Scangauge II vs cruise control

[rjacob]

I bought a ScanGauge II a few weeks ago and love it. It has improved my hypermiling. Yesterday I had a Rostra cruise control installed in my 2000 Honda Civic VP (DX value package). (Yeah I know that I can probably beat the cruise control by manually operating the throttle, but we do a lot of long driving trips) Anyway, the cruise control seemed to be working fine, but then would just spontaneously disengage. It would work for 5 minutes, then shut off, then I would reset it, and it might work for another minute or two, then just shut off. I took my car back to shop, and the guy swapped out the unit, the control, resoldered everything. He took it for a test drive, and it still did it. He thought it might be the Scangauge II. I drove the car home with the ScanGauge unplugged, and never had a problem. The cruise control is contected to the VSS. Is it possible for the Scangauge to be interfering the cruise control? The cruise control will disengage if the RPM's spike. Is it possible the SGII is somehow making the cruise control think the RPMs have jumped? Is there some way to stop this from happening? I love the data I get from the SGII, but would like to use the CC for long trips. It would be nice the see the SGII at the same time.

I emailed the guys at Linear Logic, and am waiting to hear back.

Thanks,
RJ

[Gregte]

Can't you disconnect the Scangage and see if the problem persists?

I don't own a Scangage but I very highly doubt that it is altering the VSS or any other signal. That would be unacceptable.

I tried using a spark plug wire inductive pickup to get a motor speed signal from my fuel injected engine but discovered that under certain conditions, such as deceleration, the spark is stopped thus making it a discontinuous signal and unacceptable for a cruise control. The VSS should not be discontinuous though.

[Blue07CivicEX]

if for some reason the installer tapped into the OBD-II VSS signal? seems strange they would do that but maybe it was the only option... I've never done an aftermarket cruise install but if you parallel to applications off the same signal they will drag each other down unless you have a way to split the signal and keep the voltage up.

[rjacob]

Gregte:
I have done a short 10 mile drive with the SGII unplugged, and had no problems with the cruise control. I am hoping to get out for a drive today to play with it more. If not today, I will be making a 70 mile drive tomorrow on the thru-way.

Blue07CivicEx:
Yes, the Rostra CC plugs into the VSS to get the vehicle speed. It also taps into the tach wire as well.
Here is the install manual on Rostra site: http://www.rostra.com/pdf/Form4565D.pdf
What do other cruise controls do to get the vehicle speed?

[rjacob]

I did some longer drives over the weekend. After the guy swapped out the cruise control, it disengages by itself much less. I am thinking it doesn't have anything to do with the scangauge since I had it disengage once without the scangauge hooked up. But during 70 miles on the thru-way yesterday, I had it disengage just once. Still not sure what is causing it. I am doing a bunch of freeway driving next weekend, and will see how it does.