retsoorkcuf

iTrader: (1)

I have been trying to decide what to get for my 22t a 13.5 or 17.5 this will be for a indoor clay med. in size with med. traction and I'm going from a T4.1 with a 3300 kv set up and want a little more power ..with that said which do you think 13.5 or 17.5 ?

Jonny5

iTrader: (19)

Really depends on your local rules and driving skill. Most tracks around here only have a mod class. A 17.5 will be easier to drive, especially with no timing and may be the ticket if you're looking to learn to drive the car consistently. Boosting it will make it an entirely different animal- still nice and drivable on the bottom, but will rip through the middle and top end. A 13.5 just gives more of everything- more down low and a stronger pull the rest of the way. If you're fairly experienced and comfortable with more power get a 13.5, or better yet a 10.5 and boost as needed, assuming you'll be racing mod.

kcooper273

iTrader: (62)

Thanks for your input guys!

kufman

iTrader: (6)

You may have temp issues running the boosted 17.5 on a large track since it will be in the "boost" for long periods of time. When motors are running in the boost region (extreme timing) they are very inneficient. The 17.5 may still be the way to go, but you will have to pay attention to temps.

Buckaroo

iTrader: (3)

It's all in the boost profile and the motor you choose. The RevTech doesn't like boost profiles at all, the D3, SP, Reedy, and X12's love it.

This is from my friend Harry, and might help you some (some might disagree, but if you can't get a boosted profile to be fast and cool with this method, you need to step up in motor):

Boosted profile from scratch
When I'm starting a profile from scratch, I use the rough kV to figure out where I want my RPM range.

For 17.5 I take 2400 * 7.2 [you can use the battery ending voltage if you think your profile is pretty close, otherwise I use nominal voltage] = 17,280.

You can use this for your end RPM, but I usually knock around 1k RPM off that figure, so call the end RPM 16,000.

For start RPM, I usually set it for the top 60% so 16,000 *.4 [take 40% off] = 6400. Pick something close from the list of calculated Start RPM values.

After that, it's just a matter of fine tuning to preference. If you want more pull off the corner, raise the Start RPM up about 1,000 RPM. If you want to smooth out power deliver on bottom end, lower the Start RPM about 1,000 RPM. Repeat as necessary.

The amount of boost you run is gearing dependent.

I only use Turbo if I'm visibly lacking in straight away speed, and don't think the added speed is going to hurt corner entry at the end of the straights. The most Turbo I'll run is around 10, ramp 1 or 2, with .4 delay [almost always]. I don't remember if I was running any today or not.

EDIT: Forgot to mention, if you feel like you want mid-throttle acceleration snappier, lower the End RPM down 1000 RPM at a time until you're happy. If you feel like mid-throttle acceleration is too aggressive, drop the Boost down in increments of 5.

To me, if you see the car kind of "shifting gears", your profile is likely going to upset the car and make it needlessly hard to drive, and slower. I'd rather see the car accelerate smoothly, but very quickly instead.

FYI: I use 3400 kv as my rough estimate for 13.5, and 4200 kv for 10.5's. Every company's motor is a little different, but the above calculations have served me well when building a boosted profile.

kcooper273

iTrader: (62)

Got my tax return coming Decided to go with the Hobbywing Xerun 2S ESC and a 17.5 motor. Just haven't decided what 17.5. Thanks for all your input!

(Ended up w/a Tekin 17.5 combo. Ahh the memories....3-23-15)

vw addict

iTrader: (38)

then why not a MMP or RS Pro or Viper combo or.........

kcooper273

iTrader: (62)

I'm still cheap......Haha

goose ae

iTrader: (19)

I run a 17.5 boosted on a large outdoor clay track. If you gear properly heat is not an issue and i was out running guys with 7.5 and 6.5 motors

trickedout

iTrader: (31)

Why would he. Hobbywing is Right on par with Tekin and Viper and a step above Castle in my book.

svndayNZ

iTrader: (20)

Hi guys, what about boosted 13.5 vs 17.5 in a class like touring? Are the differences that noticible considering similar gearing and boost.

idrummerboy13

iTrader: (15)

not my gold an black can

the 13.5 boost class is starting to become a mess, many new guys who have boost enough to run down the mod guys on the straight but crash every corner because they can't control the power. I would respect a 17.5 boosted buggy class just because it will make better drivers and it is much more of a pinpoint game...I only noticed this since i switched to mod....

Zerodefect

Exactly.

I'm not really any faster with an 8.5 compared to my 17.5 setup. Only on bigger 1/8th scale tracks that are grippy. Any place slick...forget about it, deosn't matter what I run.

If ever there was a class where everyone should be able to run whatever motor thay want, 2wd SCT/Corr is that place.

ducatibrandon

Old thread but I find my stock 13.5 struggles with these so called "Non" boosted 17.5s here at my local tracks.

kcooper273

iTrader: (62)

Well this thread was from 3 years ago when I was a noob, but your stock 13.5 should outperform a stock 17.5 all day long. I would check your gearing, or maybe you have a bad bearing in your motor that is causing a lot of drag.