17.5 boosted timing and gearing – HobbyWing Xtreme Stock

In this post, which I will edit several times over the coming weeks, I’m going to be exploring some 17.5 boosted setups: gearing, endbell timing, and ESC timing.

I am going to be setting up 2 cars. Both are Sakura Zeros running Thunder Power 17.5t motors. This post covers car #1, which has a Hobbywing Xtreme Stock ESC. Car #2 is running a SpeedPassion Reventon Pro and is covered in another post. Sakuras have default internal ratios of 1.9 (= 38/20) but I’m using an optional 19-tooth center gear to change this to 2.0 (=38/19).

Car 1 Car 2
Chassis Sakura Zero Sakura Zero
IR 2.0 2.0
Motor Thunder Power 17.5 Thunder Power 17.5
ESC Hobbywing XTreme Stock Speed Passion Reventon Pro
Firmware V3.0_110930STOCK STO1 v19

So for Car #1 here is what I’m starting with…

Internal ratio 2.0
Spur 80
Pinion
Final ratio
Motor endbell timing
ESC Hobbywing Xerun Xtreme Stock
ESC firmware V3.0_110930STOCK
PC software Hobbywing USB Link V3.1
Program card LCD Program Box HW310 V1.0
Program card firmware V1.08_120504

I may just stick with the default settings (yet to see what they’re like) but here are some ideas for a setup based on a perusal of RCTech.

Paramete Default Tip 1 Tip 2 My value
Final Drive Ratio
Endbell Timing 0-5 degrees
2. Drag Brake 0
3. Voltage Protection 3.0 V/cell 3.0 V/cell
4. DDRS Punch 9 5 9 7
5. Brake Force 75% 75%
6. Reverse Force 25%
7. Initial Brake 0%
8. Neutral Range 6% 6%
9. Boost Timing [units] 34-55 25 20 36
10. Turbo Slope [units/0.1s] 18 18 24 18
11. Overheat Protection [*C] Enabled Enabled
12. Turbo Timing [units] 20-30 25 40 24
13. Start rpm 3000 3000 1000 3000
14. Turbo Delay [s] 0.2 0.1 0.1 0.2
15. Timing Accel [rpm/unit] 150-300 350 100 200
Notes Craig W on post 179 X12 17.5 FDR=6.4 to 7.4 drsmooth on post 126 rctech with Novak SS 17.5 FRD=7.56

I think the way the timing works is that there is no timing (except for endbell timing) until the motor hits “Boost start rpm” eg 3000 rpm. From then on, the timing is applied at a rate given by “timing accel” eg 1 unit/200 rpm. If you’ve got 36 units of boost, you’ll be hitting full boost at around 3000+36*200=10200 rpm. Turbo is a separate quota of timing, eg 24 units, which comes on after all boost has already been applied, and only once the throttle has been wide open for the “turbo delay” period eg 0.2 seconds. Turbo is dumped on at the temporal rate “turbo slope” eg 18 units/0.1 s (it is not rpm-dependent). If you have 24 units of turbo, they will be all applied in just 0.125 seconds. Together, the boost and turbo should not add up to more than 64 units (any excess amount will be ignored).

My plan is to set the FDR to around 6.0 and adjust the boost start rpm (or maybe rate) and put the saved timing into turbo instead.