Performance Engine - Oil temps ???

[Shane Noone]

Hey Guys,

This is a subject that has raised it's ugly head again recently.  Over all my years of racing, I haven't ever heard anyone agree on am operating oil temperature range for a modified air-cooled T1 motor.

The only guideline's I ever had was that to use a remote filter and cooler with a thermostat in that typically opened to allow oil through to the remote cooler at a temp of around 70 - 80 degrees celcius / 158 - 176 degrees farenheit.

The next guideline was that a good quality mineral based engine oil would break down at around 120 degrees celcius / 248 degrees farenheit.

So, my question to all of you is what is an acceptable operating oil temperature range for our hi performance motors ??

Cheers,

Shane.

[tonybone]

Hi mate.
I'm guessing the oil temps are up now ! On the new build ?! What's she running at.?
Most will reply that head temps are more important as this alone can have a direct impact on oil temps!

Be back home to UK next week so will meet up and chew this one over!

Tony

[stretch]

Shane, I run my car on Millers CFS 15w 60.  According to the manufacturer you can run it at 125 degrees C continuously with a peak of 150 degrees C.

I'm not suggesting that an aircooled VW motor will run fine at these temps, but, as far as I see it, as long as I stay below 120 degrees C then i'm not adversely affecting the oil.

As for head temperature, that's a whole different argument.

What temp does your car run at on a decent journey?

[Bruce]

Do you run an oil cooler inside the fan shroud?
What is your oil's temp?

[Shane Noone]

Hey Tone, actually oil temps on crusing speed typically 3-3500 rpm's ( 50 mph ) max is around 95 degrees celcius / 203 degrees farenheit - climbs to 100 C / 212 F and I don't let her get any hotter - at that point I'm using the electric fan over the external cooler to pull heat out of the oil there....but I agree head temps are the crucial factor -then again what should the head temps be ?? there seems to be even less information.

Martin, yeap the millers CFS is good stuff and it had more longevity at higher temps as a full synthetic versus your typical mineral oil.

Bruce, Yes I run the standard doghouse set up plus the external cooler fan assisted.

Interestingly from other feedback on a UK forum a selection of guys running various 2 litre motors with various cams and compression ratios all report similar crusing oil temps between 80 C / 176 F at the low end and 105 C / 221 F at the high end with most seeing an average of 95 C / 203 F.  That's kind of curious isn't it ?

Two articles I came across, one suggested Gene Berg research listed the safe upper oil temperature at 113 C / 235 F and that anything above this would cause engine studs to come loose, case halves to warp along the sealing edge and premature bearing wear...

Second article was listed figures from VW for their air-cooled industrial engines. This suggests a normal healthy range to be between 170 F and 220 F / 76.6 C and 104.4 C
Engines running warm to hot at 220+ F and 250 F / 105 C to 121 C
Engines above this running critically too hot.

So has anyone else on here got any information on safe operating oil temperature range ??   Or even safe operating Cylinder Head Temperature range as this is also crucial for maximum performance from our motors...

Cheers

Shane.

[javabug]

A pal and I have been discussing this stuff in depth lately. Here's something he's come up with:

Oil temp min:             130 degrees F
Oil temp max:                        220 degrees F (measured at sump)
Oil pressure min:       10 lbs/1000 rpm
Oil pressure max:      80 psi
CHT cruise:   350 to 375 degrees F
CHT climb:                 450 degrees F

This is from a spec sheet from Revmaster. http://www.revmasteraviation.com/

There's so much (mis)information out there you have to be careful who to believe. We've found a lot of info in the aviation world that I would take as trustworthy. Think about it — if those guys get something wrong the stakes are pretty high.

I don't run an oil temp gauge in my car yet, but I do have the standard VDO CHT setup. Another thing to keep in mind with gauges is there's what, at least half a dozen different places to put an oil temp sender on our cars? Each one will give a different reading. Use the gauge to be sure there aren't big, unusual changes that indicate something has gone wrong. If you're trying to monitor and keep your oil exactly 188ºF in the middle of the sump to the left of the pickup tube, you're just going to drive yourself crazy.

Too high or too low will indicate problems. If you're within the correct range, I'd say you're good to go.

[Shane Noone]

Good Info Mike. Think it's generally agreed as you mention to use temperature's taken at the sump ( bulk of oil ). I have also seen cautionary advice about innaccuracy of " most gauges " typically reading 4 - 10  degrees C low between 100 - 130 degrees C.....this will drive you nuts straight away.

Personally I have had several different hi performance engines of various specs driven on the street and run at the strip, from 1835cc to 2276 to 2332 cc. All quite different combo's of parts. Compresson Ratio has always been set between 10 - 12:1 and strangely the oil temps I have observed using the same sender type ( VDO dipstick ) and electric VDO gauge typically showed a cruising temp between 90 - 100 degrees C / 194 - 212 degrees F climbing to 105 C / 221 F on a warm air day say in the 70's F  - If it climbed to 110 C / 230, then I would be worried and find some way to try and cool possibly drop into 3rd gear to increase fan speed at the given road speed.

Mike, when you say you have the standard Cylinder Head Temperature kit in place - what exactly is that kit ?  For example, is it the VDO ring that sits under a spark plug and wires to a gauge

Cheers

Shane.

[javabug]

Shane, yes the VDO with the ring on #3 spark plug. In addition to the situation that those gauges are only truly accurate at I think 70ºF, another thing the airplane crowd says is that the spark plug-ring style sensor tends to read about 40ºF hotter than a gauge with the sensor in a dedicated boss in the head casting.

[Neil Davies]

I used that CHT gauge set up, but had the sender on #3 top head stud, held to the stud with another nut.I knew that it wouldn't be the same reading as under the plug, but I wanted to be able to have the plugs all projecting the same amount into the combustion chamber. As for gauge readings, I can't remember, but it did bother me that the one gauge was in F and the other was in C!

[benlawrence]

Ive never in my life bothered with oil temps i ran a gauge for about a week once and found that it just made me paranoid driving the car i disconnected it and never looked back, the last stroker did thousands of miles with no issues the new one gets marginally warmer but never gets hot enough to concern me and will cruise on the motorway at 65 for mile upon mile, i always worked on the principle if you weld your finger to the dipstick when pulling it, its too hot 

[leec]

Surely location of your oil temp sender will have an effect on the reading as well?
Lee

[benlawrence]

Surely location of your oil temp sender will have an effect on the reading as well?
Lee

I had many a discussion with my builder and freind dave about this, i ran mine in the back of the sump, he ran his in the dead spot in front of the oil pressure switch, we didnt get a chance to compare temps as i'd junked mine a long long time ago, but his ecu needs a temp sensor, funnily enough ive just been for a real hard drive lots of redline, 4k rpm cruising on the motorway 20 mile round trip, pulled it into the garage fan was running (80 degs stat) but clicked off after a few seconds of switching the motor off, inside the engine bay was warm but not hot dipped the oil and it was tepid, Ive had an aircooled vw in varying guises on the go for the best part of 23 years the only time i came near to cooking a motor was an old 1914 in my 64 back in 95 when the cheap nasty repro tar board on the firewall distorted and got sucked to the back of the fan housing, luckily i could feel the motor going soft and i pulled over on the motorway, lifted the lid and it was roasting, i tore the tar board out and threw it in the back seat but that wasnt before i burnt a huge blister into my finger from pulling the dipstick!!!! the motor survived but you could say that theres the perfect excuse to install a gauge, but if you have any amount of mechanical feel for your car then you know when its getting hot, the only guage i swear by is oil pressure. One day i may live to regret it but hey ho 

[Andy Sykes]

I guess sensor placement is key but that all depends on how you log it

1 bottom of the case you are getting a lot of heat soak
2 oil return you are getting the temp drop on your oil cooling
3 in the head not a true temp

I think you won't get a true reading from one you may need an average on more than one ? I do a lot of work in BMS and we always take an average of more than on sensor. But I guess you are only talking a few degees difference from where ever you measure it on our engines

[richie]

This is only a theory, but if it takes X amount of hp to move a bug at Y amount of weight then it will produce Z amount of heat to make that hp, so basically the oil temp will be very close at a given mph cruising regardless of engine spec?

cheers Richie

and if you measure oil temp in the sump how do you know what temp it is actually going into the engine? particularly if you have a remote cooler? what matters is the temp/viscousity of the oil the bearings etc see surely?

[dragvw2180]

 I wonder how hot the VW beetles run in the arab countries as an example where temps can climb WAY over 110 degrees and cars are driven every day with nothing other than all factory sheetmetal for cooling ? Mike McCarthy

[modnrod]

I wonder how hot the VW beetles run in the arab countries as an example where temps can climb WAY over 110 degrees and cars are driven every day with nothing other than all factory sheetmetal for cooling ? Mike McCarthy

All standard 1584 TP doghouse late models run OK at 70mph until conditions get to 110F and under 15% humidity I've found. Over here I normally see oil temps start to continue to climb well over 100*C when conditions get worse than this, and slowing down doesn't help much (fan speed drops). Pancake motors this happens at 10F less. Baja bodywork at the back adds another 10F temp capability at least. Big oil coolers each side of the gearbox work well until you throw a few rocks through them, so for me that means they work well for about 6 miles! 

I had to get home from down south a bit once in the good old days when I lived in the Northen Territory (tropics), and had 80MPH+ in a Squareback for over 30mins during the wet season. Temps were 110F-120F but with 80% humidity, and the oil temp hovered around 120*C for the whole trip.
I always used a good oil.........