Is Battery up to the job?

[jonk]

I get the impression most S2 or 944s in general are slow to crank. Mine has a brand new Unipart battery the last owner put in. Is 64 a/hrs enough, or is this likely to not be enough when the weather gets cold or the car is left for a few days? Most sites recommend at least 70 so does that mean this one will be too light duty and die after a day or two or a cold snap?

Thanks guys

 

[944Turbo]

Is Battery up to the job? if it starts then yes someone will probably be along with a more helpful answer soon.
tony

 

[jonk]

Fair point, have started and driven it every day so far though. May just leave it for a few and see what happens...

 

[Wardy 944]

My car turns over really slowly for the first couple of compressions, then speeds up until it starts, I'd always assumed it was a trait of such a large capacity engine?

I'll have a look at the a/hrs on my battery tomorrow and report back.

 

[Diver944]

My original owners manual says 63ah but I remember the last time an OPC serviced mine about 12 years ago and they said the recommendation was then 70ah. I recently bought a Bosch Silver 096 which is 77ah and it made a huge difference this winter []

 

[DavidL]

2nd vote for a Bosch silver 78a/hr. No issues there.
One also spins my 4.2 V8 rangie but exactly what the compression is I don't know.

 

[Indi9xx]

We recommend a minimum of a 72ah on a 944.. also check the voltage drop on the engine-chassis and battery-chassis earth straps.. also there is a big difference between two available starter motors for the 944S2 (and turbo) which make a vast difference in cranking speed.

 

[bmnelsc]

In Canada our batteries include a CCA (cold cranking amps) rating in addition to amp hours. We always go for the highest rated battery that will fit in the space available. I put in an Interstate 72ah (CCA around 780?) as Bosch batteries are hard to find here.

My S2 still does not crank nearly as fast as my V6s (with cr of 10-1) and seems to turn about 6 times before it starts. Doesn't really affect performance but it does make that big 4 sound kind of agricultural rather than the highly tuned power plant it is. Is this down to the starter installed or does this big 4 need a few spins to get enough air down there to start?

 

[zcacogp]

I am told (can't remember who by) that all 944's will crank a few times before firing to build up the oil pressure, and that no spark is generated until it has cranked 'enough'. How much 'enough' is and whether this is done by measuring the oil pressure before energising the coil I don't know. (I doubt the latter tho'.)


Oli.

 

[eddieedmo]

here is an interesting point.Normally my S2 cranks over twice and fires.When the battery has been disconnected it fires immediately first start after battery re-connected then reverts to cranking over twice before firing ?

Anyone know why ?

Nick []

 

[Wardy 944]

I've had a look at mine today and it says 74 a/hr.

 

[sawood12]

Not sure why the 944's crank so slowly. I'd imagine that there is far more friction and resistance to overcome in a 2.5ltr or 3,0ltr engine with more than 4 cylinders by virtue that there is simply more friction due to a greater area of metal sliding against eachother, more inertia due to extra cylinders and more moving parts, and the fact you have more than one piston on its compression stroke at any given time. It is clear that the slow cranking speed of the engine was intended by design rather than an unintended consequence. Can't think why though. Maybe it has something to do with wanting to reduce the initial stresses in the con-rods as cylinders start to fire up, or to initiate better distribution and mixing of the air and fuel to aid initial combustion, or something like that.

Having said that, slow cranking aside, if your engine and electrical system is in fine fettle then you should have no problems with starting.

 

[Hairyarse]

I thought the slow crank was due to big engine size, I.e. 3.0 litres but only 4 cylinders. Not sure the technical reason but guess 750cc per cylinder is quite a lot!

 

[944Turbo]

ORIGINAL: eddieedmo

here is an interesting point.Normally my S2 cranks over twice and fires.When the battery has been disconnected it fires immediately first start after battery re-connected then reverts to cranking over twice before firing ?

Anyone know why ?

Nick  []

Dont know for sure but I wonder if its connected to the fact (according to titanic about 8 years ago) you are supposed to let an S2 idle for 10 mins after reconnecting the battery, while it revs itself and settles the idle - wonder if it 'forgets' not to start immediately.
Tony

 

[bmnelsc]

ORIGINAL: zcacogp

I am told (can't remember who by) that all 944's will crank a few times before firing to build up the oil pressure, and that no spark is generated until it has cranked 'enough'. How much 'enough' is and whether this is done by measuring the oil pressure before energising the coil I don't know. (I doubt the latter tho'.)


Oli.

This is interesting. I have noticed that if I let go of the key before it starts during the initial sequence - it will fire almost immediately on the second start (e.g. crank-let go-switch back and crank again right away). I was wondering if this was waiting for oil pressure or insufficient air getting down there. Maybe the lifters are not opening the valves enough until the oil pressure has come up?

The withholding spark sounds plausible and terribly sophisticated. I'm certainly going to use it on those Luddites who imply my S2 doesn't sound Porsche-like on start up[]. Now to search the wiring diagrams for a link between the oil pressure sender and DME relay or ???

 

[Hilux]

Lots of ECU`s will only trigger the spark when they see a minimum amount of revs (something like 250rpm)

The braided earth straps are prone to breaking down. To see the benefit of a direct earth take a jump lead off a starter bolt and direct to the negative terminal, I bet it nearly turns the car over. The starter has to earth through the engine/gearbox to the body and then back to the battery via the body. Any deterioration (resistance) and current wont flow properly. Use a jump lead to bridge each earth strap too to see if that improves it.