Oil Temperature

[Davis]

What do you consider good oil temperatures? What impact (or relation) does water temperature have on Oil Temperature?

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#63ITB Rabbit GTI

[Bill Miller]

Davis,

I usually say oil temps in the 230* - 235* range w/ the water running 180* - 190*. That was both in my ITB A1 GTI, as well as w/ my l-p HProd car. Stock radiator w/ electric fan (only used on the grid/in the paddock) and a small oil cooler.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608

[Knestis]

I don't think I've ever seen an overcooled VW - where oil is concerned - but you want to be sure that it is at least 220*, so that it's hot enough to boil out any water that accumulates in the sump.

I've seen SSC Golfs go as high as 320* since they can't run coolers. I didn't put a guage on mine this season for exactly that reason - I didn't want to know how hot it was. http://Forum.ImprovedTouring.com/it/smile.gif

K

[Davis]

Looking at the second part of my question this morning, I don't think I worded it very well. I am trying to learn two things: 1) acceptable or desirable oil and water temperature ranges, and 2)if there is a direct correlation between water temp. and oil temp. i.e. if the water temp. increases 10 degrees the oil temp. increases "X" degrees. The answer to these questions leads to a further question to be asked later.

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#63ITB Rabbit GTI

[VW16VRacer]

You have a tough question for the answer I think you are looking for. Kirk and Bill are right on the oil temp, you need enough to burn off moisture but not too much to break down the structure of the oil. Oils are made to run at a specific temp. 200 to 250 is good for Mobil 1, so said one of the Mobil engineers to me, up to 350 is still ok so long as it gets changed on a more regular basis. With that said there is no clear forumla for the rise in coolant temp and the rise in oil temp. Oil is subject to more "direct heat" from the engine than coolant is, coolant is far easer to remove heat from than oil is. One of the reasons coolant has a wetting agent in it is to make it easer for the coolant to disapate heat in the radiator, it increases surface aera of the coolant to absorb in the engine and disapate heat in the radiator. One reason VW used the coolant to oil cooler is that you can remove heat from the oil with the coolant (larger surface aera in a oil to coolant cooler than a large oil to air radiator) and then the coolant can disapate that heat faster in the radiator, it is also more compact, cheaper to mass produce and was supose to be less prone to failure than a oil to air cooler, but many in my busness will argue the last point.

There is no forumla that I have ever seen that would give you the information you are looking for. The outside temp, how hard the engine is running, oil quality, oil quanity, cooling system efficiency are all factors that would change your results. My advice is to run some sort of oil cooler. If you are looking for the smallest radiator (lightest weight) possible to do the job I would look elsewhere to loose weight. If you are having overheating problems look into the flow through the radiator and run a thermostat. Coolant needs to spend a certain amout of time in a radiator to disapate the heat. A lot of problems are produced by removing the thermostat. I have seen cars overheat on long tracks because the coolant is moving so fast through the system that is can't loose the heat. We have run my car on the dyno and found a factory temp thermostat, in the Pacific NW, will actually increase fuel mileage. I went from 1 gal every 7 minutes to 1 gal every 9 minutes changing from the cold thermostat to the factory temp. I only use the cold thermostat in the heat of the summer at long fast tracks like Thunderhill in August or PIR in July. Others in hotter reagons will most likely use the cooler t-stats.

I run, on my A2 16V Golf, the factory oil cooler (euro-GTI) oil to air cooler filter mount and the cooler 911/944 oil t-stat, a 8"X12" cooler and the larger alum./plastic tank A/C radiator and have never had a cooling problems and don't ever worry about it. 195 to 230 coolant temps and 220 to 260 oil temps even when it is 103 out side temps.

Jon

[racer_tim]

Jon, I only run a hollow t-stat, that I removed the spring and the disc. It's basically just a washer to ack as a restrictor.

I run an oil cooler on my LP GP Rabbit GTI and don't have any problems with overheating at Thunderhill either.

The last race there this year, I was renting the car and he lost the fan belt about 1/2 way through the first practice. Water temps were around 240 and we just let the car cool down slowly before we added more water into the system. I'm VERY glad I decided to go with the syntetic Kendall GT motor oil. Oil temps didn't even go up when the water went to 240.

Also remember that the hotter the oil gets, the thinner it gets. As oil temps increase, pressure will fall.

Use all 3: water temp, oil temp, oil pressure.

Get a set of idiot lights and also point all of the gauges so that in normal conditions, all the needles are straight up, so a quick glance will tell you something is wrong, and do something about it, before you spin the #3 rod bearing, or overheat the head.

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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html

[This message has been edited by racer_tim (edited December 12, 2004).]

[Davis]

Thanks much for the information. It has helped me formulate some ideas, however this is the situation that prompted the question.

The engine is the 1.8, 8V. The car generally runs cool. Oil temp. in about 220 to 240 range, water temp. about 160. This past weekend the weather was cold and rainy in Arizona (Yes, it happens sometimes!). Oil temp. ranged between about 210 to 230. Once on the track at speed, the needle for the water temp. never left the peg....less than 140(?). I was going to block some of the radiator for the race to get the temp. up, but had two (more experienced racers/mechanics) tell me that as long as the oil temp. was where it was, I shouldn't worry about the water temp. I should just leave it alone.

From the answers given in this forum, it appears that I probably should have gone with my original instinct and blocked some of the radiator. Opinions?

Last part of this question relates to temperature and horsepower. It is my understanding that running cool reduces hp. Is this correct? If so, how much hp are we talking about with a difference of 20 degrees (say from 180 to 160, or from 160 to 140).

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#63ITB Rabbit GTI

[This message has been edited by Davis (edited December 12, 2004).]

[joeg]

Any and all internal combustion engines make more power when they are hot. In other words, if you could guarantee no detonation and temperature spikes, a consistent and steady 220-230 water temp would be ideal for power.

The problem is you cannot make such a guarantee. It gets expensive experimenting at those levels too.

You do not harm an engine by running it cool like running it way hot, but in a circumstance as what happened to you, you should change your oil and filter immediately after the weekend as the cool running may have diluted the oil with fuel and left condensation in.

Cheers.

Mont

[This message has been edited by Marzracing (edited January 10, 2005).]

[racer_tim]

Davis, I have controlled water temps by blocking off the grill with tape. Like I said in my earlier post, I don't run a t-stat, so if it's cold, I need to block off some part of the radiator with tape, to get water temps up to around 190 or so.



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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html

[Davis]

Marzracing,

Did you say you were from Mars or did I miss something.

You know I'm a "geezer"and don't understand things like "Bring it on Davis LMAO, ROTF". Tell me when I come in.

Thanks everyone (even the aliens)for the responses.

P.S. How did you get to be a "junior" member? It's been many years since you've been a junior anything!

[This message has been edited by Davis (edited January 05, 2005).]