Modified Thermostat for higher MPG's... - Page 39

shoebear · April 8th, 2012, 20:03

Hey there, flatlanders!

My daily commute tops out at 7343' elevation at the end of a medium length steep grade at 75mph speed limit. Furthermore, I can be at 14,110' (the top of Pikes Peak) within an hour of leaving my house (or less, depending on traffic and road conditions). At my house (6300') water boils at 201*, which means I have less coolant temperature margin than most.

Even if you don't live and drive in high elevation, you may want to vacation here sometime, and you have to plan for the extremes. So it seems to me that a 205* t-stat would risk coolant boil at high elevations unless you were using waterless Evans. Any thoughts?

If I did ever convert to Evans, a quick trip up Pikes Peak with a loose radiator cap seems like a fast way to purge leftover water. Water boils at 186* at the top.

I just picked up a Stant Superstat 45379 like GreenENG has (p36, post #528). Even though that's a 195* t-stat, he reports running at 205*. When I get it installed, I'll post my results back here for comparison. When I left to get it, I hadn't seen GreenENG's post yet -- otherwise, I might have just gotten the regular Stant because of my high-elevation concerns. BTW, the regular Stant would have been $8, the SuperStat was $10. According to the Stant website, the Superstat regulates temp more evenly with fewer and narrower temp swings compared to a regular t-stat.

shoebear · April 9th, 2012, 19:55

The Stant Superstat 45379 is in, and a few non-freeway miles got the temp up to 202*F (briefly) on my ScanGauge. I'll be commuting tomorrow, so we'll see where it stabilizes on the freeway.

From what I can tell HERE and HERE, G12 at 50/50 at sea level with a 15psi coolant cap boils at about 265*F. The air pressure at the top of Pikes Peak is about 8psi, or 6psi below sea level. At 3*F / psi, that would lower the boiling point by 6 x 3 = 18*F to 265 - 18 = 247*F.

I can think of three reasons to leave some margin between the max temperature reported by the temp sensor and the actual boiling point of the coolant.

I suspect there are hotspots within the cooling system, and I wouldn't want any part of the coolant to get above boiling.
In case the coolant cap was a little weak and didn't hold a full 15 psi.
I'm sure cavitation becomes more likely as the coolant approaches the boiling point.

I have no idea how much wiggle room to leave, but I'll make a WAG at 25*F. So on Pikes Peak, I want my max coolant temp to be 247*F - 25 = 222*F, which should be within the operating range of the Stant Superstat 4537.

If 25*F margin isn't enough, it sounds like VW permits up to a 70/30 mix of G12, which would raise the boiling point by 13*F.

Comments?

I'll report back tomorrow evening after my commute.

SD26 · April 10th, 2012, 01:24

Quote:

Originally Posted by josh8loop

SD26,

When you assembled your "Hybrid" T-stat, did you notice when you pressed the rear section on that it seemed a bit loose like you could have changed it's position by hand pressure alone? I'm wondering if the inconsistancy of temperature regulation is from the rear bypass disc changing it's position once in service. Remember when the T-stat increases temperature it's length is modulated according to engine temperature. At certain temperatures the rear section is pressed up against the round hole in the block, and if it's not pressed on tightly it may cause it to shorten some changing it's temp regulating characteristics.

No looseness at all. And I was wondering if that was what was happening when I had very inconsistent temperatures on the first thermostat that I assembled.

So, I did a second one from completely different parts.

But I do have a concern on the disc itself. Seems that in my removal of that "back" section of the thermostat, the "shaft" that the disc is mounted and retained to gets a little deformed from my removal processes. Thus, my disc doesn't remain as parallel to the block as an unmodified one. What seems to happen is that my support for the removal leaves something to be desired, and the area that is turned down to keep the disc on is deformed enough to make a difference. I'd like to figure out a way where something could be inserted into that area to pull it off the thermostat rather than doing it from the outside where it can deform that disc area. Haven't given it a ton of thought as of yet, but there's certainly a way to do it.

SD26 · April 10th, 2012, 01:35

Quote:

Originally Posted by shoebear

I suspect there are hotspots within the cooling system, and I wouldn't want any part of the coolant to get above boiling.
In case the coolant cap was a little weak and didn't hold a full 15 psi.
I'm sure cavitation becomes more likely as the coolant approaches the boiling point.

I have no idea how much wiggle room to leave, but I'll make a WAG at 25*F. So on Pikes Peak, I want my max coolant temp to be 247*F - 25 = 222*F, which should be within the operating range of the Stant Superstat 4537.

If 25*F margin isn't enough, it sounds like VW permits up to a 70/30 mix of G12, which would raise the boiling point by 13*F.

Comments?

Well, aren't you answering your own questions?

For sometime, I always found that Evans was easy to default to. Why? Well, first, the boiling point of 375*F. That should be more than enough for you. Next, that's at zero PSI, so, if you have a problem with your cap, you still have a 375*F boiling point. With that, cavitation is pretty much eliminated. Yeah, I suppose that one could get it, but you're probably reaching a point of huge destruction for that...or it might be representative of the heat in the egr...

Next, water... It is the enemy. If it's in your oil, your fuel, or anything else, you'll get rust, corrosion, or other oxidization. Same thing goes for coolant. If you can eliminate water there too, there are minor things like better life on hoses over the long term. At least that is my experience.

dieselfuel · April 10th, 2012, 06:25

Shoebear,

Just cut to the chase and use the Evans HDTC. As a bonus, it will not corrode your cooling system (the heatercore is a real, no pun intended, bear to replace).

Running Evans and very satisfied,

df

shoebear · April 10th, 2012, 19:40

OK, here are the temp results for the Stant Superstat 45379, as reported by my ScanGauge --

Once up to full temp on the freeway, the coolant hovered between 197-200*F. After a hill climb or acceleration, a few times it got up to 202*F, but quickly dropped back down. This isn't quite what you folks are looking for -- but it's a great improvement for me. I had been running 177*F, but recently dropped to about 171*F -- so 197*F is +26*f.

It also gives me a bit more margin between operating temp and boiling, which makes me feel better.

I will probably go to Evans at some point; I agree that it's superior. But G12 is one of the best water-based coolants, and so I'm not it a great hurry. If it ain't broke...

aellen · April 11th, 2012, 20:07

I just did Josh's 205 mod, and got my readings up to 106.3 C on my vcds. Not sure about that and I am not liking it. So I put my old one back that regularly gave me a 99.6C reading with the heater OFF. I'll keep that one in use. I think a 223F reading is too high, and not worth the risk,.....

dieselfuel · April 12th, 2012, 06:06

223 is fine if you're running Evans HDTC. Otherwise, yes, it's too hot, imo.

josh8loop · April 13th, 2012, 21:34

Quote:

Originally Posted by aellen

I just did Josh's 205 mod, and got my readings up to 106.3 C on my vcds. Not sure about that and I am not liking it. So I put my old one back that regularly gave me a 99.6C reading with the heater OFF. I'll keep that one in use. I think a 223F reading is too high, and not worth the risk,.....

If you are able to, it would benefit the group for you to remove the rear bypass section of the "Hybrid" and press it on so it's a little longer than before by about .030". This may reduce the temperatures you are seeing in theory at least.

SD26 · May 29th, 2012, 00:11

Managed to run a couple tanks through the wagon. Remember that I had a 205, but my temperature results were a little goofy. I removed the 205 hybrid build by myself and installed a 198F Wahler tstat in my 2003 wagon.

On the trip south, I had the massive 18" wheels on, and they just kill my MPG, so I found a set of Avus 15's. Threw those on, and things got better.

My last two tanks were about 56 and 57MPG. Pretty happy with that. No shutting off the engine going down hill or anything. My daily commute is about 27 miles one way, and I don't get on the interstate at all.

Would like to grab 60MPG. Would like to put in a hybrid yet too. I think I mess up the bypass disc during the removal.

Tom W. · June 7th, 2012, 14:23

I've been running w Evan's since 1996. Good stuff. It takes a looong time to get the water out.
Also, your coolent level sensor may no longer work- The sensor in my 86 IDI depends on the electrical conductivity of normal coolent to tell if the level is low. Evans doesn't conduct electricity(this is a good thing for engine longevity) so my coolent sensor always thinks I have no coolent. One solution is to bend the 2 probes of the coolent level sensor so that they are within about 1/16 of an inch from each other (normally they are about 1 inch apart).
I normally block off part of the radiator on the 86 w cardboard in the winter, to get my engine temps up to "Normal".
I forgot to take the cardboard out one spring, and that summer I was averaging over 65MPG (I normally average 52MPG)
I've left the cardboard in place ever since...................
Hmm, wify has some mini blinds she's not using...................

nicklockard · June 8th, 2012, 15:38

I had PM'd Josh about this idea a while back:

As many know, thermostats are wear items. The bimetal springs slowly fail toward more open. Eventually, they all fail to full-open, all the time. In my experience using ScangaugeII device to track temperatures, most OEM t-stats last about 3-4 seasons before they begin to exhibit this failure. Aftermarket ones like NAPA branded usually perform worse out of the box and degrade in the same time frame.

16 months after installation, a 90C t-stat will open sooner and your engine warmup times will roughly double. That is lost fuel economy and more engine wear.

So when I was talking to Josh about this idea, he pointed me to this discussion on the Jeep forums.

So, rather than replacing t-stats every 4 seasons (minor PITA), I think adding a secondary, in-line, in-hose thermostat like this at the entry to the radiator will keep warm-up times consistently short. Even as the main t-stat begins to open sooner and cooler, the distance to the other in-line, in-hose t-stat will mean that it sees cooler temps (the hose itself radiates some heat), and will thus help regulate engine temperatures better.

There is a downside: if your car needs maximum, full-flow cooling, then adding another flow restrictor won't help. On the other hand, if your has over-sized cooling system and struggles to warm, like the Tdi engine family, this could improve FE and reduce engine wear by reducing warmup times.

I'm going to buy one for my car and report later.

josh8loop · June 8th, 2012, 17:39

Quote:

Originally Posted by nicklockard

I had PM'd Josh about this idea a while back:

As many know, thermostats are wear items. The bimetal springs slowly fail toward more open. Eventually, they all fail to full-open, all the time. In my experience using ScangaugeII device to track temperatures, most OEM t-stats last about 3-4 seasons before they begin to exhibit this failure. Aftermarket ones like NAPA branded usually perform worse out of the box and degrade in the same time frame.

16 months after installation, a 90C t-stat will open sooner and your engine warmup times will roughly double. That is lost fuel economy and more engine wear.

So when I was talking to Josh about this idea, he pointed me to this discussion on the Jeep forums.

So, rather than replacing t-stats every 4 seasons (minor PITA), I think adding a secondary, in-line, in-hose thermostat like this at the entry to the radiator will keep warm-up times consistently short. Even as the main t-stat begins to open sooner and cooler, the distance to the other in-line, in-hose t-stat will mean that it sees cooler temps (the hose itself radiates some heat), and will thus help regulate engine temperatures better.

There is a downside: if your car needs maximum, full-flow cooling, then adding another flow restrictor won't help. On the other hand, if your has over-sized cooling system and struggles to warm, like the Tdi engine family, this could improve FE and reduce engine wear by reducing warmup times.

I'm going to buy one for my car and report later.

Nick,

This will be a really neat experiment. Are you planning on installing it directly after the plastic water distribution fiting? This might be a good location since the added T-stat wax pellet section must get coolant flow in order to sense the coolant temperature as you know. The plastic water distribution fitting on the upper radiator hose has a small hose that runs back to the engine and establishes a small coolant flow through this miniature loop at all times-this flow loop is also approximately the highest point in the circulating coolant flow path, and is responsible for shuttling air that is in the coolant system directly to the reservoir. If your added T-stats wax pellet section was in the flow path of this miniature coolant flow loop it would be seeing the outlet coolant temperatures. Where were you thinking of installing it?

josh8loop · June 8th, 2012, 17:55

One of the guys on the Jeep forum used this thermostat:

http://imageshack.us/photo/my-images/21/1013026.jpg/

Federated (MotoRad) 237-192

I would go with this type of setup as long as the outside diameter of the T-stat will fit into the inside diameter of your top radiator hose. You would also want to find one with a suitable temperature range for your liking. If you went with this type of T-stat you would want to place it before the plastic water distribution fitting.

..

josh8loop · June 8th, 2012, 18:15

Thinking this dual thermostat thing through a little bit further brings an interesting possibility with bad consequences. What if the original thermostat in the vehicle opens up fully(which closes the internal engine bypass loop) and requests coolant flow through the radiator only to receive none since the added thermostat is not yet open? In this scenario coolant flow would all but completely stop until the added T-stat allowed coolant to flow through it.