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.

[Nogoodwithusernames]

What does your tune look like? I followed John Connolly's advice/thread over on the Samba for trying to tune my Megasquirted 1.7 T4 (In my Squarback) for lean cruise and could never get head temps down under 350F, running 12.x at cruise now and heads are 320-340F at 60-70MPH. Varies a bit with ambient temp. I only get 19-21mpg with mixed driving though.

I do run a stock working Tstat in both the 914 and the Squareback, with all tins (including custom sled tins to keep it out of ambient airstream on the VW), but I've never checked position at various loads or temperatures on either so I don't have much to add in that regard. I will say I don't drive the 914 when it's 90+ outside because that's miserable without AC, much preferable when it's 60-70F outside.

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.

[JamesM]

What does your tune look like? I followed John Connolly's advice/thread over on the Samba for trying to tune my Megasquirted 1.7 T4 (In my Squarback) for lean cruise and could never get head temps down under 350F, running 12.x at cruise now and heads are 320-340F at 60-70MPH. Varies a bit with ambient temp. I only get 19-21mpg with mixed driving though.

Few questions

What spark plugs (part number) are you running?
What cam?
What AFR were you running on lean cruise?
What ignition advance on cruise?


the squareback is a little more of a brick so I would expect head temps to possibly be a little higher than a 914, but my 2.0 test car (MS converted bone stock 2.0) never saw over 350 when I took it on its maiden voyage to California and back. 37 MPG on the stretch back between Barstow CA to Mesquite NA, was driving conservatively to see what I could get, so 65-70 MPH. Had a couple outer wheel bearings failing at the time as well along with a corner balance issue, not to mention most of the route was going up in elevation so I suspect I may be able to do even better.

I got 23mpg on my last camping trip in my 1.9 wbx 85 vanagon running basically the same system with a very similar tune though, so I would think for sure you should be getting better than 20 in the square as nothing is more of a brick than a vanagon loaded with camping gear.

Not sure what other details I can give about my tune, 12.8 @ 28 deg at max load, leaning slightly to low 13s around 75%, then a very abrupt transition with everything below 75% targeting 15.5 @40 degrees advance. You want to make sure NOTHING is producing AFRs between roughly 13.8 and maybe 15 as that is where you are going to be hotest. the further you can stay either side of that range the better from a heat standpoint. Idle is around 13.5-13.8 with idle speed being stabilized by timing control (NO IAC) TB opened up enough to require the timing to be in the 0 to 5 retarded range. Some custom shaping in the higher vaccum areas around 2000 rpm to ensure everything drops back to idle ok. This is on a 2.0, on a 1.7 that might need some minor tweaks given the slightly higher compression and smaller bore.

when I initially put the plug and play MS system together my initial thought was to have a d-jet mimicking tune and then my own "Special" tune for people to pick from. I roughed both of them and and drove around on each, the "special" tune was so much better in every way I never went back and fully refined the d-jet mimicking tune. I probably will eventually just to have it, but I see little point to it now.