View Full Version : vacuum ejector necessary for cruise?

Tony Hanna
05-15-2007, 05:45 PM
I decided to replace all the old dry rotted vacuum lines on the Spirit before I put the plumbing back together from having it off to change the shifter cable. I'm prettymuch done with all the important stuff (map, fpr, bov) but I'd like to keep the cruise functional as well. Is the vacuum ejector (the triangle of vacuum lines/T's) absolutely necessary for operation of the cruise, or will it do ok without? If I will be ok without it, what's the proper way to hook the cruise servo up? There is an "F" fitting going to the cruise servo now with 1 line attached to the brake booster, and another that's hanging open at this point which originally went to the vacuum ejector.
Any help would be appreciated.

05-15-2007, 11:00 PM
The servo gets most of its vacuum from the brake booster. That extra leg goes to a special T fitting that has a venturi in it. The idea is that when you are in boost, there is no vacuum reservoir to keep the servo working. The turbo blows air through the T, which vents into the airbox and creates a vacuum for the servo via the venturi.

If you are using a Mitsu, your cruise will act weird at highway speeds because it is making boost (it gets much worse if you have a grainger). If you have a Garrett or a bigger turbo, you can probably live without it. I don't think T2 cars came with it.

Tony Hanna
05-15-2007, 11:45 PM
Sorry Russ, I should have been more specific. '91 Spirit R/T.

05-16-2007, 12:05 AM
The way I plan to get by without using that vacuum setup is to simply run an external vacuum resiviour. I did run my R/T without an additional vacuum source and it did OK with the cruise. Going up a long hill it did need input from the right foot to keep a steady speed. It will only pull the throttle open oh-so-far without more vacuum. There was definitely never any boost when the cruise was on.

FYI: my entire vacuum harness had been totally redone and modified. Any extra stuff was promptly put in a box with the rest of the items from the engine bay not being used.

05-16-2007, 03:28 AM
I got rid of the ejector and it will not get boost with the cruise on. It's good *most* of the time. you have to "help it" on the hills. I am going to try a reservoir from a V-6 to see if it helps.

Tony Hanna
05-16-2007, 05:45 AM
Thanks for the tips guys! I think I've got the "vacuum ball" out of some sort of older GM vehicle laying around here somewhere. If the cruise doesn't work well, I may locate it and use it as a reservoir. Finding a place to mount the thing might be a challange though.

Tony Hanna
05-21-2007, 06:16 PM
Well, you guys called it! Cruise works fine on flat ground and slight or short grades, but pulling a long steep hill causes the speed to drop off. I guess I'm going to try a reservior. The vacuum ball I have is going to be an absolute pain to mount if I can even find the thing so I've been considering just building a reservoir of my own design by capping both ends of a piece of 2.5" exhaust tubing and installing a couple vacuum barbs and a checkvalve. Here's the question. What kind of volume should I be looking at (length of 2.5" pipe) to allow an ample reserve for pulling long hills?