Thermosat 1.8 turbo

[T-Cut]

I suspect the definition of, and the specifications for, the original soft, medium and hard relief springs was lost years ago. From my experiences, they're now simply in-line thermostats with a couple of temperature options. Relief spring differences can only be assessed by observing the effect of engine revs on the temperature profile. This can be done using a proper gauge or by driving in diagnostic mode. I (and I hope many others) would be interested to see some results, if anyone is prepared to do the work.


TC

[JOHNDQ]

Originally Posted by T-Cut

Have you got a grey one fitted? How does it perform against the original factory fitted buff version?


I tested the relief spring pressure on a gray one from LR and it was far higher than my old buff one. That doesn't seem to fit with what the SELOC Wiki group promotes does it. I currently have the MGR black type that Xpart/Rimmer were specifying back in the day. However, as SELOC indicates, it has a high relief pressure, which I can verify from my running experience with it. It does however run several degrees lower than the OEM buff system. Basically, the whole PRT situaton is now in a complete fog and little better than guesswork (IMO).


TC

Run the grey on my ZS and 200 track car and the cream on the daily 25. The ZS and 200 warm up up a fair bit slower

[T-Cut]

Originally Posted by JOHNDQ

Run the grey on my ZS and 200 track car and the cream on the daily 25. The ZS and 200 warm up up a fair bit slower

The grey one is SELOC's (current) recommendation for the 1.8T.

Have you an actual temperature readout for each engine?

Do the relief spring tensions create differences in the temperature profile vs engine speed?

The warm up times are independent of the thermostat relief pressure - unless the warm up revs exceeds the relief pressures, which iare presumably different between stats.

TC

[JOHNDQ]

Originally Posted by T-Cut

The grey one is SELOC's (current) recommendation for the 1.8T.

Have you an actual temperature readout for each engine?

Do the relief spring tensions create differences in the temperature profile vs engine speed?

The warm up times are independent of the thermostat relief pressure - unless the warm up revs exceeds the relief pressures, which iare presumably different between stats.

TC

Have data logging on the 200 via the engine ECU (highest ever logged was 92 on track in 34 degrees ambient temperature last summer) but only going on how long it takes for the other cars doing same trips to work and how long before the needle reached the cold mark on gauge. As for pressure not needed to look into it can only say it's easier to blow through the grey than cream.

[T-Cut]

Originally Posted by JOHNDQ

can only say it's easier to blow through the grey than cream.

That's because the relief valves are vented to a greater or lesser extent. The valve seats have two free-flow slots which allow coolant to bypass the thermostat itself. The relief valve itself may be drilled with holes that vary in size, so no PRT actually closes off the relief loop. The relief valve springs have a lift pressure around 1 to 2 psi, which is down to the water pump speed. It's all independent of the coolant vapour pressure, regulated by the filler cap relief valve.


TC