Modified Thermostat for higher MPG's...

Pat Dolan · Oct 19, 2011

josh8loop said:
DF,

There is actually only one coolant temp sensor on the engine which lives in the coolant outlet flange just underneath the vacuum pump. It feeds it's signal to the cluster, and ECU to my knowlege.

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Josh:

First of all, please let me congratulate and thank you for an excellent thread. Took me a couple of days to find time to read it all, but not a minute of that was wasted time.

Have you, or anyone else found the way that the ECU drives the coolant temp guage on the panel. I am totally frustrated with the lack of temp sender resistance vs. temp values from Bentley. Be nice if that showed up somewhere.

The axle shims you need WERE listed at Bildon Motorsport (I used some on my daughters A3). Maybe try calling them http://en.wikipedia.org/wiki/Comparison_of_the_health_care_systems_in_Canada_and_the_United_States

Was going to try the NAPA UNR 33209 thermostat - but it is only 90C-195F. Will hold out for at least 92 degree Behr or better yet a 95 if anyone can find such an animal from any manufacturer. Our OEM thermostat died in 7 years on ALH, but the VW replacement did not last another year (dont really know why I bought one from them, can not remember manufacturers mark either).

Of course, the big deal out here with thermostats is interior temp - heater performance. With 87 degree stat, it sucks in MkIV.
Regards - Pat

josh8loop · Oct 19, 2011

robnitro said:
Page 38 to 43 on that PDF.

Rob,

Thanks-I needed that!

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josh8loop · Oct 19, 2011

Pat Dolan said:
Josh:

First of all, please let me congratulate and thank you for an excellent thread. Took me a couple of days to find time to read it all, but not a minute of that was wasted time.

Have you, or anyone else found the way that the ECU drives the coolant temp guage on the panel. I am totally frustrated with the lack of temp sender resistance vs. temp values from Bentley. Be nice if that showed up somewhere.

The axle shims you need WERE listed at Bildon Motorsport (I used some on my daughters A3). Maybe try calling them http://en.wikipedia.org/wiki/Comparison_of_the_health_care_systems_in_Canada_and_the_United_States

Was going to try the NAPA UNR 33209 thermostat - but it is only 90C-195F. Will hold out for at least 92 degree Behr or better yet a 95 if anyone can find such an animal from any manufacturer. Our OEM thermostat died in 7 years on ALH, but the VW replacement did not last another year (dont really know why I bought one from them, can not remember manufacturers mark either).

Of course, the big deal out here with thermostats is interior temp - heater performance. With 87 degree stat, it sucks in MkIV.
Regards - Pat

Pat,

Thanks for the kind words, much appreciated! I have been trying to figure out the whole CTS and resistance thing also, also how it integrates in the system. The info Rob mentioned in his link above, pages 38-43 may help you a bit too. I'm having trouble viewing PDF's from home right now, so I have to view it from my other access point. I've never tried the Behr thermostat, but it's supposed to operate a little higher in temp. If you try it, it would be interesting to gather that info. As far as I can tell, the Behr 92 C unit is the highest you can get without making your own "Hybrid" unit. Do you make consistent driving trips frequently that you use similar driving techniques on?

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Pat Dolan · Oct 19, 2011

The TDI is actually my wifes DD, but is indeed used very consistently. At the moment, my VCDS cable is missing, so I can not get that data until it turns up. However, the problem with insufficient cabin heat is so obvious, THAT part will be immediately obvious by where the temp gauge sits and how the interior feels.

josh8loop · Oct 19, 2011

josh8loop said:
Just for informational purposes, if someone wanted to replace their thermostat and didn't want to experiment with the "Hybrid" construction method, and good second choice might be:

http://www.autopartswarehouse.com/sku/Volkswagen/Jetta/Behr/Thermostat/2002/TDI/4_Cyl_1-dot-9L/BEH117392300.html?tlc=Engine+%26+Drivetrain

That would give you 197.6 deg F (92 Deg C). This is the highest direct fit type that I have found for the ALH engine. Most replacement T-stats from Wahler and other OEM brands seem to only go to 87 Deg C(188.6 Deg F) The Behr unit mentioned above seems to be of a good sturdy construction, and may possibly out last Stant types FWIW.

Pat,

Thought I would drag this back up in the Forum-This is probably the one your talking about. Also, since ou guys are so far north, and super cold up there, I would think you would most likely never be able to get the 205 from the "Hybrid" T-stat. Even in Florida with 75 degree mornings and doing 50 MPH I have a hard time maintaining 203 on my digital in line thermometer. If I go faster than 60 or so, I can then reach my 205 plus temps. For you, I would think radiator blocks for certain times of the year, and also perhaps super insulating the engine compartment might help you retain coolant temps by keeping air flow through that area to a minimum. FWIW

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boertje · Oct 19, 2011

josh8loop said:
OK, gotcha-just using the ATF as gear box fluid. Next time I change my gear box fluid I will go w/ the VW stuff myself. As far as the tire wear, it appears that I am going to need to shim the rear passengers side spindle to get it corrected. Trying to find out the particulars on that right now as far as where to get the shims, and whether or not the bearing will need to be replaced when I do it. I'm fairly sure it will need replaced though.

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Josh, FYI, that gear box you have had G070 VW fluid in it while I had it. Shifting was velvet smooth at all temps.

dieselfuel · Oct 20, 2011

Later today, I'll take temp readings with mu vcds. Now that's it's between 45-65F ambient temps, I'm curious as to what coolant temps I'll see.

As a side note, the car seems to warm up faster with the hybrid stat. Does that make sense...?

I'll post my findings later today.

Pat Dolan · Oct 20, 2011

dieselfuel said:
Later today, I'll take temp readings with mu vcds. Now that's it's between 45-65F ambient temps, I'm curious as to what coolant temps I'll see.

As a side note, the car seems to warm up faster with the hybrid stat. Does that make sense...?

Yeah, it does. The 87s seem to start opening somewhere even lower than that, and IMHO it seems a lot of the leak a fair bit. It doesnt take much flow to stop the warmup process dead in its tracks.

Just for reference: the WARMEST cars bar none I have ever owned or driven was a pair of Jetta MkII TDs that we ran to 500 and 650k kms. They were not only very warm, they were warmed up to comfortable heater output in even less distance than our similar 1.8 gassers (we tend to rate out cars and trucks heater capacity by how far from the house towards the big city it takes before you can feel the relief coming out of the vents on a -40 day - and the old Jettas would do that in 2 - 3 kms, the MkIV takes over 10km and NEVER gets really comfortable on a cold day.

Tom W. · Oct 20, 2011

ditto that on mk 2

Pat Dolan said:
Yeah, it does. The 87s seem to start opening somewhere even lower than that, and IMHO it seems a lot of the leak a fair bit. It doesnt take much flow to stop the warmup process dead in its tracks.

Just for reference: the WARMEST cars bar none I have ever owned or driven was a pair of Jetta MkII TDs that we ran to 500 and 650k kms. They were not only very warm, they were warmed up to comfortable heater output in even less distance than our similar 1.8 gassers (we tend to rate out cars and trucks heater capacity by how far from the house towards the big city it takes before you can feel the relief coming out of the vents on a -40 day - and the old Jettas would do that in 2 - 3 kms, the MkIV takes over 10km and NEVER gets really comfortable on a cold day.

I have a mk2 D, and I can feel heat on my feet before I get out of the neighborhood(slightly less than 1 mile) - whereas the MK4 TDI I don't feel heat until somewhere around mile 3-4.

Josh, thanks for this loop. You're the man!

dieselfuel · Oct 20, 2011

Well, I'll say this: My wife always complains there isn't enough heat. Now, with the hybrid installed, she's always complaining it's too hot, lol!

Ah, you know women, can't live with 'em, can't live without 'em. LMAO!

dieselfuel · Oct 20, 2011

O.k., just came back from a 20 mile drive, city and highway.

Ambient temp: 6.7C (44F)

Highest Coolant temp (via VCDS) 108.9C (228.02F)

I believe if I would have kept driving, I would have seen the 109.7C that I recorded in the summer with the A/C running. And, I did have the heat on about mid-way on fan setting 1, during todays test.

Looks like the TDI's are really effecient and stable, no matter what the ambient temps are.

josh8loop · Oct 26, 2011

Tom W. said:
I have a mk2 D, and I can feel heat on my feet before I get out of the neighborhood(slightly less than 1 mile) - whereas the MK4 TDI I don't feel heat until somewhere around mile 3-4.

Josh, thanks for this loop. You're the man!

Thank You

Having input from you all really helps things along!

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josh8loop · Oct 26, 2011

Recently got a ScanGuage2 for my car. I've been watching the temps reported from the CTS. Most driving my SG reports engine temps of around 206-207 Deg F. Looks like it is reporting 4 degrees higher than my digital inline coolant temp indicates. Maybe sometime soon I will play with CTS signal and FTS sensor signal alteration.

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dieselfuel · Oct 26, 2011

Josh,

Do you own a VCDS...? It would be nice to compare the two. I wonder if the VCDS is recording a different temp than the CTS.

I'm running 225-230F, in Ohio during the fall, and you're in Flordia and running 207F...? We both have the "same" t-stat...

josh8loop · Oct 26, 2011

dieselfuel said:
Josh,

Do you own a VCDS...? It would be nice to compare the two. I wonder if the VCDS is recording a different temp than the CTS.

I'm running 225-230F, in Ohio during the fall, and you're in Flordia and running 207F...? We both have the "same" t-stat...

DF,

The SG is reading the same temp information the computer would see, so the temperatures would be the same. From what I see here, it looks like the max I have seen with my setup is around 218 Deg F. I had a strange feeling a while back that your T-stat might have been running a little higher than mine for some reason-that's why I questioned you about it. Maybe a slight variation in the heat engine portion of the T-stat or an overall length difference. By the way, do you still have the box that T-stat came in that I put together for you? It has some numbers on the inside lid of the box-what are they?

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dieselfuel · Oct 26, 2011

Still have 'em. I used the one that you thought was the highest temp, "B" iirc.

In the spring, I'll switch to the other hybrid and see what temps I get.

What are your thoughts....?

josh8loop · Oct 27, 2011

dieselfuel said:
Still have 'em. I used the one that you thought was the highest temp, "B" iirc.

In the spring, I'll switch to the other hybrid and see what temps I get.

What are your thoughts....?

DF,

On the inside of the thermostat box for the thermostat you have installed in your car are some as found and as left numbers. Could you post them?

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dieselfuel · Oct 28, 2011

josh8loop said:
df,

on the inside of the thermostat box for the thermostat you have installed in your car are some as found and as left numbers. Could you post them?

..

"b"

1.154

1.158

josh8loop · Oct 28, 2011

dieselfuel said:
"b"

1.154

1.158

Well, that's darn near exactly what my numbers on mine are too. I was pretty sure I matched exactly what I did on mine, but figured I would double check any how. I wish I had some time to do a bit more experimentation with mine. I would like to lengthen it a bit and reinstall. I believe with a longer rear bypass section it will force more coolant through the radiator a little earlier in it's actuation which will cause the engine to run a bit cooler. I found that there is about .250" behind the rear bypass disc when it's at room temperature. In that instance it's easier for the coolant to take the bypass loop instead of going through the radiator loop. With a slightly longer unit(.020") or so, the coolant would rather go through the radiator a little bit sooner.

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dieselfuel · Oct 29, 2011

I'm fine with my hybrid in the cooler months. Late next spring, I'll try the other hybrid to see what temps I get.

What I need to know is, does high coolant temps and advanced timing harm a TDi engine.

And, does a higher coolant temp retard timing, or is timing taken from fuel temp...?

I was talking to a guy who mods gaasers (Mustangs, Corvettes). He mentioned that he uses a lower temp t-stat and gives the engine lots of timing. When I inquired why he uses a lower temp t-stat, he said that high coolant temps with lots of timing will kill an engine. He has an 09 vette and uses a 160F t-stat (stock, I believe, is 108-190F).

Anyhow, if the high temp is alright with the ALH and a performance tune, I'd like to be able to fool the ECU into not cutting back (retarding) timing due to high coolant and/or high fuel temp.

Later on, I'll check my fuel temp, I can't remember what temp I was getting after I installed the hybrid and was recording coolant temps of 230+F.

robnitro · Oct 29, 2011

I don't believe your fuel temp will change much from a normal T stat.

I used a stant from metalmanparts (around 93-98C on vag com) and I noticed that even when idling in cooler weather (50-60F) the fans come on for a short period now and then. I'm wondering if the set point for the fans can be changed, or is it because when the thermostat opens, the coolant is so hot already that the sensor inside the radiator demands the fans to come on, unrelated to engine temp?

dieselfuel · Oct 29, 2011

Alright, here what I got :

Ambient temp: 50F

Coolant temp: 107.1C

Fuel temp: 43C idling; 33.3C while driving

TDI Timing graph: Fuel temp: 137 (I'm assuming F); Timing: 50 (just under the middle blue line.

I was surprised of the timing. I thought it was too low.

robnitro · Oct 29, 2011

Timing is best around 70, it's just the static timing which won't advance your timing under load (unless you mess with adaptation ch 04). I have mine set to 80, and it really only affects the lowest timing I can get at idle (around 3.5 btdc).

Ski in NC · Oct 30, 2011

ECU might retard timing with high coolant temp as part of NOx control. Use vcds to monitor timing degrees btdc as engine warms up. See if timing drops as coolant temp rises up to tstat open temp. Preferably do this while cruising steady speed on a flat road. If timing drops, that may take away some advantage of the higher coolant temp.

Gassers like cooler temps as their concern is preignition or detonation, all which come on sooner with higher temps and timing advance. No such concern on a diesel.

dieselfuel · Oct 30, 2011

Update: Realized I used the default graph when I checked the timing yesterday. Re-checked it today with proper graph ahd it was : Fuel temp 110 Timing 55 (dead on!) just above the center blue line.

dieselfuel · Oct 30, 2011

Ski in NC said:
ECU might retard timing with high coolant temp as part of NOx control. Use vcds to monitor timing degrees btdc as engine warms up. See if timing drops as coolant temp rises up to tstat open temp. Preferably do this while cruising steady speed on a flat road. If timing drops, that may take away some advantage of the higher coolant temp.

Gassers like cooler temps as their concern is preignition or detonation, all which come on sooner with higher temps and timing advance. No such concern on a diesel.

Where in the VCDS should I monitor this...? Measuring blocks, adaptation, basic settings...? What group...?

Thanks,

df

dieselfuel · Oct 30, 2011

Would it be possible to graph timing in relation to coolant temp...?

Ski in NC · Oct 30, 2011

Its in the measuring blocks, somewhere in the first few. Shows requested and actual timing in btdc or atdc.

dieselfuel · Oct 30, 2011

Alright, I'll give it a shot and then edit this post with my results.

df

Edit: Inconclusive. Couldn't find the channel you were referring to. I used channel 5 in measuring Blocks. Between 40-107.2C coolant temp, the timing may have been cut back 3-5 degrees (16.9 btdc to about 14 degrees btdc at 107.2C).

So, I'm not really sure the timing is being retarded due to higher than normal water temp. I think the preceived loss of power I was experiencing a few months ago was due to heat soak. With the coolant temp being 109C and the ambient air temp being 90F or so, and high humidity, IAT was probably causing heat soak. IAT today is around 70F, ambient air temp is 50F.

So, when ambient air temp was 90-98F, the IAT was probably at least 110-115F.

df

Growler · Nov 24, 2011

Originally Posted by josh8loop View Post
Just for informational purposes, if someone wanted to replace their thermostat and didn't want to experiment with the "Hybrid" construction method, and good second choice might be:

http://www.autopartswarehouse.com/sk...&+Drivetrain

That would give you 197.6 deg F (92 Deg C). This is the highest direct fit type that I have found for the ALH engine. Most replacement T-stats from Wahler and other OEM brands seem to only go to 87 Deg C(188.6 Deg F) The Behr unit mentioned above seems to be of a good sturdy construction, and may possibly out last Stant types FWIW.

I installed one of these MK2 high temp thermostats today. VCDS says on a 20 mile loop to work & back, got up to 93.2C so it seems to be working properly.

THanks for the idea guys. Ill keep an eye on my mileage. I am hoping to improve my poor mileage.

aaron

Modified Thermostat for higher MPG's...

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