Calibrating Chuff Rate With QSI’s Progressive Chuff And the Quantum Programmer

The progressive chuff in the QSI steam decoders is most impressive after calibrating the chuff rate to achieve 4 chuffs per wheel revolution. This is done using both the CV Manager and the Q2 Upgrade software.

What’s Required

Details of this addition and an outline of the procedures may be found in the Calibrate BEMF Synchronized Chuff Rate (Section 5.3.2) of the latest version of the Q2Upgrade User Manual, available for free in PDF format from QSI Solutions. You will also need the latest version of firmware for your installed version of the Quantum decoder, again, available at no charge from QSI Solutions.

A Quantum Programmer is required for installing the new and modified firmware, as well as a copy of the latest release of Q2Upgrade. While it is not absolutely necessary, the latest version of Quantum CV Manager software is also highly recommended, as it permits virtually seamless running and programming of a Quantum-equipped loco during the calibration process.

Finally, you will need a section of test track long enough and close enough to your work area to permit you to observe the position of the drivers at the instant that a short air release emanates from the speaker in the loco. My preference is for a circular test track in my workroom, located near my railroad computer; this allows me to set things in motion, and then by merely swiveling my chair, observe the loco as it progresses around the loop. This is also one of those occasions where a set of stationary rollers would be handy, if you have them.

Putting it into Practice—Gathering the Data

Once you’ve assembled the necessary hardware, software and firmware, and decided on a place to work, the first step is to be sure that you have a record of all of the CV settings for the loco you are about to calibrate. Quantum CV Manager is an excellent choice for this chore, as it can retrieve all programmed values very quickly, and store them in a file on your computer. In order to do this you’ll open CV Manager, start a new page (go to “new” in the file menu) select the appropriate steam option from the drop down menu, for regular steam it will either be 3010 for G scale or 3050 for HO scale, for Articulated steam it’s either 4000 for G scale or 4050 for HO scale. Put the programmer in service mode and click on the centralized drop down menu at the top of the main window and select “All CVs” then click the retrieve button located underneath the same drop down window.

Once this is done, select the Config tab, and set bit 3 of CV56.0 to “1” by checking the box marked “Calibrate BEMF Synchronized Chuffs.” You can verify the setting of CV56.0 by starting the loco; instead of the normal chuff sounds, you should hear only a short air let-off approximately once per driver revolution. In order to get the short air let-off as close throttle the loco to speed step 3 and adjust the slider for CV 56.12 (Chuff Interval Scale Factor), until you get approximately 1 air let off per revolution. CV 56.12 works as the coarse adjustment to the chuff rate. This will be the last time that you adjust CV 56.12, this value will govern the starting point for all chuff calibration in this particular locomotive. For most HO locomotives the value of 56.12 is in the 90-100 range.

The Q2Upgrade User Manual recommends that the following steps be run at speed steps 3, 5, 10, 15, 20, 25, and 30, with the engine and throttle in 128-step mode. We’ve discovered with the progressive chuff that you can retain an accurate chuff rate up into speed steps 60-70 on many locomotives.

With the engine on your test track and running at speed step 3, note the frequency of the short air let-off. If the air let-off occurs exactly once per driver revolution nothing else needs to be done. However, if it occurs more often, you will need to adjust CV56.13 (Chuff Interval Trim) upward to extend the interval; if it occurs less often than once per revolution, you need to reduce the value in CV56.13. CV56.13 works as the fine adjustment for the chuff rate. Here’s where running on your test track using Quantum CV Manager is truly handy: you can use a “Test Cab” to run the engine, and use the Program button to change the value in CV56.13 without changing anything else. Just keep adding or subtracting a few points at a time until you find the value that gives one “puff” per revolution.

Now, create a small table on a piece of paper, with two columns, marked “SS” (for speed step) and “CV” (for CV56.13). Write the values you just used, that is, “3” in the SS column and whatever value you arrived at for CV56.13 to achieve one “puff” per revolution at SS3.

Repeat this process for SS 5, 10, 15, 20, 25, and 30, each time writing down the speed step and the corresponding value for CV56.13 that results in one “puff” per revolution. It is recommended that you continue the calibration increasing 5 speed steps at a time until you can no longer keep accurate track of what 1 “puff” per revolution is. For my Broadway Limited AC4 with a Quantum Revolution A installed, my table looked like this:

CV56.12 Value	Speed Step	CV56.13 Value
98	3	113
	5	91
	10	85
	15	85
	20	83
	25	78
	30	71
	35	64
	40	58
	45	53
	50	49
	55	46
	60
	65
	70

Given the relatively small drivers on this particular loco; by speed step 60 the wheels were spinning so fast that it was impossible to figure out the 1 “puff” per revolution so that’s where I stopped.

Modifying the Firmware File

With this chart in hand, it’s time to close Quantum CV Manager and open Q2Upgrade. Select the “Load Q2 File” option, and open the .q2 file that applies to your particular locomotive. Next select “Cut & Paste Sounds” and click on the “Change CV Default Values” button go to the “Config” tab at the top of the page and change CV56.12 so that it matches the value you came up with during the first step of the calibration process, click “OK” to close this window. Now click the “Calibrate Chuff Rate…” button. This will open a dialog where you will enter the values from your table. Click the “Add…” button, then enter your first set of SS and CV values as indicated, and click “OK” to save them. Continue clicking the “Add…” button and entering values until you have transferred your entire table to Q2Upgrade. If you entered them out of order, you will notice that the table has been automatically sorted according to the speed step values. Click OK to save and close the table.

Go back to the “Load Q2 File” page. Optionally, you can add a comment in the space provided if you wish to document what you have done to the file. Note that the Soundset number has changed, since you have modified the file. If you wish to use a different soundest number, click on “Change Soundset Number…” and enter a value between 1000 and 65535, as prompted, then click OK. Finally, click “Save File As…” and either edit or keep the preferred filename for your new firmware file. Click Save. You have now created a new firmware file for your locomotive, which includes the Chuff Interval Calibration data.

Final Step—Upgrading the Locomotive

At this point, there are just a couple of chores remaining. First, you must upgrade your decoder with the new firmware file you have just created. Put the loco on your programming track connected to your Quantum Programmer, open Q2Upgrade, and install the file. The steps for installing your customized file are exactly the same as for installing a “factory fresh” file: read in the loco’s current configuration; load the new Q2 file; then (after an optional Confidence Check), upgrade the loco.

It is important to note that the process is iterative. The whole calibration procedure can be repeated to achieve even better results. When you repeat the process load the last Q2 file saved (the one you just saved after doing the original chuff calibration), because if you load the original Q2 file you will be discarding the previous iterations and starting over.