I have a spacerless reroute and no heater core on my setup. With the stock Miata setup, you can't run without a thermostat because the water never gets to the back of the motor. With a reroute, this issue goes away.

The problem I have is that too much water gets through the heater core feed, which is just routed straight back to the mixing manifold. It's a contributing cause to high coolant temps for sure. I want to cap it off, but I am worried that with a thermostat, the coolant system pressure will be too high since the only loop with the tstat closed is through the turbo.

If I were to remove the tstat, though, and cap the heater feed/return, then all is well - provided the water doesn't get through the radiator so fast that it never cools at all.

Anyone running a setup that even remotely mirrors one of these who can give me some empirical data to work with?

Thanks guys.

 

you could put a restrictor in the hose before the hardline...

 

And you could also look into adding a swirl pot at this point.

 

I don't see that being an issue. Despite the fact that the water will be flowing more rapidly through the system, the percentage of time that any given water molecule spends in any given area will be roughly the same.

Overcooling is the issue I'd be concerned with here.

A restrictor (and keep the thermostat) would be a good solution. Another might be to use the BMW-style bypass thermostat, and eliminate the heater outlet at the back of the head.

 

No heater core here. All I did was drill 3 small holes about 3/16's in the top of the t-stat so that water can still flow through while the t-stat is closed. Has been fine for 4,000+ miles and my water temps never go over 200 while driving.
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Joe, the last thing I am worried about is overcooling. It's going to be 95 degrees tomorrow.


Perfect. I'm gonna do this and cap off my heater core feed. Thanks, Phil.

 

You bet man.
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How much did this help actually? I am about to plumb the heater core return from the water pump to the radiator inlet to achieve the same.