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FAQ Archives: Cruise Control Conversion on MG TD
Question:
As sinful as it may seem, because of a leg problem, I must install a cruise control in my 1951 MGTD. Has anyone done this before and what type is recommended? Who manufacturers units that would be compatible with the MG and how easy are they to install? I have done a minimal bit of research and find there are types with magnets around the drive shaft and another which goes in line with the speedometer cable for most cars. But I don’t know if either are compatible with an MG. Any information, comment or recommendation would be appreciated.
John’s Answer:
I believe there are three types of sensing units: high tension coil wire; driveshaft magnet; and the speedo one (which is new on me!). I’m certain you can make an attractive installation as I’ve seen some in MGBs that simply disappear into the firewall. You might consider changing your throttle to a cable design at the same time, as an MGA with a pedestal on the firewall. I receive several inquires per year about cruise control — I’d like to hear what you do, how you come out, on this one!
Update from TD Owner:
| Thanks John for your reply. I have finished the installation of the cruise control in the MGTD. It went something like this: I found that JC Whitney carried four cruise controls, but only one was applicable to the MG. Basic cost was $99 PLUS LABOR (MINE!) So what did it entail? Well, for starters, the cruise control required a vacuum line. There are no vacuum lines in the TD. So I had to make one. Off came the hood (bonnet). Next I took out the breather and two-thirds of the intake manifold (there are three major pieces). I drilled in the center of the tubular “equalizer” intake manifold mounted to the engine block. Next I had to tap it to make threads for screwing in the vacuum hose nipple fitting. What a bear this was. Very thick aluminum or maybe it was cast iron. It took forever and I had visions of braking off the tap in the hole. I covered the bit and tap with grease to minimize metal filings falling into the manifold. I screwed the tap in and out very slowly. The diameter of the manifold was quite small thus the tap hit the opposite side before it was fully seated. Anyway, I coated the threads of the nipple with “make-a-gasket” solution and screwed the nipple in as far as it would go. I am confident it is a good seal. Next I had to install a magnet on the drive shaft. Using a floor jack, I raised up the car and placed stationary jacks on each side. Then I crawled underneath, listening for any creaks of the 2000 pounds about to fall. I got the magnet wired on, then had to make a bracket to hold the sensor. I tapped the supports on either side of the drive shaft and mounted the pick-up sensor and routed the wires pass the master cylinder up in front of the firewall and into the cockpit through the hole where the wire harness passes. So far so good, but then I received word from the NEMGTR that I should reverse the polarity of the MG, making the battery’s Negative terminal chassis ground as is standard today. This would make the installation straight forward. Until getting the advice, I had planned to put in relays to circumvent polarity problems. I was told how simple it was to reverse, so decided to try. Initially the car would not run after making the switch. Whoops! Who says haste makes waste? I forgot the previous owner had installed a capacitive discharge ignition system and had transistorized one of the two fuel pumps (MK II has two as standard, but I have them electrically separated). I removed the cap, discharge system, which was designed for a positive ground system, and then everything ran fine. But soon I ran out of gas. I switched to the untransistorized fuel pump, and I was up and running again. Upon investigation, I discovered I had fried the transistor in the old fuel pump. I removed the three-component electronic circuit and restored the fuel pump back to its original mechanical configuration. It now runs fine. Next, the servo was designed to pull the accelerator cable near the carburetor. There is NO cable in the TD, it is all metal rod linkage. This really limited where I could connect. Also, I had to find a place for the servo motor itself and the 43 inch cable attached. My main objective was to hide as much of this installation as I could so it would not appear obvious when showing the car. There were four possible locations but only one really met my objective. The manual said not to install the servo in the passenger compartment as it would be constantly operating and could be distracting. I figured the manufacturer had never considered putting it in a car with a noisy XPAG engine. Besides, the TD is a convertible and I figured the noise would not even be noticed. So I installed the servo under the dash on the right side, passed the cable down behind the interior panel, through the floorboard, curved up over the exhaust pipe, pass the transmission and then up through the left floor board where it was attached to the accelerator pedal. I had to keep all bends in the cable to a minimum of 4 inches so it would not bind. My adrenaline might start pumping if the cable should snag and not release while going 60 mph. Next I made all the electrical connections, to the coil, to positive 12 volts, to the brake light switch, to the ignition etc. Not knowing if this system would work, I did not cut any wires in case I had to return it. So, miles of wire were bundled up in the passenger compartment as I took off for my first test drive. 1) The servo responded only at 3500 rpm and was very erratic. I returned home and called the distributor of the Taiwanese product. I was told to change some dip switches. Off I drove again after making the changes. 2) I was able to actuate the cruise control anywhere between 2500 and 3500 rpm, but could not get it to respond above 3500. The system has a means of nudging the speed upward in half a mile an hour increments. I tried this, but it would not go any higher than 3550. I could feel the accelerator pedal being pulled by the cable but it would not hold. I returned home and made another call, getting a different technician. He said to change more dip switches and to reinstall the shorting plug which the manual said to remove for manual shift cars. 3) Wonderful! The cruise control performed flawlessly. I took the car up to 4500 rpm (the max I dare rev this 48 year old engine) and the cruise control kept it there. I did notice that sometimes when I actuate the control, it will speed up the car about 5 mph and then settle down to about where it was programmed. Probably has something to do about the magnet, the questionable smoothness of the XPAG or who knows what. Hakuna matata – not a problem. I could not even detect any noise coming from the servo. My hunches were right. Now my project is to shorten all the wires and tidy up the installation. The system, as installed, is virtually invisible. You see nothing in the cockpit, the controller/programmer flips down from under the dash and locks in place. In the engine compartment the ONLY thing you see is the vacuum hose. This can easily be disconnected and removed for show purposes. Then the only noticeable modification is the brass nipple on the manifold. However, it is now painted engine block red like the manifold and is directly under the breather and thus almost completely out of sight. I read on the internet about the installation of a similar cruise control on two American cars. One guy said it took him three hours, the other said three days. In my case, I took a day planning the installation, seeing where and how everything would fit and analyzing many options. Then I took two and a half days to reverse polarity and install the system and a half day to run tests and make phone calls of distress. The installation is fully functional. |
