![]() |
|
|
|
Registered
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
|
Transmission Temp Stickers - JackOlsen?
Hi Jack, based on the below post, I ordered some non-reversible temperature indicator stickers to see how hot my tranny really is at the track this weekend. I got the ones that look like the image below, but in 200-225-250-275. They have all kinds of different ranges and temperatures.
Question is: Where did you put your sticker? What do people think the hottest place you can put a sticker on the outside of a 915 is? sticker measures 29/32"x1 49/64" or about 23x45mm. I'll also report my results here after the DE weekend. Quote:
__________________
Andy Last edited by KobaltBlau; 08-31-2004 at 09:42 AM.. |
||
![]() |
|
Administrator
Join Date: Feb 2000
Location: Los Angeles
Posts: 13,334
|
I have some of those, too. But I've never used them. I have an oil-temp gauge on my tranny. The sender on mine goes under the drain plug, I believe.
__________________
Jack Olsen 1972 911 My new video about my garage. • A video from German TV about my 911 |
||
![]() |
|
Registered
|
does the tranny oil carry the most temp? if so, i would put it on the high tide line of the fluid. that way, convection will drag the hottest oil up to your sticker. (maybe i am overthinking this).
__________________
poof! gone |
||
![]() |
|
Registered
Join Date: Nov 2002
Location: Planet Eugene
Posts: 4,346
|
I think you should stick em all over and find the hottest exterior place.
One good bet might be where there is not a lot of wind gong past, but there is a lot of hot oil and meshing gears..... |
||
![]() |
|
Registered
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
|
I guess the real question is how much cooler a good spot like randy described (lots of hot oil and meshing gears) is than the gear oil itself. Hopefully it's within 20F so I can register 200 if it gets to 220F for example. any wild guesses on this?
__________________
Andy |
||
![]() |
|
Registered
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
|
bump
__________________
Andy |
||
![]() |
|
![]() |
Registered
Join Date: Nov 2002
Location: Planet Eugene
Posts: 4,346
|
"When you measure... you know." Lord Kelvin (aka Wm. Thompson, or Billy to his budds)
YOu can run a fine wire Tcpl down thru the vent hole - you don't want it caught in the meshing gears..... It would be very complicated to model the thermal profile from inside to outside - 20 oF is just a WAG. I wouldn't hazard a guess on this. On a camping trip with a bunch of other graduate students years ago (well, actually decades ago) it was very cold and we agreed the wine was too cold. So I decided to put it in a hot springs to warm up despite their claims it woud explode. After a moment the cork blew out, it tilted and sunk. Our only wine.... Back at the office I decided to model what happened (instead of working on my actual PhD project). It was susprisingly difficult, but I just couldn't stop -- and ater a several weeks of non-stop work I realized the answer was.... to give up. |
||
![]() |
|
Registered
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
|
Randy, thank you for your thoughtful input.
I take the story about the wine directly to heart. Really sounds like something I'd do. If my 200F (lowest) dot doesn't turn black this weekend, I won't really know much. In retrospect I would have gotten the same stickers that Jack has, starting at 175F. If something turns black I can at least start guessing. Maybe I can coordinate with Jack to put a sticker on the same place that I did, and compare it with his gauge readings. That might actually be useful to others using the stickers. Well, I'll try it this weekend, the ambient temps are currently forecasted in the low 80s. stay tuned!
__________________
Andy |
||
![]() |
|
Registered
Join Date: Aug 2002
Location: Galivants Ferry, SC
Posts: 10,550
|
Maybe grist for another thread....
Can/should we put these stickes on the body of the oil filters...to "really" see what the oil temps are ??? ---Wil
__________________
Wil Ferch 85 Carrera ( gone, but not forgotten ) |
||
![]() |
|
Registered
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
|
Similar heat transfer problem, but would also be interesting. I am planning to stick one to a head somewhere, but since it's not down by the plug it will be a pretty inaccurate CHT. If nothing else, sticking one on a head should show me that they work. you get 10 for $14.XX so it's not massively cheap to stick them all over the place.
__________________
Andy |
||
![]() |
|
Registered
Join Date: Nov 2002
Location: Planet Eugene
Posts: 4,346
|
Wil - no.
A sensor only measure the temperature of the SENSOR. Heat will travel from theoil thru the boundary layer, thru the metal of the can the filter is in and across the glue or subsurface fo the sticker to the sensing part of the sensor -- that is 3 resistances. They are in series so add them up. The temperature of the sensor (at steady state) will be the result of that input plus the exchanges from the surface of the sensor -- convective to air and it could be free, forced or mixed convection. Then there's radiative exchange with everything that is within the view of an ant perched on the sensor. We can neglect evaporation etc. to make it easy. Yeh it's easy.... Look for my wine bottle reminiscence posted on a thread here w/in the last coupla days. Best, - Randy |
||
![]() |
|
Registered
Join Date: Jan 2003
Location: MESA AZ
Posts: 505
|
I have used temp guages just like that on helicopter transmissions, and if you put 2 of them right next to each other, they can read differently. In my experiences, hey are not too accurate, so if you really want a good idea maybe you could put a few and average them. Just a thought
__________________
1967 912 2.7 1977 MGB (bright yellow) 1985 Honda Spree Moped (great for towing rollerbladers) A flute without holes, is not a flute. A donut without a hole, is a Danish. |
||
![]() |
|
![]() |
Registered
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
|
I put them in 3 places on the transmission, and 1 on the thick flange on one of my heat exchanger inlets just to make sure the stickers work (I'm sure they will, just a sanity check I guess). We'll see tomorrow...
__________________
Andy |
||
![]() |
|
Registered
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
|
Here's my report:
I placed stickers in 3 different places that I thought were out of the main airflow, but below the fill line of the transaxle. There are really not that many big flat places to put this kind of sticker. The stickers were placed: 1. on the dip underneath the diff housing, on the engine side to be mostly out of the airflow 2. on the passenger side of the end housing way out on the nose of the transaxle toward the front end of the car, but below the fill line 3. on the driver's side in a recess made for one of the bolts holding the main gear case to the differential, near the big differential thrust plate. I used the recess about on the level of the fill plug. these descriptions may be hard to visualize but if you look at the 915 it should be pretty obvious. Here were the conditions: DE at Second Creek Raceway in Denver 20 minute run sessions stock 3.0 engine aluminum case 915 swepco 201 in transaxle most of the track is run in 2nd and 3rd gears altitude is approx. 5000 feet, and humidity is very low, so any convection cooling is somewhat less effective than at sea level. ambient temp ~85F Results: all 3 stickers got gray on the 200F dot, they all looked the same. This means that the sticker itself got almost to 200F. In retrospect, I would have used the stickers Jack (Olsen) originally recommended, 175/200/225/250F instead of my 200/225/250/275F stickers. Based on Hayden (of Wevo)'s description in another thread of the fluid inside a splash lube trans being a torrent, this consistency across the stickers makes sense. The question, of course, is what is the difference between the fluid temperature and the temperature of a sticker stuck to the outside of the aluminum case? I would not be worried about dino gear oil temperatures under 235 or 240 (just my uneducated opinion), and I am making a totally wild uneducated guess that the difference between the sticker temp and the fluid temp is not substantially more than 20F. This is totally unfounded and could be totally wrong. In any case, I am willing to conclude that my gear oil temps are under 240, and I should not be too worried. I plan to try some synthetic gear oil next, which I've done a whole bunch of research on, which according to the expert is fine at temps up in the high 200 range. Stay tuned for a post on that in the next couple of months.
__________________
Andy Last edited by KobaltBlau; 08-31-2004 at 09:41 AM.. |
||
![]() |
|
Administrator
Join Date: Feb 2000
Location: Los Angeles
Posts: 13,334
|
Those results sound credible, to me.
I have heard that unlike motor oil, gear oil begins to break down at around 200 degrees, but I haven't been able to get confirmation of this by experts. If you're in the 200-225 range in 85 degree ambient with 20-minute sessions, then what's going to happen on hotter days with longer sessions? It would be interesting to see more testing, but it doesn't look like it would take too much to push the trans. temps into the 260 range I saw with my 3.6 and mag-case transaxle.
__________________
Jack Olsen 1972 911 My new video about my garage. • A video from German TV about my 911 |
||
![]() |
|
Registered
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
|
Thanks, Jack.
I agree with what you're saying that it wouldn't take much to get the temp higher. In my particular case I don't run much longer than 20 minute sessions, but ambient temps up to 95F or more are certainly possible, and could push the temps into concern zone. In other words, I think my results are consistent with yours considering the difference in our conditions and cars. The (very knowledgeable) tech I talked to at red line oils said that he would not be worried about their 75w-90ns in a 915 until the temps were above 285-290F. This probably has no bearing on what temps swepco 2XX are good for, and I have not run the red line stuff.
__________________
Andy |
||
![]() |
|
Registered
Join Date: Nov 2002
Location: Planet Eugene
Posts: 4,346
|
"what is the difference between the fluid temperature and the temperature of a sticker stuck to the outside of the aluminum case?"
- Ther is just no simple way to determine this. It is a very difficult heat transfer problem. Didn't I answer this before? You need to measure the oil temp with a small thermocouple. |
||
![]() |
|