SD1 Thermostat

[Nige]

Hi,

Can anyone tell me the correct temperature thermostat which should be used on the SD1 (3.5 V8 Twin SU Carbs)? I thought it should be one which opens at 82 degrees, but when I took my old one out, it had 78 degrees stamped on it.

Which is the correct one and would using the wrong one cause problems?

[ChrisJC]

I think 82 is the correct one, but I doubt if it makes that much difference.

Chris.

[ramon alban]

Not a carb person, but 78 seems very low, compared to boiling water.
I believe the running temp should be around 90 and the perceived wisdom, as I recall, is 82 for summer and 88 for winter.

Assuming all water galleries are clear and the cooling system is working OK , pump, rad, viscous, etc, the running temp will then be a little higher than the stat, depending upon the ambient seasonal effect.

If the engine is running too cool the fuel/air ratio would be automatically adjusted (efi) (carbs ??) to be a little on the rich side. More fuel = less mpg = oil washed from bores = more wear = carbonned plugs = coking = preignition. what what?

[ChrisJC]

It's on carbs - so I doubt if it will make much difference. I've got an 88deg in my 4.6, but I wish it was an 82.

Chris.

[ramon alban]

It's on carbs - so I doubt if it will make much difference. I've got an 88deg in my 4.6, but I wish it was an 82.

Chris.

Even so, if the engine is too cool the oil temperature would be below what would be "normal" so the lubrication efficiency would be lower.

As a point of interest I dont think I ever heard of an SD1 stat at 78 degrees?

I still think 78 is too low because it is "tending" towards having the stat stuck open.

[v8man]

on a perfomance engine some reputable engine builder says
65-75 degrees being the optimum,if EFI fuel enrichment turned OFF
as max power is generated when coolant is at no more than 80 degrees,
if your engine makes 300 bhp with coolant temperature at no more than 80 degrees,
it only makes 270 bhp if coolant is at 100 degrees 10% reduction on power,
reason most cars ran hot is for emissions y some range rovers run a 96 degrees thermostat ,
also reason for cracked blocks are way to hot running temperatures,
some old classic range rovers ran 72 degrees thermostat,
if you want your car to be on 80 degrees you should fit a 78 degrees thermostat
i was told all ways keep temperature at no more that 80 degrees
cheers
Gil

[Paul B]

on a perfomance engine some reputable engine builder says
65-75 degrees being the optimum,if EFI fuel enrichment turned OFF
as max power is generated when coolant is at no more than 80 degrees,
if your engine makes 300 bhp with coolant temperature at no more than 80 degrees,
it only makes 270 bhp if coolant is at 100 degrees 10% reduction on power,
reason most cars ran hot is for emissions y some range rovers run a 96 degrees thermostat ,
also reason for cracked blocks are way to hot running temperatures,
some old classic range rovers ran 72 degrees thermostat,
if you want your car to be on 80 degrees you should fit a 78 degrees thermostat
i was told all ways keep temperature at no more that 80 degrees
cheers
Gil

I was told that you want the engine as hot as possible for better performance, as heat is energy and a cooler block sucks heat/power from the engine quicker, hence why you can run higher CR with ally heads.

Anyway, I was also told that the Rover v8 doesn't like too much temperasture as it warps easily, so I have a 82C thermostat in mine, an electric water pump and a Kenlowe electric fan. I've set it so the fan comes on just over 80C, (which is about minimum on the Kenlowe adjuster) otherwise it tends to come on as I'm driving along. I've never seen it above 85C on the gauge, even in steaming motorway crawlalong.

[ramon alban]

It seems that different members get "told" different things to do regarding temperature.

According to the Rover Efi technician training manual the Efi temp sensor has the following profile.

TEMP-------OHMS
-10°C------9100 to 9300
0°C-------- 5700 to 5900
20°C-------2400 to 2600
40°C-------1100 to 1300
60°C-------500 to 700
80°C-------300 to 400
100°C------150 to 200


Elsewhere in the Rover documentation it recommends a substitute resistance of 250 - 280 ohms for a failed temp sensor, to fool the ECU into thinking the engine is at working temperature.

That seems to indicate that the optimum temperature for an efi 3.5 V8 is between 80 and 90 degrees.

In addition in the rover SD1 workshop manual it specifies the standard thermostat as 88 degrees for all 3.5 models.

So with due acknowledgement to what we may have been "told" the original Rover documentation seems to indicate that the operating temperature should be between 80 and 90 degrees for standard cars.

[Slothie]

It seems that different members get "told" different things to do regarding temperature.
:
:
:
So with due acknowledgement to what we may have been "told" the original Rover documentation seems to indicate that the operating temperature should be between 80 and 90 degrees for standard cars.

That's what I thought... I needed a new thermostat for my Trike and the guy in the shop looked up the part no for my SD1 engine and got me an 88 deg thermostat. This struck me as a bit high at the time, but looking up on the internet I saw 88 deg stats being sold all over the place.