[Jezza86]

this partially crazy idea works on the assumption that a average jimny thermostat is partially closed most of the time
if i were to block the airflow through some of the radiator surface area this would cause the thurmostat to open, flowing higher volumes of water through the motor and not blocking in the pump as much. blocking in the pump increases the load back on the motor. another option would to place a PRV inline that resircs back to the pump intake when the pressure on the pump outlet is high.
anyone seen this done, the radiator restriction or pump bypass?

[alien]

^^ those guys would be doing that so that their in-cab heating works better, not for fuel economy =)

[Gwagensteve]

EFI motors already run quite a bit hotter than carb motors. If the idea is to prevent pumping loss at the pump I reckon the fuel saved would be barely measurable.

[greyghost]

I've done this. blocked the radiator on a carburettor car, but the reason was to stop the carb from icing up. iced up carbies are un-drivable and down right dangerous.
these guys in the trucks are driving in temperatures well below freezing, and they will be doing it to keep the heat under the bonnet and stop the diesel from freezing.
in fact i have a very old and not very common radiator blind for my classic car, i used to run it all the time but the car has seen very little use lately so I've taken it off.

[Gwagensteve]

Totally- the diesel truck guys in North America are doing it because it's like -25 and that's not warm enough to run properly.

[Reubs]

Tridon list a "high flow" variant for most of their thermostat listings. They look like a regular thermostat with extra openings around the outside of it. The cost more ($10-20 extra) but perhaps that would do what you want without risking overheating your engine Jezza.

I imagine the longer time to get up to operating temp wouldn't net any fuel savings for short drives but it may give you that miniscule power boost if there is one to be had!

[Jezza86]

my thoughts were centered around the mechanical V eleterial water pump concept.

a constant speed electric pump is more efficient and provides lower load on the engine, despite being run by the alternator, because it isn't doing 600 to 6500 RPM.

my jimny with ~16% reduction at 100kph is siting ~900 rpm higher then before, which means the water pump should be delivering more flow then before, but under very similar engine load, therefore the thermostat would not be further open to accept the additional flow. was watching a video on the eleteric pumps and a sales guy mentions that some pumps can sap 5-10Kw of the shaft power.

now i get that he is probably talking about the "wrong" mechanical pump, on a drag car, doing 15 million rpm for 5 seconds, but people still put electric pumps on cars, and see a difference in fuel and power. which is why im optimistic that optimizing the mechanical pump or radiator may reap a reward, at least at constant speed with high incoming air flow.