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Sound Value 4-6-2 CV Chuff Rate Settings

Started by CArailroader, September 27, 2019, 04:04:07 PM

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CArailroader

Hi all,

I just recently purchased an HO Sound Value USRA 4-6-2. I read the thread at https://www.bachmanntrains.com/home-usa/board/index.php/topic,35808.0.html and I saw no mention of the Chuff exhaust rate. I was wondering if anyone else had this engine and had changed and fine tuned the Chuff Rate.

Thanks

Trainman203

#1
See https://soundtraxx.com/content/Bachmann/SoundValue/HOScaleSteam/bachmann_ho_462_sv.pdf

The default value of cv 131 is 75.  Steam engines had 4 chuffs per driver revolution.  The sound Value decoder will never be chuff-count perfect at all speeds so what you are looking for is to be minimally off that number at the most number of speeds below 4 or 5 steps on a 28-step system or 10 or so out of 128 steps on other systems like NCE such as I have.  Above these speeds the engine is going too fast to count the chuffs anyway.

Put your engine on the track and run at either 4 or 10 steps depending on your system.  If the chuff count is less than 4 at the cv default value of 75, most likely, adjust upward in increments of 10 until near 4 per turn,  then fine tune.  Historically over time, tuning cv's on over 50 engines, I've found that a cv 131 value around 150 often works, though I've had some as low as 125 and others sometimes around 175.  Try this process and these numbers and report back.

Irbricksceo

its been a while since i did mine, but as i recall it was roughly 85 to match closely at "road speed". its a tad fast at crawl but really close at speed.

Modeling NYC in N

ebtnut

FWIW, I try to match the 4 chuffs per revolution at fairly low speeds.  Once you get up to "road speed" you can't really see whether the rate is exactly 4 per rev, whereas at low speeds you can see if the chuffs and revs are in sync.

Irbricksceo

Quote from: ebtnut on October 17, 2019, 11:44:10 AM
FWIW, I try to match the 4 chuffs per revolution at fairly low speeds.  Once you get up to "road speed" you can't really see whether the rate is exactly 4 per rev, whereas at low speeds you can see if the chuffs and revs are in sync.

I think it depends on how you run it. i very rarely have the pacific crawling, it spends 90% of its runtime at speed step 50/128, stock motor CVs, so thats where i matched it, and i can definitely tell that its in sync. for a switcher, if i HAD any with sound, i'd match lower.
Modeling NYC in N