engine oil temperature

Post by **dave friday** » 03 Oct 2008, 08:17

well..... what should it be,and ware to mesure it, my temp sensor is in the sump[gets up to 120c on a very long hill]most oil specks quote 100c a lot[viscosity] and i read that on one marine engine the oil temp fed to the bearings was adjusted to 180to 210deg f [optimum] and the return [after the bearings] was250+deg f.So should i/we be checking the oil temp at the oil feed to the bearings?[at the oil filter flange/high pressure switch?].
nice and sunny here!.

Post by **lambrettalee** » 03 Oct 2008, 09:41

mine runs between 84 > 97 on the gauge

Post by **dave friday** » 03 Oct 2008, 09:48

Hi Lee, where is the oil temp sender?.

Post by **Syncro G** » 03 Oct 2008, 12:58

My take on it is...
Measureing sump temp isn't that bad as its the reservoir used to lube/cool things. When you hoof it the bearing exit oil temp will always go up as its removing heat form components, but so long as it can still pickup nice cool oil from the reservoir (sump) its not too bad as this has enough thermal capacity to cool stuff (and it cool enough to act with corect viscocity). When the sump is hot however the oil starts off thin and without much cooling capacity so everything gets super hot and thin - lift off or cook it. 120deg sump temp is too hot, though that temp doesn't seem to be hard to achive in a JX without external oil cooler. Around 80-100°C seems to be the accepted optimum working range for oil.

I'm guessing the oil coolers (same place as filter) are after the oil pump and before the bearings? Depending on wether the oil presure switches are before or after the filter/cooler, it might not be possable to measure post cooler temp as it enters the bearings anyway, therefore the sump sender might be measureing vertully the same. This would also be as close to max oil temp you can get as it'll be cooler when it enters the bearings, post cooler. The hottest oil will be leaving the bearings but will quickly join the sump where the large volume will stabalise its temp, fastest way you can cool it I suspect so no easy improvemnts possable.

Like I say thats my understanding of it, what do others think? (I'm on the verge of fitting oil temp guage and external cooling).

Post by **HarryMann** » 03 Oct 2008, 14:36

Agree in theory and expectation that 85~ 100C would be ideal figure to run at...

I thnk we chatted about this in Devon, Dave? As it's used as a piston coolant and also runs through the turbo bearings as you know, it's going to get hot, paticularly at higher revs (more heat per second)

120C would be a good max to lift off and try to get some cooling going on. 130C and I'd really be wincing a bit but a good fully synth will stand that for a while, but not a good idea.

Currently, my 1.9TD with a 19-row cooler can be anywhere between 100C and 115C under normal (fastish) motoring in hot weather when well warmd up. It hit 120C once coming back from Spain through France, or thereabouts, but not for long.

My take-off is on top of filter housing, not the sump.
A good fully synth will give a bit more of margin and require less frequent oil changes despite the temps reached.

Oil pressure goes down almost inversely proportional to oil temp, that can be seen easily.

Having oil temp, oil press and EGT I now feel a lot more confident of where I am with this thing! Just got to put the inlet air temp gauges and senders on this weekend, T1 and T2, and I'll have a real instrumentation feast..

I drive on EGT with oil temp max over-riding that. EGT tells you immediately if the overall engine load changes, right down to a marginal gradient or wind change; oil temp tells you a minute or two later, but quicker than I would have believed!

Post by **Syncro G** » 03 Oct 2008, 17:06

Hows this EGT stuff work then? Can you get a nice little VDO guage for it? Is it expencive? Gonna do oil and boost first, but if it shows it stays cool it'd be rude not to give it a small tweek

.

Post by **HarryMann** » 03 Oct 2008, 18:12

Hows this EGT stuff work then? Can you get a nice little VDO guage for it? Is it expencive?

Thermocouple in the manifold, as near to middle of exit as possible, some put them after turbo, but then an allowance is made for reduction, so best before. AndS put his in side of manifold flange, mine's straight down through the dimple in the manifold collector above turbo flange, slightly angled... maybe have a photo. They usually fit into a ferrule, using an olive to create a gas seal, though I've found they don't come out that easy. Probe is directly in exhaust flow..

Gauges can be digital or analague, mines analogue up to 1,000C, guessing the gauge was about £40 and probe with a metre or two of s/s braid protection, about £30.

One thing is that the junctions from the probe to gauge should not be soldered, as the first joint is the 'cold' junction, and dissimilar metals can create 'another' working junction - so small crimped sleeves that push fir onto pins and hopefully the correct extension wire should be used.

It's a good gauge to have on a boosted and well-fuelled diesel, esp. a TD.

Mine's a Westach from AirworldUK (Bucks). Don't know if VDO make them or not, Andy Simpson has a digital EGT.

Some pictures of EGT here...

https://club8090.co.uk/wiki/Di ... nstruments

Post by **Syncro G** » 03 Oct 2008, 22:51

Cheers for that Clive, looks like a good place for instrements, not expencive eather, which to be honest I wouldn't have expected in an aviation market!
http://shop.airworlduk.com/exhaust-gas- ... s-29-c.asp
Gotta be analogue, the 2" round one doesn't look bad; 900°C enough? (it sounds enough

) Would need the screw in thermocouple rather than a clamped one I'd emadgine?
A bit of a toy though so I think it'll be a long way down the to do list.

Post by **HarryMann** » 04 Oct 2008, 00:39

Yes, 900 enough, I didn't know so went 1000...

Have looked down to see 950 before now, but only for a second or two, all down to fuelling setting.

850 reckoned to be about max long term

Peter's not expensive for aviation stuff, but as always, these bits add up!

Post by **dave friday** » 04 Oct 2008, 11:36

Thanks all,the construction of the sump sender i fitted [vdo]is a brass one ,seems to be a one piece unit so might be sencing sump metalwork +/- oil temp.The oil temp seems to follow water temp untill the oil gets hot enough for the water to oil cooler to not be able to cool the oil!.Most of the time the oil temp sits at 95/99c at55/65, its only on long hills it gets to 120c[approx].Harryman where did you buy your oil temp sender/s.
ta.

Post by **HarryMann** » 04 Oct 2008, 11:52

VDO one I think, but have to watch the size, there is limited space on top of the oil filter housing, might have had to reposition a pipe, I'll photo it... bit messy I seem to remember..

This might help...

http://www.cscoupe.org/tech/gauges/gauges.html

http://www.bus-boys.com/bbvdo.htm#tempoil