A friend at the Roadfly Jaguar forum advised me that misinformation was being posted here about the voltage reduction (resistor) system which I designed. I'll just post a quick correction to some facts about it here, and offer to email a paper describing it to anyone interested; full details to be found there. Then I'm back to Roadfly, as one forum is all my schedule permits.

Does the voltage-reduction system reduce peak hydraulic pressure? Yes, to about the same levels as the relief valve. (My measurements, admittedly less accurate than those of the relief-valve designers, *are* accurate enough to clearly demonstrate the dependence of peak pressure upon the voltage driving the motor. (It would be a very remarkable pump / motor indeed that had no such dependence.)

Can the system damage the pump's motor? It cannot. DC motors such as this one can work over a wide range of operating conditions. In the voltage-reduction system the pump runs at 8-9 volts, a very comfortable operating point which actually results in reduced power consumption by the motor, perhaps extending its service life.

Any other advantages? Compared to the relief-valve system ...
- it costs about $10 to $15, compared to $280+ (no money to me; just the cost of resistors),
- it is easier and less invasive to install, no need to disturb the pump itself,
- it can easily be completely uninstalled.

A review of the threads on Roadfly would, I believe, show to an unbiased observer that the folks who designed the hydraulic solution did a fine job but simply did not see that there was a voltage-pressure dependence that could be exploited to achieve pressure reduction. (They still seem unwilling to acknowledge this dependence, though they could easily measure it it they wished.)

I will forgo a description of some of the "cons" of the relief-valve system although, having read some of the posts here by my detractors, I am sorely tempted.

Edit: The most recent version of the PDF file describing the Voltage Reduction system is always available at ... www.scorekeeper.com/jaguar/jaguar02.htm


Thanks,
Dennis

 

Dennis,

I've been watching this in the background. I'd like to try this resistor on a couple of XK8s that come through my shop and my own too. Do you have a value for the resistor you are using, where to buy? Maybe I can give a little FB too.

Thanks,

 

Please see my comments on the second posting of this topic http://forums.roadfly.com/forums/jag...9551023-1.html and the first segment of this entire post http://forums.roadfly.com/forums/jag...9531938-1.html

 

Jeez the pissing contest migrated all the way from one forum to another!

Doug

 

Polite opinions are welcome. So far, that's all I've seen.

 

Installed the resistor solution to the high pressure hose convertible latch leak problem after independent research on both the affects of reduced voltage on DC motors and the affect of corresponding reduced pressure.

Conclusion was that the up cycle time was extended by about 5 seconds with a dramatically reduced pressure spike at the latch closure. The DOWN cycle time was extended by about 3 seconds.

I measured voltage and resistor temperature during the installation process and found it completely within expected and tolerable results.

Total cost of a 0.20 ohm, 100w, 5% eBay resistor and 4 crimp-on connectors was less than $10. I connected the resistor a manner that permitted the install and potential removal without any cutting of OEM Jaguar wires and without a heat sink. Up cycle temperature rise of the resistor was about 40 degrees from ambenient as read on a cheap IR therometer.

I believe that Walt's mechanical pressure management solution is a much more elegant system as would be a sensor driven, processor controlled voltage feedback system. As Walt has posted, the cost would be approximately the same at about $300.

 

As I had stated previously (either here or at the other forum), my primary concern with the resistor solution is the fact that these cars are so glitchy in the electrical system to begin with. Everything on these cars seems supersensitive to fluctuations in battery condition--memory seat controls that work sometimes and not others, weird warning lights and messages that come on at weird times and then disappear, etc. I have read from other sources that this is at least partially due to the complexity of the electrical system such as the use of multiplexing circuits. It seems that tinkering around with the electrical system by installing resistors in the circuitry is asking for problems, not to mention what the long term effect will be on the pump motor itself.

Doug

 

Testpoint or Dennis,

Did you have a specific vendor that you used, or an ebay link or Ebay vendor?

Thanks,

 

http://cgi.ebay.com/1-x-0-2-ohm-0R2-...item3efacfc372

This resistor is shipped directed from Singapore via airmail but it still takes 10 days to 2 weeks. Less than $10 shipped.

Available from US sources in 0.20 ohm, 1% for anywhere from 4 to 10 times the cost. My cheap VOM was not truly capable of verifying the very low resistance but the engine-off voltage to the pump was about 8v under load. That would probably be 9 - 10v with the engine running.

 

Thanks TP, much appreciated

 

Stevetech,

0.20 to 0.25 ohm is the resistance value needed.

As Test_point said, these are a bit pricey, but ...

Two 0.1 ohm, 50 watt (wattage really matters here!) resistors from www.mouser.com ... part # 580-850FR10E

 

Dennis,

Thanks, I think I'll be OK regarding mounting and installation. I just wanted to make sure I had the same resistor range which you and TP have tested. I am looking to produce the same voltage and pressure curve shown in your analysis. I've ordered a dozen resistors and will use the first on my own car when I get them.

You (and TP) might want to get your writeup and tests put in a sticky. This offers an alternative to the pressure relief valve which is a good option too, with a different approach.

Best,

 

Stevetech,

Not to beat a dead horse, but please do look at the installation notes. One or two important things might not be obvious (this learned from working with people who have done installations.) I would post the PDF here -- the whole story in four pages -- but it seems my "new guy" privileges do not permit it. Or maybe I just don't know how to do it.

Thanks,
Dennis

 

Hope you don't mind if I post it. (Had to reduce the file size though) Where would I find Stevetech's improved procedure?

Reposted in higher resolution at originators request! (Post #25)

 

Hlgeorge,

This may be more "new guy" stuff, but it seems I am not allowed to access the PDF of my paper which you posted. Could I ask you to take it down (if possible) until I can see it? I'd like to be able to verify that reducing the file size did not do any harm to the contents (It's got my name on it and all ...)

I'm just not familiar with how all this works here. Can a moderator help?

Thnaks,
Dennis

 

Yeah, I think it is the new guy limitations. It did not change any of the content. I have emailed you a copy of the reduced file for you to see for sure.

 

Dennis:

Yes, it is "new guy syndrome". I think you need 10 posts, or Admin can override the min posting requirement. You can also go to the new membership section and "welcome" some new members to get your count up sooner.

I did take a copy of the PDF when George posted it - Thanks.

Nice writeup and professionally done. Should get stickyed when you are satisfied with it and you are full membership.

 

Dennis is to add the 'no cut' installation to his document when he returns home but here is a picture. The idea being to solder male/female clips to the resistor and an extension wire to allow use of the Jaguar connectors without cutting. If you want to remove, just put the connectors back together.

 

TP, This is precisely what I was thinking on my own. Looks like we're all on the same track.

 

Moved the voltage reduction/resistor method to its own dedicated thread (along with relevant posts) to not muddy the original one any further.

Proceed.