geolab

I am the one in the dark these days, trying to change carrier and someone mentioned Dubai ...

Started with logic so: when you lock the car in hot summer (even in winter in Dubai), and the auxiliary blower stays on (monitoring phase) for 15 minutes, not for hot air in cabin.

Above 120 km/h and or engine temp above 110*, the auxiliary blower is on max. speed, always, summer or winter, cabin heater off.

Anybody who went under a 993 with engine running, would know that the blower outlets through the engine tray blow burning air, ask me how I know

If it wasn't for cooling engine, why make outlets then ?

and after my primitive logic, I deduced it from the electric diagrams and then learned it in the Porsche training material.
regards

Holger3.2

Using technical thinking, you have a point, maybe the problem or the confusion about it is the double function of that pipe.
In the first place, i think, the blower gets 'additional' hot air out of the engine compartment, which can be used for heating (in cold climate) or it would be released to the environment through the funny little gates below the engine. Therefore, the pipe would be a heating and cooling device, depending from what part of the car you're looking.
So based on experience, a lot of guys removed the blower coz they don't need to much heater capacity (bypass would be enough) or don't drive if its cold(...so they think). if you now remove the 'heater-tube (again that's the Porsche term*)' you would not be able anymore to serve your interior with hot air. However, the heat would still be pressed under the engine. If you remove the blower and bypass, than the tube would be useless. Result would be that you cant remove anymore additional hot air from the engine compartment. That might be bad or not. I don't know.
On the other hand, its primarily an oil cooled engine ... so long as the oil temperature is ok!? This, of course is measured at the oil cooler, not at the engine compartment, so the problem might come if you stop the engine and the fan is cooling down the oil cooler but not the engine itself anymore, so i thought that the blower kicks in only when the engine is off??

Anyway, where does the whole removal idea come from? From Porsche Rennsport coz they removed all of that stuff in its cup cars. Therefore, what's good for them is good for me, even in Dxb (which is btw. a great place for work challenges, but not really for living; if i had the choice, I would prefer Paris), it works for me! But i use the car only on the track, and it never overheated like other ones here. But I don't idle in traffic jam for 3 hours either ...

You mentioned additional the Porsche training... nice one but not many of the Porsche user are attending, i guess. And as a factory, of course i have to stay on the safe to very safe site and have to cover ALL possibilities. That i saw very close and impressive when my friends here just tested the Macan for several month here. They do things out of principal, which we would never think of. But again, they have to cover ALL possibilities. They also have still seat heater in all their GCC version cars...

* just checked out of curiosity ... that the English term, the German term in the PET is much more accurate, its 'Luftverteilerrohr' which means 'air distribution pipe'

geolab

Hallo Holger, thanks for your answer.

Since there is no oil for cooling in cylinder and head, I call it air cooled
There is oil from squirters under cylinders, and on top of heads for lubrication, yes.

the auxiliary blower stays on when engine off and car locked, if engine temperature above 71* celcius.
and monitoring of engine temp stays on for 15 min, not oil cooler fan here.

Porsche training is the book, I did not attend the course, but have the book. I will post a copy page.

The cup cars do not have all this, and a cup car with engine idling and car stopped, is as rare as a zero income tax country

If it was me, I would never ever remove the cooling system.
Maybe RS bypass, but I will keep the system.
VW beetle had the same cooling system as well, if I remember correctly

k722070

interesting theory.
geolab, do you believe the cooling happens from air being moved through the cross pipe by the blower motor while the engine is shut off?
or air being moved through the heat exchangers and out the little flapper boxes?

Holger3.2

Lets stick to 'air distribution pipe'; comes the closest ...

Oil cooling fan is running at the oil cooler, means of course in the right front fender ... it is 'normally' controlled by the CCU and would even run with stopped engine only switch of if the temperature reaches specific values. That might be the reason why there is additional blower at the engine compartment.
The oil cooler fan operation is often forgotten when aircon is removed. Needs a manual switch at least.

Luckily i'm living in a income tax free country (which does not mean that you don't have to pay to the government!!!) but idling race or track cars are still extreme seldom... except it rains (its not the lack of rain tires then, its the flooded track which stops you ... )

And for sure the old standard beetle never had such cooling system, not even a extra blower. The theoretical present heating system was fed by the common blower on the alternator via 2 extra hoses (since the 60th). Engine stopped, airflow stopped. in winter the air got never hot; as in Summer, you mostly couldn't close the little outlets beside your feet which might be the reason for the German term that you have 'heisse Sohlen' when you had a fast car (translated hot sole...) coz you drove faster to get out ...
If you could close the outlets, the blower pressed just against the Pipe, no extra gate like at the Porsche.

geolab

When engine is shut and temperature is high, the auxiliary rear electric blower blows fresh air inside the engine snail, through the cross pipe, to finish down in the heat exchangers and out of the flapper boxes. Monitoring stays on for 15 minutes, meaning it could stop, and goes back on, if temp in engine compartment is back up.

geolab

My meaning was that the VW beetle has the cooling of the heat exchangers by the upper stage fan.
in the picture, fresh air comes from upper fan, through pipe number 4 and hooked to the exchangers number 12, to cool down the head temps. As well as pressurized air flowing from upper fan on cylinders
This system is mechanical, not electrical of course
In the 993, it is both

Exploded View of an Air Cooled VW Beetle Exhaust

k722070

yes, I have no problem with your explanation of what is happening, I'm just trying to understand how you believe it cools the engine.
do believe the cross pipe acts as a heat sink to cool the engine?
or do you believe blowing air through the heat exchangers cools the engine?
or is it a combination of the two?

Holger3.2

On the beetle, the airflow will stop if the cars heater system is not opened, at least on my beetles (all built in the 60th) there where NO valves, gates or anything likely that would still allow the air to flow around the header.
Further if the engine is off, simple no airflow. So my guess, no cooling system by purpose ...
a friend drove his 1300 Standard first roundtrip from Hamburg to Athen (as Test); than to the Khyber Pass (roundtrip again) and the coming year he tried Captown... on the way back the car got finally destroyed somewhere in the African plains ...; to my knowledge he had never had a heat issue ...

geolab

To cool the engine directly, no. But to cool the heat dissipated from the cell cats, yes. To be clearer, check the heat cover above catalytic converter that hooks to
the cross pipe, and englobes it so that any heat rising from converter ends on the cross tube. Thus less engine compartment heat, then less engine heat

definitely yes

k722070

thanks, I'd never heard that theory before.
I had assumed the heat shields were to stop heat from possibly damaging the bumper cover and to help heat up the cross pipe for more immediate cabin heat in the winter.
in my case it doesn't matter since the blower motor has been gone for years anyway.

Cupcar

I think it is called a "heating tube" because it capitalizes on the huge amount of heat coming from the catalytic converters below it to heat the alloy pipe and thus the air within it for the purpose of heating the passenger compartment.

It would also act as Geolab states as an engine compartment cooler both when doing passenger heat but also when the blower fan runs after hot shut down of the engine.

It is really a heat exchanger.

cavlino

Very interesting discussion thanks for sharing.

Holger3.2

Just stumbled over this thread again and thought that an update couldn't be bad

On the weight, i'm now down to 1,161 Kg or 2,555 lbs. That achieved by getting more stuff out, specifically by 'lighten' the bumpers, getting rid of cruise control, a/c pump console (just cut it out), catalytic converter, of course heat exchange pipe :P, engine isolation, changing to OZ Alleggerita HLT rims and 9kg Varley Red Top Battery, by adding secondary oil cooler, straight pipes an a Vbox system. Still have my sunroof, but that is another ongoing project.

In terms of overheating, the installation of the secondary oil cooler (not the expensive ones you can buy for the car but a common cooler with custom made frame) worked extremely good, even last summer were we had up to 48C on a trackday ...

The car made now 8,500 km on the track only and seems stronger than ever!