Alan

I was working on a description of the cruise control operation for a document I'm writing and in considering the inputs the CC has to play with something ocurred to me...

The CC only knows its state (determined from the control stalk inputs and stored) the vehicle speed and the brake & clutch (on a manual) status.

On a manual when declutched the CC goes into a suspend mode & auto-resumes at the same settings after you reengage the clucth

So what happens if you are 'cruising' at 50 and you declutch - select neutral & reclutch. It seemed to me the CC would have no idea you aren't in gear...

While shifting to neutral at speed isn't recommended & is a bit pointless - I tried it anyway... enquiring minds what to know...

On reclutching in neutral the engine ramps quickly in revs heading for the redline... just as I thought. You'd think there would be some limit - but actually the CC has no idea what the engine revs are - only vehicle speed.

Not sure if after adding throttle for a while and seeing no speed increase it may give up - I wasn't about to find out by bumping into the rev limiter... I let it rev to 5.5K and declutched into gear again.

Not sure if there is an equivalent AT test - can you shift into neutral at speed? I'm sure it will do the same thing (possibly faster).

Alan

AO

I think I did that once...

Did you also know that if you were going 80 and slow way down, then hit resume... the car will hit about 4-5 pounds of boost!

VehiGAZ

My old 1997 Honda Prelude SH did the same thing, IIRC. I used to do all sorts of experiments like that on the long drives between Kankakee IL and St. Louis.

Other notable inquiries included:

"How fast do you really have to drive to average 90 mph on a 270-mile highway trip between Kankakee IL and St. Louis?" and

"What's the best way to throw a lit quarter-stick out of a 1997 Honda Prelude SH driving in excess of 90 mph between Kankakee IL and St. Louis?"

(The answers are: A - set cruise control for 115 mph for as much of I-57 as you can, and B - out the sunroof is highly preferred)

dprantl

Yes, I know that! It's not good. My CC really doesn't work so well; as soon as the car slows down a little past the set speed, the car lurches forward with instant boost and then it goes, "oh snap" and lets off completely. Then the process repeats.

Dan
'91 928GT S/C

Altharos

Mine does that when I'm trying to CC at about 60kph (about 30ish mph?) but at higher speeds where the car has to rev to move it works a bit better. Its nothing like the newer CC's though, I don't really think the 928's one would save any gas at all, mine just doesnt want to sit at revs until im doing about 85-90mph, at which point cruise control is almost becoming a waste of time, road quality in the north island of NZ is pretty...variable, 90mph around a repaired corner can be a bit hair-raising at times.

Nightfly

Mine seems to be forgetful, or maybe has a short attention span; vacuum lines seem o.k., so I don't think that's it. But occasionally, it will let the speed drop a bit for a minute or so, maybe by about 3 or 4 mph, stay there for a minute, then resume. I've never had a car with CC that did this before. Then again, I don't use it much, so it probably doesn't matter unless I sell it to someone who would. Is my car getting senile?