A tricky cooling problem. Overflow tank with pressure cap needed?

[Roberts14]

Hi there,

I have a SR20det in a Silvia. Last year it worked great stock with no problems.

Then I mounted a new radiator, larger turbo, new head gasket, new injection and so on. Thats when I got cooling problems.

Accordig to the injection and my stock coolant temperature gauge Im at 65 degrees C at idle, and while under heavy throttle I reach about 75 at max. So im not boiling.

Yet, water mysteriously dissappears. Ive checked a dusin times, and there is NO LEAK. None. But, after some high rev, heavy throttle runs, it lookes like water has escaped through the overflow tank (there is water there). But It does not look like theres enough there too explaine the massive coolant loss.

There is no white smoke at the tailpipe, like there should be if thats where the coolant goes.

Could it be that I need a radiator cap with higher pressure rating (the current is 1.1, and I tried another 1.1 with no luck)? Or do I need a overflow tank with a pressure cap?

By the way, I have aprox. 350 HP at the wheels, and the car is punished to the redline every time it runs.

Thanks Robert