Post
by spider » Fri Jun 19, 2015 9:18
I do have an in principal understand of what your trying to do there hbard and I am looking on with interest. The point Tim raised re: Fail Safe was one thing I had in mind when I read your post, however clearly there must be some ways that it is done, I have a truck and 2 cars here that are drive by wire from the factory, so I guess there must be an acceptable way.
I also get / see that you're looking to mount your stepper motor more or less direct to the carb, I do see many advantages in that. One aspect though in doing this that I feel you may need to take in to account is that of the heat from the Exhaust which is almost adjacent.
That set up on my Moke is part of the Cruise Control. The actuator is actually a Vacuum Diaphragm Unit (it gets the Vac fom the Inlet manifold). I have fitted many of these to Minis and Mokes over the years, and in the early days, 'played around' with trying to find a way to hook them direct to the carb, there was a number of set ups I tried and none were much good. I tried it via the pedal and while I was sure it wouldn't be too good, it actually works a treat. This has been how I've done them for around 30 years now. The Vac Actuator on this set up is fail safe in that it has two solenoids, one to allow Vac in (yes OK don't niggle that point) and the other to let the Vac to atmosphere, the latter is powered all the time and on loss of power, it vents to atmosphere and so returns to Idle.
It's 'resolution' is very very good, for example, when going from the flat to a hill, it puts on the power just so and holds the speed to within 2 kph - unless it's a particularly steep hill or your travelling at less than 60 kph, it's not perfect, but it's Oh so nice on the longer trips. Yet while it can put power on gently, it can also open the throttle almost as fast as you can with your foot.
Old Mokers never die, they just smell that way.