Modified Thermostat for higher MPG's...

jayb79

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Exeter,NH
Yes that is what the cooler is for. But when its hot it is less effective. This may not be the problem of low power, but it would be interesting to know what the temp of the fuel in the tank is after a long hiway ride.
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
Yes that is what the cooler is for. But when its hot it is less effective. This may not be the problem of low power, but it would be interesting to know what the temp of the fuel in the tank is after a long hiway ride.



Gotcha, glad to see my understanding of it's operation was confirmed. I will have to get with HoneyDew some time and do a logged run on the highway and monitor via VagCom some different parameters. Timing VS temp will need to be one of them for sure.
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
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.




An additional reason the fuel coolers are used on the autos could also be the 11mm pump instead of the 10mm one. Remember reading about how it heats things up a bit more. Just thought of that!
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
I thought I would at least make a mention of the difference in MPG that I may or may not be getting. I have 460 miles on the new 205 T-stat, and it seems to be trending in the right direction ever so slightly. I realize that many factors come into play with mileage numbers, but even thinking about these I feel I may have gained a little. Here are some numbers that have been acheived with the car-these are some in-town numbers, and hwy numbers mixed:


Old T-stat(184-186 Deg F):

47.3
45.5
43.7

New T-stat(205-208 Deg F):

48.9
48.0
46.4
47.6
46.4


It is a little too early to make hard conclusions as I need to get some mileage on the new "Hybrid" t-stat, but I like where it's heading. I have a ventectomy, so I fill to the top vented. Next on my agenda will be installing some means of monitoring when the fans kick on and off. If they stay on(which I have not witnessed) it could eat my MPG gain lunch. Another thing that needs sorted out is to hook up to Vag Com and see if the timing is retarded due to the higher coolant temps. If it does, I may have to get a chip tune or something to counteract it.
 
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algirdas

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Cincinnati,OH (Dubwerx)
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98 jetta AHU
Hi Josh,
This is great work!
Inspired me to look thru the options available from Worldpac, the parts supplier for a shop I work with.

I found a Wahler 92 degree Celcius = 198deg F.
Fitment is 1984-1992 VW Jettas with 1.6 diesels.

VW part number: 056 151 113F
Part # on Wahler box: 4256.92D50

Its a readily available part that's higher temp than stock.
Didn't have to mod it so I just installed it in my 98 Jetta yesterday.
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
Hi Josh,
This is great work!
Inspired me to look thru the options available from Worldpac, the parts supplier for a shop I work with.

I found a Wahler 92 degree Celcius = 198deg F.
Fitment is 1984-1992 VW Jettas with 1.6 diesels.

VW part number: 056 151 113F
Part # on Wahler box: 4256.92D50

Its a readily available part that's higher temp than stock.
Didn't have to mod it so I just installed it in my 98 Jetta yesterday.





Good find! I'm sure others will be interested in finding out how it works out for you. I'm guessing your engine doesn't have the rear bypass section? Can't wait to hear your mileage, or make that Smileage :) results with it.





PS

I'm not sure if those engines have fuel temp, and coolant temp sensors on them that feed information to the computer? If it does, it may pull back timing at the higher temps reducing the positive results of the higher temperature. Just a thought.
 
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josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
Just got 47.6 MPG in town(remember this is w/ an 01M). I can say I am still seeing an upward trend. Can't wait until I do the 5-speed soon :)


BTW, Still havn't installed LEDs to tell me when the fans kick on, but I have seen them come on briefly.
 
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ChuckV309

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Cent. IL
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2002 Jetta TDI, 1996 White B4V, 2005 B5.5
Just a tid bit of info about the Scanguage temp reading. It tells you the trans fluid (on an O1M auto) temp under the normal water temp area. I didn't know this until the valve body had a problem and the torque convertor would slip and my temps ran up to about 260 on the scanguage. I think you can reprogram it so that it tells you the coolant temp, but don't know how.
 

UFO

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A mile high
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2001 Beetle
Just a tid bit of info about the Scanguage temp reading. It tells you the trans fluid (on an O1M auto) temp under the normal water temp area. I didn't know this until the valve body had a problem and the torque convertor would slip and my temps ran up to about 260 on the scanguage. I think you can reprogram it so that it tells you the coolant temp, but don't know how.
There is an xgauge that does that. It's on this site somewhere, should come up on a search...
 

Mako

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VW ISO
GAUGE TXD RXF RXD MTH
Transmission Temperature 686AF10105 031A04410505 2808 00090005FFD8 TFT F
Coolant Temperature 686AF10105 031004410505 2808 00090005FFD8 WTR F
Note: VW Coolant and Transmission Temperature cannot be displayed at the same time.
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
I updated the above listing of fill up MPG's since the new T-stat was installed. The latest fillup was was 46.4 MPG.
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
Well,

It looks like I may be having turbo issues. See this thread:

http://forums.tdiclub.com/showthread.php?t=318697



Not sure it is from the higher temps for the last 1000 miles or not. I bought the car used at 104,000 miles and it now has 156,000 on it. It could have been on it's way out any way. I will be closely monitoring it over the next week, and memorial day weekend I will inspect again for shaft play. Until then it may not wise to try temp mods until I get this sorted out.
 
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dieselfuel

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Dec 28, 2008
Location
ohio
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2003 Jetta TDI
Just for kicks, thought I'd check the coolant tank temp tonight. Ambient temp: 72F

Coolant temp: 190F!
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
Update,


At first I thought I may have been experiencing issues with my Turbo due to higher engine temps. Over the last week or so(with the Hybrid T-stat still in) I have been carefully monitoring things. While in the investigation mode I went ahead and installed a temporary oil pressure guage to make sure my oil pressures were still in acceptable range at the higher temps. Oil pressure was perfect even at the higher temps, so no problem there. I think the turbo issue was all in my heard, and I must have been hearing things.

This experience has brought to light a couple things in regard to running slightly higher coolant temps however. Namely the use of a larger and more effective oil to coolant heat exchanger. This will allow the oil temps to closely mirror the coolant temps, and would be a great idea to have while experimenting. Additional info can be found here about the oil cooler upgrades available:

http://forums.tdiclub.com/showthread.php?t=306808&page=3
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
Just for kicks, thought I'd check the coolant tank temp tonight. Ambient temp: 72F

Coolant temp: 190F!





DF,

Not sure where you were going with this? Is that good or bad? Does seem to me that your coolant temp is somewhat independant of your outside ambient temp, a good thing and indicative of an effective t-stat IMO.
 

dieselfuel

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Location
ohio
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2003 Jetta TDI
Just thought I'd check it since when I replaced it during the cooler months, I only achived 185F or so, and I was a little disappointed.

Anyhow, I'll pick up those t-stats this weekend and get them to you. I'll send a PM to you when I mail them.
 

chrisfiat

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Jul 14, 2006
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farmington nh
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97 jetta
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.
so how is this different from a normal tstat function??
this is exctaily what happens during warm up.
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
so how is this different from a normal tstat function??
this is exctaily what happens during warm up.
This is just something I noticed after I removed my T-stat and exercised it in a boiling bath. The difference is that the boiling bath is 212 deg f and normal TDI operation would be below 200 deg f probably. In any case I think it was a fluke, and we have learned alot since then. I wouldn't recommend the proceedure you are talking about, however the construction and testing of the "hybrid"' T-stat has yielded some MPG increases.
 

josh8loop

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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
Just thought I'd check it since when I replaced it during the cooler months, I only achived 185F or so, and I was a little disappointed.
Anyhow, I'll pick up those t-stats this weekend and get them to you. I'll send a PM to you when I mail them.
DF,
I gotcha-sounds good. Just send the t-stats when you are ready, and when I receive them I will get them together for you like you mentioned. That will be good to hear your results also, especially since at that time we will both have 5-speeds(mine goes in this weekend if all goes according to plan). Bye bye and good riddence to that stinking 01M !! BTW, I am also going to 5 degrees advanced in Adaptation(at 3 now)- so that ought to help a bit too.
 

dieselfuel

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Dec 28, 2008
Location
ohio
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2003 Jetta TDI
I'm looking for a NB. I want to mod it with a Franko6 cam, Titan nozzles, and a wavetrac lsd. Not to mention a hybrid 'stat and Evans. :>)

Yeah, I know, one car at a time! But, I need a car to replace my '86 Cutlas Supreme. And my daughter wants a Beetle. Gotta set it up properly for her. lol!

I'll get those to you. I'm going out now. I'll e-mail you later today.
 

dieselfuel

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Dec 28, 2008
Location
ohio
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2003 Jetta TDI
Josh,

I have 2 13379's. The 13352's were out of stock. I oredered 2 and it will be a couple of days til I have them in hand. So, it looks like I will ship them to you next week.

Also, the guy at Advanced told me of a couple of places locally I might to able to source the Evans HDTC. Ye Haw!
 

josh8loop

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Vero Beach, Fl.
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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
When I went to see if I could get the 13352 it was out of stock also, and had to be ordered. Must not be too common. When you receive them, and before you pay for them take a close look to verify that all the parts look interchangeable on them between the 13379 and the 13352's. They should be, but you never know when a manufacturer is going to get crazy changing the design and throw a money wrench on our plans :)

Looks like my Wife's cancer may be back, this time in her right shoulder so I will be taking her to Shands hospital in north Florida on Friday through Sunday next week, and we will see if they are going to want to do a biopsy. Life can certainly be interesting at times! I should however have a second to get those T-stats put together for you when time allows.


Also, today I had the Vag Com hooked up to the car for the first time while also having the "Hybrid" 205 T-stat. It was interesting that my coolant temp sensor was reading about 7 deg C higher than my digital temp guage I installed. I had a feeling it was reading different, and this confirmed it. Also I kept track of my fuel temp. Starting out this AM it was 39.4 deg C, and peaked at about 54 Deg C after 40 minutes of driving. Not sure exactly just how much fuel temp change it takes to significantly effect timing on these cars, certainly something to look into. We don't want the car pulling back on the timing and taking our MPG gains away that the "hybrid" T-stat is giving us.

I also noticed that my transmission temp wasn't a whole lot hotter than it ran with the standard thermostat. It ran about 109 Deg C with the "Hybrid" stat VS 104 Deg C with the standard stat. My current transmission didn't like the hotter temps because it is in such poor condition. Guys with an 01M transmission in good condition, and equip with a new valve body would most likely be fine with the higher temp T-stat from my experience. I have however begun the swap to the 5-speed:D
 

josh8loop

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Vero Beach, Fl.
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2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
Fellow MPG seekers,


A while back I wondered exactly how much room there was behind our double valve thermostats and the engine block. Specifically how much space was between the rear thermostat bypass disc, and it's corresponding engine land area. This wekend while performing my 5-speed swap, and replacing the hard pipe coolant O ring(that is under the IP) I found my answer. I couldn't believe my eyes when I looked in there and could see the rear of the thermostat in all it's glory, and the matching engine land area behind it. If any one would like to post the photo for me, I could email it to you.


It looks like there is about 1/4 inch of room. This is vastly different(more) than what I expected to find. This means that the thermostat could actuate a full .250 " and just be to the point of closing the engine land area. Very interesting! It lets me know that the assembly of "Hybrid" T-stat dimensionality is less critical than previously thought. The next Hybrid thermostat I assemble for testing on my vehicle will be lengthened by .010-.020" to see if I can get it to hold right at 205 degrees. From my understanding of how this all works(which might be flawed) this ought to allow more coolant to be forced to flow through the radiator a little earlier(lower temperature) than my current unit which likes to stay anywhere from 205-209 deg F.
 

dieselfuel

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Location
ohio
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2003 Jetta TDI
Hi Josh,

First, I want to say I pray that your wife is o.k. You and her are in my thoughts and prayers. Keep the faith.

Second, good find concerning the space behind the t-stat.

And, how did that 5 spd swap go? I envy you! lol! That's a big project.

I think you'll be really have with the 5 spd manual trans.
 

josh8loop

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Sep 15, 2009
Location
Vero Beach, Fl.
TDI
2002 VW Jetta TDI Manual(performed 01M to 5-speed swap) - 183,000 miles and climbing!
Hi Josh,

First, I want to say I pray that your wife is o.k. You and her are in my thoughts and prayers. Keep the faith.

Second, good find concerning the space behind the t-stat.

And, how did that 5 spd swap go? I envy you! lol! That's a big project.

I think you'll be really have with the 5 spd manual trans.






DF,

Thanks for the thoughts, and especially the prayers! It is hard to keep the faith, and not have some bitterness about what my wife has had to go through. Thanks for the encouragement. The 5-speed swap is on going. I had some major setbacks when Fed Ex lost my package for 4 days. Thankfully it should be delivered this AM, but I won't be able to get the work done probably until next weekend realistically. Certainly didn't turn out the way I planned!

I am however looking forward to having a mnual and the fun/increased MPG that it will bring. One thing that is weighing on my mind is that I hope my work practices while installing the new real main seal were good enough and will not leak on me. Many guys have had issues with this installation from what I read. I would hate to have to remove the gearbox just to do rework.

Among the repair work I will have completed when this is all over includes:

01M to 5-speed grearbox swap
lower radiator hose replacement
coolant reservoir to hard pipe hose replacement
Oil cooler O ring replacement
Hard coolant pipe to block seal replacement
complete suspension refresh
E-brake cable replacement
front brake line replacement
brake fluid flush
PS fluid flush
crank position sensor O ring replacement
new rear main seal
New front brakes
and a few items Im sure I forgot :)
 
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