R400 Duratec: thermostatic sandwich plate for oil cooler

[John Vine]

The oil temperature on my wet-sump R400D rarely reaches 80C. The oil cooler is mounted in front of the rad, plumbed in via a standard non-thermostatic sandwich plate:

Fitted, it looks like this:

In an attempt to reduce over-cooling, I propose to replace this plate with a thermostatic one:

Does anyone have any experience of such a mod?

JV

[Pendennis]

Hi John, it will be straight forward, as Mocul instructions, but personally if your car is predominately road going I could not see any need for any oil cooling. Why don't you simply remove the present sandwich plate and see what temperatures you maintain?

 

[John Vine]

That's an interesting idea --  bit of lateral thinking there!  However, I've already got a thermostatic plate ready to go, so maybe I'll try fitting that first and see what it does for temps.  Then, if they're still on the low side, I'll go with your suggestion.

From what specs I've managed to find, the thermostat opens at 80C, which seems about right to mitigate over-cooling.  Below 80C, presumably there's still some oil flow to the cooler?  If the stat closed completely below 80C, I imagine there'd be a substantial pressure drop when it did open?

JV
 

[Pendennis]

I suspect it works like a three port valve, thus always maintains full flow irrespective of thermostatic position without any resistance so no decrease in pressure drop

[John Vine]

I think you're right. 

I've just come across this article from speedflow.co.uk.  It appears that the oil cooler ports are always open.  The flow to the cooler is reduced, rather than closed off, whenever the bypass is open (below around 78-80C, depending on the stat).

JV
 

[7 wonders of the world]

not a 3 port but there is a constant bleed thro the cooler so the cooler is always at system pressure and purged of air.

[Rob Walker]

I have tried the Mocal thermostatic sandwich plate on several duratec"d Caterhams.  In my experience they stay open once the wax thermostat has opened the valve, then the oil temps drop too low and it can pull down the whole engine temps in cold weather.  I recall return trips back from south coast ferry ports late at night the oil and water temps were pulled down below 40C.  I think that pendennis has hit the nail on the head dont run an oil cooler unless your racing.  IMO the excess oil temps sometimes seen when cruising at 4500rpm on say motorways with a wet sumped engine is due to windage and I would like to try running with no oil cooler and an apollo tank with the idea that there may be a build up of froth/foam within the block & sump causing drag& friction with the result excess heat.

[Dave J]

following my exprience I agree with rob above, i made a cover for the oil cooler when used on the road and finally removed the cooler and thermostatic plate all together.

[John Vine]

Interesting feedback -- thanks, chaps. 

If I were to remove the plate and cooler altogether, what oil temps might I expect on the road in ambient temps of say 35C, or on track?

ETA:  Or is covering the cooler the simplest way forward?  (That way, I'd still have a cooler if I needed it.)

JV

[Rob Walker]

If you already have the cooler the best way is simply to block it off with some foil tape and only open it up if your oil temps are getting above 100C.  Sorry to say that the Thermostatic sandwich plate is useless in our installation.  Could be that the oil pressure is too much for the detent on the spring within the stat to overcome and close once opened, I dont know .

[John Vine]

Thanks, Rob.  That's what I'll do for now.

Looking at the Mocal thermostatic sandwich plate, it seems that the cooler-circuit bypass is open when the oil is cold, and gradually closes (overcoming the spring) as the temperature rises and the wax element expands. Are you saying that, once closed, the bypass is then forced open again (overcoming the expanded wax element) by high oil pressure?

JV

[John Vine]

This is the blanking cover I've just fitted (a piece of plastic cut from an old nosecone cowl):

So, I've now blanked off about 15% of the total rad area.  Is that likely to cause a problem?

JV

[Pendennis]

No your be fine, but your temp gauge will tell if you are

[John Vine]

Thanks.

JV

[Pendennis]

When you think about it the water radiator was always hindered by the oil cooler before it was blanked off. Is that standard Caterham setup?

[John Vine]

That's true, but with no blanking there'd still be some airflow (albeit hotter) through the section of rad behind the cooler.

Re set-up:  yes, that's the way CC specified the cooler mount.  Photo from the Assembly Guide:

JV

[Pendennis]

Interesting, there will be arguments whether it should go in front or behind water radiator but suspect CC put it there as it suits their application. Personally I would like it behind the rad. 

Obviously your engine oil is important but generally the Duratec likes water and oil at 90*C

[John Vine]

I rarely see 80C on the gauge, let alone 90C.  How accurate is the standard CC temp gauge?

JV

[7 wonders of the world]

Oil cooler should be in front of the rad, mounted as close as possible to it, and wih the fins in the same orientation (unlike the CC install) so as not to restrict air flow thro both radiators.

[Pendennis]

Problem is the fins never are in same orientation and unless they are and at same pitch your creating turbulent air at this point which ultimately means the air won't flow anywhere near as good as it would be designed for 'in free air'

Always a compromise and that's why mine is behind in free air with a cool ducted air path

merry Xmas

[John Vine]

Just tested the blanking plate over a 30-mile route, ambient temp 8-10C.  Oil now 85-90C, water (same gauge) about 80C or perhaps a little less.  I was expecting the water temp to be a bit higher.  Can anyone tell me what thermostat my car (2008 R400D) is likely to have?  (I've not yet had cause to delve and find out.)

JV

[Pendennis]

If it's the brass two pin type, their temperature range should be written on the side of the brass section

[John Vine]

Ah, but that would be the sender?  My two are standard CC items, like this.

What I'm after is the thermostat type. Would it be 78C, 82C or something else?

JV

[Pendennis]

I refer to a thermostat switch (2 wire) which should have temperature range on side of brass body. 

Are you after sender or thermostat? That link is for a sender! 

A sender is a device (sensor) for measurement of temperature, not a switch so won't control temperature of engine.

[Pendennis]

Are you implying this switch

https://caterhamparts.co.uk/cooling-fans/38-cooling-fan-switch.html

 

If so I suspect its 82c