metalnut

iTrader: (36)

Hey all,

I'm not really a "rookie", but motor timing is one of those areas where I'm still very green.

I have a 2WD SCT with a 17.5 Trinity D3.5 maxzilla motor (high torque rotor). I'm running blinky software and the motor is set at the factory default 0 degrees on the can. I run the truck for about 20 minutes at a time on our track, and come off around 120-125 degrees (measured on the end of the can).

On the infield I'm competitive, though the "fast guys" outdrive me just based on skill. On the straightway, the "fast guys" definitely pull on me, and you can tell their trucks have a much higher top speed.

I'm geared within the "stock" range for my truck, about 1-2 teeth higher than some of the other guys running the same truck. Since my temperatures are very reasonable, I feel that I'm geared correctly.

So... should I be adding motor timing?

As I understand it, advanced timing lets the motor spin faster on the top end, but you sacrifice bottom-end torque. I could gear up, say 1 more tooth on my pinion, and I'd also get more top end speed and less bottom-end torque. So which do you do when?

If someone could link me to a good read on the subject, I'd be happy to read it. I've only found opinions, and many contradicting at that. Thanks!

ThePanda

iTrader: (68)

120-125 is low temperatures try just gearing higher first

Grasschopper

iTrader: (54)

Yea if you can run for 20 min and come off at those temps you're under geared. Races are half that length at most and you can safely be 40 deg warmer on the temps. What is your gearing?

That said I've read several places that for 17.5 racing you should also max out the end bell timing.

MarkA

iTrader: (21)

If you max the endbell timing on a heavy SC truck, your laptimes are almost certain to take a hit as you'll never get the needed torque back through gearing.

The answer is in the question:
17.5/blinky SC is a momentum class. Faster in the turns leads directly to faster on the straights, period. When I ran 17.5 SC, I never went faster over an entire lap than I did with the endbell in it's OEM position regardless of motor. They key is twofold. First, as your driving improves, you'll find it comes with the magic bonus of picking up straightaway speed. Second, the biggest thing I found to gaining non-driving/line based speed in SC is weight. A competitive 17.5/SC truck is at or near minimum weight. And it's not hard to cut weight. For example, some SC bodies are +/- 4 ounces of each other just in the body. Are you driving with a Mcdonald's quarter-pounder taped to your roof compared to the other trucks?

Back to the motor/gearing side of the equation though - have you tried gearing down, i.e. take the 1-2 teeth off that you're higher than the other fast locals? These trucks are so heavy that you may actually be lugging the truck and that's hurting your top speed.

BlueGlowBoy

iTrader: (2)

+1. in any sort of stock racing, corner speed equals straight-line speed. If you can get on the gas 2-3 feet earlier, or carry that extra 0.5mph around the corner, you will have so much more top-end by the time you hit the brakes....

metalnut

iTrader: (36)

I agree with everything you've said, but I'm already aware of all of these things I really do get the importance and impact/result of proper setup and good driving. My truck is just barely over the weight minimum, I'm very meticulous about my setup, and I practice for many hours every week to get better. So those steps I'm taking.

But.. back to my original question. Our track if fairly large with a long straight in the back. I'm on full throttle and at my truck's maximum speed about 1/2 way into the straight. This is why I started wondering about timing.

It seems everyone has a different opinion, but I figured there must be science behind it. Advancing timing just allowed the motor to go into higher RPM than stock timing, correct? So, at a sacrifice of bottom-end torque you're gaining some top end speed. If that's the case, though, why does everyone I talk to in stock SCT say they're running higher can timing?

tajar66

iTrader: (6)

I agree with the under geared part. I would also start there. Give it a shot, then turn the timing up keep an eye on your temps when doing both.

MarkA

iTrader: (21)

You have the science correct, it really is that simple of a trade-off. The only thing I would add is that advancing the timing tends to narrow the powerband into only really making any when it's "wound up." The rest of it has me stumped - you're reaching the top speed of your truck earlier than you probably should be and you're running more gear than the other racers but if they're carrying a ton of endbell timing, you should be getting an advantage back everywhere else.

metalnut

iTrader: (36)

I think the "advantage everywhere else" is lost for me just do to my less-than-great driving skills. So I'll take responsibility for that. My theory.. the fast guys may be geared like me (or close to) but have advanced can timing. They're fast in the infield due to their driving skills (momentum, traction, etc.) and on the straightway their timing kicks in and they pull ahead of me.

Of course I could be very wrong

But see, that's the root of my question.. once I'm geared to run around 150-or-so degrees, let's say, WHY would I want to advance the timing? Just to gain top end? In that case, wouldn't it make sense to be geared slightly lower to offset the torque loss of advanced timing by running a slightly smaller pinion?

whatthefuggy

iTrader: (12)

try to bump your timing up like 3 settings. check your temps but it wont hurt anything as it should only go up about 30 degrees max. but have pinions and maybe a spur or two and be ready to gear it if u still lag behind

CH3NO2_Junkie

iTrader: (13)

If you are full throttle and at max speed 1/2 down the straight then its a gearing issue.

metalnut

iTrader: (36)

Well, I uppsed my pinion 1 tooth. I'm now coming off of the track around 145-150 degrees. The car seems more mellow in the infield, but I've definitely gained some top end speed on the straight, as expected. My times have improved a bit as well, though it's a new track layout so it may just be me getting used to it. Further testing will tell

Timing still set at the factory default, by the way.