Voltage Reduction System - Convertible Hydraulics
#141
02-16-2011, 05:58 AM
Veteran Member
#142
02-16-2011, 10:16 AM
There is nothing new under the sun. I did not know this, but a common practice in the auto industry for some time has been to insert a resistor in series with the fuel pump to lower its voltage. This is, of course, exactly what we're doing here for the convertible top hydraulic pump.
In the fuel pump application, the resistor is automatically switched in and out as needed. When needed, it is switched in so the pump will not create too much pressure(!) and also to lessen power dissipation in the pump. It is switched out when high flow from the pump is needed. Resistor values are typically chosen so as to lower the pump voltage to 8-10 volts. In our convertible top system, the target is about 8 volts.
(This practice is now giving way to PWM (pulse width modulation) as a means of fuel pump voltage control. PWM is more energy-efficient and can provide variable pump voltage. But PWM would not be a good choice for our purposes because of cost and complexity, and because energy efficiency is unimportant with the convertible top pump running so infrequently.)
Here's a thread selected almost at random that discusses this practice ...
http://www.rx7club.com/showthread.php?t=786591
The resistors shown are heftier than the ones we use, but this is so because they have to work full-time.
So the "resistor method" is not such a peculiar idea after all. Sometimes the problem picks its own solution. It's deja vu all over again.
In the fuel pump application, the resistor is automatically switched in and out as needed. When needed, it is switched in so the pump will not create too much pressure(!) and also to lessen power dissipation in the pump. It is switched out when high flow from the pump is needed. Resistor values are typically chosen so as to lower the pump voltage to 8-10 volts. In our convertible top system, the target is about 8 volts.
(This practice is now giving way to PWM (pulse width modulation) as a means of fuel pump voltage control. PWM is more energy-efficient and can provide variable pump voltage. But PWM would not be a good choice for our purposes because of cost and complexity, and because energy efficiency is unimportant with the convertible top pump running so infrequently.)
Here's a thread selected almost at random that discusses this practice ...
http://www.rx7club.com/showthread.php?t=786591
The resistors shown are heftier than the ones we use, but this is so because they have to work full-time.
So the "resistor method" is not such a peculiar idea after all. Sometimes the problem picks its own solution. It's deja vu all over again.
#143
02-16-2011, 10:21 AM
Veteran Member
My '89 Jeep Cherokee also has a resistor in series with the fuel pump.
It is supposed to reduce pump noise and extend pump life. FWIW, after 22 years and 185K miles, the fuel pump is one of the few parts (other than the engine and drivetrain) that has never failed.
It is supposed to reduce pump noise and extend pump life. FWIW, after 22 years and 185K miles, the fuel pump is one of the few parts (other than the engine and drivetrain) that has never failed.
Last edited by WhiteXKR; 02-16-2011 at 12:21 PM.
#144
02-16-2011, 11:58 AM
Veteran Member
Actually, now that I think about it, the fan speed control for the climate control system on most cars (at least on older ones) is just a resistor pack. Turning the dial just switches different resistors in and out of the circuit. Chrysler Sebrings have a notorious problem with their resistor pack because the low speed resistor burns out frequently. When that happens the fan will only blow on high speed. I've changed out several of them. So there's another example in which a resistor is used to control the power output of a motor.
#145
02-18-2011, 06:49 PM
Thanks, DougBoost, for the kind words. I have been helped so often, by so many people on this forum, that I could scarcely count the times. So the chance to make any contribution is welcome. Quite a place, this is.
Today, in the midst of the worst northeast winter in memory, I woke to a 60+ degree day in Annapolis, Md., confidently put my pressure-reduced convertible top down, and drove home to NJ. Nobody saw this weather coming a week ago, but we'll take it.
Today, in the midst of the worst northeast winter in memory, I woke to a 60+ degree day in Annapolis, Md., confidently put my pressure-reduced convertible top down, and drove home to NJ. Nobody saw this weather coming a week ago, but we'll take it.
The following users liked this post:
Mark104 (03-03-2011)
#146
03-03-2011, 03:27 PM
I just ordered this:
.22 Ohm 100w resistor. It's not as cheap as the ebay one, but it'll probably arrive a little more quickly:
http://www.newark.com/jsp/search/pro...FC-GB100000001
.22 Ohm 100w resistor. It's not as cheap as the ebay one, but it'll probably arrive a little more quickly:
http://www.newark.com/jsp/search/pro...FC-GB100000001
#147
03-03-2011, 11:35 PM
#148
03-08-2011, 06:42 PM
duplicate Jag connector source?
After a series of mishaps both related and unrelated to my '99 XK8, and right after I resolve my current "cylinder wash" starting problem, I think I'm ready to install your no-cut solution to the pump's electrics. Thanks for your instructions copy-very well done!! To avoid lost time searching and fiddling with misc non-fitting connectors, has anyone found a straightforward source for a 2-line connector that duplicates the stock unit or a compatible connector that works right off the bat?
#149
03-08-2011, 07:20 PM
Veteran Member
Installing a pair of male/female connectors would, indeed, allow installing the resistor where ever you choose. But that is not necessary. The no-cut installation could be shortened into only about 3 inches between the Jaguar connectors and zip tied into an attractive installation.
No, I do not know of compatible connectors.
No, I do not know of compatible connectors.
#150
03-09-2011, 09:53 AM
Thanks mucho for the suggestion. And, again, thanks to those who came up with this approach.
I'm thinking that this pump-pressure solution is so elegant that it demands an elegant application. Simply put, my aesthetic sense is kicking in. Having two "stock" conectors sitting side by side would be really impressive and, for the Concourse types, very appropriate.
I'm thinking that this pump-pressure solution is so elegant that it demands an elegant application. Simply put, my aesthetic sense is kicking in. Having two "stock" conectors sitting side by side would be really impressive and, for the Concourse types, very appropriate.
#151
03-09-2011, 12:19 PM
Thanks mucho for the suggestion. And, again, thanks to those who came up with this approach.
I'm thinking that this pump-pressure solution is so elegant that it demands an elegant application. Simply put, my aesthetic sense is kicking in. Having two "stock" conectors sitting side by side would be really impressive and, for the Concourse types, very appropriate.
I'm thinking that this pump-pressure solution is so elegant that it demands an elegant application. Simply put, my aesthetic sense is kicking in. Having two "stock" conectors sitting side by side would be really impressive and, for the Concourse types, very appropriate.
#152
03-09-2011, 12:23 PM
#154
03-10-2011, 12:56 PM
#156
03-11-2011, 11:51 AM
Thanks for the picture since I got mine from there and it was less than half the size I expected after reading the doc! As hlgeorge noted, 100W is a lot of power to dissipate.
#157
03-11-2011, 12:25 PM
Doug, where did you get yours (if the info is handy)?
#158
03-11-2011, 06:15 PM
I got mine from Newark also. Great service (online ordering showed they had 26 in stock, gave lots of email confirmations, tracking number, etc.). Took less than a week to get.
I was a little concerned I didn't know the trick to pull the Jag connector apart but there is no hidden tang or lock, it's just quite snug due to little "ramps" on the male side of the connector body. I installed it in same manner as Testpoint and even added some electrical tape where my leads went into the connectors just to be sure there'd be no shorts if things bounced around a little.
Works perfectly with key off, and nice to know we have pressure in reserve if need it simply by starting the car!
I was a little concerned I didn't know the trick to pull the Jag connector apart but there is no hidden tang or lock, it's just quite snug due to little "ramps" on the male side of the connector body. I installed it in same manner as Testpoint and even added some electrical tape where my leads went into the connectors just to be sure there'd be no shorts if things bounced around a little.
Works perfectly with key off, and nice to know we have pressure in reserve if need it simply by starting the car!
#159
03-16-2011, 08:08 PM
Just finished and it works great! 16 ga heat resistant wire and 1/4" connectors from auto zone 3/16 connectors from Radio Shack directly to resistor (Newark) took about an hour. Zip ties made everything tidy. Now a trip to JAGPRO in Bellmore NY for fluid and filter changes and a once over and I hope to be good to go! 
Thanks Guys!
Thanks Guys!
