cam drive - belt or chain

[D Ward]

ORIGINAL: sue11sam

Hmmm thats why you have 12 litres of the stuff slopping about the car, I am not suggesting the air part of the cooling partnership is unimportant, I am saying that the oil part is probably a higher contributor to your cooling capacity than you think. Why do you think it takes my garage 30 mins to bring my engine to temperature with a leaded blind on the air inlet . It would be interesting if you disabled the water pump on a fluid cooled engine.

So on your car I take it that apart from the grill on the engine cover, the engine compartment is completely air tight and air can only enter via the engine cover grill ? Maybe special order from Porsche, air tight engine encapsulation option, although I can't seem to see that option listed on my old 993 price list.
My 993 has a large hole under the engine, so big a hole in fact that i once removed the engine and gearbox thru said hole, so even with the engine cover grill covered,the engine would still draw huge amounts of air in, covering the grill will just trap more hot air allowing the engine to warm slightly faster.
The reason it takes so long to get up to temperature, is one due to how much air the engine air pump is pumping and two, there is no load on the engine.

If your still convinced the oil is the main cooling source in your AIR COOLED engine, dont bother with covering your engine lid grill next time you need to warm the engine, just take of the belt to the air pump, then leave it running for half hour, three minutes should have the gauge in the red, another couple should have it seized up nicely.

Please post how you get on, may save someone else thinking hey I got 12 liters oil I can drive with a broken belt

Dont forget to mention to porsche when you order a new engine, that you want an oil cooled one

 

[sue11sam]

ORIGINAL: D Ward

ORIGINAL: sue11sam

Hmmm thats why you have 12 litres of the stuff slopping about the car, I am not suggesting the air part of the cooling partnership is unimportant, I am saying that the oil part is probably a higher contributor to your cooling capacity than you think. Why do you think it takes my garage 30 mins to bring my engine to temperature with a leaded blind on the air inlet . It would be interesting if you disabled the water pump on a fluid cooled engine.

So on your car I take it that apart from the grill on the engine cover, the engine compartment is completely air tight and air can only enter via the engine cover grill ? Maybe special order from Porsche, air tight engine encapsulation option, although I can't seem to see that option listed on my old 993 price list.
My 993 has a large hole under the engine, so big a hole in fact that i once removed the engine and gearbox thru said hole, so even with the engine cover grill covered,the engine would still draw huge amounts of air in, covering the grill will just trap more hot air allowing the engine to warm slightly faster.
The reason it takes so long to get up to temperature, is one due to how much air the engine air pump is pumping and two, there is no load on the engine.

If your still convinced the oil is the main cooling source in your AIR COOLED engine, dont bother with covering your engine lid grill next time you need to warm the engine, just take of the belt to the air pump, then leave it running for half hour, three minutes should have the gauge in the red, another couple should have it seized up nicely.

Please post how you get on, may save someone else thinking hey I got 12 liters oil I can drive with a broken belt

Dont forget to mention to porsche when you order a new engine, that you want an oil cooled one

I think if you read the thread that I suggested that I believed that the oil cooling capabilities of the car contributed more to the overall cooling effect than had been expressed before, I have not mentioned not running with belts or indeed advocating running any distance with a broken one. I still think that if a belt does fail (quite unusual these days with modern materials) and the car had been at normal operating temperature when it failed, it would be ok to drive at low revs, a short distance to a safe place to park.

 

[vitesse]

I would agree with that-also ,just as with a watercooled car,turning on the heater with fan on full,windows wide open will help to disperse heat-although I don't know whether the heater fan runs if the belt sensor is triggered.

 

[A Ward]

Hi

Referring back to the earlier post in which you said that there was 70:30 split in favour of oil for cooling the engine and that the vehicle would be ok to drive just keep the revs low ""

Don't know what the split is between oil cooling and air cooling on a 993 is (must find out) but suspect its 70/30 in favour of the oil, therefore not critical if the belt breaks, but fix it asap, and keep the revs down

My advice (and that of several others) was to pull over safely ASAP and stop the car due to the increased risk of engine damage.

I have backed up my comments by putting genuine Porsche technical information and data regarding the vital and important role that air plays as the primary function in cooling the engine, and the fact that running without this air cooling available (fan belt broken) would be extremely detrimental to your engine. The manual that comes with the car even states that you should pull over and stop the engine immediately.

The original poster was asking about the timing chain and belts regarding renewal "" and was rightly advised that the timing chain should not need renewal/adjustment; but that the fan belt could wear with age "" it is after all subject to large amounts of radiant heat in the area that it runs. The advice was to be aware of it and the importance that it plays in the cooling of the engine"¦quite rightly they were advised to not continue driving the vehicle and pull over/stop the engine"¦as Porsche also advise.

Lastly the effect of turning the heating up to full and running your fan would not do any favours either "" the Porsche 993 does not have a traditional heater matrix like a normal "˜water-cooled' car "" but actually uses the kidney shaped heat exchangers that sit underneath the engine by the exhaust system "" the residual heat from these is used to heat the air that is blown through the ducting by the air motor. It is also unusual in the fact that it also has electric heating to supplement this "" so cranking the heat up would actually result in more current draw on the battery and thus the alternator would be loaded and creating more load on the engine.

There have been a few "˜tongue in cheek' comments added to this posting "" but the details that I have provided have come from Porsche 993 manuals "" written by the Porsche engineers who designed the 993 and that the Porsche technicians refer to in order to maintain/fix them. My concern is that people would read your comments (which you have been unable to substantiate) and think it was ok to run the car around without the 'air cooling' in the event of a belt failure, provided they kept the revs low - this could be very expensive for some poor indiviudal.


Hope that helps