the stock water pump on the jc cosmo's have a funky dual thermostat system. they also have a valve which can open or close one of them off with vacuum and a solenoid.

heres how it works: the valve would be closed (rear tstat blocked) when the engine is cold, giving it a faster warm up. once it reaches operating temp it opens, and uses both tstats. i have noticed on my car (no valve) that when its cold outside (below 60f) that the engine will run cooler than 80c. normal operating temp is 83-90c, but on a cold night it will have a hard time getting to 80c, if i had a valve it would be closed to keep the engine between 85-90c.

thoughts?
questions?

mike

 

Thought:
Thermostats suck Get an electric pump and have it be controlled by the Haltech.

Not what you wanted to here, but that's what I'm gonna have to do... wish I could be of some more help...

 

Geez, I'm gonna try my luck with an NA water pump.

Hmm, maybe you could rig up some sort of choke cable that would take the place of the solenoid? Just operate it manually if the engine is too cold.

 

i dont really have a problem. i just step on the gas harder and it warms up. i just figured out what that valve was for. i have tested like 4 of them and so far they are all bad.

mike

 

Maybe that's why 20Bs have a reputation for running hot? Could it be in the funky thermostat design? Wish I would have kept my 20b water pump around, but its down in texas.... I could really use it right now

 

Kurgan, are you using a T2 or NA water pump?

 

Bah, a T2... don't do it. It doesn't fit with the stock twins... OH wait, you're going NA... it'll work fine for that.

 

But I'd like to up the power some day. That new E11 is looking really great and costs less than a supercharger. I was quoted 3k for the Atkins SC kit that fits a 20B.

For 3k I could get the E11 (1500), FMIC (1000), a new radiator and/or (most of) an aftermarket exhaust (500). I'd just wire both turbos open and leave it at that. The NA water pump can still be used with a SC on an old 4 port 13B/12A if I cut threads in one of the holes and plug it with a bolt. Reinstalling it on an '86+ engine would be no problem.

I'll get into the funky 20B water pump when the time comes.

 

its not hard to swap water pumps, as long as you have the ginormus radiator the 20b needs, the na 20b sould be fine with the na water pump, its just that when you add 2 water cooled turbos things get hot. my friends fd would run about 96c with the stock turbos and radiator, and it was very load dependent, it go hotter when you got on it and colder when you weren't, we put a single non water coooled turbo on it, and all of a sudden it would run at 87c rock solid, the turbos add a lot of heat, if you have no turbos though....

mike

 

So if I got a single oil cooled turbo, and my radiator was large enough, I may not need to upgrade it?

Maybe I'll just use the NA water pump on the 20B while in NA mode, then when I can go into phase two, I'll reinstall the stock 20B water pump, intake manifold, turbo(s), new rad, FMIC, E11, the list goes on and on. This would free up the NA water pump for use on one of my 13Bs with a future supercharger.

 

thats what i would do. the k2rd car was running an fc water pump, with a turbo and i guess it was ok.

mike

 

The way i understand the dual stat cover to work is:
when under no boost conditions the rear stat is closed
off no matter the engine temp, once you get boost the
valve opens and allows a surge of coolant to pass through the
lower temp stat, then once off boost it closes again. i think it
was an effort to try to pre cool the motor during boost,
then close to keep the temp at the front stats temp range.
now that its cool here i am running plenty cool even without the fans on...
matt

 

In the factory workshop manual, it shows the front thermostat set to start opening at 97`c then fully open by 110`c & the rear to start opening at 82`c & be fully open at 95`c.

Now, if the rear one is controlled by the vacum diaphram how does it all work from there. When does the ECU switch vacum to that diaphram???

I cant read Japanese in the manual but am sure some of you guys have sussed it out over time......???