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Posted by: 914werke Mar 16 2023, 05:25 PM

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.

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.
How about KISS 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

Posted by: technicalninja Mar 16 2023, 06:03 PM

That's possible a good idea...
Done right it might help with air leaks as well.

I've used DEI sticky back sheets on firewalls and evaporator cases many times and it does kick ass on stopping heat transfer.

I'm very interested in what you find/try. please post results.

It would be very helpful to change the area above the engine lid to a high-pressure area instead of the low-pressure area that currently exists.
That would help better than the plastic flaps on the bottom do...

Posted by: mepstein Mar 16 2023, 07:07 PM

An oil cooler with a fan pack seems like the way to go. Proven to work, even when the cars not moving. Just look at 911’s for the engine cooling evolution. Fans hardly got bigger. Tin and layout stayed mostly the same. The big difference was increased oil cooling. I’m sure there are alternatives for dropping a couple degrees but I can’t think of another - works every time on any air cooled engine - than cooling the oil.

Posted by: Lockwodo Mar 16 2023, 07:37 PM

Wondering how to tell how well the tins are sealed? Is there a smoke test that can be used? With the engine idling, if I remove one of the tin seals (for example, the grommet over the CHT) what should the velocity of the escaping air be?

Posted by: 914werke Mar 16 2023, 07:43 PM

Not debating that adding oil cooling does the job. It is tried & true, but comparing a /4s oiling circuit to a /6's is apples & oranges.
Ive seen a # of /4's with additional oil cooling setups ... that are completely unnecessary.
Often preventing engine temps coming up to allow the motor to perform optimally
Not everyone lives in Texas or Arizona

Posted by: technicalninja Mar 16 2023, 07:52 PM

Some of us freakin do...
It can be hotter than hell here.
That's one of the reasons I have an automotive ac shop.
People will pay GOLD for cool air when it's 100+...

I'm going to do anything and everything to improve cooling my air-cooled wonder.
That's why I'm interested in your idea.
Hadn't thought about it before you mentioned it but...

You're right!

Posted by: 914werke Mar 16 2023, 10:15 PM

Interesting question. Ive never used smoke to validate the cooling tin sealing.
I dont know what kind of "pressure" to expect in such a sceaniro.
That test would be feeding smoke into the impeller opening while stationairy so you may also need a fan blowing air under the car from the front to recognize the low pressure tumble effect of the flaps at the bottom of the car.

Posted by: Superhawk996 Mar 16 2023, 11:13 PM

Bottom line: reflective heat shield on the interior of the tin isn’t going to amount to any noticeable cooling improvement.

Why not?

There are three modes of heat transfer taking place in cooling an engine.

Convection (this is the dominant one via the fan)
Conduction
Radiation

Let’s talk about radiation 1st. Radiation emitted from an object (the engine) is not affected by what surrounds it regardless of whether it is surrounded by air, steel tin (914) or a fiberglass shroud (911). Radiation emitted from the object is determined by the temperature of the object to the fourth power. I.e temperature of the object is the dominant factor.

Radiant energy travels though a vacuum. Radiant energy travels though gasses (air) with minimal loss of energy. Radiant heat energy isn’t effectively cooled until it is absorbed into another object, at which point that object is cooled by either convection or conduction.

Even if you were able to prevent the radiant heat energy that is emitted from the engine from being absorbed into the tin completely, you would still have heat conduction into the tin since the tin is attached to the heads and the case.

So you might ask . . . why not insulate the tin from the engine to reduce the thermal conduction?

Let’s consider 911 cooling shrouds that are fiberglass. We could also consider the new carbon fiber T4 “tin” that Type 4 Store is now offering for the 914. In either example, the conduction from the engine to the “tin” is greatly reduced because fiberglass and carbon fiber are not as thermally conductive as steel. Would you agree that neither of these (better insulated) shroud configurations or materials make a huge difference to the overall cooling?

Finally, don’t forget that the inside surface area of the tin (or 911 shroud) is also being cooled by forced air convection. By placing what will effectively be insulation layer inside of the tin, you’re losing the contribution of convective cooling of the tin that has absorbed that heat radiation the engine produced. Some heat is being conducted out of the engine into the tin by conduction, and then the inside surface area of the tin is then convectively cooled by the fan (on the inside) and ambient engine bay air on the outside of the tin.

Do you want to lose this convection cooling effect that the tin provides even if it is very minimal?

Sorry for the long answer.

Posted by: Superhawk996 Mar 17 2023, 11:06 AM

I was thinking about this a little more.

What might be interesting is to have the “tin” made of aluminum. Aluminum conducts heat better than steel. Why not use that to help draw heat out of the case and the heads a little more quickly. Making use of the enhanced conduction to get the heat into the aluminum shroud. Then it can be carried away by the forced convection provided by the fan.

Taking this a step further, could some fins be placed in strategic areas inside the tin to add even more surface area to the shroud so that the convection is more efficient? Fins would have to be parallel with the air flow to minimize flow restriction.



Copper is even more thermally conductive than aluminum. Pricy but amazing at thermal conduction



Would sort of look cool all polished up on outside.

Might be time to think of extending the copper metal shaping to a set of 914 “tin”.



I think I should at least finish the Norton before I get that distracted.

Posted by: Superhawk996 Mar 17 2023, 11:38 AM

Still thinking about this. Not sure copper “tin” would net much improvement.

Why not?

The convective cooling of the engine by air is a function of the temperature delta between the air and the cylinder heads.

If the cooling air effectively gets pre-heated by picking up lots of heat from the tin, then the air is less effective at cooling the head.

In this case, I’m not sure how much of a temperature rise would occur if the “tin” was really effective? Would be interesting to do some CFD thermal modeling to understand it better before making parts. Would also be interesting to set up a bunch of thermocouples to measure it if parts were made.

About a year or two ago I did work up some napkin sketch assumptions showing that getting cooler ambient air into the engine compartment didn’t make as much of a cooling improvement as some thought it ought to. This is because the temperature delta is dominated by the head temperature which is 2-3 times hotter than ambient air.

Example delta Temp = head temp - ambient air. So we end up with something like 300F (head) - 100F ambient air = delta T of 200F

So let’s ASSUME that the copper tin allows the cooling air to preheat by 20F more than steel.

Now we have 300F - 120F = 180 delta T for the air available to cool the head. 10% less delta Temp available to cool the head.

See why this might not actually net improved cooling?

Posted by: GregAmy Mar 17 2023, 12:40 PM

Coming from a background in general aviation...I suggest you're overthinking it.

Our cooling systems are ridiculously simple. It's not "laminar" flow in any sense of the word, that air is coming and going all over the place. Our cooling systems are nothing more than dumping as much air as possible to the top of the engine so that it flows to the lower pressure bottom side, taking heat with it.

You can either increase the pressure on top, or decrease the pressure below. Or both. Either will improve airflow and BTU scavenging.

We all agree on one method to decrease below pressure, and that's to ensure the firewall plastic flapper thingies are in good nick. That deflects undercar airflow, causing turbulence in the engine compartment, reducing underside pressure.

You could seal all the edges of the tins on the upper sides, like maybe using aluminum ducting tape, to seal off areas where pressure may be escaping.

Another method is to relocate the oil cooler so that you can remove the cooler flappy thingie (I love my technical terms) which, in my mind, is partially responsible for the differences of CHTs between #3 and #1 (another factor could be the direction of axial/radial flow from the front fan).

Our stock cars have additional surrounding seals to block hotter underside air from creeping up and being recirculated into the cooling intake fan (and induction). Delta-P and Delta-T, and all that.

One of the tricks that the 4-banger 914 racers used for SCCA Production racing was to run a large dryer hose going all the way forward to one of the headlight door holes to provide cool ram air to the front of the stock engine fan and housing. Chris Foley could show you a photo of that.

Material of the engine covers is likely insignificant. If your cooling system is working well, the engine tins should be relatively cool to touch, since they are constantly being cooled by airflow. They will be hot due to conduction from the engine, but not as hot as they would be if there was no airflow...

An GA airplanes, we always talk about ensuring that the upper engine compartment area is sealed really well, so that incoming ram air can adequately flow down through the cylinders and heads to cool things down. Every time someone complains about increased CHT (when operated within parameters) it's almost always due to significant leakage through degraded (or even missing) engine compartment seals.

Not-so-ironically, one of the cooling improvements in some Experimental aircraft is to add a containment box over the top of the engine, just like our cars, so that you're not depending on the engine compartment door, seals, and such to contain and direct that upper ram pressure.

Finally, since a lot of us are increasing the BTU output due to modifications, then ultimately we'll hit a BTU-scavaging limit of the current system...and that's when we start looking for alternate designs.

I say just make sure your stuff is in good shape. KISS, right? - GA

Posted by: technicalninja Mar 17 2023, 01:40 PM

Insulating the tin should mean less heating of the air in the upper engine compartment.
Less heating of the carbs/FI everything on top.
It also might help seal leaks if you did it right.

It should actually increase temps underneath the tin.
Getting rid of the oil cooler (remote cooler install) and eliminating both of the flaps are in the cards for my car (down here in hell) but this might not be a good idea in the cooler climates.

I think the biggest heat capacity gains is ensuring the coolest air at the highest pressure enter the fan housing.

I believe (and I might be wrong) the reduction in temp ABOVE the tin is where the gains are with this idea. Designing/bending/modifying the existent tin to force more air through the fins on the heads and jugs will also be looked at.

Figuring out how to direct airflow (without increasing aerodynamic drag) into the upper compartment will be one of the things I concentrate on.

Posted by: Nogoodwithusernames Mar 28 2023, 02:08 PM

Might be a bit OT, but I've seen things on TheSamba before that a couple of holes up in the corner of the top tin over #3 can help relieve turbulence caused by high static pressure and will increase cooling at higher RPMs.

Jake Baby supposedly found it in some of his testing but I haven't found an original reference to that anywhere yet.
But Ray Greenwood also accidentally found it and his response to me was as follows.

"No I do not remember that he [Jake Baby] posted a diagram or size. But, when I was drilling holes for testing, I was drilling 3/8" holes. I had one in the farthest back corner of the top sheet metal tin for 3/4 right before it turned downward io the crevice. I was trying to check the temp of the head fins there. I drilled one more about 2" further toward the case to try to check the cylinder fins.

Between those two 3/8" holes....I was plugging each after I used them.....with duct tape...but it came off on a drive....and I saw about a 50* drop in head temps on #3. I double taped it and repeated the route and the head temps went back up. "

It is something I am wanting to test in the near future in my T4 converted VW Squareback and possibly the 914.

Posted by: NARP74 Mar 28 2023, 02:34 PM

Between those two 3/8" holes....I was plugging each after I used them.....with duct tape...but it came off on a drive....and I saw about a 50* drop in head temps on #3. I double taped it and repeated the route and the head temps went back up. "

2 3/8 holes did that?

Posted by: yeahmag Mar 28 2023, 02:38 PM

That's really interesting... Got any pictures of where these holes were made?

Posted by: Al Meredith Mar 28 2023, 03:17 PM

lets remember that oil has gotten much better in 50 years .

Posted by: emerygt350 Mar 28 2023, 03:21 PM

Does an oil cooler do anything for head temps? During normal driving My oil is so cold it concerns me. My head temps are fine and change quickly based on load. It's early in the season of course and my 2.0 is stock besides the exhaust and kn filter.

I would suspect a remote oil cooler in a normal engine would just result in oil that is too cool for far too long. At least in my engine. I am very interested to see what the temps in my car look like under race ish conditions. In autocross I end up at around 220 oil and the heads don't get that hot 310. But that is pretty much redline for 60 seconds in second and third gear. Not exactly normal.

P.s. finger lakes region, we have an air force runway so it is a pretty linear and high speed autocross.

Posted by: emerygt350 Mar 28 2023, 03:25 PM

A very very important thing to remember.

Posted by: 914werke Mar 28 2023, 03:32 PM

Overthinking it... quite possibly. But Im thinking your characterization of the the T4 air cooling flow is probably ... a bit harsh

Musing a little more...
On the early 1.7L's they had a funky oil bath air filter element & a.... pre-heater system.
The heat was derived from a duct attached the rearmost cyl. tin (#1) & ...via flow of air from front to back of motor forced by the Impeller.
Why not use that same design application to, if as you say, dump cooling air to the rear cylinders on both sides ? You could use the Fan that is already in the Eng bay for additional flow?

Posted by: Geezer914 Mar 28 2023, 04:28 PM

Spark plug wire seals!! Plug those holes.

Posted by: 914_teener Mar 28 2023, 04:56 PM

Jake and others use an exothermic coating on the cylinders themselves while masking the fins. I've written a couple of threads on this coating.

Absolutely agree that the airflow is NOT laminar and the the principals are quite simple.

Now....it may actually help to plug all the holes. Racing headers and engines increased performance ( via scavanging) by insulating the headers to increase air flow. So kevlar tins may actually help scavange.

I would submit that the stock heat exchangers actually might aid in air scavaging across the cylinders (which are creating most of the heat) with the cooling air as it is directed downwards. The German engineers with the materials they had availble...what they were doing. If something worked better then...they would have done it.

External oil coolers also help although I never ran one and ran my car many many times in stock config in 120 Degrees plus ambient.

My two bits...and from experience.

Posted by: Superhawk996 Mar 28 2023, 05:12 PM

Might not be quite that simple.

You need to be conscious that pressure differential dictates direction of airflow.

Example: if the auxiliary fan isn’t running - the engine fan will blow air out of the auxiliary fan - decreasing airflow available to the engine.

Similarly if the auxiliary fan was able to overpower the engine fan you could end up with degraded cooling. Not likely but something that should be considered. Probably would want a one way flapper on the aux fan to prevent that sort of reverse airflow - similar to the little flaps down on the heat exchangers.

What complicates this is that the engine fan is operating at variable speed while the auxiliary electric fan will operate at fixed speed. Might be hard to ensure the balance never results in airflow being pumped in the wrong direction.

Posted by: Geezer914 Mar 29 2023, 04:30 AM

Biral cylinders?

Posted by: VaccaRabite Mar 29 2023, 05:48 AM

Not really. Oil temps and head temps tend to move independently of one another. I tend not to think highly of using oil temps as "the" indicator of engine temp. Like you, I also monitor head temps. Keeping the oil cool is good in that it keeps the oil from premature breakdown - which was more of a problem in the past then it is these days. But head temps is what's going to determine if you are going to loose a valve seat and munch a cylinder. Oil provides some cooling of the heads, but only some.


This is not my experience, but it really depends on how the cooler is set up. In my 2056, the oil cooler is shut until the oil hits about 180 degrees, and then flow is opened to the cooler. At 205 the fans turn on. My oil temps stay around 215 on long drives with a heavily loaded 914. For my new engine I'm going to try the cooler without the fan pack first and see how that does for temps. I'd like to eliminate the electrical draw of the fan pack if possible.

Ideally an aux cooler is not always on, but has some sort of thermostat control to allow the engine to warm up. Shoving cold oil through your cooler isn't good for anyone.

Zach

Posted by: 914werke Mar 29 2023, 09:02 PM

Posted by: DRPHIL914 Mar 30 2023, 06:08 AM

@Superhawk
@http://www.914world.com/bbs2/index.php?showuser=453
-simple thoughts from a simple mind)
i probably need to go back and absorb better some of what you posted i just skimmed it, but thinking about the different things here just a couple thoughts and questions,
and i am not an engineer nor did i stay in a holiday inn express last night, although i might tonight so i might have better thoughts on this tomorrow,
but for now,
my first question is about the air flow and pressure pulling/pushing air over the cylinders. It seems that the back side of the motor is a dead end, and so as mentioned before by others turbulence ensues, flow is disrupted , reduced heat exchange and extraction, if its + above and - below, can an additional fan below pulling air from above, or creating negative pressure how ever you want to say it, could this help? just like our pulling fan on the aux oil cooler? I mean a 50 degree reduction in head temp from acouple of 3/8" holes?? might not got hru the trouble of other approaches if its really that simple, but would a fan under pulling air from thetop down over and out help? seems it might.-
- thought #2: regarding the air from from the front impeller and the use of heat exchangers- is it possible that any air flow being directed out the bottom to the j-tubes and thru the heat exchanger(especially in warm weather when its not needed), if the little flapper is open and letting air go out below instead of all the air being directed over the top of the motor, this would in the heat of the summer hurt the effectiveness of cooling the top of the motor, less air flowing thru the top.

- also i watch my head temps and oil temps and you do see that when the oil finally gets full circulation as the aux cooler thermostat open and the extra oil flows the head temps decrease, ( in answer to another persons question about oil effecting head temps, yes it does)
-i have a 2.1 motor - i run 20/50 oil( high zppd valvoline dino oil )and higher compression etc so having the auxcooler is a must, even in 80 degree weather down in Amelia Fl a few weeks ago, my fan was not turning on so those oil temps went up a good bit idling in traffic, no air flow over the Aux cooler, i think it was around 230, but next stop i fixed the wiring to it and got it working and after that even sitting in traffic, and also under harder driving, it never went over 210, and head temps btw in this situation also were reduced.
I have new tin and alll new tin with new seals, spark plug hole seals in place etc. so just keeping it to the air flow issue, seems that allowing air to go out the lower side hurts flow to thetop, and maybe a fan under sucking air from the top could help? other wise any way to get air to flow better over theback side of the motor from top down should help - id like to see a picutre of where those 2 3/8" holes were placed as well.


Phil

Posted by: ClayPerrine Mar 30 2023, 08:15 AM

If you want to improve the engine cooling, you need to realize that the designers of the 914 didn't realize that the air intake for the engine compartment is in a low pressure area. The air moving over the top onto the rear decklid creates a suction at the engine compartment.

So the engine runs hotter than designed. But there is something that can be done for it. Upgrade the Floor Pan Air Deflectors.



These were added to improve the engine cooling by creating a low pressure area under the car to pull out the hot air. They were a step in the right direction, but they can be improved.

Go to your local big box home improvement store and buy some rubber garden edging that is taller than the factory air deflectors. About twice the height works. Then attach it to the front edge of the engine compartment, running the whole width of the car.

It's rubber, so it won't hurt it if it drags a little on speedbumps, and if it is too low, just shorten it up a little. The extra width and length will cause a low pressure area under the car when moving, and that will draw air through the engine.

It helps to have all of the holes blocked and all the engine compartment seals intact and functioning. An external oil cooler will also help.

Living in Texas, anything we can do to lower engine temps is a good thing. And this is a cheap and easy thing to do.


Hope that helps.

Posted by: 914werke Mar 30 2023, 09:11 AM

So if stock, the areas that are used to "feed" unheated fresh air for engine intake ...are limited to the open side grills.
It seems sealing those areas (to prevent that air from being sucked) & (semi) pressurizing the top of the engine with outside cool air would improve engine cooling? Except .. when not moving

Posted by: yeahmag Mar 30 2023, 10:58 AM

What am I looking at here?

Posted by: technicalninja Mar 30 2023, 11:40 AM

That's the early pre-heater thing for additional heat to the air filter housing referenced a few posts back.
That one is perfect!

Posted by: 914werke Mar 30 2023, 03:16 PM

yup 4 parts. The top tin with the specific cutout, the R tin piece with specific cutout, the metal duct & the plastic tube.

Posted by: r_towle Mar 31 2023, 09:20 PM

These are oil cooled engines using air.
Complete and proper tin, with every piece sealed properly along with sealing off all air passages from top to bottom , that seems to be all we need except really hot areas of the world, or when you raise the HP up over 150 ish

Posted by: searunner Apr 1 2023, 04:40 AM

My experience.
Some years ago I have one 911 S2.4 1972 around 190 HP it have 13 LITER oil circulation a big Oil tank and a big OIL cooler that in the RIGHT front wing
NO electric FAN cool the radiator
OBVIOUS the cooling of the engine was the OIL- helped in part by the AIR and ENGINE FAN
the 914 engine have less power and in theory can have les cooling necessity BUT
the cooling system of the 914 is less efficient than the 911 so if the use is in warm land (as ITALY or TEXAS) cooling the OIL can be a big help to engine- the advantages was the better OIL low temperature and oil viscosity

Posted by: emerygt350 Apr 1 2023, 02:19 PM

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.

Posted by: Superhawk996 Apr 1 2023, 04:46 PM

Sacrilege - just look at all the folks shooting for 190F oil or getting completely freaky when oil hits 230F

But. . . Interwebz mythology won’t die

Posted by: wonkipop Apr 1 2023, 04:56 PM

even works in real hot areas of world.
beetles were legendary in outback australia.
back when water cooled cars regularly overheated.
beetles just kept going no problem.

the only ones that suffered a bit were the type 3 with the suitcase motor.
you had to back off in summer out on the open road.
hold them at 55 mph cruise. then they were happy.
the horizontal oil cooler laid over cylinder 3 was a flaw.

the type 4 probably has the best designed cooling system of them all.
perhaps in a hi po version with increased capacity it gets dicey, but not in stock form.
they sorted out the oil cooler location and ducting.

interesting conversation here, but for my two bobs worth i think engine tin material is kind of a marginal gain if anything. a bigger fan and more air flow is probably the answer. ducting to the fan? the type 4 sedan and wagons all had a dedicated sealed boot and duct to the cooling fan and could draw the air in from optimal surfaces on the external body work.

Posted by: 914werke Apr 1 2023, 05:51 PM

Posted by: r_towle Apr 1 2023, 05:58 PM

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

Spark plug seal, heater tubes or covers for those
Cleaning out all the junk in the fins of the cylinders.
Getting the outer gasket properly sealed to the lip on the tin ( gun cleaning wire brushes, on a cordless drill, just sayin)
The two little air diverters on the bottom of the firewall.

I echo the VW beetle and VW Bud are both long living vehicles in super hot climates.

Posted by: wonkipop Apr 1 2023, 06:49 PM

i guess if you think tinware material is contributing to the problem or could improve cooling you would roll your eyes.

for me, like i said - an interesting conversation going down in this topic.

of relevance is something i have always noticed, which is the tinware and the magnesium fan casting are actually reasonably cool to the touch when the engine is running.
particularly the fan casting which does not seem to get hot at all. probably not surprising given the amount of air moving through it.

they certainly get very hot after shut down. particularly the fan casting.

i've always thought the mid engined application of the standard VW engine ran a bit against the grain of the air path in the rear engine cars. particularly the way the tin curves back around at the opposite end to the fan in the rear engined cars. its a real full seal that sends the air back along the underside of the engine so it can be drawn out of the car at the low pressure point at the underside of the tail. the 914 has a bit of a problem in that respect as its trying to send air flow in a counter direction.
sure there are underside air guides and plastic deflectors to assist but its a kind of an inbuilt problem with turning the engine around. i'm not sure VW or porsche got it entirely correct. its probably the only way they could do it without a major redesign of the engine tin but that would have defeated the purpose of using as many standard components as they could to keep it economically viable.

i suspect a lot of the heat shedding issues with higher performance engines might be along the underside of the cylinders and heads rather than the upper surfaces that are in the initial air flow?

it would be interesting to know if the same engine in the 912E ran slightly cooler.

PS
of interest in this regard was some special tin that was developed for the type 3 engine for hot climates (like australia). all the early engines did not have it. and overheated.
its a piece of tinware that wraps around the cylinders on the underside and is similar in some ways to the small deflectors in the type 4 that are up between the cylinders.
its more extensive a deflector in the type 3 hot climate spec engines. the problem was definitely on the underside of the cylinders with these particular cars. the beetles here did not have that deflector. ran cool enough without them. the twin carbies also helped the engine run that tiny bit cooler.

Posted by: emerygt350 Apr 1 2023, 06:52 PM

The 912 comparison would be very interesting.

Posted by: 914werke Apr 1 2023, 07:13 PM

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 .....

Posted by: r_towle Apr 1 2023, 08:51 PM

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

Posted by: einic Apr 2 2023, 02:28 AM

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.

Posted by: searunner Apr 2 2023, 02:57 AM

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

Posted by: 914werke Apr 2 2023, 12:42 PM

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.
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. Who is up for it

Posted by: 930cabman Apr 2 2023, 12:57 PM

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.

Posted by: 914werke Apr 2 2023, 01:09 PM

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 http://www.914world.com/specs/JakeRabyHeadTemps.php 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"

Posted by: wonkipop Apr 2 2023, 03:39 PM

ha ha. a lot of work thats for sure.

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!

Posted by: r_towle Apr 2 2023, 03:59 PM

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.

Posted by: moto914 Apr 2 2023, 04:51 PM

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?

Posted by: wonkipop Apr 2 2023, 05:04 PM

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.

Posted by: r_towle Apr 2 2023, 06:04 PM

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

Posted by: 914sgofast2 Apr 2 2023, 06:13 PM

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.

Posted by: moto914 Apr 2 2023, 06:56 PM

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.

Posted by: wonkipop Apr 3 2023, 06:47 AM

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.

Posted by: Superhawk996 Apr 3 2023, 08:26 AM

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.

Posted by: wonkipop Apr 3 2023, 06:02 PM

@http://www.914world.com/bbs2/index.php?showuser=22428 i enjoyed reading your post @ #8.
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. 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.

Posted by: Superhawk996 Apr 3 2023, 08:19 PM

@http://www.914world.com/bbs2/index.php?showuser=24231

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?

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.

Posted by: wonkipop Apr 3 2023, 09:05 PM

incorrect. at least 20 hp.

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

Posted by: searunner Apr 5 2023, 03:25 AM

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


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Posted by: wonkipop Apr 5 2023, 07:48 AM

@http://www.914world.com/bbs2/index.php?showuser=23809

yeah the 911 "tin" ware is a whole other ballgame (as i conceded in an earlier post).

they are fibreglass anyway. non conductive.
and the engines are dry sumped and kind of super oil cooled.
+ the fan is massive.

there is other scientific stuff going down with the old 911 engine.
but interestingly its an upright fan blowing air down over the cylinders, kind of like the original beetle.

whereas the type 4 motor (leaving aside it being dropped into a 914) is actually designed to be a compact flat package. the old "suitcase" engine or as i think americans labeled it the "pancake motor". its real parameters are to to with its application in VW sedans and station wagons. and i'm sure metal for ducting was more economical than fibreglass which back in the 60s and 70s would have been exotic.

i'll just add that the space shuttle had black tiles on the bottom of it, which was the bit that got hottest during its missions. not silver and not white. also had various little areas of black tile dotted around its upper surfaces.

and the blackbird SR-71s that flew over russia on spy missions at fairly high speed back in the 60s and 70s were black despite the intense friction on their external surfaces.

its interesting stuff. heat and how to get rid of it.

Posted by: wonkipop Apr 5 2023, 08:09 AM

@http://www.914world.com/bbs2/index.php?showuser=23809

to expand naively on the space shuttle for instance.
and when i say expand, i mean very tentatively, because i ain't no NASA engineer.
but.

you are re-entering the atmosphere.
and you got heated plasma (ie air turning into something else very hot) below the surface of your vehicle, the last thing you want to do is reflect that heat and add to the temp of the plasma........
so you absorb it with black stuff.
thats thick enough to suck it up.
the fabulous tiles. like space age pottery.
they suck the heat up and don't conduct it to the aluminium structure they protect.
which would soften, melt and lead to destruction of the vehicle.

then as the spacecraft slows to less than about 7 times the speed of sound and gets into the lower atmosphere the said tiles can begin to radiate the heat out to the cooler air.
no plasma anymore ( super heated air ). and the equation reverses.

so long as you don't loose any tiles!

i think that is how it worked on the space shuttle in terms of black surfaces.

with a VW engine i think it works by the black tin absorbing engine heat because its being radiated at by the engine, but on the opposite surface the air is cooler so it radiates towards the cooler body, the air and looses the same heat that its absorbing on the other side. in effect it forms a pathway for the enclosed engine to lose some heat out to the surrouding air and also to not reflect the engines heat back at itself, but rather to draw some of that heat away from the engine in the radiant spectrum.

the fibreglass on the 911 engine cooling shrouding probably does a sort of similar job because it does not reflect heat back at the enclosed engine. however it would also not form a pathway for getting the heat out. maybe they didn't need a pathway out for the heat they just worked out they needed a non reflective and non conductive surface.

?

i don't really know. just stabbing a guess at the basics.

Posted by: moto914 Apr 5 2023, 08:43 AM

Good additional thought. Thanks

Posted by: Mikey914 Apr 5 2023, 10:53 AM

The 2 deflector design works very well. You have 4 vortices aligned with the cylinder areas that are creating a low-pressure area immediately behind them. The are not a scoop in a traditional sense. The do cause the air in the engine compartment to be pulled down and carried off. Increasing the efficiency of cooling. Think of the fan pushing air, and the low-pressure area sucking it.
This is one of the reasons we added "winglets" to the design. Keeping the air from rolling immediately over the edge and helping to increase the low pressure. It a 3% increase in efficiency. Not much, but if we are going to create something why just copy it??




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Posted by: 914_teener Apr 5 2023, 12:57 PM

Come on Mark...ya just looked over the port side of your airship on the end of the wing and thought it was a good idea!

Posted by: 914werke Apr 5 2023, 01:57 PM

Interesting how did you test for the 3% ?

Posted by: wonkipop Apr 6 2023, 01:35 AM

this is getting good.
if @http://www.914world.com/bbs2/index.php?showuser=3348 is serious thats probably how you do it.....in terms of attempting to tweak some extra cooling efficiency for all you dudes who insist on hotting up the type 4.

get that air to move through.
and assist the fan to move extra volume.

i dunno what the maths is, but if you get it accurately calculated its probably where the extra cooling can be found.

Posted by: Mikey914 Apr 6 2023, 09:42 AM

To be clear that's a 3% increase in the efficiency of the airfoil. Not the cooling capacity. Yes, a drop in the bucket, but a +.