20v Blacktop oil temperature high with cooler

[tofu20v]

I have a slightly odd setup for my oil routing, but it seems fairly common for AE86s with 20v engine swaps.

The oil filter is relocated to the strut tower, above the exhaust manifold, and then routed to an oil cooler. The whole kit is a Greddy one, thermostatic with AN10 lines.

The oil temperature after a very short few pulls will rise up to 110 deg C. I found a YouTube video of someone in Japan with the same setup who said their engine reaches that too. Ideally it'd be 90 - 100 deg is my understanding. Sitting at 70 mph on the motorway will cause the temps to start rising beyond 100 deg after a short period of time, so I end up needing to stick to 60 and even then it can creep up (4.77 diff so sitting between 4-5k rpms, was not an issue with the 4.3 it had before)

I have a 10 row Greddy oil cooler, I've checked all the lines and the cooler - all hot to the touch after a drive. The oil temp sensor is inside the plate to reroute the oil from the stock filter position.

I've recently tried heat wrapping the manifold, and buying Funk motorsport 250deg heat sleeves for the lines that go near the manifold coming to/from the engine. Is it really possible for the oil filter position to cause it to heat up so much? Or is my oil cooler just not big enough for a 20v? (Seems strange considering they had none from the factory).

Here's some pictures of my setup, ideally I'd move the filter elsewhere but when I try to think of ideas I realise why previous owners in Japan put it there. I could get a sandwich plate and keep the oil filter in the stock position below the manifold - not sure if that would help at all.

https://imgur.com/a/W74qzW0

Any insight such as how other people's 20v swapped 86s or opinions on the setup's affect on oil temperature would be helpful, thanks.

[jondee86]

If you are reading the oil temp close to where it leaves the block, then 100-110degC is optimum,
Under race conditions decent synthetic oil can handle 115-120degC for short periods, but you will
need to change your oil more often.

Cheers... jondee86

[totta crolla]

If l remember correctly engine oil temps are based on engine rpm.. makes sense..
You are using higher cruising rpm's due to your lower FD
so you would expect higher temperatures.
Maybe you could try to lower coolant temperature or ideally fit a larger oil cooler.
Heat exchangers, oil/water are apparently more efficient than oil/air coolers.

[tofu20v]

If l remember correctly engine oil temps are based on engine rpm.. makes sense..
You are using higher cruising rpm's due to your lower FD
so you would expect higher temperatures.
Maybe you could try to lower coolant temperature or ideally fit a larger oil cooler.
Heat exchangers, oil/water are apparently more efficient than oil/air coolers.

This is something I'm curious about, as my coolant temp runs quite cool - at 70 - 80 deg depending on how hot a day it is or what kind of driving im doing. In solid hot traffic like entering a show it'll creep up to 90 but no problem really.
Someone else suggested to me that the coolant should be helping to cool down the oil - but besides the seperate jackets in the engine block I don't know where this would be or could go wrong?

I was thinking of getting a larger oil cooler like a 25 row koyorad rather than my 10 row greddy, but it's odd that I used to be able to give the car a rag on the road without oil temp going above 100, and now it goes towards 110 just from doing some high rev pulls on a spirited drive and doesn't really cool down that quick. The lines are pretty hot into the cooler and to the oil filter relocation - but I'm wondering if the thermostat in the oil filter relocation unit is dodgy all of a sudden.

I also just installed a new oil temp sensor however - but it is one specifically made for my Omori gauge by Auber instruments in America - and reads pretty correct, so being a few degrees out would be strange as my understanding is a sensor's resistance will either match a gauge or be completely out?

Thanks!

[jondee86]

Sounds like the oil temp is just floating as it would in an engine with no oil cooler.
Did you change anything other than the sensor between the time the cooler worked
normally and how it is working now ? For example, looking at this diagram it would
seem that the cooler would not work if the hoses were crossed over.



Oil temperature probably does increase with revs, but that is a side effect of the
increase in engine load when the engine is working hard. Cruising at high rpm's does
not put a huge load on the engine, and the increased airflow means that both your
radiator and oil cooler are more efficient. I used to remove my clutched radiator
fan when racing my 86 and it never overheated until I towed another car back to
the pits after one race

Cheers... jondee86

[davew7]

I would try to put a heat shield around the oil filter and adaptor. Is you temp sensor located near the exhaust system, or is air flow restricted in the engine bay?

[tofu20v]

Cheers for the replies guys.

I would try to put a heat shield around the oil filter and adaptor. Is you temp sensor located near the exhaust system, or is air flow restricted in the engine bay?

I bought some aluminium heatshield that I plan to form into an open top box around the oil filter. Temp sensor is located on the block part of the filter relocation so pretty close to manifold. For airflow, I have my oil cooler fitted horizontally up front next to the horns behind the bumper - but it's a stock kouki bumper so air flow isn't great beyond the grill and the two holes behind the number plate. https://imgur.com/V3OONhP

I have another of these Auber sensors and checked it connected to the gauge in a cup of boiling water, as well as a thermometer in there. The gauge was reading exactly 10 degrees C higher than the thermometer... 90 vs 80 deg C, then 89 vs 79 deg C. I think that answers my question and solves my worry about the sudden increase in temp since changing sensor and putting on the exhaust heat wrap (both done at the same time). In reality where I'm reading 110 deg C it's really just 100 deg C like it's always been when giving it some or cruising. My only issue at the start with the higher final gear ratio was that it was pushing my oil temp a few degrees over 100 after several minutes of sitting at 70 mph/near 5k RPMs. Hopefully the heat shielding for oil filter, heat wrap for exhaust manifold and the sheathing around the oil lines will help mitigate or stop this issue.

Cruising at high rpm's does
not put a huge load on the engine

I'm glad you've said this, as I was concerned if sitting at 5k ~ would be hard on my engine when going on long drives to shows/meets or another trip to the ring! Ideally I'd get a taller 5th gear but those aren't cheap with customs and shipping in the UK - let alone installing it into the gearbox! Eventually..

I've read in articles and forum posts like this https://www.skillshack.co.uk/post/correct-reading-temperature-gauge/ that you can "calibrate" a sensor - gauge reading by introducing a resistor into the wiring. I'll try out a potentiometer and see what rating of resistor I need to get it most accurate at a few temperature ranges where I can. I think ideally I'd get a different sensor to remove weak points (my wiring skills are noobish) but I can't find info to help figure out what I'd need. The sensor I'm using is PT1000 RTD.

[jondee86]

Good sleuthing Precision gauges that actually indicate the true temperature are usually sold
as a factory calibrated matched pair (gauge plus sensor). As mentioned in that article, trying to
match a sensor and a gauge from different manufacturers can give less than satisfactory results.

In the short term I would suggest that you cut a clear plastic cover for the dial of your gauge
from something like a phone screen protector. Calibrate the gauge 20-100degC with the sensor
in hot water (or to 120 if you use cooking oil). Carefully mark 80 and 100 on the plastic with a
paint pen or similar and ignore the original scale.

Cheers... jondee86