To disable cooling flaps or not, The endless debate Options

[Superhawk996]

ditch the stat.

Cabman - love ya to death but please stop propagating the ditch the thermostat advice.

The flaps and thermostat are there for a reason.

The majority of engine wear occurs during the warmup phase of operation this is true of all engines and is backed by decades of SAE research and documentation.

Disabling flaps and delaying warmup results in accelerated wear.

Even worse, air cooled engines depend on expansion of the heads to increase clamp load between the cylinder and the head as the engine heats up. Delaying warmup results in more likelihood of blowby between the head and cylinder and between the cylinder and the case.

And even worse yet on a carbureted car where the delayed warmup reduces fuel atomization, and increases cylinder wash down - really accelerating wear and diluting oil.

I’ve read all the anecdotal stuff of “my engine is fine”. You may think so but the reality is you are only looking at a tiny snapshot in time of the engine life and wear. As a hobbyist, you likely won’t ever have the opportunity to compare engine life of engine A that ran properly vs engine B that has the flaps disabled.

And I’ll concede that because a hobby car only gets driven infrequently - that partially negates the wear argument(s).

But let’s not keep propagating the shade tree mindset that the thermostat & flaps aren’t necessary for proper operation and longevity of T4 engines.

Once he’s in there deep enough to identify the cause, it should be fixed properly not jury rigged.

[VaccaRabite]

Late to the conversation.

I have always run with my Tstat disconnected for a couple reasons -
1) I cold not source a functional one. This may not be a problem anymore - they may be more common.
2) I’m missing the lower tins. It was my impression that the tstat would not bellows properly without the lower tins in place. Right now I’m running heat exchangers so I could source a set and put them on, but sometimes I run headers and can’t use them.

Do I have the wrong information ? Does the tstat work as intended without the lower tins in place? and by lower tins I’m referring the ones that are often missing that sit below the heat exchangers, and not the tins sandwiched between the jugs and the pushrod tubes. Those are in place on my car.


Zach

[JamesM]

Late to the conversation.

I have always run with my Tstat disconnected for a couple reasons -
1) I cold not source a functional one. This may not be a problem anymore - they may be more common.
2) I’m missing the lower tins. It was my impression that the tstat would not bellows properly without the lower tins in place. Right now I’m running heat exchangers so I could source a set and put them on, but sometimes I run headers and can’t use them.

Do I have the wrong information ? Does the tstat work as intended without the lower tins in place? and by lower tins I’m referring the ones that are often missing that sit below the heat exchangers, and not the tins sandwiched between the jugs and the pushrod tubes. Those are in place on my car.


Zach

Its an interesting data point that I would love to see more on. I feel like someone has to have tested this before somewhere.

I personally suspect that the lowest tin, the ones that attach to the head exchangers may have been more for pushrod tube protection than cooling related, but I couldn't say for sure. This is based mainly on two things. 1. the fact that there is tin between the pushrod tubes and the cylinders that direct air around the cylinders, this for sure is needed for proper cooling but the 2nd lower tin, not sure how much more that will add and 2. WBX vanagons have similar tin pieces below the pushrod tubes despite not being air cooled at all.

but if the function is to trap heat around the thermostat... that is something else to look at.

Your first issue is no longer an issue as Awesome powder coat has these new now.

[emerygt350]

I think I may have read somewhere that the lowest tins had something to do with flow across the bottom of the engine but I might be just imagining things... Considering how quickly the tstat closes the flaps after parking a hot engine, I could believe performance might differ missing the tins.

[JamesM]

I think I may have read somewhere that the lowest tins had something to do with flow across the bottom of the engine but I might be just imagining things... Considering how quickly the tstat closes the flaps after parking a hot engine, I could believe performance might differ missing the tins.

Pretty sure I read the same thing at some point, but the amount of things I have read on the internet that are based on hot dog (IMG:style_emoticons/default/stromberg.gif) is pretty vast. could very well have been an assumption on someone's part that then got parrot'ed as fact.


These days if I don't see data to back a statement everything is subject to question.


There is an old thread on the samba with some argument about it, one side saying it was only to protect the pushrod tubes and the other saying it is a cooling component. I am totally in the camp of Porsche/VW not having put parts on a car without a purpose but after seeing the same tins on a WBX Vanagon, I question what that purpose actually was because no one car argue it had anything to do with air cooling on that motor. That and I haven't actually heard of/seen any overheating issues that have been directly correlated with those two specific tin pieces missing, though one comment mentioned his engine ran slightly cooler without them, so possibly it was intended to trap heat? Again though... Water cooled vanagons

[wonkipop]

I think I may have read somewhere that the lowest tins had something to do with flow across the bottom of the engine but I might be just imagining things... Considering how quickly the tstat closes the flaps after parking a hot engine, I could believe performance might differ missing the tins.

Pretty sure I read the same thing at some point, but the amount of things I have read on the internet that are based on hot dog (IMG:style_emoticons/default/stromberg.gif) is pretty vast. could very well have been an assumption on someone's part that then got parrot'ed as fact.


These days if I don't see data to back a statement everything is subject to question.


There is an old thread on the samba with some argument about it, one side saying it was only to protect the pushrod tubes and the other saying it is a cooling component. I am totally in the camp of Porsche/VW not having put parts on a car without a purpose but after seeing the same tins on a WBX Vanagon, I question what that purpose actually was because no one car argue it had anything to do with air cooling on that motor. That and I haven't actually heard of/seen any overheating issues that have been directly correlated with those two specific tin pieces missing, though one comment mentioned his engine ran slightly cooler without them, so possibly it was intended to trap heat? Again though... Water cooled vanagons

definitely the upper lower tins are there for cooling. the little curved dividers that split the airflow between the cylinders and direct it across the fins on the lower surface of the cylinders.

i am less certain regarding the lower air guides running between the heat exchangers and the bottom of the case. they are certainly doing a job squirting or directing hot engine air towards the rear of the car --- and they definitely protect the clutch and speedo cables from being damaged by engine heat and possibly have a role in assisting the gear linkage rod from heating and maybe thermally expanding along its length.

certainly in the early 914s these lower guide tins were not adequate at directing the heated cooling air and getting it out from under the car, see the little rubber "spoilers" added each side in front of the engine bay in the later cars. these solved the problem of air extraction at least while the car was on the move.

those lower guide tins are on all stock VWs, but i would suggest that in the rear engined configuration of most VWs they work quite well as they squirt the air straight out of the back of the car with no potential for trapping air under the car. in the case however of the 914 they only really serve to direct air to the area under the trunk where it can and does pool in a trapped "bubble" --- at least when the car is at standstill --- which happens a lot in urban situations. i don't think they ever really effectively solved this issue with the 914. its not really ducted or directed out as immediately as it is in standard VWs. its an adaption of what they always did with the standard cars that does not really entirely work.

at least thats my take on it.

down here in upside down land a lot of people used to remove them on your standard VWs back in the day. but also what they made sure they had is what is called tropical tins. especially on type 3s. these are those small curved tin dividers higher up between the cylinders. the early type 3s that came to australia did not have them initially. those engines cooked.
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EDIT - as a thought regarding the thermostat and without buying into the flaps connected or not argument i would think this.

i believe it would be wise to run those bottom air guides with a functioning connected thermostat as this would ensure the thermostat was in the heated airflow exhausting from the engine and it was responding accurately controlling the flaps, ie fully opening the flaps. i think there would be risk the thermo might be slightly cooler than it should be if was in the passing airflow under the car when its at speed and moving.

i also believe that without those guides it would be wise to disconnect the thermostat.

i myself have been running without functioning thermo and the flaps disconnected for 37 years (16 of which the car was stored). i'm contemplating getting it all functioning again. i just have to save some money and send off the states for a good rebuilt original thermo (seems there really is only one source for these). if i do the guides will go in as well.

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