Hotter thermostat for FE - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

NachtRitter · 01-30-2011, 01:26 AM

Changing the thermostat to the 195* F version seems to be a popular mod for the VW TDI group for better FE as well. Looking into doing that soon on my TDI, now that I have a few tanks under my belt.

nemo · 01-30-2011, 11:35 AM

On my car the operating temperature range 194 to 225. The cooling fans with the air off won't come on until the temp reaches 220 degrees then turn back off at 197 degrees.

watercat · 01-30-2011, 01:51 PM

I think my new stock stat is a 180f so I'll boost it to a 195f. I installed a wink mirror in the car last night so there would be no blind spots driving around with my mirrors removed. So many tweaks to do.

roosterk0031 · 01-31-2011, 10:45 AM

Replaced my T'stat Saturday, what a pain compared to the old V8's, running temp was 165-170 via SG, now 195-197. No obvious pickup in MPG via SG, this morning commute was pretty much average 31.5. Will take a few tanks to really be able to tell. My SG isn't callibrated prefectly, but going to leave it alone for now.

UFO · 01-31-2011, 03:23 PM

Quote:

Originally Posted by roosterk0031

Replaced my T'stat Saturday, what a pain compared to the old V8's, running temp was 165-170 via SG, now 195-197. No obvious pickup in MPG via SG, this morning commute was pretty much average 31.5. Will take a few tanks to really be able to tell. My SG isn't callibrated prefectly, but going to leave it alone for now.

I can't tell you why, but my scangauge completely missed the mileage improvement with my thermostat change. It was hard work to keep my tank mileage at 40mpg, and I barely made it when I filled the first time after replacing the stat. And the scangauge was way off, as calculated mileage showed a 6mpg difference.

gone-ot · 01-31-2011, 03:37 PM

...just remember, the boiling point of 50%/50% mixture of water/antifreeze with a 15 psi cap is something like 245ºF, well above normal 212ºF boiling point of water alone.

...water/antifreeze mixture alone is good for about >225ºF

...each pound (1 psi) of cap pressure is another +3ºF.

comptiger5000 · 01-31-2011, 05:53 PM

^ Yup. Most engines are perfectly happy up to 220* or so, with no adverse effects. Some are good to 230*. Taking a look at factory e-fan kick-on points (where applicable) can give you some idea of how hot you can push it safely.

roosterk0031 · 01-31-2011, 08:50 PM

New best on drive home today, 35.4 SG mpg, falling snow had me driving slower and my foot's getting better at letting up going up hills.

ECONORAM · 01-31-2011, 10:14 PM

Quote:

Originally Posted by NachtRitter

Changing the thermostat to the 195* F version seems to be a popular mod for the VW TDI group for better FE as well. Looking into doing that soon on my TDI, now that I have a few tanks under my belt.

The contrary actions are so funny to me. Here people want to put in higher temp Tstats. On the "performance" forums people put in lower ones (ie 180*). Trading HP for FE.
My RAM has a 193 Tstat, and that seems to work fine. The main issue is the boiling point of the water/coolant mix. The pressure is what pushes the boiling point above 212. That said, if you switch to Evans Engineering coolant...you get a 370* 0psi boiling point. If I got that swapped in, I'd want a 250* Tstat! Then the issue would be reprogramming the ignition to not cut timing....

Quote:

Originally Posted by stovie

in my opinion the warm air intake is heating the wrong thing for example the temperature where i'm at is 38 degrees at night and thats how cold the fuel is in the morning so ya you can heat the air but the thing your trying to improve is the evaporation of the fuel that really sucks at 38 degrees. i have no return fuel line so i'm trying to see what happens when you heat the fuel line with the coolant line from what i've read so far i should be able to hit 180 degree fuel without vapor lock in the line.

I was contemplating a WAI for my truck...by ducting air that came through the radiator fins into the filter box. Figured I should do some A-B-A testing for any results.

comptiger5000 · 02-01-2011, 10:45 AM

Econoram - At 250*, you have to start worrying about head gasket integrity, and particularly issues with cracking or warping heads. They just weren't designed to run that hot. 210* - 230* is the hottest running temp most modern engines will hold up to on a continuous basis.

As far as temp, a hotter t-stat would actually make more power. However, on many performance forums, they'll drop from a 195* to a 180*, as it is an easy way to drop the intake temps, particularly on V8s like mine that run coolant through part of the intake manifold. The intake temp drop overcomes the reduced efficiency from lower coolant temp when power is the only factor. If they could get the intake temps down while keeping the 195* t-stat, they'd get even more power.