Well after playing around with this yesterday, here are some conclusions I have come to:
1. The steam pressure that these locos operate at is almost exactly the same as the safety valve trigger pressure, within a pound or so, unless the engine is under a heavy load. This is usually the starting pressure when you start a session which almost guarantees that the valve will immediately go off at session start.
2. The pressure reduction when the valve triggers is maybe a pound or so, so the valve monetarily closes and within a few seconds has to open again because the pressure builds right back up to the trigger point again. Hence the Phht...Phhhtt ...Phhht constant noise. I would imagine if this were happening in a real steam loco situation, that the engineer would push the fireman off the loco at the first opportunity.
3. Adding water to the boiler, has zero effect on pressure. ( seems totally unrealistic)
4. Letting coal run down to around 30% minimizes the build up of steam pressure as quickly
5. Running at low speed, or on a flat, pretty much guarantees that the safety valve will be triggering constantly until the coal level burns way down.
6. Running with the train brake constantly dragging for miles , will load up the engine, and help lower the pressure. Somehow, I doubt if railroads use this as an operation procedure, but correct me if I am wrong.
All of this of course, seems to be cured, by editing the the engine spec for the loco, that I have posted in this thread. The loco starts at a lower pressure, so no immediate valve actuation occurs, the buildup of the steam pressure is much slower, and the loco runs 10 15 pounds under the trigger point of the safety valve, which to me seems pretty realistic ( but I am not an expert in steam loco operations, by any means). Anyway, I have now replaced another one of my favorite locos, the FEF locos with this modified Engine Spec, and for the first time they run properly too, including the ones on my route under AI control.
http://forums.auran.com/trainz/showthread.php?95761-RRMODS-UP-FEF-Steam-Locomotive-Release
If I can get one or two more locos to work properly with this new engine spec, and not have to listen to this safety valve screaming at me, at all, during a run, I will be a very happy engineer.
