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Winter Driving Machine Book Posted by Saana88 [Email]  (#207)  [Profile/Gallery]
(more from Saana88) on Tue, 23 Oct 2007 17:53:34
In Reply to: COLD weather saab, David Young, Tue, 23 Oct 2007 09:59:27 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Hey David!
I've spent nearly all of my life in upstate New York. Part of it was in the middle of the lake effect zone, part of it was in a different lake effect zone (college in Buffalo), and now I'm in the Mohawk and Hudson river valley storm areas, along with the occasional lake effect. Every year I get to watch everyone rediscover their snow driving reflexes.
First of all, I have to respectfully disagree with Mr. Chapman. The ignition and injection systems on C900s are not advanced enough to notice the discrepancy introduced by a block or oil sump heater. There is no oil temperature sensor on the car unless you have fitted an aftermarket set of racing gauges. The temperature sensors (two at most) have very simple functions. One tells the gauge on the dashboard how warm the coolant is to alert the driver of overheats or cold-start conditions. The other (where applicable) tells the fuel injection computer how warm the coolant is (and by conduction, how warm the engine is) so it can hold the injectors open a little longer during cold starts to compensate for poor ignition and expansion losses in a cold engine. This is akin to starting a campfire hot to get a good bed of coals ready for cooking, then letting it die down (adding less fuel) when it has reached normal temperature. 900 engines, by their brillant designs, are a self-contained compact unit. Instead of having the oil sump hanging down in the weather, it is mildly shielded by being on the top of the transmission case. This location also means your engine oil heats more quickly in cold weather. Whether the coolant is 40 degrees from a warm start or from the action of a block heater overnight is irrelevant. The coolant is in contact with a large surface area of the engine, both block and head. Since it's still below 89 celsius, the engine thermostat is closed and allows very little heat loss to the radiator and heater cores so the block heater heats the engine water jacket only. The only other sensor on the car that measures any sort of temperature information is the air mass meter (where applicable, again) which measures the mass (and therefore temperature and density) of the intake air. Since that air is still cold, the air mass meter computes the right mixture regardless of whether or not the engine has been preheated. I've read the Saab fuel injection manual. It says that the computer will only sense a fault and turn on the check engine light (and go into limp-home mode) if the engine temperature sensor reads an engine temperature of less than -90 celsius or above 160 celsius. If you go off the bottom end of that range, hell really has frozen over, and I guess it's a good thing you're in a Saab.
"Excessive warm-up period, e. g. thermostat fault (stuck open) or prolonged idling in extremely cold weather" is how the manual puts this.
I've made my '88 900 four-door into what I consider the penultimate winter car over the past three years.
I cannot agree more with sloopjohnb. Machinery is NOT designed to be run in cold weather right off the bat. While I disagree with one of my ex-neighbor's attempts to bypass this (idling a truck with a very loud exhaust for half an hour right outside my bedroom window at 5:30 in the morning all winter long) I occasionally subscribe to a less-guzzling version of the same method. What's going on: everything is cold. Metal, such as your engine block and moving parts, the cylinder head (made of aluminum) and all the joints and electronics are all cold. Your fuel pump is cold. Your transmission fluid is probably the coldest of all. The pistons have cooled and contracted, hence the need for cold-start enrichment. Your engine oil will be thick and may not flow well. The same applies, as importantly, to the transmission fluid, as well as your CV joint grease in the inner and outer driveshaft joints. The electrolytic solution in your battery is cold.
Fine, but how do you fight this?
If the temperature is 20 degrees or lower, allow the car to idle for a minute or so. Drive off gently. According to the owner's manual, your 900 should not be driven at full throttle until the temperature gauge needle exits the white-colored bottom of the range. I take this a little farther by saying the car won't go over half throttle in this state, and nothing over 2500 RPM. You don't want to snap a driveshaft in this weather.
Use a cold-weather synthetic engine oil AND transmission lube. In ridiculously cold settings, your transmission fluid has cooled to the point it cannot lubricate the synchronizers and you will grind your way through the gears. That's bad. Any fluid of indeterminate age in your transmission should be assumed to be no good in cold weather. Using a thin fluid of extremely cold, burnt-out fluid to match the rotational speeds of two mechanical gears just doesn't work. You're going to get a dozen opinions on what to use for gearbox lube from this bulletin board. I almost don't care (for cold weather purposes) as long as it's synthetic. I use Saab's synthetic transmission lube. It's orange, and it's available from one of my favorite site sponsors.
Make sure your driveshaft joints have intact rubber boots and plenty of grease in them.
Get a big battery. 850 CCA seem to do the trick for me. At -20 Fahrenheit, my battery is operating at about 40% efficiency. I may experiment with an insulating blanket this winter. More important is to have the right liquid level and concentration and CLEAN TERMINALS.
USE FOUR SNOW TIRES. Not "all season" crap, I mean ones that were actually designed for winter. Hint: the US DOT "M+S" rating has NOTHING to do with winter or cold-weather traction and is pretty useless. Only two snows will make your 900 understeer, which is how I killed one of mine. True snow tires can handle cold temperatures. Most multi-season tires' tread compounds start to simply loose their grip below freezing. The compound, not the pattern or amount of tread. These things are worth their weight in insurance money. They're predictable, good in slush and snow and on ice (even though mine are presently studless). They last around 40k and combine a number of unique features that make you safer in the snow. If you can't get them or they are too expensive, there are a number of snow tires that will get you there. Especially in slush and deeper snow, narrower snows (185/65R15 are the stock size) will chew down instead of floating over your driving surface medium. I have this argument every winter with BMW drivers. Virtually every European cold-weather snow tire testing photo I've seen has incredibly narrow tires on the car. A good Saaber friend (with '86 900Ts and the older bolt spacing wheels) has a set of snows on early 900 rims. Only 5 inch wide rims give him the opportunity to mount 170-series tires. Your 900 will probably have 5.5 inch wide rims, so stick with what can safely be mounted on that wheel (again, 185/65 here). Sorry, Pontiac. Narrow is better.
I'm looking for the part number, but I've heard NAPA sells a screw-in block heater that fits 900s.
I really am partial here, but the older 8 valve cars with mechanical fuel injection seem to like the winter better. They have fewer electronic sensors to feed. My winter car is an 8 valve 900. The additional low-end torque and pretty-linear torque curve of an 8 valve non-turbo 900 is ideally matched for snow driving. The valvetrain takes less of a beating in cold-weather starts.
My only complaint about these cars in the snow is where the brake lights are. They're right above the shelf-of-a-bumper, so keep them clean. '86 and newer US cars will have a third brake light, which will help as long as your rear window is clear. In last year's token blizzard, I used hand signals for one of my turns because I knew the lights were obscured.
Here's my checklist for my winter car, aiming to make her the best winter sled I can find.
I've already mentioned the Hakkas.
I've already mentioned synthetic engine and gearbox oils.
Fit the 89 degree thermostat. I've tried the 82 degree variety and didn't have any heat below 25 degrees Fahrenheit. That wasn't fun.
Fit winter wiper blades. The curvaceous surface of the 900 windshield makes standard blades turn into ice rotators. The winter blades won't get the corners very well, but they will work.
Use the orange washer fluid. Find some that's on sale for $2 a gallon and buy 3 jugs. This stuff is awesome, especially in salt spray conditions.
Replace the in-line washer fluid check valves (inside the hood near the nozzles) every couple of years. They're cheap.
Make sure the rear defroster works. On 1990 and older 900s, the timer relay is under the hood, where it tends to only last 10 years or so. You don't want to have to hold the button down to get the rear window cleaned off.
Treat your lock cylinders with de-icer.
If it hasn't been done in twelve years, pull out the door latch mechanisms and overhaul them. Soak them in brake parts cleaner, let them dry, then lubricate all the moving parts with a LOW-TEMPERATURE grease that has a good content of silicone. The factory grease will gum up after a decade or two and your doors won't close. Cover the silicone lubricant with a good grease to keep it in there.
Coat your door seals with more of the silicone-based lubricant so they won't stick to the car.
Check the front suspension (ball joints, etc.) with the suspension unloaded to be sure the ball joints are solid. Pot holes happen. This is why your snows should probably be on steel wheels. Be sure to insert a spacer between the upper A-arm and the body to check these, otherwise you can't do the job.
Be sure the mini-skid plate beneath the transmission case is intact. Slush bombs happen. Many have met their death on this piece of metal on my 900. There are mud flaps in front of the rear suspension arms for a reason you may be about to find out.
And if you can, stick with a base model. Power windows are a huge pain in the neck in cold weather. Consider ripping out the AC if it doesn't work. The base car weighs a significant 100+ pounds less than the more luxurious models. That's another hundred pounds you have to get moving, steer, and stop on ice. In the really bad storms, you'll need the extra inch or so of ground clearance on non-turbos too. Leather is very cold when it's very cold.
ABS versus non-ABS is an item of personal preference. If you don't have good reflexes, ABS will keep you stopping in a straight line a little better. Then again, mounds of snow in front of your front wheels and maybe a little bit or a rally slide may stop a non-ABS car shorter, but you have to be comfortable with it.
I tend to love my '88 because that was the first year for rear-wheel parking brakes on the 900. The brake system for that year and newer has better modulating feel and shorter stopping distances on dry pavement. The front calipers are more reliable. With some creative applications of a rear-wheel parking brake, you can change directions quickly in the snow, just like they show on all those (otherwise stupid) Datsun/Nissan commercials. Use the throttle and service brake for understeer control, and then (practice and don't overuse this first!) use the parking brake for a little creative oversteer, like in slush-filled intersections. You may get accustomed to watching where you go through the side windows. Plus, all your friends will ask you if your car is rear-wheel drive.
Now for the fun stuff. Some people spend hoardes of money on stupid accessories to make their cars look and sound flatulent. I've customized my 900 (though you can't tell by looking at it) for cold weather.
I have a Saab accessory for the car. It is a heat exchanger that sits in the upper radiator hose and heats up your washer fluid. It's such a great idea! You won't need the AC thermoswitch that sits up there anyway. (AC won't activate below around 30 degrees.)
Consider retrofitting your 900 with heated mirrors from an '88 and newer S or Turbo car. It's easily done.
Fog lights are a nice touch, especially in heavy precipitation. I'm pretty sure midwestern snow is similar to our lake effect, so you may find yourself tooling down the interstate at 45 miles an hour with the headlights off, because they will just make it impossible to see where you're going. Get mounting brackets and a switch from a junkyard car. Everything '86 and newer is pre-wired for them, just drop in a relay and switch and wire up the lights.
Consider adding headlight wipers from a '91 or newer car. This will require grinding off bosses or replacing your headlights entirely, but they're a whole heck of a lot safer than having to pull off the road to clean the lights or driving when you can't see where you are going. A shot of Rain-X on the headlights may help here as well.
Quoting JP from a few years ago: "Weight transfers and other fun bits of driving physics that were hard or illegal to explore on dry public roads are every day events in the snow. You get to practice all this stuff with less grip and slower speeds."
That's the list for now. I'll think of other things later. Even though it's hell on the paint, I like driving my 900 in the snow more than I should. All those other cars just turn into overweight lemmings with incompetent drivers and crappy wide tires.
Previous post, note the replies
, Tue, 23 Oct 2007 17:53:34 <-- Viewing This Message, Wed, 24 Oct 2007 13:51:14
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