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TDI Fuel Economy Discussions about increasing the fuel economy of your TDI engine. Non TDI related postings will be moved or removed.

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Old April 11th, 2011, 13:03   #91
dieselfuel
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Can the fan temp operating be changed with the VDCS? Otherwise, a resistor would have to be used.

3% isn't all that great. But, the could be other hidden savings, like possibly, never having to replace your heater core, or your radiator. I understand the dash has to be removed to replace the heater core (what b***sh$%!).
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Old April 11th, 2011, 14:18   #92
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I know it's already been stated in this thread, but don't forget the effect of high temperatures like that on the engine oil ...

High temperature reduces the absolute viscosity, which reduces film thickness. In engines that are apparently sensitive to the viscosity (like the P-D's, which appear to be on the hairy edge with engine oils in the normal viscosity and temperature range), this COULD send it to the wrong side of that hairy edge.

In some applications, I'd be concerned about the temperature of the pistons, too.
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Old April 11th, 2011, 15:36   #93
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As far as 3% fuel savings, I'm guessing a TDI might do better than the big rig diesels- so many other factors, including mass, wind resistance, etc. in our favor. I hadn't thought of it, but Dieselfuel is right- running a zero pressure (waterless) cooling system means no heater core blow outs.

I know my fuel mileage on my 1.6 IDI spikes up on really hot summer days compared to winter mileage. In the winter, the best I've ever done is 46MPG. In summer, I get at least 55MPG when the temperature is over 85F over the exact same long distance route(I've often gotten over 60MPG) How much of that MPG increase is due to higher operating temps, and how much is from other factors,(warm air is less dense, hense less drag, tires are hotter/higher pressures=lower rolling resistance, etc) I don't know.

Regarding oil temperatures:
All oils have a specific continous duty operating range temperature stated by the manufacturer. For example, Mobil synthetics http://www.mobil.com/australia-engli..._v_mineral.asp are designed to be able to run continuously at 356F (180C). Since engine oil temperatures almost always stay within 20F of the coolant, running our coolant at 215F, 230F, or even higher, should not affect a properly rated synthetic lubricant.
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Last edited by Tom W.; April 11th, 2011 at 15:54.
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Old April 11th, 2011, 20:35   #94
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That's good to hear, Tom. I'm currently using Mobil 1 TDT!
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Old April 11th, 2011, 20:41   #95
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Brian,

I don't tow with my TDI, but iirc, someone here mentioned who does, stated their oil temp never got above 265F. Also, I think they stated their coolant temp never got over 225F.
I notice you have a bike. Do you tow it with your TDI? Have you ever recorded the oil and coolant temps? I'd be interested what they were.
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Old April 12th, 2011, 11:06   #96
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Ok, I got a 215F thermostat heat engine. These are custom made for Evans by (I think) Stant. Evans builds thermostats for their own research. Evans says the only problem they have run into with using a 215F thermostat is that you have to figure out a way to keep the cooling fan from coming on until 230F. They typically wire in a resistor into the fan temp sensor- just like Dieselfuel suggested.

I'm comparing it to the heat engine in a standard thermostat and it is dimensionally EXACTLY the same size, so it would be pretty easy to swap it into an existing TDI thermostat, for those who want to "build their own"

The rep at Evans indicated that you may be able to buy one for $15- The guy I talked to is David Wright- ph#1-610-323-3114 -he's technical sales manager in the performance dept.
Word of caution: Evans has these custom made, they currently have some in stock for their own projects, this is a custom part with limited quantity/availability.

Lets start heating things up!
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Last edited by Tom W.; April 12th, 2011 at 11:11.
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Old April 12th, 2011, 14:19   #97
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Good info, Tom, good info! I'll be calling Evans and see if I can purchase one.

Now, we need to see if the vag-com can adjust the temp at which the fan turns on.

Would blocking the radiator give the same affect? Assuming ou could get to 210-215F? What about just disconneting the fan altogether? (Again, I never tow with my TDI).

A few things to ponder, I guess....
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Old April 12th, 2011, 16:49   #98
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DF,

In the Bentley service manual in section 19-8, they mention the radiator fan thermo-switch operating temps:

Stage 1
Switch on .......................197-206 deg F(92-97 DegC)
Switch off........................183-195 deg F(84-91 Deg C)

Stage 2
Switch on ........................210-221 Deg F(99-105 Deg C)
Switch off.........................195-208 Deg F(91-98 Deg C)



On the ALH at least this thermo-switch is a three pronged on and off device mounted to the drivers side of the radiator that actuates the fan and it's respective speeds. Resistors in this simple on and off scheme wouldn't work. Don't be confused with the resistors others have placed in series or parallel to the coolant temp sensor that feeds the ECM. This doesn't effect the Fan speeds from what I can see in the schematics. We would have to create a simple adjustable circuit that would allow us to set our own temperatures for fan actuation.
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Old April 12th, 2011, 17:04   #99
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"Lets start heating things up"


I wish I wasn't having 01M transmission problems or else I would be HOT on my hybrid 205 Deg F thermostat testing and evaluation. For now I MUST be very careful with things.
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Now have Nokian Entyre Low RR tires!

Last edited by josh8loop; April 13th, 2011 at 04:43.
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Old April 12th, 2011, 17:35   #100
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Radiator temps and engine temps are separate components. I think the motor could run at 220 and open the stat and buy the time that coolant reaches the switch it would most likely be cool enough so that the switch would not go on. The radiator is always going to be much cooler then the engine if it is working correctly. This is assuming a moving car.
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Old April 13th, 2011, 09:24   #101
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You've now given me the information to feel fairly confident in the use of a 92*C ~ 198*F Thermostat in my AHU. The cool part is that they make a fan switch that matches this thermostat for my car.
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Old April 13th, 2011, 10:00   #102
dieselfuel
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I have a feeling, you could dis-able the fan all together, under most circumstances (NOT towing, though).

Again, this is assuming Evans HDTC is being used, as directed.
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Old April 14th, 2011, 09:17   #103
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Quote:
Originally Posted by G60ING View Post
You've now given me the information to feel fairly confident in the use of a 92*C ~ 198*F Thermostat in my AHU. The cool part is that they make a fan switch that matches this thermostat for my car.

Now you have me curious, would the T-stat for the AHU fit for an ALH? 92 Deg C would be better than my stock 87 Deg C I have in there now. Hmmmm.......
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Now have Nokian Entyre Low RR tires!
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Old April 14th, 2011, 09:54   #104
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I'm fairly certain it will work. http://www.germanautoparts.com/Volks.../Cooling/208/6
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Old April 14th, 2011, 11:01   #105
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Quote:
Originally Posted by G60ING View Post
You've now given me the information to feel fairly confident in the use of a 92*C ~ 198*F Thermostat in my AHU. The cool part is that they make a fan switch that matches this thermostat for my car.
Higher temp fan switch? could you find the part # and post it? Any idea @ what temp it switches on? TX!
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