Modified Thermostat for higher MPG's...

[josh8loop]

For those that don't want to read through the many pages of this long Thread, here is the Cliff Notes version. Basically I found out that two thermostats can be purchased and parts mixed and matched to give a thermostat that will control at around 205 Deg F for the ALH engine instead of the stock 195. Jump to page 3 post 39 for the part numbers. Page number 4 post 59 shows some photos of the transformation. I have some assembly videos on the construction that can be seen here:

http://www.youtube.com/watch?v=AU8IAcGIYVo&list=UUd7-nt4jVRMYngwv-0WSMbw&index=8&feature=plcp


http://www.youtube.com/watch?v=x7hodv7Rsvg&feature=related



Remember this is all experimental, and Mod at your own risk. Also, it is not recommended that you fiddle with coolant temps if you have an automatic transmission. With that said, in 15K plus miles I have had no mechanical issues from doing this, and am noticing a 3-4 MPG bump from my previous worn out stock thermostat. I have however replaced most of my old coolant lines, hard coolant pipe seal, and other brittle plastic coolant fittings. At this point we have at least two others that are trying this modified thermostat, and feeding results occasionaly. One of our members also mentioned that a stock MkII thermostat rated for 92 Deg C(197.6 Deg F) will fit the ALH engine too-not quite as high as the "Hybrid" unit, but the mkII version is a drop in replacement. For the longer version on the development of the "Hybrid" version, please read on........ ......







Fellas,

I have recently come across information where people have modified their existing thermostats with parts from other thermostats to gain higher coolant temperatures. See here:

http://www.cadvision.com/blanchas/Ranger/Thermostat.html

Since our thermostats are of the double valve thermostat type it would be important to make sure the end product functioned exactly the same as the old one in terms of internal engine bypass flow control. Not saying that this would be the best idea on the block to help us achieve higher overall engine temperatures, or the most easy to construct, but sense we cannot purchase over the counter T-stats in the ranges desired we are forced to get creative.


Here is a Stant part number of a t-stat that is rated for 205 deg F:

14252(remember your in the non-cliff notes version. Skip to page 4 post 59 for some photos and the part number I ended up actually using to make the "Hybrid")


I hope to do as side-by-side comparison of this thermostat and a replacement for my TDI this evening and see what the potential for swapping the internal parts would be. If the parts look interchangeable, I hope to purchase one of each, and test the 205 degree one to see if it will actually open at 205 degrees. If it opens correctly, I could begin the swap process and testing the results in the car.



One final question I would want to get resolved before proceeding, is it safe for our cars to run at a sustained 205 deg F temperature?

 

[GoFaster]

I wouldn't do it - especially on a P-D (which yours isn't).

Higher coolant temperature means higher oil temperature, which means lower absolute viscosity, which means less protection in the critical camshaft/lifter interface. Given that even using 5w30 oil in those engines rather than 5w40 seems correlated to camshaft/lifter failures, this is likely to put it over the edge.

Camshaft/lifter wear-out situations aren't unheard of in the ALH engines, either. It isn't as big of a problem, but still ... thinner oil (lower absolute viscosity) is not heading in the right direction. It doesn't matter if the absolute viscosity is lower due to use of lower nominal viscosity oil, or due to higher temperature; the cam/lifter interface sees it the same way.

 

[jettawreck]

I wouldn't do it - especially on a P-D (which yours isn't).

Higher coolant temperature means higher oil temperature, which means lower absolute viscosity, which means less protection in the critical camshaft/lifter interface. Given that even using 5w30 oil in those engines rather than 5w40 seems correlated to camshaft/lifter failures, this is likely to put it over the edge.

Camshaft/lifter wear-out situations aren't unheard of in the ALH engines, either. It isn't as big of a problem, but still ... thinner oil (lower absolute viscosity) is not heading in the right direction. It doesn't matter if the absolute viscosity is lower due to use of lower nominal viscosity oil, or due to higher temperature; the cam/lifter interface sees it the same way.

I wouldn't do it either. Higher temps in coolant lead to higher temps in critical areas as pointed out. These engines use oil cooling on the undersides of the pistons for a reason. Internal temps can spike quickly with load no matter that the coolant temp is relatively steady.
Especially would not do if I lived in warmish climate.

 

[shizzler]

My supposed "195f" stant t-stat allows as much as 209 degrees in normal driving (albeit with reduced airflow to my radiator - grill blocks).

I know cam wear is a real issue on the PDs... but I would suspect most issues of premature wear on an ALH are due to using the wrong oil in the first place (or a very punishing driving style - excessive time at high rpms, etc).

Quality synthetic oil does not break down until well over 300 degrees F. How many of you have an oil temp gauge? Before I got my hotter t-stat and blocked my grill off, my oil would run around 180f at 70mph cruising - a.k.a COLD! On hot summer days I have pushed it as far as 250f on hill climbs. This is still NOTHING to worry about. We test modern diesel engines at work for 500 hours straight at full rated power conditions and oil temperatures of 270f or MORE. No problems.

The theory and concern you guys are talking about is sound, but perhaps a little too cautious. Higher oil temperatures is a good thing. The decrease in viscosity should not be enough to warrant excessive wear.

However to the OP - why would you want more than 205 f coolant? In my opinion this is about as reasonably hot as you'd want it to be. I don't think you'll find much more increase in efficiency from running much over 200f - it's the people stuck down below 170 with faulty thermostats that pay a penalty in economy. And if you take your engine, fully heat-soaked on a humid summer day, and try to blast up a mountain, you're going to be sorry if you cross mush more than 230f, which is entirely possible.

Proceed with caution - and monitor those gauges (not the dash gauge!) closely.

 

[UFO]

Higher engine temperatures can also close internal engine clearances. You may end up hurting fuel economy by running higher than normal.

 

[GoFaster]

The theory and concern you guys are talking about is sound, but perhaps a little too cautious. Higher oil temperatures is a good thing. The decrease in viscosity should not be enough to warrant excessive wear.

In a P-D, the use of 5w30 instead of 5w40 appears to put them over the edge. Increasing the temperature only a few degrees can have the same reduction of absolute viscosity that the use of 5w30 instead of 5w40 does.

The ALH engines aren't as sensitive, but camshaft/lifter wear is not completely unheard of on those, either.

 

[josh8loop]

Fellas,


Thanks for the warning in regards to oil viscosity etc. That seems very important especially with the PD motor. I also find it interesting that many guys with the 7.3 L diesels are running higher temp thermostats(203 Deg F). Sounds like they are getting a little better FE, and performance. I realize that this is not the same motor and all and many things are different between them but I still feel comfortable running at a nominal 205 Degrees.

This weekend I went ahead and purchased two thermostats. A Stant 195 replacement for my car, and a 205 Degree Stant thermostat that I mentioned earlier in the thread. I noticed that quite a few parts were interchangeable between them, most notably being the "Heat Motor". I went ahead and characterized the T-stats in water, and noted their min and max travel limits. This will be helpful to have when evaluating the completed hybrid T-stat. I have disassembled the 205 degree unit, and am in the process of carefully disassembling the 195 degree unit now. Once the hybrid unit is complete, I will test it extensively to make sure it has a high opening temperature repeatability. In the end, this may not be the exact method I will use to control the ultimate temperature of my engine, but I am learning lots in the process.

 

[AndyBees]

I bet the increased fuel economy you are trying to achieve will be disappointing to you......... and, you will destroy the engine in the process! Sort of like High Blood pressure.......... gotcha! Bam!

 

[david_594]

I went with a 93 degree Celsius thermostat for a few years, going from my 87 degree stock one and notice no significant improvements in fuel economy(which was the goal).

During hot summer days though the cooling fans would come on for an after-run cycle after shutting the car down which ended up being the major factor in me swapping back to an 89 degree thermostat.

If you do decide to do it, let us know how it works out. I get the impression you understand the risks and that running the motor hot could have negative consequences.

 

[ihatespeed]

Just a little food for thought.. Back in 2006 nissan had major engine failures in their 2.5l altimas, turns out the engines were running a little hot, Nissan intended it.. they did not foresee the oil consumption issues and the resulting engine failures. the fix was to lower engine oil temp by a little bit. There were many 10000-12000 mile engines replaced that year. water temp and oil temp are two very different things. and just because synthetic oil does not catastrophically fail under 300 degrees does not mean its still performing properly and within grade.

 

[Quanger]

Too risky in my opinion as well. If you think the cold is hurting your fuel consumption, just stick with blocking the front end with those foam pads. MPG drops in winter because of the cold starts as well as winter fuel.

 

[KB3MMX]

Fellas,

I have recently come across information where people have modified their existing thermostats with parts from other thermostats to gain higher coolant temperatures. See here:

http://www.cadvision.com/blanchas/Ranger/Thermostat.html

Since our thermostats are of the double valve thermostat type it would be important to make sure the end product functioned exactly the same as the old one in terms of internal engine bypass flow control. Not saying that this would be the best idea on the block to help us achieve higher overall engine temperatures, or the most easy to construct, but sense we cannot purchase over the counter T-stats in the ranges desired we are forced to get creative.


Here is a Stant part number of a t-stat that is rated for 205 deg F:

14252


I hope to do as side-by-side comparison of this thermostat and a replacement for my TDI this evening and see what the potential for swapping the internal parts would be. If the parts look interchangeable, I hope to purchase one of each, and test the 205 degree one to see if it will actually open at 205 degrees. If it opens correctly, I could begin the swap process and testing the results in the car.



One final question I would want to get resolved before proceeding, is it safe for our cars to run at a sustained 205 deg F temperature?

205F has never and will never hurt any diesel engine as long as the coolant pressure and mix ratio are correct to prevent boil.
Basically the temp difference you are trying to achieve is like the Powerstroke guys doing the 203F thermostat.
If oil is really a concern, run a 5w-40 synthetic but it won't get anywhere near hot enough to damage anything at a measly 205F , geesh. If you were talking about a 215-220F thermostat, I might be a little more cautious but even that isn't enough to damage a properly mixed and pressurized cooling system.
Gas engines are a different subject and have different things to battle with higher heat like detonation or preignition, vapor lock,etc...

 

[josh8loop]

Fellas,

Thanks for the input on this topic, greatly appreciated! I will admit, this project is a little over the top, but I feel pretty confident that if I am careful I can pull it off. Now whether or not I see MPG increases, and if the risk of making my own thermostat that could possibly fail while in service is worth it is another story alltogether.

 

[josh8loop]

KB3MMX,

Thanks for the encouragement. I had seen the 7.3 liter diesels, and their 203 deg F thermostat upgrades, and noted that they mentioned increased performance, and MPG. That, and the fact that it seems hard to get a thermostat that accurately functions at the rated temperature is what basically started this whole thing. My wife recently took a hard fall breaking the ball that connects her arm to her shoulder so that has made my project take a back seat at the moment. This is also allowing me ample time to consider the risks and rewards of such a project.

I am glad you also mentioned the properly mixed coolant, and proper pressurization to prevent boiling. I have recently replaced my coolant reservoir, and coolant cap along with some other cooling related parts and seals, so I know they are up to the elevated temperature/pressure. A scan guage needs to be in my future if I move forward to the trial part of this evolution.

 

[Ski in NC]

Another thing to consider: These engines use an Al head on a Fe block- There are different thermal expansion coefficients. As engine heats and cools, head tries to expand more than block. Stress appears in both. There may be some relative motion (scrubbing) on head gasket, depending on coefficient of friction and clamping force.

So putting a hotter tstat will cause more range in the thermal cycle from cold engine to hot engine. Head gasket may not be happy with that.

Not sure if this is an issue with these engines (head gaskets seem pretty reliable) but other engines with this Al/Fe combo have had problems (e.g., some toyotas).

 

[UFO]

Not sure if this is an issue with these engines (head gaskets seem pretty reliable) but other engines with this Al/Fe combo have had problems (e.g., some toyotas).

Not to mention Mercedes' first foray into Al heads... OMG

 

[09R/T]

I say go for it, not sure what all these guys are worried about, my cummins came stock with a 205, and hauling a 16,000 pound trailer never saw above 270 for oil temp...WITHOUT A COOLER. My hemi came with a 203, and it has aluminum heads and iron block.

Bottom line is it's only 13-15 degrees warmer than a stock t-stat. As mine was a stock 190 in mine, and I am in the process of finding or building a 203 for this one!

 

[Ski in NC]

Cummins has an oil cooler from the factory. On right side of block in the front.

 

[09R/T]

Cummins has an oil cooler from the factory. On right side of block in the front.

Yes it does, but mine failed so I removed it untill I could get another one, I already monitored oil temps, they came up a whopping 15 degrees without the oil cooler.

 

[Dimitri16V]

it shouldn't hurt... older VWs came with 90s thermostat

 

[josh8loop]

Fellas,

While recently doing some experimention with my old(1.5 yr) thermostat and comparing it to newer T stats I immersed them into at/near boiling water to determine opening temperatures etc. I have recently noticed since then my 2 tanks of fuel have given me better mileage. Is it possible that stroking my old T stat and reinstalling it helped with higher coolant temperatures increasing my mileage? I was averaging about 39-43 MPG in town before the R&R of the T-stat and my last fill up from 520 miles was 44.7 MPG.

 

[shizzler]

well..... has your coolant been hotter?

 

[Drivbiwire]

Another thing to consider: These engines use an Al head on a Fe block- There are different thermal expansion coefficients. As engine heats and cools, head tries to expand more than block. Stress appears in both. There may be some relative motion (scrubbing) on head gasket, depending on coefficient of friction and clamping force.

So putting a hotter tstat will cause more range in the thermal cycle from cold engine to hot engine. Head gasket may not be happy with that.

Not sure if this is an issue with these engines (head gaskets seem pretty reliable) but other engines with this Al/Fe combo have had problems (e.g., some toyotas).

As long as you have the OEM TTY head bolts thermal expansion issues with the head and block won't ever be an issue.

If you were foolish enough to use non TTY bolts good luck!

Running a higher temp thermostat should not be an issue. Especially in hotter climates a higher temperature thermostat is a good idea. This gives the coolant more time in the radiator to shed heat, and also results in a more stable primary cooling system temperature.

If you are pulling a trailer a 200-205 thermostat and a larger coolant oil to coolant heat exchanger would be an ideal situation. This will minimize temperature differential of the oil with more passes in the exchanger and minimize the viscosity range change with the higher temps.

In all cases only use a good quality synthetic ie M1 TDT 5w40.

Higher temps would give you tighter tolerances in the cylinders, which is where in my opinion the slight bump in efficiency comes from.

The head and block can safely handle this range since this still falls sighing normal temperatures for a TDI.

One last thing, make darn sure you are running a 70/30 ratio of G12 or 60/40 with G12+.

 

[josh8loop]

Shizzler,

Not sure about the coolant temps. I don't have a Scan Guage yet, and haven't had a second to measure the temps of the coolant. Just seems strange that the Removal/Stroking/Reinstall of the T-stat seems to have given slightly higher MPG's over the last 1100 miles(2 tanks).

 

[josh8loop]

DriveBy,

Thanks for the great insight. My bolts are all......well come to think of it, when I bought the car the guy who had it mentioned they had the head redone, and a TB. One of the valves went into the cylinder if I remember correctly, and caused minor damage. I think he mentioned the top of one piston had a very minor mark on it from the incident. I'm glad you bought this point up, perhaps I may want to replace some of those with proper bolts. Chances are they used the original bolts they took out instead of replacing them.

 

[josh8loop]

Fellas,

If anyone has a little free time, and might be able to verify my results with a little experimention on their end I would appreciate it. Basically all I did was to take my properly functioning thermostat out of my car and heat it up to boiling temps, and cooled it back down to room temperature about 6 times in a span of 1 hour. I used the microwave, and submersed the T-stat into a Pyrex measuring cup with distilled water and turned the microwave on until boil started, and removed it until it cooled down. I reinstalled it with a new O ring, and have been logging mileage numbers since then. It might be better if someone with a scan guage would do this that way they could compare usual water temps to water temps post thermostat exercise.

 

[shizzler]

Dude. I would not recommend playing around with your coolant system with a scan gauge or at least a vag-com hooked up. That silly gauge on the dash is not an accurate indicator of coolant temps and could get you into trouble.

 

[UFO]

Fellas,

If anyone has a little free time, and might be able to verify my results with a little experimention on their end I would appreciate it. Basically all I did was to take my properly functioning thermostat out of my car and heat it up to boiling temps, and cooled it back down to room temperature about 6 times in a span of 1 hour. I used the microwave, and submersed the T-stat into a Pyrex measuring cup with distilled water and turned the microwave on until boil started, and removed it until it cooled down. I reinstalled it with a new O ring, and have been logging mileage numbers since then. It might be better if someone with a scan guage would do this that way they could compare usual water temps to water temps post thermostat exercise.

Without knowing coolant temperatures before and after, this is an exercise in futility. I know I was running coolant temperatures around 160F and struggling to get 40mpg in mu commute, then I replaced the thermostat with a new one. Now my coolant temperatures are around 190F and I easily get 45mpg on my commute, provided the mornings aren't too cold.

 

[NarfBLAST]

Dude. I would not recommend playing around with your coolant system without a scan gauge or at least a vag-com hooked up. That silly gauge on the dash is not an accurate indicator of coolant temps and could get you into trouble.

I made the correction highlight in bold to your post... I think this is what you meant?

 

[dieselfuel]

Drivbiwire,

As long as you have the OEM TTY head bolts thermal expansion issues with the head and block won't ever be an issue.

If you were foolish enough to use non TTY bolts good luck!

Are ARP TDI studs alright? (Not the Cosworth studs).

Thanks,