Engine management problem or just the way it is
- Thread starter pegasus
- Start date
Diver944
Active member
Have Sean and Bruce ever come across a definitive reason for the comparatively slow starting of the S2 cars?
One of our members ( Rob in Birmingham) spent a lot of time investigating several years ago and determined that there was a parameter in the Motronic for S2's that specifically delayed the firing of the injectors until a certain rpm had been reached (which is what I think Oli is referring to).
My Turbo which has a 3.2 engine derived from an S2 fires so much quicker than my S2 - but then virtually everything is new so you would expect that
My '83 Lux starts as quickly as my 1 year old van (but it is a Reno!) cold or hot unless I stray on to the throttle.
Mike
Mike
George Elliott
New member
Interesting post, I was not aware that the engine management software effectively has an inhibit on sparking at startup until "X"rpm @ "Y" seconds. Its a good idea as it promotes oil circulation before startup. Perhaps that contributes to the engines bomb proof reputation. It is certainly possible for motronic to control this, and as these are the first (watercooled) engines Porsche made with electronic management / pulse senders on ring gear etc, I can imagine the engineers taking up the opportunity to do it.
I agree the slooow turrrnover is distinctly out of character with todays modern engines (which have no character) but it does contribute to the character of the car. I have got used to it.
Pegasus asked why is this so, what's different between "the average 4 Cyl petrol car engine" and a 944 engine.
Feel free to add your unique factors to the list:
Most engines are approx 1.6 litre, a 944 is 2.5litre minimum.
A 944 Crank alone weighs 29kg, so the reciprocating mass is huge (Crank/Flywheel/Rods/Pistons/Driveshaft/one gear shaft)
The starter motor wires are about 7 foot long
The starter motor would need a significant additional current supply to turn the rotating mass at the "normal" starting rpm of a modern car.
Then add in age, wear, cold weather, thick oil, short winter journeys with the lights and demister on, and it makes sense to me that they have engineered a slow spinning starter motor setup.
You'll get use to it, at least it always starts, (but I carry a DME in the Glove compartment just in case.)[
]
And it will still be running when the modern engines have been crushed
Do I recall the opposite problem on 996's, where the engine barks up and blips itself to 1500rpm tick over? If so, no wonder they have the reputation they have for wear and failure.
George
944t
964
I agree the slooow turrrnover is distinctly out of character with todays modern engines (which have no character) but it does contribute to the character of the car. I have got used to it.
Pegasus asked why is this so, what's different between "the average 4 Cyl petrol car engine" and a 944 engine.
Feel free to add your unique factors to the list:
Most engines are approx 1.6 litre, a 944 is 2.5litre minimum.
A 944 Crank alone weighs 29kg, so the reciprocating mass is huge (Crank/Flywheel/Rods/Pistons/Driveshaft/one gear shaft)
The starter motor wires are about 7 foot long
The starter motor would need a significant additional current supply to turn the rotating mass at the "normal" starting rpm of a modern car.
Then add in age, wear, cold weather, thick oil, short winter journeys with the lights and demister on, and it makes sense to me that they have engineered a slow spinning starter motor setup.
You'll get use to it, at least it always starts, (but I carry a DME in the Glove compartment just in case.)[
]And it will still be running when the modern engines have been crushed
Do I recall the opposite problem on 996's, where the engine barks up and blips itself to 1500rpm tick over? If so, no wonder they have the reputation they have for wear and failure.
George
944t
964
George Elliott
New member
Just done some further investigation, try typing "Bosch versus IMI" into YouTube....if you are interested.
George
944t
964
George
944t
964
Posts made and opinions expressed are those of the individual forum members
Use of the Forum is subject to the Terms and Conditions
