[Fot] Oil temp

Enquiries Road & Track enquiries at roadandtrack.net.au
Wed Aug 25 15:49:55 MDT 2021 

i offer general comments from trying to understand this issue with modern
race engines, however in days gone bye , i had my share of issues with oil
pressures in race 2500 enignes

simplistically, high temperatures result in loss of kinematic viscosity and
therefore reducing both pressure and metal-to-metal protection

in extreme cases, molecular bonds can get broken and not fully or even
partially recover, so oil can be irrevocably "damaged" and the operator
cant tell that unless the oil gets tested

most oils are tested and rated at 90C, so about 200F. experiments suggest
about 250F is the point where most off-the-shelf oils can exhibit
significant degradation in many properties, especially kinematic viscosity

dont forget, the temperature at a contact surface could be momentarily (and
locally) much higher than what a probe in the sump might indicate as an
'average"

most oil suppliers will tell you if the oil temperature is much in excess
of water temperature, you need to address that

if a reliable sump probe is indicating the oil there is much over 220F, i'd
be doing more study to get to the bottom of the issue.

if you are trying to select an oil for a race engine, go looking at the
data on kinematic viscosity at  the 90C (test point)  and that will give a
clue to the oil that will best hold its viscosity at elevated temperatures.

Terry

On Thu, Aug 26, 2021 at 6:37 AM dustin nicholson via Fot <fot at autox.team.net>
wrote:

> Thanks guys, all the responses to the group and me individually are very
> helpful and appreciated.  My responses and summary:
>
>
>    - I already suspected the sensor or gauge were inaccurate, after your
>    responses I'm even more confident that's what's going on.  I will be
>    snaking a thermocouple down the dip stick tube right after shut down to get
>    a comparison reading.  If needed, I might also put the sensor in boiling
>    water to test accuracy.  One idea suggested is that if I have a 10V gauge
>    hooked up to 12V it could give a 20% higher reading therefore 290 degrees
>    is actually 232 degrees.  Y'all have no shortage of ideas I never thought
>    of.
>    - I will take your collective advice and add an oil cooler and high
>    flow thermostat to allow the oil when cold to reach temperature.  My
>    previous FP Spitfire didn't need one as it ran too cool with a huge cross
>    flow radiator even with the fan off (only used the fan on the grid).  I
>    guess TR3's are a different animal.
>    - There is no oil return line from supercharger near the oil temp
>    sensor.  I think that was the question from Mike H.
>    - I will be removing the supercharger and going back to SU's... at the
>    same time that I raise the compression and maybe swap to a lumpier cam.
>    But that won't happen until after a race weekend or two, CVAR Authenticity
>    Steward is giving me time to get compliant.  I don't want to give up the
>    supercharger power until I can gain at least some of it back!
>
> Thanks,
>
> Dusty Nicholson
>
> 1955 TR3 #72
>
> 1957 TR3 #43
>
>
> On Wednesday, August 25, 2021, 02:56:25 PM CDT, Barr, Scott <
> sbarr at mccarty-law.com> wrote:
>
>
> Hear, hear!  I don’t believe the gauge if you’re getting 170 measuring the
> pan and the pan is where the sender is for the oil temp.  I’d try a new
> sender and a new gauge before I tore it all apart.
>
>
>
> And you said it’s a race car not a street car??   Did no one else say
> “wait…..supercharger??”  I’m not one of those originality over all guys,
> and think a supercharger on a race car is a cool addition.
>
>
>
> Scott (B.)
>
>
>
> *From:* Fot <fot-bounces at autox.team.net> *On Behalf Of *Doug Mitchell via
> Fot
> *Sent:* Wednesday, August 25, 2021 12:57 PM
> *To:* dustin nicholson <nicholsondustin at yahoo.com>
> *Cc:* FOT Triumph <fot at autox.team.net>
> *Subject:* Re: [Fot] Oil temp
>
>
>
> Looking at the problem from another point of view, I would question the
> accuracy of the gauge. If you are seeing a 120 degree difference, something
> isn't right. Is the guage mechanical or electrical? If it is electrical,
> there could be a mismatch between the sensor and the guage. I'd try another
> guage if you have one.
>
>
>
> On Wed, Aug 25, 2021, 12:51 PM dustin nicholson via Fot <
> fot at autox.team.net> wrote:
>
> Amici,
>
>
>
> I'm sorting out a new to me race car and don't like that the oil
> temperature gauge reads around 290 degrees.  I've never had an oil temp
> gauge on previous cars so I'm not sure what's normal (240?) but 290 seems
> high to me.  Yes?
>
>
>
> More temp info:  Air temp is near 100 degrees.  Water temp is steady 185
> degrees.  Big aluminum radiator with electric fan.  No oil cooler.  Oil
> temp sensor is in the aluminum finned oil pan.  IR temp gun says the
> outside of the pan is 170 degrees.  Maybe the oil temp gauge is wrong?  I
> wouldn't expect such a big difference between the outside of the pan and
> the oil temp.
>
>
>
> Engine info:  mild engine, stock compression, fast road cam (270 is my
> guess), supercharger with the medium size pully, pump gas
>
>
>
> Maybe I'm worrying about nothing.  I just know that racing in 2 weeks at
> Eagles Canyon in Texas is going to be hot and I want to make it through the
> weekend.
>
>
>
> Thanks,
>
>
>
> Dusty Nicholson
>
> 1955 TR3 #72
>
> 1957 TR3 #43
>
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