Hi everybody,i am in need for info on a thermostat choice for an A6 4.2l 2001(awn) vin.Searching the internet i came across three options for my car rated as follows :82 degrees Celsius ,87 degrees celsius ,92 degrees celsius .I am wondering what it's the best fit since coolant temp is stated to influence engine performance including fuel consumption .i also came across a post, but i don't recall if my engine was listed ,stating that stock thermostat was replaced with a higher temp one in order to reduce cabon built-up or something .I run stock everything and i prepare for a timing belt job .Any help on the matter is greatly appreciated .Thank you .

Edit by auditech79: Don't ever post your VIN number on an open forum, you would be amazed what a criminal can do with that.

 

I would go with OE style thermostat. 87 degrees if memory serves. I'm not exactly sure how using a higher temperature thermostat will help reduce "carbon buildup". Sounds like one of those urban legend things.

Are you doing the TB yourself? I wish you luck. My alternator went bad so I did the TB while I had it all apart. Was a real PITA. Took a LOT longer than I had hoped but I did have to take it all back apart twice. Once because I forgot to reinstall the oil dipstick tube (duh) and the second time because I didn't have the thermostat housing seated correctly and it started leaking when I refilled the coolant.

 

87 is a nice middle pick. The thermostat is just a gate that opens once the coolant reaches a certain temperature. I would probably go with the lowest temp but the small difference in temperature shouldn't really make too big a difference. you want to make sure you install it right, that's the tricky part.

 

Hi everybody and thank you for the responses i had no idea about the vin thing .Yes i am in the process of gathering the parts for the timing belt job ,i did not order the kit but i will use the same parts as the kit the difference is that i'll pay shipping twice .I will do the job myself i allready got the tools and half of the parts since i did not want to spend all the money at once ,i have the bentley manual and the procedure is described also in alldata ,i am in front of the timing belt the second time for this car cause the first time i changed only the belt ,everything was good but recently i discovered the belt verry loose ,so ill do the whole job this time ,last one lasted 30,000 miles .hope this will last double .Thank you and i'll keep you posted .

 

The hotter the internal temperature, the less fuel it requires, therefore the better it is on gas. The cooler the internal temperature, the more fuel it needs, therefore more horsepower.

You will have more carbon buildup with a cooler thermostat, by comparison, but you can minimize that by your choice of gasoline octane, etc.

I agree with everyone else that the middle choice, 87c, is the best option.

 

WoW I never knew that! I always thought the lower temp in the intake made the gas more dense and allowed more air/gas to flow into the combustion chamber when the valve was open. Not that a colder motor required more fuel.

In the olden days we packed the intake manifold with ice on our drag car to increase the density of the mixture and ability to get more air/fuel into the motor. A bit like thermal turbocharging.. Now I wonder if we were doing something wrong!

 

Youre right about the temperature effecting the air density. Due to thermal conductance the temperature of the block transfers to the intake manifold and thus the air. I don't think the temperature of the block has anything to do with the stoichiometry beyond air temp.

 

I know I'm right -- Just playing with Mr. cracker --

We used to block the water passages to the intake manifold to help keep it cool and iced down the carb and manifold between runs. In fact we even cooled the gas in the tank by pumping it thru a cooler full of ice when in the pits.

The blocked manifold made for a good racecar but it was hard for daily transportation.

 

I know that the subaru impreza wrx has a cooled air intake with a special tank with water that is sprayed on the radiator like air filter or something simmilar ,i'm sure someone knows about it .And again thank you all for the help.

 

Cooler = more dense, more fuel. The hotter your engine the less fuel it uses. Hotter engines are better for fuel economy, hence the factory's tendency towards this, and cooler engines are better for horsepower, therefore the hotrodders tendency towards cooler thermostats (or even removing the thermostat). Which is what I said before.