Modified Thermostat for higher MPG's...

Fellas,

A little update. As mentioned earler in this Thread I have recently installed a temperature probe in the coolant flow that goes to the overflow tank so I can monitor coolant temps while I don't have the Vag Com hooked up. This has provided me with some great information on the current temperature regulation status of my engine. My T-stat is a couple years old now, and seems to want to keep my engine at 184-186 Deg F in the morning, and 184-201(depending on load) in the hot florida afternoons. Vag Com was reading about 10 degrees off what my new digital temp sensor(confirmed by IR thermometer, and a calibrated analog thermometer) was reading. I had been a little skeptical of the coolant temp sensor readings, but now I have proof that it is not that accurate. The CTS is about 2 yrs old(OE replacement). It also indicated that my T-stat is indeed worn out, and leaking coolant through too early as indicated by the engine temp being so dependant on outside temperatures. I would expect that a properly functioning coolant temp regulating system would allow the engine to be relatively thermally insulated from the outside air temperature. I am really glad I have constructed and installed my digital coolant temp sensor, it has provided some really valuable info on my temp regulating status and will allow me to move forward on my "Hybrid" 205 deg F thermostat.......



Which brings me to my "Hybrid" T-stat update I went ahead and purchased yet another stock TDI T-stat so I could take some needed measurements, and repress my "Hybrid" unit. It all went well, and with my much improved tooling and skillset I was able to repress my hybrid unit. I am currently trying to figure out an easy way to install a coolant drain plug in the coolant line that goes to the engine oil cooler to allow simple, and relatively mess free draining of coolant so I can do testing of different t-stats quickly. Once I have my coolant drain figured out, I should be able to test my latest creation. Muhuuhaaahaaa

Good info. Keep it coming!

And, no I don't have a Bently man.

Update....

I was able to come up with a design for a drain for the lower coolant line on the oil cooler. This will help greatly in draining coolant while performing T-stat testing-much needed piece of the puzzle. It will also allow me to monitor coolant system pressure during testing too. Part has been made(5/8 hose barb inlet and outlet, with 1/4MPT thread for fitting in the center) and will hopefully be installed Saturday for some testing.

DF,

Would it be worthwhile for you too seek out a radiator thermal switch with the same thread that our current ones have? Maybe you could find the temperatures(or close) to what you are looking for. Perhaps one from a gas vehicle. VW gas vehicles of the same years according to the Bentley appear to have the same temperature settings from what I see-although I could be wrong. Would be interesting to see if they are the same part number or not. Wiring plugs could be different, but this could be handled. Just a thought.

210 or 215 would be perfect.

What is normal: 190 or 195...? I always forget for our TDI's.

195 for ours is the highest stock replacement. Unfortunately!

Ok, ok,

I was a busy guy this evening- some time opened up and I
was able to install my new coolant drain rig and my new 205 deg F t-stat.......................and the drum roll . .......



It worked beautifully in the cooler(80 deg F) Florida afternoon Temps. It held a fairly constant 205 degrees fairly independent of forward speed. On the highway excellerating it got to 208 and settled back down to 205 during 68 mph cruising conditions. The highest I saw it get to was 208, and that was when I was getting on it. Overall I feel comfortable with it's performance enough to leave it in there tomorrow on my way to and from work(26 miles one way- 45 min worth of driving due to traffic). Tomorrow afternoon will be the real test since there will be more stop and go and the temps should be in the low 90's. Overall I am
Quite excited, and am looking forward to mpg gains-especially since my car was at around 186 deg F.

What was the highest temp you saw on your stock t-stat?

208. Not bad. A little corregated cardboad in front of the radiator and you're golden! That actually might work with the Evans.

BTW, were you using the A/C?

dieselfuel said:

What was the highest temp you saw on your stock t-stat?

208. Not bad. A little corregated cardboad in front of the radiator and you're golden! That actually might work with the Evans.

BTW, were you using the A/C?

Click to expand...

Highest I ever saw on my stock poorly functioning t-stat in 90 deg weather was while excellerating hard and was 205 F-it usually liked to stay at 184-186 though.

I did forget to mention I tried the hybrid 205 unit with A/C on to see what happened-temps stayed the same! This further confirmed that the extra air flow through the radiator from the fans while the ac was on did not effect engine temperature because the t-stat was doing it's job. I wouldn't do cardboard-it seems a properly operating t-stat will keep temps where they should be no matter how much air flow
Goes through the radiator. Tomorrow will be the real test

This mornings trip to work went great, and all temperatures with the new"Hybrid" t-stat went exactly as expected. Temp liked to hover around 204-205, and the highest I saw it get to was 208 when accelerating just like last night. I did notice that the fans kicked on as the temp suddenly dropped from 207 to 203 pretty quickly, actually made me sit up and take quite a bit of notice as I thought that the sudden decrease in temp could have been from a loss of coolant. After I watched it go down to 203, and steadily climb back to 205-206, I knew it was simply that the fans had kick on. Looks really, really promissing and I'm looking forward to the trip home this afternoon when the outside temps are around 90 Deg outside-we shall see what it is able to do then



By The Way,

I mentioned radiator blocks in previous posts-keep in mind I only used it as as a temporary trouble shooting tool to help me see if my T-stat was working properly, and mileage my car would accheive if it had elevated temperatures. I still maintain from much recent experimentation and observation that a properly operating T-stat will be able to keep the engine temp regulated no matter how much airflow comes through the radiator. If you block the radiator it will reduce the radiators ability to reject heat if called upon-a scary position to be in! Now keep in mind there are exceptions to this especially if you live in frigid climates, and again YRMV

......So lonely in here.....Brrrrr

Did the fans come on (Hi speed) because the A/C was on in traffic? If this is the case then it was most likely the condenser temp that made them come on.

jayb79 said:

Did the fans come on (Hi speed) because the A/C was on in traffic? If this is the case then it was most likely the condenser temp that made them come on.

Click to expand...

JayB,

The A/C wasn't on so im reasonably sure it would have been due to temperature. I am speculating that the fans kicked in by what I saw on the digital readout-I could be wrong though. I may install LEDs with appropriate resistors that will give me visual indication when and if they come on.

Josh,

Sounds good. Are you going to use the Evans?

I'm sure you will pick up 2-3 mpg, but I'd feel better running the Evans. Plus, the Evans won't corrode the heater core or radiator. I'm willing to use the Evans for that aspect, alone. Because I know, I won't be tearing into a dashboard to replace a heater core. And, it won't be cheap to pay someone else to do it, either.

Fellas,

Here is a quick video showing my setup and results:


http://www.youtube.com/watch?v=4vezAAmd6sg
http://m.youtube.com/index?client=mv-google&desktop_uri=%2F&gl=US&rdm=4mhc099up#/watch?v=4vezAAmd6sg


The current setup is temporary, but the permanent one will basically look stock with no wires out in the open. To make the digital temp readout, I used a Harbor Freight digital meat thermometer that can be viewed here:


http://www.harborfreight.com/instant-read-digital-thermometer-95382.html


I also used one coolant "Tee" from junk VW vehicle, some coolant line clamps, some 5/16" weatherhead hose, and a phone cable I had laying around. The "Tee" had to be slightly drilled out so that the 1/8" probe could be inserted while still allowing the coolant to flow around it and into the coolant reservoir. To get the 1/8" probe to seal inside the 5/16" ID of the weatherhead hose I used a 1" piece of 1/8" ID vacuum line as a sleeve so that it would seal together. Seems to work brilliantly, and no leaks yet

Josh,

That link didn't work for me. Just a bunch of commercial videos.

dieselfuel said:

Josh,

That link didn't work for me. Just a bunch of commercial videos.

Click to expand...

Hmmm....Strange-Try that one

Looks good Josh!

Honeydew said:

Looks good Josh. That links still isn't right. I found it by searching your username.
http://www.youtube.com/watch?v=4vezAAmd6sg

Click to expand...

Thanks...must give me a different address since I am logged into YouTube, and I'm the account holder....scratching my head....Anyhow, got it this time thanks to your help!

Yeah youtube can be a bit screwy since their "improvements".

Well so far I have put 160 miles on the "Hybrid" T-stat and all seems to be well. I glance at the temperature readout constantly to monitor temps in differing conditions. Looks like the regulated temperature may be drifting a few degrees more than it first did. For instance, last night on the highway with A/C on and running 68 MPH the temps were running 208-209 deg F. Highest I saw it get to was 210 best I could tell. Normal city stays nicely around the same. Later this afternoon/evening I will be running down to Ft Lauderdale, so this will be another good test situation.

Fellas,

Just to reiterate to those who may be tempted to follow in my foot steps and modify their own thermostats, please take time to read the first couple of pages in this thread about the cautions regarding running higher engine coolant temps. Modify at your own risk.

Also, I am no expert just a novice- please correct me when information is incorrect. I am here to learn, and am glad to be a part of this great TDI community.


Well, with all that said if someone out there understands to the best of their ability what the risks are in running a higher temp t-stat and constructs their own please let us know how it works out for you. Also, I would be willing to(if someone mails me the two t-stats needed for the "Hybrid" production, and sends funds to cover return shipping) I wouldn't mind assembling a few units(on a limited basis) so that we can get a parallel testing path going. PM me if interested- good candidates for this would be those with stock injectors or close to stock, and probably not heavily chipped. Probably would need to have the ventectomy mod so fuel consumption could be closely monitored, and Vag Com or other method of temperature indication is absolutely necessary. I have completely stock injectors and no tune. My power adding mods are virtually non existent as I am trying for best mileage.

Josh,

Alright, I was able to view the video (from the link above). Nice job, Josh!

Also, I'm down for a Josh_modified t-stat. Please send me a PM with the Stant part numbers I need and your mailing info. Just let me know the details.

210F sounds great!

Josh,

I couldn't really tell from the video, but it looked like your temp guage was one mark past the center mark (when your digital guage was reading 205)?

dieselfuel said:

Josh,

I couldn't really tell from the video, but it looked like your temp guage was one mark past the center mark (when your digital guage was reading 205)?

Click to expand...

DF,

That must have been an optical illusion. The cluster temp guage doesn't move off of the 190 mark-perhaps toward the right side of it. The cluster guage reads 190 at any where from 167-217 plus IMO.

dieselfuel said:

Josh,

Alright, I was able to view the video (from the link above). Nice job, Josh!

Also, I'm down for a Josh_modified t-stat. Please send me a PM with the Stant part numbers I need and your mailing info. Just let me know the details.

210F sounds great!

Click to expand...

DF,

Thanks for the attaboy on the work-appreciated! There are two Stant parts that will be needed for the Hybrid unit-One of each:

13352
13379


I figured I would post it here again for quicker reference. I will PM you about it.

Quick Update:

I went on my trip last night to Ft. Lauderdale. So far I have put 410 miles on the "Hybrid" T-stat. It stayed around 209 on the Hwy, and the most I saw was 211 briefly. Usually see anywhere from 205-208 in town. I will fill up this afternoon, so I will post numbers then. So far it doesn't seem earth shattering. I know that my automatic transmission didn't seem to like the elevated temps-as to be expected with lower viscosity at the higher temps, so that could have been eating MPG. Manual would be ideal here. Another thing is that the engine seemed sluggish at the higher temps-I wonder if timing was retarded by the ECU(this is what it felt like to me)?



which brings up something that needs to be adressed when modifying temps and looking for mileage gains(one which I cannot answer)....




How does the engine react to elevated temps seen by the coolant temp sensor?

Fuel temps will rise when weather is hot, that will retard timing and reduce power. I think this is more pronounced with the auto trans, that is why they have fuel coolers and manuals do not.

JayB79,

I was under the impression that the aluminum fuel cooler on the fuel lines was on the return to the tank to help keep fuel tank temp from raising excessively. Is that correct?

Cool, Josh. I'll try to find those t-stats today or tomorrow. Thanks for the part #'s.