Have made a small upgrade to motorad high flow thermostats. As they just barely extend to desired length for proper closure of bypass flow, I made a small extension 
Or to brink back an old settled issue,at least in some minds.
More flow isn’t necessarily good. coolant needs some time in the radiator to transfer heat. And/or some time in the water jacket for engine heat to transfer to the coolant.
Way back when, racers using flat head Ford V8’s for “power” added wheel washers in he outlets at the heads. simulating the t’stat restriction but at any coolant temperature. Odd, as I don’t recall that they had t’stats as stock engines!! those came with the 49 version.
Carl
Dear John,
If you look back in the archives, you’ll see I did the same but from a different perspective. I installed delrin inserts into the housings. I did it that way around because the alloy housings corrode, whereas the thermostat foot doesn’t.
Also you can read up about the open length of various thermostats when heated up in a pan of water, which if it is a problem, is something that needs fixing.
As Kirby implies, the term “high flow” in this context is indeed a misnomer. Even more so, for those who have done a Lutz restriction mod. Have a read up about somebody called Bernoulli.
kind regards
Marek
Carl,
I think John is trying to make sure that the stat completely blocks the bypass port making sure all the fluid goes to the rad. That would prevent a short circuit of the flow since the pump seems to suck more from the bypass port than the return hose. That could occur if there was still some space between the disk and port.
Dan
I think that cooling system with almost 20 liters of coolant will benefit from bigger thermostat openings. It’s not about higher flow as it is mainly determined by pump, it’s about diverting more coolant through radiator rather then bypass.
I was considering that route as well but didn’t want to remove the housings and the bead of bypass hole was in perfect condition.
Is it supposed to be crimped in place? Or is it simply trapped between thermostat and bypass seat?
All incorrect. The more flow the better.
Amidst all this, I’d like to point out that a properly functioning thermostat will close off the bypass port while opening the passage to the radiator, not before! Nothing would be worse than the bypass closed off before the passage to the radiator opens.
Climped. I will fold those 4 tabs to hold the spacer in place
Total traver of the t-stat is ~10mm and spacer is only 3mm.
Dear John,
That’s not the important statistic. What you are interested in is the height of the thermostat when hot from its seat when in the housing down to the bottom of its foot. If this height is less than the seat to bypass port height on the water housing, then you’ll need your foot extension.
If this total hot open thermostat height already exceeds the housing height, then your mod isn’t really needed, as the thermostat can already fully shut off the bypass. It would bias the split towards a lower temperature, but that isn’t as critical as not shutting the bypass at all.
kind regards
Marek
As I noted in my post this is exactly the reason I made them
Data:
Stock and MotoStat with a photo of the stat housing and bypass port.
Oops! Should be MotoRad!
Dan
Yeah, I remember these. The jiggle pin is on the moving part rather than the flange.
Sorry MarekH, water flow is controlled by the thermostat, thus controlling engine temp. The water “pump” is merely an agitator that assists flow.
For flow to be controlled by the “Pump” it would need to be appositive displacement type
Water flow through the radiator is controlled by the thermostat. Water flow through the engine is not.
No.
The thermostat just affects where the water flows. It is a dumb device that reacts to temperature - it does not control temperature. It does not know how much water is flowing as it behaves the same way irrespective of rpm or “flow”.
You should chose your words more carefully.
To prove this point, measure the running temperature of a particular engine over time at constant rpm with a known good radiator and then swap out the radiator for one in a different, worse, state of repair. The result you’ll get is an engine running at higher temperatures for longer in the second case because the thing that controls the temperature, the radiator, is struggling.
Initially, the total water flow is identical in both cases and the total flow into the bypass and radiator are also the same, but the average temperature of the water coming back is higher in the second case. The next time the water comes around, that means the thermostat tries to open even more, but the same thing happens, only at a higher temperature for radiator 2. What you end up with is temperature creeping upwards in case 2 and only coming back down slowly once conditions allow, despite the same thermostat being fitted.
In this respect, people have no control over their running temperature when using a given thermostat, because it is the state of performance of their radiator which drives temperature.
In the worked example I gave on 30th June (see V12 cooling system, running too hot?) for the second radiator, this would equate to seeing identical rates of temperature increase A to B, C to E, F to G, but a shallower downward slopes B to C, E to F, so you’d see the average temperature slowly creep upward by comparison to the good radiator. (Remember rpm and flow and heat production are all held constant in this example.) Eventually, the fan would kick in and do what the radiator on its own should have achieved.
kind regards
Marek
How does the thermostat geometry work. When the water warms up does the bypass path get closed off as the thermostat starts to allow flow through the radiator…and is closed off while the thermostat continues to open as the water temperature rises and more flow is permitted through the radiator…so is closed when the thermostat is operating around its specified temperature.
Or…does the bypass always remain in the flow path and mixes water with the radiator flow…???
I thought that the bypass was closed off early in the piece and the thermostat opened and closed in response to the water temperature. This will increase the flow through the radiator and engine as the restriction of the thermostat increases the pressure on the pump …which delivers flow in response to the pressure it is exposed to.
