Guys,

Let's not start this up again, I think we all know where you both stand on the top pressure regulation issues.

Anyone who wants to research the issue can find plenty of reading already on the forum.

 

FYI,
This test was used using two different cars using the same equipment. I should also note that benchmarks were performed knowing that the information would be challenged.

This is the information that we had asked for from the application of the resister system. If you question anything it should be why was this information not available from the onset.

I will refrain from any personal attacks; it is unprofessional and not necessary.

 

I really really do not want to extend the argument here and add to the controversy. However, if the graph you presented is legit (and I have no reason to suspect that it is not) then am I correct in interpreting that there is still a pressure spike present when the resistor is used? And, if so, that is exactly the data that we were all wanting to see. Moreover, if it was that easy for you to obtain the data, why have we not seen this before from the "other" camp?

Again, I am not trying to fan any flames here but I believe my question is legitimate.


Thanks,

Doug

 

It depends on the equipment you have/can get to do the measurements. I think it is for Dennis to answer, we have asked many times for this data. Although I suspected something like this (i.e. higher spike), I didn’t think it was this high...

 

I for one am interested in the study done by Gus. I've seen a graph illustrating the three curves utilizing the original approach by Jaguar and the two others. Gus, can you expand on how you performed the test---the controlled parameters? Test equipment, open-closing sequence, how many times performed, ect. Hey guys in the end we're really after the same thing---extended life on our hyd. system. I think we can have dialogue without drawing lines in the sand.

 

Personally I wish that someone with no interest in either solution would perform an independent study.

Two different approaches to the same expensive and messy problem can't be a bad thing.

But, we can't continue to have 'the mine is better than yours' friction. It does no good to anyone.

Gus has shown his findings.

And Dennis has published an explanation of his system here, Jaguar VRS system.

All this information, should be enough for someone to be able to decide which route they want to go down, when considering their own personal criteria.

Obviously an interesting subject for many people, including myself, but let's avoid adjectives, which can not only inflame, but may take away from the discussion in general.

 

Let me first say that I am not in the business to lie to you or anyone else or do anything underhanded. I never told an untruth on this or any other forum and do not plan to do this now. I am unable to answer a few of your questions as to why you haven’t seen this info before this but here it is.

This test was operated on my car. To give us a benchmark and to check for accuracy we connected the data logger to the car by isolating the pressure relief valve and installed the data recorder and connected it to the computer. I ran the roof down and up and compared the results (normal operation no valve & no resister) of my car to Walts car and you can see the chart on my page at Jaguar roof hydraulic pressure relief valve. At that time we knew that the unit was recording properly. I then installed 2- 0.10Ώ 50W resisters in series as instructed in the instructions
(http://www.scorekeeper.com/jaguar/XK8ConvTop.pdf) to the white lead of the power source to the pump and opened and closed the roof. I then removed and reinstalled the resister to the black lead and did the open and close of the roof again and the results were the same. I will provide all information on my page, I hope, within the next day or two.

I set out several years ago to give you the facts as to how the roof system works and find the cause of the failures and I did that and I will continue. I am not out to harm or create problems with anyone. This information is what it is.

You asked about the equipment, this is it;

All the data was taken with a Data Instruments Model SA, 0-3000PSIS transducer.

The logger is a Dataq DI-148U.

The log interval was 100 samples per second.

There two cycles taken for each measurement and the cycles were compared and found to be consistent.

I hope this answers a few of your questions.

 

Andre, I am stunned and more than a little disappointed that you would say this. I put experimental data out there a year ago. It has been available for download in a PDF report ever since. See my next post in a moment or two please.

 

(Please excuse if this is sort of disorganized. It is surely incomplete. Until next Friday, my keyboard time will be at a premium.)

So today we have some new (so far un-vetted) data and an accompanying pronouncement that this data enables one to "know" that system X is superior to system Y. Really? Well, a few
issues to work through first, if nobody's in too much of a hurry.

The new data conflicts with my own measurements from a year ago
(www.scorekeeper.com/jaguar/jaguar01.htm), and this is fair game for discussion. So first off, whoever did the measurements should post here and describe in some detail how the data was gotten. A photo of the experimental setup showing the resistor in the circuit would be helpful. Most important, we need to know what the voltage was across the pump (not the source voltage) when the pressure was measured. Nobody is entitled to have his results unquestioned, taken as gospel.

A few more issues:

- Objectivity of the data: the late, great Richard Feynman wrote about this (in "Five Easy Pieces", I think). It is a demonstrated fact that experimenters who want a certain result, or expect a certain result, tend to get different results than those who are disinterested. This does not necessarily mean these people are dishonest, only human. I think it's a fair bet that whoever did these measurements was not disinterested. Can anyone tell us?

- Relevance of the data: far as I can see, the only truly conclusive set of measurements was not peformed. This would be on a single car, a set of data showing peak pressure as a function of applied voltage.

- Apparent conflict with other observed results. We are invited to conclude that peak pressure does not depend on voltage. Yet aside from hooking up measurement gear, our convertible tops and latches are themselves a kind of measurement equipment. The dependence of pressure on voltge has been seen in many user cars where latch closure was achieved only engine on, not engine-off. This is inexplicable if the peak pressure is independent of voltage.

If someone with a preference for one system or the other feels the need to compare pressure reductions in the two systems, fairness would dictate that this be done by some disinterested 3rd party and that both designers have some input as to the experimental setup. (This was not
offered to me in the case of the data presented today, as is standard protocol in technical circles.)

IMO, nobody should be convinced of anything or even swayed by what's been presented today so far, billed as a "comparison". Given the editorial comments that have circulated here over the leat year or so, an independent 3rd party is a must for any such comparison.

 

Dennis--I guess all we really need for an apples-to-apples comparison is a plot of measured pressure in the system versus time similar to the numerous graphs of the system operation presented by Walt and Gus. I am not sure if you had presented that or not.


Doug

 

Omg!!

 

The results that have been published are what the test equipment recorded. No interpretation is required. You are free to conduct the same tests. In fact you have been asked on numerous occasions to do just that.

 

Hi Dennis, first of all I admire that you have worked on a solution (even though I favored another one), and have committed so much time to it, so please don't take this personal. I have mentioned to others that your solution was also an option (if you didn't mind some of the drawbacks I mentioned).

There seems only 1 way that could solve it permanently, and that is to replace hoses, so I am not promoting the pressure relief valve as final solution either.

You can only do one thing now and that is to do your own tests with professional equipment, but even if you would get different values, it will already show that the results will not be the same in all cars for whatever reason.

 

Gus, thank you for coordinating these tests with laboratory-grade equipment.

Can you indicate whether the engine was running or not during each of these tests?

 

The engine was running at idle the entire time.

 

Andre,

As you know, the measurement gear I used was pretty primitive, but that does not mean one can't tease good data out of it. The voltage/pressure dependency measured with it is was clear and repeatable, and -- more importantly -- confirmed by the subsequent experiences of people who have installed voltage reduction in their cars.

Even with no resistor installed, the voltage and pressure changes resulting from engine on v. engine off were clear. Test resistors added more clear voltage / pressure change. Users have subsequently found that the peak pressure must have been reduced to something close to the value needed to close the latch (~1000 psi) since engine-on v. engine-off sometimes matters there.

These data have been available for about a year at www.scorekeeper.com/jaguar/jaguar01.htm

Now some new data has been reported. It includes only one resistor value, without a pump voltage measurement (which is required to confirm a correctly installed, correctly functioning resistor.) This data is said to conflict with all that's above, but is in fact too sparce to say for sure (no apples-to-apples comparisons; i.e. same car, varying pump voltages... measure resulting pressures.)

Because we are asked to take the quality of the measurements on faith (the machine drew the line, case closed) ... Because of the "Feynman" effect I mentioned earlier ... because of a previous report from the same camp of system behavior never seen elsewhere (and impossible with a proper installation) ... all of that taken together makes this new measurement an interesting result, but not at this point anything more.

For anyone who believes that the best test gear wins, I will have to concede that point. (but if anyone has such gear to loan me, I will glad to do measurements with it.)

Generally, measurement data is assessed on its own, and also by doing cross-checks with other known facts. Along those lines ...
If, as it is claimed for the new easurement, voltage does not drive pressure then:
- The industy would not have abandoned relief valves in favor of electrical pressure control in convertible top hydraulics, and
- manufacturers would not install series resistors or ECUs with fuel pumps to control pressure.

But these things are true. Another pretty big grain of salt.

 

A system that is designed to be electronically controlled, can't be compared to a system that isn't with the addition of a resistor, these arguments don't hold up here. To compare, you would also need to offer a pressure meter, computer and other parts that would precisely control the pressure (wouldn’t be surprised if another type of pump/motor would also be needed). So I agree that such a system would be better, but it’s cheaper to place a pressure relief valve then…

 

Hey Gus--strictly as an aside I like your new website for all things Jaguar--looks very slick!


Doug

 

Thank you Doug. I have been working on it just about every free moment to get it finished. I have a lot of information to add but little time with building or new home.

 

Andre, I can't agree here. By the same reasoning we would have to say the system was not designed to be relief-valve controlled. The designer, curse him, made provision for neither.

A DC motor driven pump is "electrically-controllable" by defualt ... its peak pressure will vary in response to applied voltage. (The challenge would be to build such a pump that was not electrically-controllable.) I agree, if we were starting from scratch, we would probably fit a pressure sensor feeding info to an ECU to achieve a desired pressure (just like a returnless fuel injection). A nice closed-loop design. There would be no need for a motor of different design. (Anyway, different how?)

But that would be an expensive retro-fit. The series resistor is open-loop and so less precise. But the motor has no way to tell whether its voltage has been reduced by a resistor or by an ECU. All it "sees" is the voltage applied to it.