[R H Steele]

First from this thread: post#7
http://www.elvastowe...780&qpid=230730

ErickC, on 31 December 2017 - 07:34 PM, said:

So I've been meaning to post about this, but I've been kind of busy with work and school. Anyway, the last few test versions of OR are definitely ignoring the smoke colour parameters in the ORTS_engines block. My custom smoke .ace had a pure white main channel, based on the premise that OR multiplies the colour parameters by the values in this map, and everything worked fine until around the time of the 3D cab mouse control update (I can't remember exactly when the problems started). Suddenly, all of my diesel smoke turned white. I edited the colour channel of the smoke texture to pure black, and now all diesel smoke on engines with an OR block turned pure black. The colour channel of the smoke texture is being used as the smoke colour with no respect to the OR smoke colour parameters whatsoever.

...and what i have seen in X4017 --- there appears to something in the code that allows exhaust characteristics from the default msts file to be rendered in the sim when using a OpenRails folder .eng file. As shown below. There are two screenshots. One with a single exhaust that appears to be too low in "y" axis. Adjusting the "y" axis in the OR include file produces...TWO exhaust plumes??? Obviously the higher plume is the result of the adjustment to the include file, the lower plume still being read from the default msts eng file.

I am assuming that Eric and the others are seeing this dual effect also, but being manifested in a different manner?
Using the ORTS diesel engine block, I still see the exhaust color changes rendered in the sim. White, grey, black, and bluish idle smoke - all present.
Log attached, although nothing in it to indicate this effect.
Single Exhaust Plume

include ( "..\\DRGW_SD45_5338.eng" )
Wagon (
	include ( "..\\..\\Common.Std\\Locomotives\\Std_TypeF_Coupler.inc" )
	include ( "..\\..\\Common.Std\\Locomotives\\Std_Loco_BrakesTS.inc" )
	ORTSAdhesion ( ORTSCurtius_Kniffler ( 7.5 44 0.161 0.7 ) )
	ORTSAdhesion ( ORTSSlipWarningThreshold ( 70 ) )
	ORTSBearingType ( Roller )
	ORTSDavis_A ( 1896.44 )
	ORTSDavis_B ( 57.9457 )
	ORTSDavis_C ( 8.337645 )
	Comment( == Assumptions -Locomotive diesel/electric - speed - 65mph (105km/h), Roller Bearing, 6 axles, frontal area - 14.5m2, WagonWeight - 176.1 ton (metric), Drag 1.0 == )
)
Engine (
	Effects (
		DieselSpecialEffects  (
		Exhaust1
			(
				0 4.59 2.2
				0 1 0
				0.14
			)
		)
	)
	include ( "..\\..\\Common.Std\\Locomotives\\Std_Eng_SD45.inc" )
)

default msts eng file

Engine ( DRGW_SD45_5338
	Effects
	(
		DieselSpecialEffects
		(
		Exhaust1
			(
                    	0 4.59 2.2
				0 1 0
				0.15
			)
		)
  	)   	
	Wagon ( DRGW_SD45_5338)
	Type ( Diesel )

Dual Plumes (msts default and OR include

Engine ( DRGW_SD45_5338
	Effects
	(
		DieselSpecialEffects
		(
		Exhaust1
			(
                    	0 4.59 2.2
				0 1 0
				0.15
			)
		)
  	)   	
	Wagon ( DRGW_SD45_5338)
	Type ( Diesel )

OR include with "y" axis raised

include ( "..\\DRGW_SD45_5338.eng" )
Wagon (
	include ( "..\\..\\Common.Std\\Locomotives\\Std_TypeF_Coupler.inc" )
	include ( "..\\..\\Common.Std\\Locomotives\\Std_Loco_BrakesTS.inc" )
	ORTSAdhesion ( ORTSCurtius_Kniffler ( 7.5 44 0.161 0.7 ) )
	ORTSAdhesion ( ORTSSlipWarningThreshold ( 70 ) )
	ORTSBearingType ( Roller )
	ORTSDavis_A ( 1896.44 )
	ORTSDavis_B ( 57.9457 )
	ORTSDavis_C ( 8.337645 )
 	Comment( == Assumptions -Locomotive diesel/electric - speed - 65mph  (105km/h), Roller Bearing, 6 axles, frontal area - 14.5m2, WagonWeight -  176.1 ton (metric), Drag 1.0 == )
)
Engine (
	Effects (
		DieselSpecialEffects  (
		Exhaust1
			(
				0 6.59 2.2
				0 1 0
				0.14
			)
		)
	)
	include ( "..\\..\\Common.Std\\Locomotives\\Std_Eng_SD45.inc" )
)

Attached thumbnail(s)

• 
• 

Attached File(s)

•  OpenRailsLog.txt (13.91K)
  Number of downloads: 327

[railguy]

Here's the exhaust "problem" that I've noticed and it's been around for a long time. There is some sort of undisclosed mathematical relationship between the OR exhaust parameters and the MSTS exhaust parameters. I've played with this for a couple of years and still have not exactly figured out what the relationship is. For the doubters, take an OR include file and "marry" it to two different diesel locomotives, each with MSTS exhaust parameters that differ from one another and see what happens. Or zero out all the exhaust parameters in the MSTS .eng file and leave the OR exhaust file unaltered and see what happens.

[R H Steele]

Yeah, in agreement here. How would you suggest this be written up as a bug report...some sort of undisclosed "linkage" is occurring here.
What I've done is change the MSTS parameters (diesels smoke effect lines and the effects setting affecting diameter) to either match or augment the ORTS engine lines...the results are okay.

[railguy]

Well, a start would be to divorce the OR exhaust settings from MSTS .eng files altogether if all the needed exhaust parameters are present in the OR Include file (and I'm not even sure what those all might be). Also, there needs to be transparency as to how the various parameters interact with each other, rather then having folks have to guess at it.

As I've mentioned elsewhere, exhaust behavior in a diesel locomotive is strictly related to what is happening with the diesel prime mover--thus, exhaust parameters need to key off of what that diesel engine is doing--most notably engine RPM, not throttle position. My example that I used elsewhere is a locomotive using the diesel prime mover for Head End Power. The throttle position may be at idle, but that prime mover is running at full RPM to make HEP for the train. The exhaust calculations should be looking at the RPM, not the throttle position.

[ErickC]

That's simply not correct, an unloaded engine produces less exhaust than a loaded one. The exhaust mass flow is determined by the air aspirated plus the fuel flow. If you don't believe me, watch a semi at high idle versus the same semi pulling a trailer at the same RPM. You're going to notice a difference in the exhaust flow (you're also going to notice a difference in the noise the exhaust makes, which is why the NALW F40s never sounded right). The 645E3 driving an HEP generator behaves in the exact same way. When the throttle is at idle, the engine only needs to overcome bearing friction and accessory loads to run at the demanded RPM. However, as the field excitation of the main alternator is varied to provide more traction power, the load on the engine increases, even though the engine speed is constant. The engine must now counter the added resistance of the main alternator. If no additional fuel were metered, the engine speed would decrease until it reached an equilibrium. To counteract the additional load, additional fuel is burned to maintain a constant engine speed, and the exhaust flow increases.

For your viewing pleasure, first, an F40PH entering HEP mode - notice the lack of exhaust, and, second, here's another F40PH departing. Observe the near-complete lack of exhaust as the engine is under light load when first departing, and the sudden plume at 1:30 or so when additional power is added.

Exhaust volume is a matter of load, and the particulate emissions are a matter of combustion efficiency (which is why the colour varies during power changes), although the flow tends to have subtle pulses that vary with engine speed, as I've demonstrated before. The current OR system is OK-for-now, but could use some more sophisticated simulation in the future (for example, tying total exhaust velocity and flow to load - which the sim already calculates - while allowing us to set the pulse rate independently). I'd argue we need a sound variable tied to engine load as well, and a way to emulate constant-RPM for locomotives equipped with engine-driven HEP (or for any modern GE using their screwy speed settings).

I do, however, agree with the need to divorce the OR exhaust from the MSTS exhaust. And OR is definitely ignoring the colour values in the engine block lately. Hopefully that will get fixed soon.

[railguy]

^I recognize that a diesel engine under load may smoke more than an unloaded one--I've only been around diesel engines for over 50 years! My point is that the current diesel parameters are tied to throttle setting, and not really to either RPM or load. One thing that OR does that MSTS didn't even think about is simulating over-fueling from slow spooling and/or turbo lag. My only issue with that is that the smoke for that increases with throttle setting, when, in many diesel engines, especially those 4-cycle turbo GE's, it actually works the opposite--the engine will smoke like crazy from turbo lag when coming off idle, but, as the RPM increases (and turbo RPM spools up from the increased exhaust flow), the amount of turbo lag smoke decreases. The smoke parameters also need to be able to compensate for differences in engine behavior--for example, 2-cycle EMD's have a significantly different smoke pattern that a 4-cycle GE. OR is partly there with that, but not completely.

The other thing that the OR exhaust smoke does is pulse, much like the exhaust from a steam locomotive pulses. Except at the very lowest RPM's, diesel engines don't smoke that way--reason being that that the smoke puffs from 8, 12, 16, or 20 cylinders basically merge into into a continuous stream as far a what the human eye can see. At higher RPM's, about the only time that I see a prototype diesel locomotive prime mover pulse smoke is when one or just a few cylinders are misfiring. That is the exception, not the rule, and can happen most often when a diesel is first started from a cold start. Tying the exhaust pulse rate to engine RPM could potentially solve that problem, but the number of pulses would always be pretty large. For example, if my math is correct, a 12 cylinder 4 cycle GE idling at 310 RPM would have 15.5 exhaust pulses per second. Now, 24 frames per second looks continuous to the human eye, so if that engine is very much above idle at all, the exhaust stream would appear continuous. A diesel locomotive rolling down the track in OR at speed with little individual exhaust pulses leaving a little trail of smoky dots is completely unprototypical.

Smoke color is another gnarly issue, though OR does try to emulate it. Obviously, no smoke at all indicates full combustion. Partial combustion cause unburned products to be exhausted and that makes smoke, but different types of incomplete combustion produce differing smoke colors. A good diesel mechanic can look at diesel exhaust color and pretty much be able to tell what is happening in the engine. White or thick grayish smoke indicates that either that raw unburned fuel is being exhausted, often occurring when starting a cold engine until there is sufficient compression to ignite the fuel in one or more cylinders; whitish smoke in a warm engine, ominously, can indicate that coolant is entering the cylinders, usually from a leaking head gasket. Brown or black smoke is a sign of incomplete combustion--causes can be excessive load for the RPM, turbo lag or malfunction, poor compression, injector fouling, and other issues. The idiots out there who brag about "rolling coal" out of their diesel pickup haven't figured out that visible smoke is a symptom of partially burned fuel being exhausted--that unburned exhausted fuel doing nothing to propel the vehicle. Blue smoke generally indicates one of two things--that the engine has blow by of crankcase oil entering the combustion chamber--typically noticeable when the engine is decelerating in RPM, or when an idling engine's temperature is dropping below the threshold where it can combust fuel completely. Typically, absent of poor compression, an engine with decelerating RPM's should smoke little or not at all because its fuel supply is at an underfueling condition. Most all electronically fuel injected gasoline or diesel engines now are equipped with Deceleration Fuel Cutoff (DFC) that completely stops injection of fuel in a declerating engine until it reaches its new throttle/RPM setting, when fuel injection will then resume.

Of course, with Tier 4 prime movers, a lot of this is a moot point--other than heat waves (which I haven't figured out how to make OR emulate), there should be no visible particulate emissions at all under any load condition. On those locos, I just zero out the exhaust emissions in the exhaust settings.

[ErickC]

I've already shown you some very good proof that diesel exhaust does indeed pulse with engine speed depending on the cycle. I respect your time around diesel engines, but you're not observing closely enough. Watch the video clips again. You can even watch them in slow motion. You can see that the pulses are very, very definitely linked to engine speed, along with the audible pulse. I may have only spent 30 years observing diesel exhaust, but what I see is consistent. So the only way for what you're saying to be true would be for every engine I've ever viewed to be misfiring. I have a friend who works for BNSF - who also observed the same thing - and says it's related to scavenging and my best guess is that it's the effect of some kind of pressure wave resonance.

[railguy]

OK, I think that I now understand what you are saying. My definition of "puff" is a completely discrete puff of smoke from the exhaust. What I see in the videos is a discrete variation in the exhaust smoke--it never completely stops when the engine is loading or under load (a complete stop and fully discrete puff is the case in some adjustments of the exhaust parameters in OR, especially when the exhaust is combined with motion of the loco). One thing that I believe that we can both agree about is that those puffs/variations become much more indistinct as the RPM of the prime mover increases. I would say that the 2-cycle EMD's tend to smoke with fewer highly distinct variations as the RPM increases because they have double the number of exhaust strokes per engine revolution compared to a 4-cycle GE or Alco. (Many people think that EMD 2-cycles actually run at higher RPM's than 4-cycle GE's because of the way they sound, but that is due to the 2-cycle exhaust note--the two designs are pretty similar in RPM ranges.) The 2-cycle EMD's, especially the non-turbo models, tend to emit some smoke throughout their RPM range, mostly because the 2-cycle design is slightly less combustion efficient because exhaust gases are never completely scavenged from the cylinder. As a side note, the B&M 567 shown in the video, in my opinion, was also showing its age with the bluish exhaust--it probably didn't have optimum compression, anymore.

Another factor that OR, thankfully, considers is RPM change rate. The 2-cycle EMD's spool up much faster than a 4-cycle GE or Alco. (Ask any engineer about which type engine he/she would prefer to switch with and the near universal answer is a 2-cycle EMD. An engineer buddy of mine told me that switching the same amount with with an EMD could be done in 7 hours, while a GE would take 8 hours, just because of the additional time it take a GE to spool up.) I build that into my OR smoke adjustments.

Thank you, Eric, for sharing your opinions. I think that we're both chasing after the same thing--authentic looking exhaust in OR.

[ErickC]

Yes, I think we are both chasing after the same thing, acknowledging that the current system is a bit simplistic. That there can be some confusion is why I tend to use the term "pulse" instead of "puff," because the flow is definitely constant, just not uniform, and with a heavy rhythm. There is a definite correlation in the sound, as it also becomes less discrete with higher engine speeds. I tend to think that, since OR already tracks the engine load, and since it's a definite factor in the exhaust flow, a more complete simulation of the visible and audible exhaust is possible, it's just a matter of the OR team having the time to deal with it at some point.

[railguy]

I re-watched some of the videos in the linked post that you mentioned above. A couple of observations. Not uncommon in older locos, some of those had some combustion issues due to age, possible malfunctioning injectors, poor compression and other potential maladies that would affect their smoke production. Then there is the matter of governors. That's a whole subject in itself. Years back I had a friend who was a electrical engineer that worked at Woodward Governor in Fort Collins, Colorado. The discussions that I had with him on engineering of governors was, frankly, way over my head as a non-engineering type. For years, they made most of the mechanical governors for diesel railroad locomotives. Most late generation diesel locomotives have electronic or electronic/mechanical governors (many still made by Woodward, I think) that can much better regulate fuel and RPM to lessen smoke emissions. Back when, reasonable cost, bulletproof reliability and getting the job done took precedence over fuel efficiency and exhaust emissions. That has certainly changed.

One other note, Eric. Over the years, you have made some pretty darned neat models for MSTS/OR and I want to thank you for that. I gather that you're working on some new potential goodies--those will be much appreciated. Oh, and, yes, I do get a kick out of those old 567 GP's out there. Smoky or not, they were a pretty bulletproof design. Not many mechanical things that are close to my age or older are still out there running and earning a living.