Rinty

Vern:

For me, the main issue with starting an engine in very cold conditions is how many seconds it takes for the oil to get from the sump to the valve train. I recall reading a technical article that stated that at -20C, conventional 10W-30 could take up to 25 seconds to get up there. Of course, 0W-XX or 5W-XX synthetic that many 911 owners use, is going to get "upstairs" much more quickly, but it's still going to take a few seconds. To compound the matter, the engine may not have been run for some time, and the oil that previously adhered to the valve train components may have drained off.

Getting back to your battery, for your next one you might want to consider an absorbed glass mat type, as these fall off more slowly than lead acid batteries, I understand. I had good luck with one of these in my 1982 BMW motorcycle, which was cold stored in the winters.

Anyway, good luck with this.

95C4VanIsle

I'm not sure if this applies to this situation but I was told by MikeJ to pull the DME when I tried to start the engine, when it is cold outside and especially if the car has been sitting for a week or two, or longer, regardless of the outdoor temperatues. I believe he was referring to getting the oil from the sump to the valve train (bear in mind that I am technically challenged).

He instructed that once the oil pressure started to register I should stop trying to start the engine, reinstall the DME and start as usual. As I trust what he tells me it is a practice I always follow.

Rinty

And some owners instal pre-lubers, but I haven't seen them mentioned here.

g_murray

During the winter... ...and after she's been sitting for a while... ...but now the opportunity arises...

I also remove my DME and - with the battery charger STILL connected -- I 'turn over' the engine several times (say 5 bursts of '3 seconds' turning). After doing this the oil pressure needle has very much come back to life! Then I simply re-insert the DME relay, git my a$$ back in the car and start her up.
Whilst everything is turning over - I turn off the battery charger then disconnect the battery CHARGER cables (from the car battery) - check under the 'trunk' to make sure everything is OK, then button her up and go for a 100+ mile drive.

Aaaaaaah, winter driving. Everyone around me is slogging around in their filthy SUV...

Gerry

cmat

"Whilst everything is turning over - I disconnect the battery - check under the 'trunk' to make sure everything is OK, then button her up and go for a 100+ mile drive."

Hope this doesn't mean you are running the car without the battery connected. That would be asking for serious trouble.

g_murray

Oooops, my bad, as they say, I SHOULD have typed battery CHARGER! (I fixed this in the post too!)
G.

IXLR8

Especially if you have 20W-50 in the engine as I do. Not an issue since I won't be starting it till next spring, and if I needed to, I can always pre-heat my oil.

I haven't bought into the 0W-40 Porsche recommendation, not on an air cooled engine.

IXLR8

I've been doing that for ages to all my stored vehicles when I bring them back into service.

jaholmes

My 993 goes through batteries if left for a couple of weeks without a tender. In the winter it's in an insulated garage, but still cold. Get a black & Decker battery tender from HD to save the battery.

I have a Toyota truck that sits outside all winter and may not be driven for a month. The damn thing starts every time without hesitation. Not sure if the 911 takes a lot of torque to turn the motor or what but some batteries are not up to the task if they are not 100%.

Rinty

Alex:

Do you have an easy way of doing this?

The 993's 11.3:1 compression ratio isn't overly high, but a significant factor might be the voltage drop from the battery to the starter motor; it's quite a distance. It is a factor in "smaller" aircraft that have their batteries in the tail section.

A few weeks ago, a Rennlister who lives in Alaska posted that he drives his 993 to work every day. IIRC he said it starts well down to about - 10 F, (-23 C) at which temp he has to go out every few hours to start it. That's pretty cold.

IXLR8

I'd use the same box fan heater pointing upwards that I have used the odd time for the same purpose on my motorcycles when I absolutely needed to start them. You leave it within a few inches of the engine block for a few hours. This of course is inside a cold garage.

I know. I used to ride my motorcycle in temperatures down to that daily to and from work in real winters that are similar to yours.

bgiere

I have stored my cars for many,many winters here in Ohio...I use Optima batteries in the street car and Odyssey batteries in the race cars. I put them away in November and bring them out in April...I never start them unless I absolutely have to. No trickle charge. Never had a battery go bad and all I do is give them a couple hours on the battery charger in the spring...The Optima's will be six years old this spring.

arjag

I can add some wisdom gained by recent experience to the thread. My 993 was new to me in November. I at least got to enjoy it for a month before putting it away for the winter in December. I bought a trickle charger for it, but as I have in the past with my other cars, I took it off the Pcar and put it on another battery for a couple of weeks thinking how fast can a battery discharge in a heated garage? I keep the garage at about 10-15 celsius (thats 50-60 F) at this time of year.
I tried to open the car yesterday and the immobilizer was behaving strangely. I searched threads on immobilizers and thought that the unit had gone south and that I was in for some $$ for repairs. Further investigation and I noticed that the clock had lost time and the radio code was lost. Hmmm, could it be a low battery. Sure enough, after an night on the charger the car is "back to normal". Leads me to believe that the car cannot sit for more than a couple of weeks without being on a charger. Either that or my battery is weak!
Needless to say, for the price of a charger, I'll be buying another charger and leaving the Pcar on for the rest of the winter.
Strange because none of my other cars will drain as quickly. Then again they are older (at least 20 years older than the Pcar) so much less drain from electronic gizmos.
Alex
1998 S

IXLR8

For a Flooded Lead Acid (FLA) battery, the general rule is 0.01V per day with no load on it. ie: disconnected. So in 100 days, it will self discharge by 1V.

An Absorbed Glass Mat (AGM) or Gel battery self disharges at a slower rate.

BTW, all batteries self discharge quicker in a warm environment.


I parked my daily driver with a 10 year old battery and it started as if nothing happened, more than 2 months later.

IXLR8

Here are some stats and facts based on a measurement.

My stock 993 with no aftermarket accessories to draw any extra current has a current draw of 22 milliamps (0.022A). That means I will lose about 1 Ah in 45 hours or nearly 2 days. Yes I know about Ah and that it isn't linear ...Peukert's number if you are interested.

The fact that my battery is in a cool garage at about 5°C means it should self discharge very slowly, slower than the usual 0.01V per day.

Therefore, since my battery drains down to 12.15V (about 50% discharged) in a matter of two to three weeks tells me it is on its last legs. With a date code of 37-05, time for a new battery next season.

A healthy battery should start a car that has been sitting for two or three months.