T4 Engine tin: thermal design Options

[914werke]

I found that it takes a lot of detailing to properly seal off the top of the engine.

(IMG:style_emoticons/default/agree.gif)
Remember Some of what were talking about here was already present from the factory.
For instance the front tin sections creating the well for the fan & alternator had/has weatherstripping like material to seal up those pieces.
why that wasn't applied to all the tin ..... (IMG:style_emoticons/default/confused24.gif)

[r_towle]

I found that it takes a lot of detailing to properly seal off the top of the engine.

(IMG:style_emoticons/default/agree.gif)
Remember Some of what were talking about here was already present from the factory.
For instance the front tin sections creating the well for the fan & alternator had/has weatherstripping like material to seal up those pieces.
why that wasn't applied to all the tin ..... (IMG:style_emoticons/default/confused24.gif)

Kind of my point.
Now, we have all removed , refinished, and reinstalled all the tin
Those gaskets were put there to prevent the fan from sucking in hot air from below.
There were other gaskets around the oil cooler too.

Rich

[einic]

Gene Berg performed several attemts to improve cooling on the type 1 engines and found out that every change that improved cooling in one place redused cooling another place. He concluded that the best cooling whas the VW original.
Adding oil coolers whith thermostat was the best improvement.

[searunner]

You don't want low oil temperature though. Optimal oil temp is at least 210. Lower than that you can end up with all kinds of impurities and end up weakening the oil and damaging the engine. I see lots of water cooled engines that people put low temp thermostats in which never allow the engine to reach even 180 degrees. Not a good plan.

I agree with you - and on my car, the cooling radiator has a thermostatic valve that opens at +/- 180°F the oil cooler circulation, and has an efficient electric fan thermo
controlled also.
https://photos.app.goo.gl/FFAR6U3otKWEfJQF7

NOTE:
914 has half oil in circulation very little OIL cooler radiator and half power have a thermostat that controls the low temperature of air if too cool BUT
haven't any possibility to contrast the overheating if occurred
OIL COOLER radiator
advantages were that the cool (185*) cooling directly the internal of the engine, (the head of the engine is the critical part)
moves the warm to the radiator (when this is needed) increasing the hard work of the engine fan WHEN REQUIRED
the AIR cooling is less efficient than LIQUID (OIL) difference is near to 50%

one other advantage is that when the warm engine was stopped the fan of the oil cooler can continue to work (Thermo controlled) for some minutes pulling down the oil temperature

[914werke]

(IMG:style_emoticons/default/idea.gif)
To prove or disprove the theory that the OE facilities for T4 engine cooling (specifically in the 914) are sufficient & cant reasonably be improved upon with simple measures might be an involved task. (IMG:style_emoticons/default/sad.gif)
First you've got to define what the goal is?
Are you trying to reduce temperatures because .... you think the heat is bad?
As has been discussed there are two distinct methods of heat dissipation at work on our motors. Air & Oil.
Also two specific areas for measuring the operating health: crankcase oil temp & head temperature.
How much heat is good? when does it cross that heat threshold into being bad? where? Oil? Heads? Both?
Once you answered those questions, Id suggest a simple comparative scientific experiment

A lot of work. (IMG:style_emoticons/default/wacko.gif) Who is up for it (IMG:style_emoticons/default/biggrin.gif)

[930cabman]

Gene Berg performed several attemts to improve cooling on the type 1 engines and found out that every change that improved cooling in one place redused cooling another place. He concluded that the best cooling whas the VW original.
Adding oil coolers whith thermostat was the best improvement.

I would put my 5 bucks with this. As I recall the T4 was the improved version over the T1 VW had used for many years. Over many years of measuring the shortcomings of the T1, the stock T4 was pretty darn good. If/when we make "improvements" to our T4 engines, we are somewhat in the dark without significant testing, which Gene, Raby have done.

[914werke]

Call me skeptical.
The T1 was never installed in a production mid engine chassis (to my knowledge) so applying any testing that might have been done is out the window in our application.
What empirical testing of engine cooling of the T4 in a 914 has Jake done? There is THIS tech article that deals with head temps only,
it doesn't define the vehicle in which he is measuring nor any specific conditions from which he forms his "observations"

[wonkipop]

(IMG:style_emoticons/default/idea.gif)
To prove or disprove the theory that the OE facilities for T4 engine cooling (specifically in the 914) are sufficient & cant reasonably be improved upon with simple measures might be an involved task. (IMG:style_emoticons/default/sad.gif)
First you've got to define what the goal is?
Are you trying to reduce temperatures because .... you think the heat is bad?
As has been discussed there are two distinct methods of heat dissipation at work on our motors. Air & Oil.
Also two specific areas for measuring the operating health: crankcase oil temp & head temperature.
How much heat is good? when does it cross that heat threshold into being bad? where? Oil? Heads? Both?
Once you answered those questions, Id suggest a simple comparative scientific experiment

A lot of work. (IMG:style_emoticons/default/wacko.gif) Who is up for it (IMG:style_emoticons/default/biggrin.gif)

ha ha. a lot of work thats for sure. (IMG:style_emoticons/default/biggrin.gif)

i guess one way it could all go is to go electric with the cooling fan.
oil temp controlled and triggered.
with some kind of ability to easily adjust fan speed (ie air volume).
it would have to be variable speed and constant adjustment.
thats if you are going to go the emprical route and lots of testing.
you need someway to be in a position where it is easy to tune and adjust parameters.

simple pulley to replace impeller fan and drive alternator.
a ducted cooling boot and an electrical fan mounted in engine bay?

you get some horsepower back with a crank driven fan delete?
a smog pump is worth 2 hp. whats an impeller fan rob?
......is the alternator up to it?

good thing i have gone all preservationist and stayed stock! (IMG:style_emoticons/default/beer.gif)

[r_towle]

Call me skeptical.
The T1 was never installed in a production mid engine chassis (to my knowledge) so applying any testing that might have been done is out the window in our application.
What empirical testing of engine cooling of the T4 in a 914 has Jake done? There is THIS tech article that deals with head temps only,
it doesn't define the vehicle in which he is measuring nor any specific conditions from which he forms his "observations"

I propose, and volunteer you.
I suggest you put some numbers down, lowest and highest temps for head temp and oil/engine combo

Let’s see some data.

[moto914]

Hi. My around town & ocasional 2 hr highway runs, avoiding traffic jams (getting a snack at an exit) head temps were ok.
The interest here is in the discussion.
"Upgrade the Floor Pan Air Deflectors" Nice point.
" Front ducting to eng. fan" Stated to work.
So how about some sort of scoop routing air through floor pan deflectors, for those who performance drive. Any thoughts?

[wonkipop]

So seeing a product recently got me thinking about the result of its application & my own observations of how well (or not) the T4 handles air flow, Engine block cooling & resulting oil temperatures. (IMG:style_emoticons/default/smile.gif)

Its somewhat well known that ...in the 914.. the T4 suffers from less than optimal cooling from the front mounted impeller/fan particularly to the #3 Cylinder
& that it is vitally important to seal the tins multiple openings to contain as much laminar air flow front to back over the finned cylinders.
In a gross approach, the goal was to seal the engine compartment "intake" air on top from the eng. heated "cooling" air below the tins.
When a motor is new and all its components serviced & refreshed, the design does, or did, a pretty good job.
After years of use (neglect), elements (oil dirt mice ext) conspire to restrict that air flow.
As well as eng. heat causing hardening of rubber pieces that are intended to help contain that cooling air below.
Now almost 50 yrs on I see fewer & fewer "STOCK" engine configurations which you can guess usually means more heat to deal with.
Jake addressed the cooling air via his(?) DTM solution, but IMO its not very practical for stock or near stock motors (& expensive)

The go-to response to eliminate that heat is usually an additional or a remote oil cooler which comes with its own set of challenges. (IMG:style_emoticons/default/confused24.gif)
How about KISS (IMG:style_emoticons/default/biggrin.gif) Has anyone used any of the Fiberglass based stick-on reflective heat shielding products on the engine-sides of the tin?
Idea being rather than allow heat absorption to all the those steel pieces reflect it back to carried away by the cooling air?

BTW Im not a Porsche engineer...but I did stay in a Holiday Inn last night (IMG:style_emoticons/default/happy11.gif)

i've been thinking about your original post.
dredging my memory.
regarding in particular your thought on stick-on relflective heat shielding products on engine side of tin. (and with consideration of superhawk's comments further on in topic).

i once had the reasoning for the black paint explained to me by my old german mechanic back in the 80s when i asked him why the engine tin on the squareback was black.
i was a naive mid 20 year old thinking of hot aussie summers and light colors?

he corrected me.

he had started out as a VW mechanic and then trained as a factory porsche mechanic before coming to australia.
he explained the black paint is mostly for heat dissipation after shut down.

black absorbs on its hot side and radiates on the cold side with regard to the atmosphere and also heat sources nearby. this occurs regardless of atmosphere itself. as superhawk noted. radiation occurs in a vacuum. the lunar module used this principle on the moon to keep cool. you can read up on it. it had mostly reflective surfaces on its rear face pointed at the sun and it had patches of black in key positions where it pointed away from the sun. the black surfaces were radiators that lost heat to the cold vacuum of space in the shadows.

the way it works with a VW is the tin absorbs the heat from the hot cylinders and engine parts after shutdown on its rear face. its an efficient absorber as a dark colour. (it also conducts heat very well as its connected to the hot engine and its thin so it heats rapidly.
rather than re-radiate this back at the hot contained engine it loses the heat through radiation on the cold side which is the engine bay side. its enough of a difference that the engine can not continue to escalate in terms of heating after shut down.

to some extent it might do this while the engine is running but probably not of any significance as its the air volume moving through the engine that is doing the heavy lifting in the cooling department.

anyway, that is why VW used black engine tins. so did porsche when it came to 912s and 356s.

911s are another story. the fibreglass cooling ducting neither conducts nor has any radiating qualities. they must have done their maths and worked out it did not keep gaining temp for a short time after shutdown.

i remember i always let the engine on the suqareback idle for a few minutes after pulling in from the highway to allow it to cool down slightly on its own before i shut it down.
i used to do this on the advice of the same old german mechanic.

if that story was right about the engine tin it is perhaps not a good idea to use a reflective surface on the engine side of the tins as this would reflect the engines heat back at it. particularly after shutdown. but also perhaps during running.
i think the tins definitely are meant to absorb heat and then lose it by radiation into the engine bay. they are meant to pull heat away from the cylinders and heads that are the super hot items. i think that is why rocker covers are black etc.

it sounds anti intuitive but i believe that is the reasoning.

VW would have done their maths on this.
the same principle would affect a hi po type 4 engine producing more power.
it would be a situation where the darker tin is assisting to get rid of heat.
the volume of air being drawn into the engine bay counters any effects of radiation in the engine bay while the engine is actually running.

[r_towle]

Hi. My around town & ocasional 2 hr highway runs, avoiding traffic jams (getting a snack at an exit) head temps were ok.
The interest here is in the discussion.
"Upgrade the Floor Pan Air Deflectors" Nice point.
" Front ducting to eng. fan" Stated to work.
So how about some sort of scoop routing air through floor pan deflectors, for those who performance drive. Any thoughts?

The firewall air deflectors create more “suction” under the car to help the fan blow air down.

[914sgofast2]

Hi. My around town & ocasional 2 hr highway runs, avoiding traffic jams (getting a snack at an exit) head temps were ok.
The interest here is in the discussion.
"Upgrade the Floor Pan Air Deflectors" Nice point.
" Front ducting to eng. fan" Stated to work.
So how about some sort of scoop routing air through floor pan deflectors, for those who performance drive. Any thoughts?

The firewall air deflectors create more “suction” under the car to help the fan blow air down.

Anyone know why the factory used two (2) under the car firewall deflectors instead of one longer piece across the bottom of the car at the bottom of the firewall?

When factories stared putting air deflectors/air dams under the front of cars to force more air into the radiator in front engined, water cooled cars, they used a long continuous piece of rubber/plastic below the bumper/radiator opening.

[moto914]

QUOTE(914sgofast2) good question.
QUOTE(r_towle @ Apr 2 2023, 05:04 PM)
Yes. (more “suction” under the car) My mistake was not considering the space between the deflectors.
So should have proposed a scoop forward of the fan that allows the deflectors to work as well.

[wonkipop]

Hi. My around town & ocasional 2 hr highway runs, avoiding traffic jams (getting a snack at an exit) head temps were ok.
The interest here is in the discussion.
"Upgrade the Floor Pan Air Deflectors" Nice point.
" Front ducting to eng. fan" Stated to work.
So how about some sort of scoop routing air through floor pan deflectors, for those who performance drive. Any thoughts?

The firewall air deflectors create more “suction” under the car to help the fan blow air down.

Anyone know why the factory used two (2) under the car firewall deflectors instead of one longer piece across the bottom of the car at the bottom of the firewall?

When factories stared putting air deflectors/air dams under the front of cars to force more air into the radiator in front engined, water cooled cars, they used a long continuous piece of rubber/plastic below the bumper/radiator opening.

the deflectors are more or less lined up with the rear exit openings in the underside tin (if you have the lower air guides) or more generally lined up with the air exit areas either side of crankcase.

radiators in front engine cars are centrally located and wide. hence the dam needs to be across most of the front.

i'm sure the vw/porsche engineers had the optimum solution when it came to those deflectors and real word tested it.

[Superhawk996]

i'm sure the vw/porsche engineers had the optimum solution when it came to those deflectors and real word tested it.

According to conventional mythology, VW & Porsche had no idea what type of oil should be used, what size the oil pump should be, or at what oil temperatures the engine should operate at. (IMG:style_emoticons/default/happy11.gif)

[wonkipop]

i'm sure the vw/porsche engineers had the optimum solution when it came to those deflectors and real word tested it.

According to conventional mythology, VW & Porsche had no idea what type of oil should be used, what size the oil pump should be, or at what oil temperatures the engine should operate at. (IMG:style_emoticons/default/happy11.gif)

@Superhawk996 i enjoyed reading your post @ #8. (IMG:style_emoticons/default/biggrin.gif)
it got me thinking again.
about 15 years ago i took part in a professional forum on insulation and energy efficiency in buildings. i thought maybe the most vivid way i could get some notions across was to discuss the first "dwelling" on another planet. the LMs.
i had to bone up on what NASA and Grumman got up to.
i found it fascinating.
incredible technical object then (and still now!) and i was only really concentrating on the insulation and heat control aspects of it. mostly they addressed the issue with knowing what to do with radiant energy.
i hadn't realised there were two basic material and color schemes for the LMs.
the first batch for the early missions which landed on the moon equator. as a laugh you could call those tropical spec lunar modules. the second batch for the missions which landed much further north of the equator. temperate zone LMs. (IMG:style_emoticons/default/biggrin.gif) quite noticeable differences in areas of black material versus reflective external shields.

not to mention the problem of thermal expansion at monstrous levels that no earthly object ever endured on the rear face which was oriented towards the sun. which didn't go down and didn't stop shining on them like a blowtorch.

i am pretty sure the black tin on a VW aircooled engine is a similar study in the use of an absorbing and radiating dark surface for heat control and heat loss. one thing you can bet on is that its black for a reason that has nothing to do with aesthetics or engine dressing. i'm guessing a black or dark side down towards the engine itself is the most important dark surface and should be black no matter what. i'm still thinking about the top surface but if NASA logic is correct well it ought to be black too. we get the extra benefit on earth as you point out of convection cooling as well. heating the air carries the heat away from the surface.

[Superhawk996]

@wonkipop

You are correct.

Black is indeed the best color both for absorption and emission of radiant energy and why the OEM tin is black. Black on the inside to absorb as effectively as possible. Black on the outside to emit as effectively as possible. All about letting the radiant energy pass in & out as easily as possible to get it away from the engine. Likewise, you’ll notice any of the thermal dispersant coatings are black.

Having said that, I still had one set of my tin powder coated in red - cause’ ya’ know, it adds 10hp right? (IMG:style_emoticons/default/happy11.gif)

Ideally, I would have had it masked so that it was black inside, red outside. But that probably also tips my hand about how worried I am about radiant cooling contribution on an otherwise stock engine. (IMG:style_emoticons/default/biggrin.gif)

[wonkipop]

@wonkipop

You are correct.

Black is indeed the best color both for absorption and emission of radiant energy and why the OEM tin is black. Black on the inside to absorb as effectively as possible. Black on the outside to emit as effectively as possible. All about letting the radiant energy pass in & out as easily as possible to get it away from the engine. Likewise, you’ll notice any of the thermal dispersant coatings are black.

Having said that, I still had one set of my tin powder coated in red - cause’ ya’ know, it adds 10hp right? (IMG:style_emoticons/default/happy11.gif)

Ideally, I would have had it masked so that it was black inside, red outside. But that probably also tips my hand about how worried I am about radiant cooling contribution on an otherwise stock engine. (IMG:style_emoticons/default/biggrin.gif)

incorrect. at least 20 hp. (IMG:style_emoticons/default/beer.gif)

i think red is sort up there heading towards black anyways.
or purple. (IMG:style_emoticons/default/biggrin.gif) going with the 70s.
white or silver would be kind of not what to do.

yeah. i figure the radiant performance is more to do with cool down after running.
and its kind of negated a bit by that magnesium fan casting that just sucks up everything from the crankcase etc via conduction and turns itself into a mini nuclear reactor for 20-30 minutes after shutdown. boiling your fuel lines. that was always porsches problem with the vapor lock syndrome. the mag fan shroud. the conventional VW type 4s didn't really have that problem since the fan shroud casting was hanging out the arse and having a whose hotter contest with the muffler. but at least all the heat could sort of get away. they were really testing things going mid engined. but it kind of worked ok really. certainly a lot better than most italian super cars of the same time - at least in a joint like australia.

[searunner]

@wonkipop

You are correct.

Black is indeed the best color both for absorption and emission of radiant energy and why the OEM tin is black. Black on the inside to absorb as effectively as possible. Black on the outside to emit as effectively as possible. All about letting the radiant energy pass in & out as easily as possible to get it away from the engine. Likewise, you’ll notice any of the thermal dispersant coatings are black.

Having said that, I still had one set of my tin powder coated in red - cause’ ya’ know, it adds 10hp right? (IMG:style_emoticons/default/happy11.gif)

Ideally, I would have had it masked so that it was black inside, red outside. But that probably also tips my hand about how worried I am about radiant cooling contribution on an otherwise stock engine. (IMG:style_emoticons/default/biggrin.gif)

incorrect. at least 20 hp. (IMG:style_emoticons/default/beer.gif)

i think red is sort up there heading towards black anyways.

Only one NOTE on Black used on 914 for radiant cooling

911S 2,4 1972 engine was painted in RED
911T 2.2 1972 engine was painted in GREEN
Was one simple immediate eye distinction System??
I don't remember if the interior color was different
https://photos.app.goo.gl/LC5eWJzzKMfDSVmq5
https://photos.app.goo.gl/veb7yo2yVwMd8y4z9

My opinion for the TWO deflector underside is that Porrshe prefers to have the Air free for cooling the central OIL CUP