9 replies to this topic

[samt88]

I need to replace the thermostat in my car as it appears to be stuck open. When looking at spares I see there are different temperature rated ones, which one do I need for a 1989 998cc engine with a stage 1 kit fitted? cheers

[Dusky]

There is a number printed on your current stat;) i'd use 88° with todays fuel.

[samt88]

Cheers mate :)

[gazza82]

There is a number printed on your current stat;) i'd use 88° with todays fuel.

 

Is that unleaded with additives or with a converted head or either?

[Dusky]

Either, fuel remains more or less the same, even with additives

[KernowCooper]

88c for unleaded

[gazza82]

Any particular reason? Does it make the fuel burn better?

[Orange-Phantom]

People say the 88oC thermostat was introduced for unleaded petrol yet it was introduced for the Mini in 1976 when the emission regulations were tightened.  Max Power out of an A Series is when it's run at 70 oC which is why most race engine builders use and recommend 74 oC thermostats and that's still on unleaded fuel.  The 74 oC thermostat is not suitable for road use though, as it won't get the engine up to a hot enough temperature to burn off the contaminates in the oil.

 

Out of all the evidence I have seen for temperature of thermostats this guy here seems to have nailed it at 82oC which is what it used to be before the emission regulations were tightened in 1976 and they swapped to the 88oC thermostat.  http://www.carnut.co...blin/cool3.html

 

I'm not wanting to start a flame war, I'd just love to see some actual evidence as to why the 88oC thermostat is the one to use over the 82oC for road use other than it being better on the emissions.

[jaydee]

The 70 degs thing was because leaded fuel produced best power at coldest temp possible for the engine which means around 75 degs coolant temp (remember oil starts to be effective at 75° and engine tolerancies would be too wide with engine cold)

Unleaded wont burn correctly at that temp it simply needs more heat

Emissions play their role too

 

That said fit an 88° also because there will be a chance you heater will work better and you're going to need less time to warm up the engine.

[Orange-Phantom]

I've spoken with Peter Vickers who has the Dyno charts backup the fact that he get's more power out of an A series from running an 74oC thermostat and looses power when swapping to an 82oC or even an 88oC and this was on unleaded fuel.  This is why he fit's a 74oC thermostat to all the race winning engines he has built.

 

Also Keith Calver states that maximum power from an A Series is at 70-75oC.

 

http://www.minimania...emperature_1506

 

I've seen no evidence anywhere that states that unleaded needs a higher temperature engine to burn or operate properly and certainly nothing to say that leaded fuel produces more power at lower temperatures compared with unleaded.  As said before the 88oC thermostat was introduced for all Mini's in 1976 for emission purposes and this was when cars were still running leaded fuel.

 

To quote this Race Fuel manufacturer "Lead does not have any significant effect on overall combustion properties.  This allows us to specify certain hydrocarbons in a blend to achieve desired fuel properties, then add varying amounts of lead to target a an octane level.  This is why the myth about high octane fuels burning slower is exactly that – a myth".

 

http://www.racegas.com/article/38

 

This is what I'm trying to nail down is the evidence.  Is the unleaded / hotter engine temperature thing based on truth or is it just one guys opinion which has been repeated enough times over enough forums to become fact?  If someone can point me to some actual hard evidence that unleaded fuel requires a hotter engine temperature to burn / function properly I'll more than happily revise my thinking on the matter.

 

This all being said I agree with the other posters and Jaydee in that an 88oC thermostat for a road car is probably the one to go for if you want your heater to work properly in the winter! 

Edited by Orange-Phantom, 08 January 2015 - 09:15 PM.