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#122 of 161 Re: Coasting in Neutral with AWD? [andys120]
by Mr_Shiftright HOST
Jan 02, 2009 (3:03 pm)
I certainly understand the effects of compression braking on a FWD car, but you know this would have to be a pretty radical maneuver, like downshifting from 5 to 2 racing downhill. Just lifting off the gas on a FWD car shouldn't make any difference.
Of course, if you are on a snowy road, going fast around a turn, and you lift off abruptly to avoid an animal, say....well, that could get dicey with either FWD or RWD.
I'd guess that on a RWD you'd get power-off understeer, and on a FWD, power-off oversteer.
#123 of 161 Re: Coasting in Neutral with AWD? [Mr_Shiftright]
Jan 02, 2009 (6:05 pm)
but you know this would have to be a pretty radical maneuver, like downshifting from 5 to 2 racing downhill
Well that's just it, it's easier to avoid radical inputs to the drivetrain by being in the correct gear as opposed to coasting. A car in neutral will pick up speed
going downhill, forcing input from the brakes to keep at a safe speed whereas it's possible by downshifting to "crawl" down at a steady speed slow enough to avoid having to brake which is the last thing you want to do. To get down the steep hill leading to my home I downshift to second or third (A/T or manual) to slow the car. I've done it everyday in all weather for 11 years without the least problem.
If a person, vehicle animal or a tree limb were to force me to brake I'd be going slowly enough to smack it into a snowbank without any problems. I doubt that'd be the case if I were "freewheeling" down in neutral.
I think our friend is confused because you're supposed to put a manual shift
in neutral when braking on ice. That's something I've never done because I try to avoid braking on ice altogether.
#124 of 161 Re: Coasting in Neutral with AWD? [andys120]
by Mr_Shiftright HOST
Jan 02, 2009 (6:31 pm)
Well your FOOT might be braking on ice but your car won't be.
It's a nice gesture, but futile, as we have all seen from those YouTube videos...the pitiless, gradual slide downward to destruction...the frantic, useless flickering of brake lights, the spinning of the steering wheel to and fro, and the car just ignoring all that input and obeying the laws of gravity, thank you very much.
#125 of 161 FWD engine braking
Jan 02, 2009 (7:32 pm)
I have owned and driven FWD RWD 4WD, and engine braking is safe with all if your skills are up to the task. With FWD (or any other) on ice, I never slam into a lower gear going down hill. Touch the gas to synchronize during the shift if a down shift is necessary, then back off the pedal slowly. Keep your foot on the pedal, and increase wheel speed if slippage starts. With FWD, the rear wheels roll free when engine braking, and are LESS likely to skid than with a RWD.
If you lack the experience, practice on a large, level parking lot from moderate speeds. It does not take many tries to learn what to expect.
Braking in neutral, can get you into much trouble. The ABS may release the bakes, but there may not be enough friction to start the wheels turning to regain steering. Engine power with ABS restores steering.
Telling an inexperienced driver to shift into neutral may get him killed, and is totally irresponsible.
#126 of 161 Re: FWD engine braking [oldharry]
Jan 02, 2009 (9:48 pm)
"...Engine power with ABS restores stearing..."
So, you're saying that if the surface is so very slippery that the tire will not rotate during the period of ABS brake release then a little power application from the engine will help get it, keep it rotating...??
I would imagine should a person ever encounter a road surface THAT slippery then the primary option would be to bury the brake pedal into the floor and then hang on and pray.
"I never slam into a lower gear going down hill.."
With an automatic transaxle just how do you "ease" into a lower gear...??
Methinks you might be thinking back to the good old clutch pedal days when "easing" into a lower gear was entirely possible.
Apply even the slightest level of gas pedal pressure along with moving the shifter to select a lower gear and with most modern day automatics, especially those "coupled" with DBW, you will get a sudden burst of "acceleration", in this case MORE wheelspin.
DBW programming is typically such that it will hold off on engine RPM elevation until the downshift is completed. And unless I miss my guess the programming will be such that with this set of inputs an "expectation" of quick acceleration will be the norm.
#128 of 161 Re: Defroster [andys120]
Jan 02, 2009 (10:12 pm)
"Your manual will tell you how..."
At least not for Toyota or Lexus and likely any passenger car equipped with an automatic climate control designed by NipponDenso or Denso US.
These have a serious design flaw, not only serious but potentially DANGEROUS. These are designed to rely SOLELY on the operational functionality of the A/C for dehumidifying the incoming airstream in order to prevent and/or remove interior windshield condensation.
Not on point, you say...
Well, yes, but....
The problem in this instance results from the fact that once the passenger cabin has been heated to within a few degrees of setpoint the airflow routed to the interior surface of the windshield will be as much as 20F BELOW the setpoint, but by Denso's desire, VERY DRY.
If you drive into and area wherein the outside of the windshield needs warming then you MUST not only switch to defrost/defog/demist mode but raise the target temperature setpoint. I would suggest raising the setpoint DRAMATICALLY, maybe even to MAX, until the icing trend has definitely been reversed.
#129 of 161 Re: FWD engine braking [wwest]
by Mr_Shiftright HOST
Jan 02, 2009 (10:23 pm)
Just because AAA says it doesn't mean it's particularly useful advice. If you read the entire step by step procedure they are advocating, they apparently want you to:
1. take foot off gas as front wheels skid
2. put car in neutral
3. do not immediately steer to correct--let the car stay out of control until traction returns
4. THEN Steer in the direction you want to go
5. Then put the car in drive.
YEAH RIGHT---as if the person wouldn't be in a panic by then.
I mean, some of this stuff is right out of 1948. "Hang a brightly colored cloth from your antenna?"
#130 of 161 Re: FWD engine braking [Mr_Shiftright]
Jan 03, 2009 (12:39 am)
Apparently you have never had to stear into a skid as the car slides toward the edge of the road on Rodgers Pass. MT200.
Panic, yes, but knowing what to do beforehand often abates or at least lowers the panic level and thereby allows one to act rationally or at least moreso. When the stall warning goes off just as you depart the runway you can either panic, "freeze", and die or push the nose down just far enough to prevent a SUDDEN UNCONTROLLED return to the runway.
Education, knowing what to do, TRUMPS panic responses each and every time.
#131 of 161 Re: FWD engine braking [Mr_Shiftright]
Jan 03, 2009 (12:45 am)
Are you disagreeing that the procedure would work or is it just that you believe most would panic, freeze, and never get to step 2...??
People are a lot less likely to panic if they recognize the situation as one for which that have some preparedness, plan.