Retro-fit Cruise Control - Recommended!!!

[henry161]

My car is a '93 E34 - auto with M50 six cylinder 2.0 liter engine. I love my car but always wished it had cruise control. I recently bought a AP150 cruise control kit and fitted it. It did take a few hours to install it neatly but I am very pleased with the results - it will engage from about 20mph and controls the car smoothly using only small throttle openings. A lot of my driving is now more relaxed - it should save me some fuel and I am certain it will help me to stop getting speeding tickets too! I actually bought mine from Australia as it was half the price of those offered here in good old rip off Britain. The cost with shipping was about £125 GBP - all I needed to add was a few scotchlocks to join into some of the existing wires. I mounted the servo unit above one of the suspension towers under the hood. Connected the units cable to my throttle cable. I had to T into one of my vacuum pipes to join in the servo's vacuum connection. Apart from that it was just finding 4 wires and connecting into them and mounting the control stalk and then hiding the wiring and the brain which I did in the centre console. Once all connections are made it is a case of testing it out and adjusting the brain unit to suit the car - this is done with 5 micro switches on the brain unit and the instructions walk you through it. I think the make is command - the model is AP150 which came with a left handed control stalk but they do offer keypads instead.:)

[Zeuk in Oz]

Just remember not to use it on wet roads. ;)

[henry161]

Just remember not to use it on wet roads. ;)

Thanks - That's a great point and I will remember that - read some of the horror stories about people coming unstuck on slippy roads with cruise.

[Paul in NZ]

isnt cruise instantly disengaged when you brake?( and or on manual when you depress the clutch?)

[Michael999]

This might sound silly, but how does cruise control slow down the car when you are going down a hill where the car accelerates on its own?

[henry161]

You are correct - cruise is disengaged as soon as you touch your brake pedal or depress your clutch. The problem can happen because your feet are no longer on the pedals and this causes a slight delay in reaction time should the car break loose - this is why it is only good for non slippy roads.

[henry161]

Not silly at all. The cruise unit has a vacuum pipe which must be connected into the cars vacuum circuit. On a petrol engined car the vacuum is caused by the intake side of the fuel circuit - this means that the cruise controls brain can judge the load on the engine (bigger vacuum for going uphill, lesser vacuum for on the flat and even less for going downhill) and adjust the throttle as necessary. For example - it starts to reduce throttle as you approach the brow of a hill as it feels the gradient lessening near the top so that it doesn't send you accelerating over the other side. It is all done by little throttle openings and within a couple of MPH it keeps it constant.
Same scenario when you go down a hill - the unit closes the throttle to keep your speed down.

[Michael999]

My road is really steep, with no throttle at all my car accelerates.
Cruise control will do nothing in that situation?

[Yiorgos]

Cruise control (at least with the factory-fitted for the E34) is nothing more than just throttle control -- the device will accelerate the car to a driver-defined limit.

If you have CC set to say 40km/hr and you're going down a steep hill that makes the car accelerate faster than said speed on its own, it will not engage the brake -- CC will just not play around with the throttle at all, and your car will coast at whatever speed the steepness of the decline dictates.

[E34-520iSE]

It can run away at 60 mph downhill even if the CC's set at 30 mph - got to be careful when towing something heavy!

HTH,

Shaun

[Airborne001]

The problem can happen because your feet are no longer on the pedals and this causes a slight delay in reaction time should the car break loose -

Don't forget, that hitting the brakes AFTER you have started to slip can make things even worse.

[Paul in NZ]

i would gues that modern CC will engage the brakes to keep the speed constant even down hill.

[Yiorgos]

Probably, but 3rd party CC modules don't have this capability (as far as I know), my dad's Nissan Navara ute (2005) that has a 3rd party CC module installed by the dealer, doesn't have this function.


i would gues that modern CC will engage the brakes to keep the speed constant even down hill.

[Jay 535i]

This might sound silly, but how does cruise control slow down the car when you are going down a hill where the car accelerates on its own?

The best it can do is cut throttle to idle. If the hill is steep enough, you will continute to accelerate anyway.

I don't know if the cruise control will downshift an automatic to add some compression braking on a hill.

[henry161]

Obviously , it has its limitations. That said , there aren't really many steep hills around here and in any case - I know when I can and can't use it effectively. I still think it is fantastic and really enjoy using mine.

[Zeuk in Oz]

i would gues that modern CC will engage the brakes to keep the speed constant even down hill.
The cruise control on my 2002 ML 270 CDI Mercedes is obviously the next generation. On a steep descent when the car reaches about 10 km/h over the set speed, it changes the auto box down a few cogs to slow the car down.
Very clever !

[henry161]

Now that is clever. I look forward to getting something like that myself.