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Cruise Control Decel Function. - READ ONLY

66 messages,  Last post on Feb 14, 2007 at 9:43 AM

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What is this discussion about? Car Safety

Messages Page 1 of 7

#1 of 66 Cruise Control Decel Function. by wwest

Feb 03, 2007 (12:33 pm)

Apparently the latest versions, designs, for cruise control have been seriously revised.
 
Since late in the last century manufacturers have been doing almost everything possible, conceivable, to improve the safety factor of vehicles with automatic transmissions when operating on low traction surfaces, most especially FWD or front torque biased AWD vehicles wherein engine compression braking will be the most detrimental.
 
It has now become common knowledge throughout the industry that engine braking on the front wheels will oftentimes interfere with the operation of ABS, potentially to the detriment, obviously, of the owners/passengers.
 
For those with long term stick shifting experience think about how often you wish for a clutch as you drive along in wintertime with your automatic shift transmission, especially a FWD one.
 
Most new owners manuals state quite explicitly that engine braking cannot be attained absent a manual downshift and in some cases not even then unless you disable, completely turn off, cruise control.
 
This whole widspread episode of throttle delay, 1-2 second downshifting delay/hesitation has arisen as the result of widespread industry adoption of a new automatic transmission shift pattern/sequence adopted late in the last century.
 
The technique involves quickly upshifting these electronically controlled transmissions/transaxles upon any FULL lift-thottle event wherein should the current gear ratio be retained would result in a significant level of engine braking. The idea is to improve the safety factor by virtually eliminating engine braking that cannot be overcome by the operator absent a quick shift into neutral, an action currently recommended by the AAA, but of itself fraught with peril.
 
So, rather than retarding the timing, as was previously done, to reduce the road speed of cruise control, I wouldn't be at all surprised to see the use of rear braking only via the traction control system to initially slow the vehicle.
 
But it is now pretty clear that applying the brakes, in total, to do this will be potentially safer, overall, than the use of engine braking which cannot be alleviated by the anti-locking braking system should it subsequently be needed.
 
Even slight engine braking on an extremely slippery surface, an icy bridge deck comes to mind, can easily result in loss of control even on a RWD vehicle, but the potential for loss of control of a FWD in these insatnces rises dramatically in comparison.
 
Be careful out there....

#2 of 66 Re: Cruise Control Decel Function. [wwest] by andys120

Feb 04, 2007 (8:23 pm)

Replying to: wwest (Feb 03, 2007 12:33 pm)
What'd he say?
 
You don't have to be a genius to figure out that disengaging your CC can result in some engine braking and every owner's manual I've ever read cautions against the use of CC in slippery conditions.
 
"Tempest in a teapot?"

#3 of 66 Re: Cruise Control Decel Function. [wwest] by wilcox

Feb 05, 2007 (5:29 am)

Replying to: wwest (Feb 03, 2007 12:33 pm)
"Be careful out there...." --- We can all agree to that!

#4 of 66 wwest by tarik

Feb 05, 2007 (12:10 pm)

Maybe I don't fully understand, but are you saying that new programming of the gearbox controllers (or the CC) will shift up if you lift-off quickly enough? Or do you suggest to manually upshift in that moment?
 
Well, sure sounds like some bogus last-millenium-advice to me

#5 of 66 Must be me, but... by wale_bate1

Feb 05, 2007 (1:15 pm)

Why would anyone be using CC in inclement conditions in the first place?
 
This is some bizarre pseudo-corollary to the old climate control compressor theory, isn't it?

#6 of 66 Re: Cruise Control Decel Function. [wwest] by rorr

Feb 05, 2007 (1:28 pm)

Replying to: wwest (Feb 03, 2007 12:33 pm)
"....but of itself fraught with peril."
 
Have we been attending writer's workshop conferences again?
 
In all honesty, I'm at a loss as to just WHAT is the villian in all this:
 
Is it the cruise control? Is it the programming in current automatic transmissions? Or is it that old bugaboo, FWD powertrains?
 
I mean, the TITLE of this thread has to do with "Cruise Control Decel", but you spend your entire post discussing engine braking, ABS, automatic trannies, FWD, and the slippery conditions "fraught with peril".
 
Uh, why not just NOT use cruise control in icy conditions? Isn't this the standard instruction in every owner's manual?

#7 of 66 Re: Cruise Control Decel Function. [rorr] by wwest

Feb 05, 2007 (5:23 pm)

Replying to: rorr (Feb 05, 2007 1:28 pm)
Yes, Rule # 1, NO ONE should be using cruise control on adverse roadbed conditions. But then NO ONE should EVER drive with a Blood/alcohol level above 0.08....
 
Absent being able to enforce rule # 1 what would you have the automotive industry do?
 
Personally I would disable cruise control when raining or if the OAT were below ~35F. And I most certainly would disable it if TC, Traction Control, activated. It would not be re-enabled absent a complete and full stop and an engine restart.
 
Big Brother strikes again...?
 
The post was intended as simply an advisory of the fact that the cruise control systems seem to be evolving away from the use of engine braking and into the use of actual braking.
 
And my guess is that this "evolution" is the result of the fairly "recent" discovery by the industry that old style automatic transaxles and FWD were/are not a good match.

#8 of 66 Re: Cruise Control Decel Function. [wwest] by rorr

Feb 06, 2007 (7:15 am)

Replying to: wwest (Feb 05, 2007 5:23 pm)
"Big Brother strikes again...?"
 
Yes. And no thanks.
 
Perhaps if the wiper speed has been set to 'high' I could understand having the CC disabled. But OAT below 35F? Ah, no. Living in rural central Texas I see temps below 35F virtually every morning in the winter - yet we see 'adverse roadbed conditions' which would actually WARRANT no CC maybe 1-2 times a year.
 
Personally, I think the best 'solution' (Houston, do we even HAVE a problem?) is driver training.
 
"...what would you have the automotive industry do?"
 
On this issue? Nothing. How much nanny-engineering do we need? Radios that turn themselves off when vehicle speed exceeds 45mph? Mirrors/seats/steering wheels that CAN'T be adjusted unless the vehicle is stationary? Adaptive throttle controls that restrict vehicle speed based on tire/brake wear indicators?
 
In all honesty, I'm not entirely sure just WHERE the discussion should be going on this issue. Are we supposed to be debating engine braking vs. wheel braking as a means by which the CC decel functions? Or is this whole thing just a left handed way to attack the safety aspects of FWD powertrains again?

#9 of 66 Re: Cruise Control Decel Function. [rorr] by wwest

Feb 06, 2007 (9:36 am)

Replying to: rorr (Feb 06, 2007 7:15 am)
And what about those bridge decks with an OAT ~35F...??

#10 of 66 Re: Cruise Control Decel Function. [wwest] by rorr

Feb 06, 2007 (9:51 am)

Replying to: wwest (Feb 06, 2007 9:36 am)
"And what about those bridge decks with an OAT ~35F...??"
 
What about 'em?

Messages Page 1 of 7

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