Cruise control performance + boost?

[2seater]

     I didn't know quite how to title this, plus a little explanation. I rarely, if ever, have used my cruise control in the last decade or more. It seemed to perform poorly in a 1700 mile round trip many years ago, not holding speed, inability to adjust to rolling terrain, etc... I chalked that up to poor engine vacuum due to my first version of adding boost, a turbocharger, to the existing engine. Since that time I have installed multiple configurations of the basic 3800 I started with. Compression ratios ranging from 8.3:1 to 9.5:1, with and without turbo. Since I had installed a vacuum/boost gauge maybe 15 years ago, I have noted my steady cruise engine vacuum reading is always in the 10"-12"Hg range, at highway speeds of 55-75mph. This is on relatively flat but gently rolling terrain. It doesn't seem to matter, the engine wants what it wants. With the recent work on the red and black cars for my sons, I noted both were concerned that their cruise control would be functional. 

 

With the above scenario in mind, I started to try my cruise control over the last couple of weeks and I was pleasantly surprised it functions just fine. This is the original unit that came with my car more than 25years ago, so that hasn't been altered. I have relocated the servo to mount on the crossbar between the strut towers many years ago to allow more room for the turbo plumbing, but is original otherwise. It held speed +-1mph flat and up moderate grades and with the vacuum gauge, it is easy to see it working the throttle.

 

So this brings up some questions, primarily for supercharged engine installations and the cruise control performance. I am guessing the cruise control doesn't know what it is connected to so the calibration of response may leave something to be desired in a modified situation.

 

1- If you have a vacuum/boost gauge, what is your expected manifold vacuum reading under the above conditions?

 

2- With the turbocharger, I find the cruise control to be too aggressive in situations where it needs to compensate for a larger load or to get back to speed. What I found was, if I hit Resume and my speed isn't within a couple miles an hour of the setting, it will open the throttle fast enough that it may spike the boost to my 5psi limit before the trans. can even downshift. Curious if the supercharged installations do the same?

 

3- Will your cruise control work hard enough to get you into a boost situation?  

[Chrisssssssss]

I thought that cruise relied on engine RPM's to monitor and maintain speeds, but not positive. I will try cruise in my 98 Regal GS and see how it handles resume and boost if you want...

[2seater]

Yes, please let me know how it responds. Being a much newer system it isn’t apples to apples but still interesting. Is the Regal  supercharged? If so, is there any way to monitor manifold pressure, plus or minus?

 

 I do not know, but I suspect our old non electronic systems just read the vss for speed and add or release vacuum to the actuator.