Hi Simon,
Mine is a silver top but I have a new 2.0 blacktop in the garage as well as I'm planning to change it later this year so I can do a direct comparison.
I have a SiFab radiator and in terms of cooling capacity, I think they are very similar so I doubt if it's a radiator problem as such.
The big difference comparing the silvertop and blacktop is in the thermostat housing.
Although the basic water flow is the same and the overall shape is very similar, the blacktop takes the temperature readings from a sensor in the head and reads the head temperature rather than the coolant water temperature whereas the silver top has 2 temperature sensors in the thermostat housing. One for the ECU and the other for the gauge.
The blacktop and silvertop are very similar in most respects and I would expect that, if your cooling system is working correctly, the water temperatures would be very similar.
My engine sits at between 90 and 95 degrees all the time (on the gauge) on the move and only gets hotter when I'm stuck in traffic. It sometimes spikes a bit higher if I suddenly start doing a few full power acceleration runs but that's just the lag in the system while the thermostat catches up with the sudden increase in temperature and it the returns to normal quite quickly. Vice versa if I suddenly go from hard driving to coasting.
It's a double acting thermostat, as is yours, so the flow of water varies between the main cooling circuit and the bypass circuit to keep it within range no matter what the ambient temperature is.
I've driven mine at temperatures as low as freezing and up to about 35+ (Blenheim if I remember correctly) and It's always stayed within that range.
The fan is set to come on at 98 and go off at 95.
I don't have any air flow modifiers fitted or exhaust wraps etc.
It is entirely possible that even though you are showing 100+ degrees at the head that the water temperature is lower and more in my range but you can only check that by fitting a sensor into the water hose close to the thermostat housing.
I'm assuming you have the stock ECU and that this is controlling the fan.
What is the temperature range of your thermostat? It's stamped on it.
When I bought the car, someone had modified the thermostat and It took forever to warm up and indeed it wouldn't get above about 80 degrees in the winter.
However, when I changed the rad I put the whole system back to standard with a new thermostat and since then it's all worked fine.
IMHO it has nothing to do with the airflow or the radiator capacity and it may well be that having the sensor in the head will show different readings to the actual water temperature.
When I change engines, I'm going to use the silvertop thermostat housing so that I can keep the existing temperature measurement.
Hope this gives you some more ideas and you can PM if you want to get into more detail.
