Steve's Triumph Spitfire 1600
The ongoing saaaaaaga
Cooling System Differences:
There is a very significant difference between Spitfire and Miata Cooling Systems that should not be ignored:
While studying both systems I noticed that the Miata does not shut off flow to the Heater Core, rather the Heater Box just shuts off airflow to the Cabin. This might not sound important but I think it's very important.
Spitfire Cooling System:
Seems to me pretty much all Spitfire models had the same basic flow design.
Miata Cooling System:
Side-By-Side Comparison:
Spitfire
The Spitfire Heater Valve System basically had a fork in the hoses upstream of the Heater Valve with I suspect more resistance in the bypass line than the Heater Core so that when the Heater Valve is selected to "hot", it would get decent flow to help warm the cockpit.
If the Heater Valve was placed in the "off" position, fluid in that loop would bypass the heater core and return directly to the engine thereby allowing some warm coolant to continue to flow through the Intake Manifold.
If the valve were closed and that bypass was blocked or possibly removed by a PO the worst thing that could happen would be that the Intake Manifold would not heat and potentially cause some mild rough running, or similar, but nothing catastophic.!
Miata
The Miata was designed to have coolant flowing through the heater core at all times and because there was no bypass system one would control cabin temperature with the mechanicals of the airbox having some, or all air bypass the core.
The Miata relies on that coolant to circulate; if one were to block the passage of coolant through the Heater Core, there would be almost no flow around the aft portions of the Block and Head. The only fluid truly circulating would be the small amount that goes through the Idle Speed Control System.
I believe that this could result in significant engine problems down the road (forgive the pun).
Reality Reflection:
I'm pretty sure there are a number of guys running around out there merely using the Spitfire Heater Control Valve and most often have it closed, disallowing collant to flow as Mazda had designed. I suspect they may never have an issue due to this restricted flow especially with the limited use some of our cars see.
The Miata engine "Water Thermosensor" which sends signals to the Temperature Gauge, Airflow Meter, and the ECU is located in the aft housing that directs coolant to the Heater Core so likely one would see higher temperatures indicated if there was a problem.
So, in some respects it may actually mimic the Stock Spitfire Flow; possibly, coolant would still make it's way around the Block and Head back to the front of the engine, but would cooling be as even as necessary?
I asked myself....
Do I want to change a proven Japanese design with excellent reliability and longevity to mimic an archaic British design?
Note
The Water "Thermoswitch" item 8 in the diagram, controls only the Cooling Fan operation.
My Solution:
For now, again in the interest of getting the "Proof of Concept" working in a timely manner, I merely bypassed the Heater Core (see Cooling System section).
In the end I think the Spazda will require a “Heater Bypass Valve” something like this…..
I'll up date this section when I finally get one installed.
Cooling Fan (Radiator):
The Cooling Fan was a very easy install, in fact I never even removed it from the Rad. When I started this build I had hoped to get a Donor Car with the two-fan set-up, not just to have the Air Conditioning to play with later, but for the second fan. I thought there might be some issues cooling the Spazda, but in the end, even with only one fan and no shrouding or scoops the car remains cool in the hotest temps we've seen here since.
Electrical hook-up is also very straight forward but it does need a relay to operate. In my build I incorporated the Miata stuff and it will be covered in the "Electrical" section when I can get to it.