Cruise Control Danger!? - Alfa Romeo Bulletin Board & Forums
 
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old 11-03-2006, 09:18 AM Thread Starter
Trained (ex)Professional

1953-2018 RIP

Platinum SubscriberAdministrator
 
papajam's Avatar
 
Join Date: Feb 2003
Location: New Jersey USA
Posts: 16,232
Cruise Control Danger!?

I had the following emailed to me at work the other day and, after having been thoroughly entertained by the ensuing discussions it prompted on a another forum, I thought I'd post it here.
Off to make some popcorn...

NEVER KNEW THIS BEFORE...
I wonder how many people know about this?
A 36 year old female had an accident several weeks ago and Totaled her car.
A resident of Kilgore, Texas, she was traveling between Gladewater & Kilgore.

It was raining, though not excessively, when her car suddenly began to hydro-plane and literally flew through the air. She was not seriously injured but very stunned at the sudden occurrence!


When she explained to the highway patrolman what had happened he told her something that every driver
should know -

NEVER DRIVE IN THE RAIN WITH YOUR CRUISE CONTROL ON. She had thought she was being cautious by setting the cruise control and maintaining a safe consistent speed in the rain.


But the highway patrolman told her that if the cruise control is on and your car begins to hydro-plane -- when your tires lose contact with the pavement, your car will accelerate to a higher rate of speed and you take off like an airplane. She told the patrolman that
was exactly what had occurred.

The patrolman said this warning should be listed, on the driver's seat sun-visor - NEVER USE THE CRUISE CONTROL WHEN THE PAVEMENT IS WET OR ICY, along with the airbag warning. We tell
our teenagers to set the cruise control and drive a safe
speed - but we don't tell them to use the cruise control
only when the pavement is dry.


The only person the accident victim found, who
knew this (besides the patrolman), was a man who had
had a similar accident, totaled his car and sustained
severe inj uries.


If you send this to 15 people and only one of them doesn't know about this, then it was all worth it. You
might have saved a life.


NOTE: Some vehicles when the windshield wipers are on, you cannot set the cruise control. Like the Toyota Sienna Limited XLE is one of them.

Jim

Series 2 USA 1750 GTV (in Series 1 European clothing)
papajam is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old 11-03-2006, 09:41 AM
Registered User
 
Join Date: Dec 2004
Location: Dallas,Texas
Posts: 400
Sounds like a job for "Mythbusters" on the Learning Channel.
73gtv is offline  
post #3 of 8 (permalink) Old 11-03-2006, 10:04 AM
Registered User
 
Paradiso's Avatar
 
Join Date: Nov 2002
Location: Northampton, MA
Posts: 1,171
Jim, Jim, Jim!!!

Just for that, I'm gonna go back and paste in every moronic response from the AD on this topic.

That'll show you!

Hugs & Kisses

John

92 Spider Veloce
71 TwinSpark Spider - Soon to be 4 Sale
Paradiso is offline  
Sponsored Links
Advertisement
 
post #4 of 8 (permalink) Old 11-03-2006, 10:15 AM
Registered User
 
DaveH's Avatar
 
Join Date: Jan 2005
Location: Atlanta, GA
Posts: 776
Eh, it's true. At least on older cars its true.

I thought everyone knew this!

Think about it, if you hydroplane, a 'simple' closed-loop CC system will measure a decrease in acceleration at the wheels and try to compensate, increasing throttle. You regain grip, your wheels are no longer doing 65mph, they're doing 105mph. What would you say happens?

It wouldn't take too many lines of code to filter out a change of speed from hydroplaning and cancel CC. Or have the system that watches rpm in gear instead. I suspect modern cars do this.

In a stick shift with CC, try this*: On the highway, after you have crested a hill, pop the car out of gear without clutching. Watch the tach rapidly wind clockwise! (At least it works on a '98 Passat - I'll try the WRX on the way home today). In fact, try it with the wife in the passenger seat.

* Don't do it! The suggestion was made in jest. I will not accept liability for others' dumbness/professional drivers, closed roads/etc...

'85 GTV6

Last edited by DaveH; 11-04-2006 at 07:56 AM.
DaveH is offline  
post #5 of 8 (permalink) Old 11-04-2006, 12:36 AM
Senior Member
Gold Subscriber
 
78-AR-SPIDER's Avatar
 
Join Date: Jul 2003
Location: Portland, Or
Posts: 550
Dave
If the cc measures the speed at the wheels why would it increase to 105MPH when the system is set to 65MPH?
Now if the drag caused by the water slowes the car to 50mph and the you regain traction with the wheels at 65mph you might have a issue

Steve M
'78 Spider
78-AR-SPIDER is offline  
post #6 of 8 (permalink) Old 11-04-2006, 06:49 AM
Registered User
 
Join Date: May 2006
Location: Lakewood, Ca
Posts: 409
Where does your cc sense road speed? On most cars it is at the trans output. If the wheels are slipping/hydroplanning and still showing the set speed even if the car has actually slowed down, the cc shouldn't have any effect on it. That being said, it is stupid to let something mechanical control your car in slippery conditions unless you have traction control. I think even with traction control, you would still want to shut off cc in bad weather.
Russ Bellinis is offline  
post #7 of 8 (permalink) Old 11-04-2006, 07:55 AM
Registered User
 
DaveH's Avatar
 
Join Date: Jan 2005
Location: Atlanta, GA
Posts: 776
Quote:
Originally Posted by 78-AR-SPIDER
Dave
If the cc measures the speed at the wheels why would it increase to 105MPH when the system is set to 65MPH?
Now if the drag caused by the water slowes the car to 50mph and the you regain traction with the wheels at 65mph you might have a issue
I didn't explain my point v well.

I can see the drag of the water vs the wheel speed being a problem alright.

Keep in mind that the onset of hydroplaning sometimes gives an increase in friction/load/resistance. When the car is in full surf-mode, there is a drop in resistance. Skating along the top of the surface is seriously low friction stuff. At least that's what my rear-end accelerometer has always felt.

Theory: speed sensor is on the front wheel. Rear wheels are driven. You hydroplane, the front wheels decelerate, the rears speed up to compensate....

Or, what about fwd with an open diff? One wheel hydroplanes, and it has the speed sensor attached. The other wheel accelerates....

Or, sensor on driven wheels with an LSD. Sudden deceleration of wheels from hydroplaning. Then the wheels are sliding on the surface of the water - a very low friction condition. The CC just increased throttle due to the resistance increase at the onset of hydroplaning. Won't the subsequent sudden decrease in load/rolling resistance result in the wheels accelerating? I doubt that in all circumstances, the CC can respond quickly enough to that scenario. Going uphill perhaps....

Or, you hydroplane going downhill and you've lost any engine braking. You never regain traction....*

Surely new cars don't use speed sensors any more - other than ABS prox switches? Prop shaft speed/speed in gear makes so much more sense.

Also, the 'legend' aspect of this whole thing is a bit ridiculous. So a hydroplaning account gets misinterpreted and breathlessly misreported. BS like: "her car suddenly began to hydro-plane and literally flew through the air" - that's serious arts-degree-dropout-makes-6-o'clock-newsreader stuff. Classic of what you hear/read from mainstream (non-technical) media.


* My experience: Driving from GA to FL in 1994. Dodge Ram 'kidnapper van'. Heavy tropical-type-2pm rain storm. Going downhill. I didn't know anything about not using cruise in the wet. Holy cow did the Ram-o-van take off!

'85 GTV6

Last edited by DaveH; 11-04-2006 at 03:09 PM.
DaveH is offline  
post #8 of 8 (permalink) Old 11-04-2006, 08:27 AM
Senior Member
Gold Subscriber
 
modena782002's Avatar
 
Join Date: Jan 2005
Location: Nashua, NH USA
Posts: 1,531
On all the company cars that I've had since 2000, ('00 Taurus; '02 Impala; '04 Grand Prix; '06 LaCrosse) all FWD. Only the Pontiac and Buick had/have traction control, via spark retardation. On the Pontiac and Buick, traction control will take over in a hydro-planing situation, and give me enough time to shut the cc off. In the Taurus and Impala, the sudden RPM spike would be brief, and I was able to react quickly enough to shut the cc off.

Nick D'Eri

1972 Montreal
2008 Mercedes E550 4-Matic
2015 Ford Fusion Titanium
2008 Piaggio Fly 50
1977 Peugeot 103 Moped
------------------------
Former Italians:
1968 Fiat Dino Spider 2.0 2003 - 2013
1992 164S 2002 - 2008
1981 Spider Veloce 2001 - 2003
1974 Fiat 124 Spider 1979 - 1981
------------------------
Dad's Former Italians:
1962 Giulietta Spider 1964 - 1969
1969 Berlina 1750 1970 - 1971
modena782002 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Alfa Romeo Bulletin Board & Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome