Lotus Elan

Oil Temperature Gauge

PostPost by: type26owner » Sat Feb 07, 2004 4:34 pm

There's an oil pan drain plug which is being listed on Ebay for the Elan which appears to be a thermistor. Anyone know the specs? How did you arrange the permanent mounting of the gauge in the cockpit? What brand of gauge? I've looked into the all the possible Smiths dual gauge combinations and could not come up with a way to free up an existing hole in the dash. :(

With hindsight I should have had two extra 2" gauges holes instead of just one added to the dashboard I had built. The one was for an electrics voltage guage. I've had numerous alternator failures due to overheating but have never been stranded with a dead battery. :)
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PostPost by: BillGavin » Sat Feb 07, 2004 5:12 pm

The previous owner of my S2 built a custom dash for it, with extra gauges in place of the radio, and added an ammeter and an oil temp gauge. If I ever get my new panel built, I plan to mount two gauges on each side like a +2S - space is tight, but I think there's room: if not the ammeter will be deleted. If I were you, I'd just lose the voltage meter.

My sump is modified with side extensions: the oil temp bung is on the rear panel of the RHS extension. On a normal pan, I'd probably put it on the RH side near the rear of the sump, about an inch and a half or so above the bottom of the sump - just high enough to get the bung onto the flat part of the side of the pan. Even though the run is shorter, the LHS is out due to the proximity of the exhaust system. Even though the sender will be well forward, I wouldn't put it on that side, for reasons of both heat and accessibility.
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PostPost by: type26owner » Sun Feb 08, 2004 1:35 am

Hi Bill,
The sender I was mentioning is fitted in the drain plug and does not require any modifications to the pan. So you think monitoring the oil temp gauge is more important then the electrics. I would still have the ignition light to rely upon. I'm leaning in that direction since my alternator failures have ceased since I added thermal shielding from the exhaust.

Jay at JAE has stated that the twincam oil temp tends to run on the coolside. Is this your observation too? Most oil manufactures recommend a minimum of at least 190F.
Thanks for replying,
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PostPost by: BillGavin » Sun Feb 08, 2004 12:58 pm

It's not that I think that monitoring either is all that important. If you have the alternator and the warning light works, that should be enough. IMHO Ammeters are useful with a generator where you could easily exceed its capacity, especially at low revs, and still not see a warning light. With an alternator you should never come near its capacity, so an ammeter isn't very useful. My ammeter rarely moves noticeably and I've been thinking of removing it.

Given where you live, and the mods you have done and are doing, verifying that oil temp is safe is a good idea, but I think you'll find that your oil temp won't be a problem, except possibly on long highway trips. I use my oil temp gauge along with the oil pressure gauge to determine when the engine is warmed up enough to stop babying it - at about 140F the oil pressure drops from 80+ to a more comfortable 65psi.

My oil rarely gets over 140F. On the highway it might get as high as 190F in the summer: I can't recall ever seeing a reading over 200F. I have a modified pan, but only one more quart of capacity, and no oil cooler. I have a high pressure, high volume oil pump with spin-on filter.

I had been using Kendall GT1 20/50, but switched to Valvoline 10/30 when temps cooled off in the fall, in an attempt to get the oil to flow better and warm up quicker in the morning - only made a small difference when cold, no difference when hot. I'm not sure what I'll use for oil this year. I've also been considering reverting to a standard oil pump, or one with just the higher pressure.
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PostPost by: type26owner » Mon Feb 09, 2004 4:49 am

Bill,
Actually I'm worried my oil is running to cold. Evidenced by my oil gets jet black within just 500 miles. 140F is not enough from what I've read to heat activate the polymeric plastic thickener in most multi-viscosity oils or keep it clean. Suspect there's also a few horsepower to be gained if the oil is heated to the recommended 190F minimum.
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PostPost by: BillGavin » Mon Feb 09, 2004 12:46 pm

That's the reason I'm thinking of removing the ammeter and keeping the oil temp. I can use the oil pressure gauge and the water temp gauge, but I like having the oil temp gauge, since oil temp lags way behind water temp. Since you're talking an electrical gauge, you could wire it up and just put the gauge in the glove box and check it when you have a question, or hang it under the dash on a temp mount.

Condensation and sludging isn't a problem for me as I rerely get over 3K miles per year, and I change oil at least twice a year. I don't use the car much for really short trips, so it gets pretty well warmed up whenever it's used. I'd like to see the oil temp come up faster and farther, but since I'm not doing anything special to cool the oil, I can't just cover up an oil cooler or some other simple fix.

To some degree, this may not be much of a problem since oil temp is often directly related to throttle setting - cool oil should be adequate at light throttle, and the temp does come up rapidly when the load is increased. I've been thinking of reverting to a stock oil pan with suitable baffles. An oil to water cooler would be a possibility, but that's more weight and complexity. I suppose the low temps may be a result of picking up the temp out in the pan extensions.....
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PostPost by: type26owner » Mon Feb 09, 2004 4:10 pm

The issue I'm actually addressing here is I believe the shear stresses on the oil film in the sleeve bearings is excessively high. This causes rapid wearing of the conrod bearings in particular. I've been getting only 50K miles on mine before the copper appears. Normally this condition would lead to very high oil temperatures but the oilpan stuck down in the airstream is being cooled so efficiently you can't see this problem. Believe the only cure is to get the viscosity to the necessary range for the bearings. That means getting it hot enough.
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PostPost by: type26owner » Mon Feb 09, 2004 8:14 pm

Several months ago I discussed the twincam thermal management issues with Jay. He suggested installing an air dam. His reasoning was it creates a low pressure area behind it. Which in turn sucks down the warm air exhausting from the radiator. Warm air would thermally shroud the oilpan. That would reduce the delta T and slow down the cooling rate. This might be quite efficient in summer. I'm fairly certain it won't work for cold weather driving. Worthwhile trying it though. Every little bit helps.
Thank you Jay!
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