impressed with the hose quality and the retrofit did not take any longer to install than a factory kit would have.
#24
I suspect the reason the top function is distributed across multiple systems is because it not only controls the top but also has to communicate with the speed sensor, rear windows, chime, etc. I can see where it could be considered a more elegant solution to communicate over the bus to these existing controllers than work around/override them.
Sure makes me appreciate the rock solid manual convertible top in my 2001 Corvette! Unlike the soft tonneau cover of the XK, the hinged fiberglass one is also a thing of beauty, actually enhancing the look of the car with the "waterfall" element. Of course it's easier to do that on a 2 seat car than a 4 seater, and my wife definitely prefers the power top in her XK8 (even though I, too, cringe every time she hits the button, though the voltage reduction system gives me some peace of mind).
Sure makes me appreciate the rock solid manual convertible top in my 2001 Corvette! Unlike the soft tonneau cover of the XK, the hinged fiberglass one is also a thing of beauty, actually enhancing the look of the car with the "waterfall" element. Of course it's easier to do that on a 2 seat car than a 4 seater, and my wife definitely prefers the power top in her XK8 (even though I, too, cringe every time she hits the button, though the voltage reduction system gives me some peace of mind).
#25
I am sure I posted this previously but the best solution for the XK8 (either as part of the original design or possibly as a retrofit fix) would be for the top to be hydraulically powered (as it now is) but for the latch to be manual. It seems like virtually all of the leak problems occur with the hose that connects to the latch. It would be great if that hose could be blocked off so that manual opening and closing of the latch could be performed via some handle. I realize that this would be a difficult/impossible retrofit due to all of the microswitches that sense what is going on with all of the components in the system (including latch status). But it certainly could have been part of the original design. I cannot imagine that owners would have considered it a burden to manually open and close the latch as long as the top itself raised and lowered automatically.
Doug
Doug
#26
Sure makes me appreciate the rock solid manual convertible top in my 2001 Corvette! Unlike the soft tonneau cover of the XK, the hinged fiberglass one is also a thing of beauty, actually enhancing the look of the car with the "waterfall" element. Of course it's easier to do that on a 2 seat car than a 4 seater, and my wife definitely prefers the power top in her XK8 (even though I, too, cringe every time she hits the button, though the voltage reduction system gives me some peace of mind).
I'm hoping that after I install Gus' armored hoses and with the pressure valve I can stop holding my breath every time that pump whines into action...
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