Quote:
Originally Posted by TourerSteve
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This is the grey version that I bought from Land Rover because of the reported 'soft' relief spring. I wanted to compare it with the factory fitted buff type which provided mid- to hi-90s running and relief valve operation around 2000rpm. On measuring the relief spring loading using a 1 gram precision balance, it was almost exactly the same as the buff one I had already. From the valve opening force measured by the balance, I calculated the hydraulic pressure needed to start valve opening in the enginewas slightly over 2psi. So, it wouldn't have changed anything in regard to the pressure relief point I was getting already and I returned it unused. That's when I asked LR about their PRT relief spring ratings and they looked at me blank.
This looks like the factory fit buff version on the 1.8 turbos.
Is the black type which Rimmer suddenly began listing for the 1.8Turbo around 2008 after listing the OEM buff one for several years after the 1.8T was introduced. Back then, I bought the black one and fitted it as a test to see how it compared. Contrary to Rimmer's current description, it was at the time as an 82C stat which was part of the attraction, experimentally. I still have this one fitted and the engine does indeed run about 8 degrees cooler across the range. However, the relief pressure must be considerbly higher than the stated 'medium' because unlike the 'medium' rated buff version, I've yet to observe the pressure point via engine revs. From my perspective, I'd rate it a much higher relief pressure than the OEM buff one.
So, over the years since MGR's demise, my conclusion is that the principles on which the PRT was introduced have been virtually abandoned by manufacturers. Colour codings soon went completely out the door and very few suppliers actually identify their PRTs by both temperature and relief spring tension. Rimmer's descriptions don't really stand scrutiny on a historical basis, I believe we're comparing apples with oranges nowadays. Just because an engine operates within a particular temperature range tells very little, if anything, about how the pressure relieve system is or isn't operating. They're simply different thermostats. Outside the running of the 1.8T on a racetrack, the necessity of the PRT remains debatable IMO, especially when you can't easily verify what's written on the box. The original motivation to reduce thermal gradients and resolve the 1.8's Achilles Heel head gasket was very effectively pushed aside by the 'ultimate solution' of an MLS gasket, uprated oil rail and higher torque bolts. I reckon few people are really interested in PRTs nowadays.
TC