Modified Thermostat for higher MPG's... - Page 35

SD26 · February 17th, 2012, 13:06

Quote:

Originally Posted by Frankencar

There is a 92° Thermostat that is a straight drop-in: Wahler P/N: 4256.92D50. It's real easy to gt to on that as well.

What's stock?

I was thinking about 205 in the A3 too... Almost appears that the A3 and A4 thermostats are the same. Anyone know?

Frankencar · February 17th, 2012, 14:26

Quote:

Originally Posted by SD26

What's stock?

Stock is 87°

Quote:

Originally Posted by SD26

Almost appears that the A3 and A4 thermostats are the same. Anyone know?

The MK1/MK2/MK3 are all the same and fit in the MK4 just fine - they just don't hang on to the tabs in the neck for easy install. they are almost identical. I have a pic of an OEM MK4 on next to the Wahler 4256.92D50 here: http://frankenbuilt.com/RefInfoHighTempThermostat.html

SD26 · February 22nd, 2012, 09:52

Excellent! Thanks, guys!

Thermostats showed up a couple days ago. Should be able to perform the changes to assemble one 205* model this weekend. Waiting for new thermostat cover to show up from ID Parts along with some other maintenance items. I should be able to perform the change next weekend, I believe. I'll be putting in some "old" Evans coolant from one of my Power Strokes that I harvested before its sale last year.

I continue to see operating temperatures on my A4 at around 177F currently, for reference.

josh8loop · February 24th, 2012, 05:50

Looks like my wife and I are going to pick up a 2005 Mercedes E320 CDI in North Carolina tomorrow. It has 100K on it, and a pretty decent service history. I put a digital thermometer in my suitcase so I can check the coolant temps on the way home. I'm planning on putting a stock T-stat in soon if it needs one, and perhaps making a "Hybrid" T-stat for it too.

alloutdoorsboy · February 25th, 2012, 19:16

So I got a 92C stat in the passat today and ran it around. SGII recorded 198-207F. 207 going up a long incline. What are the maximum temps you guys are running and does it seem that the higher the temp the better the efficiency??

josh8loop · February 25th, 2012, 19:25

Quote:

Originally Posted by alloutdoorsboy

So I got a 92C stat in the passat today and ran it around. SGII recorded 198-207F. 207 going up a long incline. What are the maximum temps you guys are running and does it seem that the higher the temp the better the efficiency??

Great feedback on the 92 C unit- thanks for the info. With my hybrid 205 unit I usually run from 205-209 F, but lately seems to hover around 206-207 F. Highest I have hit so far is 213 IIRC. Some guys have posted they run slightly higher with the hybrid construction.

markd89 · February 26th, 2012, 15:14

What is a reasonable maximum water temp before there's any risk of overheating -- 220, 230, 240 ?

(I ask because I'm going to rework the cooling system in my engine swap to take it from two radiators down to one and want to know what's safe.)

TDIMeister · February 26th, 2012, 15:44

It is foolish to reduce cooling capacity. Changing the thermostat merely changes the regulated temperature, but reducing capacity is never a good idea, especially in the LA climate you're in.

markd89 · February 26th, 2012, 16:17

Quote:

Originally Posted by TDIMeister

It is foolish to reduce cooling capacity. Changing the thermostat merely changes the regulated temperature, but reducing capacity is never a good idea, especially in the LA climate you're in.

Well, right now, I have much more capacity/coolant volume than a stock TDI. I have double radiators plus the water in the long hoses going to the front heater. Everything works, but warm-up could be quicker.

For the last couple of months, I have cardboard-sandwiched one of the radiators and have been driving around just fine getting the cooling from one radiator. I don't want to actually remove the second radiator until I can test some hills when it's over 100 *F outside and make sure I don't get too hot.

I didn't mean to thread-jack, just wanted to ask how hot is too hot...

Mark

TDIMeister · February 27th, 2012, 06:42

You fail to recognize that while your particular application has much more capacity than a TDI, it's in a vehicle that is heavier, far less aerodynamic and by the year of your Bus, not one that was ever designed with watercooling in mind. What this means that your particular application would place consistently higher loads upon the engine, therefore more heat needs to be rejected. If your vehicle's warm-up "could be quicker", it is a thermostat issue and more accurately a regulation or thermal management issue.

The simple answer to your original question, "What is a reasonable maximum water temp before there's any risk of overheating -- 220, 230, 240 ?" is some margin below the boiling point of the coolant, which depends on the type, system pressure and concentration you use. If you perceive an overcapacity problem -- completely unrelated to a boiling point problem, which was my original point -- this could be addressed instead of deleting capacity by running higher concentration of ethylene glycol or going to a propylene glycol-based coolant, since they have lower specific heat capacity than water and have higher boiling points to boot.

A "safe" temperature, for the lack of more precision of the intended context and a truly better answer is one that is not far from that extensively engineered in the original engine.

markd89 · February 27th, 2012, 07:36

Quote:

Originally Posted by TDIMeister

You fail to recognize that while your particular application has much more capacity than a TDI, it's in a vehicle that is heavier, far less aerodynamic and by the year of your Bus, not one that was ever designed with watercooling in mind. What this means that your particular application would place consistently higher loads upon the engine, therefore more heat needs to be rejected. If your vehicle's warm-up "could be quicker", it is a thermostat issue and more accurately a regulation or thermal management issue.

The simple answer to your original question, "What is a reasonable maximum water temp before there's any risk of overheating -- 220, 230, 240 ?" is some margin below the boiling point of the coolant, which depends on the type, system pressure and concentration you use. If you perceive an overcapacity problem -- completely unrelated to a boiling point problem, which was my original point -- this could be addressed instead of deleting capacity by running higher concentration of ethylene glycol or going to a propylene glycol-based coolant, since they have lower specific heat capacity than water and have higher boiling points to boot.

A "safe" temperature, for the lack of more precision of the intended context and a truly better answer is one that is not far from that extensively engineered in the original engine.

TDIMeister, thanks for your detailed response. I do realize that my vehicle is heavier and not at all aerodynamic. The radiators are mounted underneath which may have less airflow than in-front as well. I knew I was building in too much cooling for the exact reasons you said. There's lots of variables and I wanted to make sure that if I guessed wrong, I would have too much cooling rather than too little.

Changing the fluid to a higher proportion of anti-freeze is an interesting solution. I'll give it some thought.

Thanks much,
Mark

dieselfuel · February 27th, 2012, 15:14

Quote:

Originally Posted by alloutdoorsboy

So I got a 92C stat in the passat today and ran it around. SGII recorded 198-207F. 207 going up a long incline. What are the maximum temps you guys are running and does it seem that the higher the temp the better the efficiency??

235F in the summer. But, as you can see, I'm running the Evans.

dieselfuel · February 27th, 2012, 15:15

I'm up 1.5 mpg this winter. I believe it's due to the hybrid t-stat. : > )

josh8loop · February 28th, 2012, 16:55

Had a hiccup this afternoon I thought I would share. As many of you know, I run the 205 Deg F "Hybrid" T-stat. Since the stage 1 fans come on at a similar temp to where I wanted to run the car at, I dissabled the stage 1 fans by cutting one wire. The stage 2 fans are still functional, and the fans come on as they are supposed to when the AC is kicked on. This afternoon while in extreme stop and go traffic my engine got up a little higher than I was comfortable running. When I looked at it, I was at 216 and climbing. I usually have no issue since I drive in such a way that I am generally always moving so I have natural forced air flow through the radiator. Moral of the story is don't dissable the stage 1 fans unless you devise a circuit to allow you to set the temperature that it comes on. This is what I intend to do in the near future.

SD26 · February 29th, 2012, 11:49

So...

Did you turn on the AC? Should have kicked on the fans, right?

Assembled my hybrid a little too small. Pressed in the one piece a little too far. Will pop it out a little to match up with a known 195 Stant that I bought to prepare for another hybrid t-stat for my A3 Jetta. Would like to make my A4 Jetta swap Friday along with some "spare" Evans coolant that I have from last years removal from my Excursion.