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.

[Superhawk996]

I want to say I appreciate all the civil discussion on this topic.

Unfortunately we’ve sort of reached the point where someone needs to do some instrumented testing to get us out of the realm of speculation on the degree that the flaps are modulating and when. I’m guilty here as I don’t have that data at hand.

Someday I’d love to put a string-pot on the thermostat bellows and the flap rod/lever to get live data on how much it’s moving, at what temps, and what engine loads.

Same for having some thermocouple data directly off the cylinders and the bellows.

Ah . . . Someday. For now I’ve got too many other projects going on but maybe someday.

[JamesM]

I want to say I appreciate all the civil discussion on this topic.

Unfortunately we’ve sort of reached the point where someone needs to do some instrumented testing to get us out of the realm of speculation on the degree that the flaps are modulating and when. I’m guilty here as I don’t have that data at hand.

Someday I’d love to put a string-pot on the thermostat bellows and the flap rod/lever to get live data on how much it’s moving, at what temps, and what engine loads.

Same for having some thermocouple data directly off the cylinders and the bellows.

Ah . . . Someday. For now I’ve got too many other projects going on but maybe someday.

FYI awesome powder coat lists the temp of their various thermostats however I am not sure if that temp is the temp where they start to expand, finish expanding or if the 85-90c they list is the range for the start and finish of the expansion? (IMG:style_emoticons/default/confused24.gif)

that says nothing of the actual curve and impact of it on the actual angle of the cooling flaps or how it compares to the actual head and oil temps

One could deduce though that given the 85c(185f) listed thermostat temp that VW intended the motor to be warmer than the 160f accelerated wear point mentioned in the studies you posted.

It would be cool to have the data, I am a data junkie as well. A huge timesaver though would be to just leave the thermostats hooked up and let them do their thing. (IMG:style_emoticons/default/biggrin.gif)

[Superhawk996]

It would be cool to have the data, I am a data junkie as well. A huge timesaver though would be to just leave the thermostats hooked up and let them do their thing. (IMG:style_emoticons/default/biggrin.gif)

You may appreciate this data which is representative of your situation in the mountains.

From Air Cooled Automotive Engines; J. Mackerle


The important point to note is that you don’t really want cylinder temp going below 70C and how the thermostat prevents that from happening on the decent.

Also note that temp consistency is improved. Higher, more consistent temp = less friction losses.

[JamesM]

You may appreciate this data which is representative of your situation in the mountains.

That's a great find and does reflect what I have experienced.


I wonder what motor/induction was used here. This all has me thinking about ways to utilizing tuning on modern ECUs to better regulate temperatures. This is something I have implemented to some extent but only focusing on keeping temperatures down. Now im wondering if there are things I can implement to increase temps under cold decel situations as it looks like even with the flaps the cooling is pretty pronounced.

[Superhawk996]

wondering if there are things I can implement to increase temps under cold decel situations as it looks like even with the flaps the cooling is pretty pronounced.

I would think you could get something by running a lean burn and advance timing short of decel fuel shutoff that might help but may be difficult to tune without knock sensors.

That data that I posted is ancient - that book was 1st published in 60’s so I would almost guarantee that was a carbureted engine.

[JamesM]

wondering if there are things I can implement to increase temps under cold decel situations as it looks like even with the flaps the cooling is pretty pronounced.

I would think you could get something by running a lean burn and advance timing short of decel fuel shutoff that might help but may be difficult to tune without knock sensors.

That data that I posted is ancient - that book was 1st published in 60’s so I would almost guarantee that was a carbureted engine.

Lean burn with advanced timing is how my heads are running 75 deg cooler than stock at cruise as it is (IMG:style_emoticons/default/biggrin.gif)

Head temps drop off quicker on the lean side of stoich than they do on the rich side. Added bonus I get near 40mpg and my oil stays way cleaner too, which itself should be better for engine wear.

Around stoich is the hottest but limiting that to only during conditions where you are experiencing extreme cooling would be the challenge.

Driving down a mountain in freezing weather is a bit of an edge case for me given they salt the roads here in winter so for now ill take the trade off, but its an interesting problem to think about.