Hi guys,

After having my car in mothballs for a few years due to making a family, I have recently rekindled my love for R/C cars and want to get back into the hobby.

I'm looking to hopefuly keep my current car and just upgrade with newer electronics, so I'll list what I have currently. I'm looking (for now, until I get comfortable with it) to run around my neighborhood streets and race my neighbors who also have cars. All on-road

What i have is a HPI RS4 Rally, with a F1 reverse ESC (Does not support LiPO), Team Orion 11t motor, Futuba 2.4ghz radio. The batteries are long since dead (NiCD) and thinking of updating to LiPo, but not sure of the benefits for my application. I would need a new ESC to support that, I believe?

The car runs with a new battery, although the motor gets stuck and I have to tap on it to get it moving, thinking I need to do a tear-down and rebuild on that, or replace it altogether.

The car has crazy accceleration, but low top end speed -- any suggestions on gearing to improve that, assuming I keep the same motor?

Any help or advice is appreciated.

Welcome back.

You don't need a different ESC to run 2S lipo, a 6 cell NiMh or NiCad will have about the same voltage. But if your ESC doesn't have a low voltage cutoff to protect the lipo against too low discharging, you need a seperate lipo voltage monitor. Does your charger have lipo charge program btw?

For better top end speed, you could try a bigger pinion gear. That will decrease acceleration, but the car can reach a higher speed on the straights. Just make sure you "up the pinion" in steps, and check the motor and ESC temperature on a regular basis during driving, as a bigger pinion will put more strain on the motor.

Originally Posted by SoloProFan

Welcome back.

You don't need a different ESC to run 2S lipo, a 6 cell NiMh or NiCad will have about the same voltage. But if your ESC doesn't have a low voltage cutoff to protect the lipo against too low discharging, you need a seperate lipo voltage monitor. Does your charger have lipo charge program btw?

For better top end speed, you could try a bigger pinion gear. That will decrease acceleration, but the car can reach a higher speed on the straights. Just make sure you "up the pinion" in steps, and check the motor and ESC temperature on a regular basis during driving, as a bigger pinion will put more strain on the motor.

I found the original box and manual for my ESC, it's actually the f1 pro which was the high end back then..definitely worth keeping if I can, I'll have to look into the lipo voltage monitor.

I have a weird gearing; my pinion is the stock 90 but my spur is 18 (stock is 31 I believe). Going to the LHS tomorrow to buy gears... I will go back to stock spur and play with the pinion..any suggestions where to start besides that?

Also you asked about my charger.. Well it died and will need to be replaced,in the short term I picked up a cheap duratrax onyx 100 and a couple 3000mah nihm batteries.

Wondering if it's worth the expense to replace my old fm radio/receiver with something more modern as well?

P.s. I found the (unpainted) inner body set...wow I forgot I bought that! I need to practice my painting before I attemp that, though.

Perhaps some people owning this car can shed some light on a more common pinion gear?

As for the radio, if it works well, I don't see no need to replace it right away. Futaba is a good brand, among the best. Btw, in the first posting you refer to it being 2.4 GHz, but now you mention it's in the MHz band?

Yeah I was at work at the time and didn't realize what kind of radio it was..definitely fm

2.4 GHz has advantages in dealing with interference, but a quality FM radio can still be useful. What type is it?

It's a futaba magnum sport. Works well so I guess no need to replace it.

Something is wrong with the motor though..it runs if I give it a push but from a dead start it won't move at all, as if the battery was dead..give it a shove and it runs until you come to a complete stop and then the problem shows again.any idea?

Your motor needs a rebuild.. usually the brushes are hanging up or the comm is worn. I still have a RS4 Sport 2 that I love. I have a couple of them. Parts are getting scarce, but still available on ebay. Your gearing I would start around 25T on the pinion. I think the spur is fixed at 90. thats all I ever run. Mine is running a Castle 5700 brushless motor, Castle esc. 2S lipo batteries and 2.4ghz radio. I run a digital servo for steering and the steering has been modified along with a Carbon Fiber upper deck. Runs in the 50's on 2S and around 65 on 3S.
Here are a couple pics of mine.

@cenracer1:
Very nice, i like!

I somehow lost my foam bumper and need to replace it as well.. heck I need a new body as well.

Rebuilding the motor I think is out of my skillset for the moment, or at least, i've never tried. I most likely will end up replacing the motor/esc with a brushless system anyhow (as funds allow).

I noticed that alot of motors these days have a kv value, instead of turns..e.g. my curernt brushed motor is 11turn. What would be a comparible motor to that, in a brushed system?

I guess I don't need anything super powerful since i'm not actually racing competitively, but I want to have upgradability in mind.

Don't confuse turns/kv with power... lower turns (higher kv) gives more RPM, but not necessarily more power.

There's lots of theories/formulas for figuring out what is comparable between brushed and brushless, the best way is to find the rated rpm of the brushed motor divide by the voltage to get kv.

A 16T double brushed motor is about 4100kv, which is close to a 10.5T brushless. It's about 1.5-1.7 to go from brushless to brushed in terms of turns, but it's not an exact science. An 11T brushed would be about 5.5-6.5T brushless.

http://www.teamnovak.com/products/br...spec_chart.htm

Wparsons is right on the money with what he said. KV and power are reversed with brushless motors... sort of. I run mostly 5700kv motors in my touring cars because I want the rpm's for speed. You don't need or want torque with these cars, but believe me there is too much with this motor anyway. There is no comparison to brushed motors in any way.. I also run the same KV motors in my slash and rustler but with a 4 pole design that has much more torque, up to 40% from what I'm told.. way over kill for a touring car. I am a speed junkie, but this combo will make the car a handful to drive if you are not skilled. The car can take the abuse but crashing is another story. The only thing I'm not sure about is the chart for figuring out brushed and brushless turns. Novak says one thing, Castle won't even discuss it and all other manufacturers have different formulas. I will say this however, I used to run brushed motors ranging from 8t and up and they aren't even in the same league as these current brushless motors are. Even the cheap HK moitors will outperform the best brushed motor.
Conundrum4000 thanks for the kind words on the car. I need to get a better picture, the lighting stunk and the wife was getting angry that I took a picture on the kitchen table. She just doesn't understand. Had to remind her the car was cleaner than the house.. and that didn't go ever too well.

Originally Posted by cenracer1

I need to get a better picture, the lighting stunk and the wife was getting angry that I took a picture on the kitchen table. She just doesn't understand. Had to remind her the car was cleaner than the house.. and that didn't go ever too well.

Oooo she didn't hit you in the head with your car. Your a brave man. The car does look rather nice on the table cloth.

Originally Posted by mredzadventure

Oooo she didn't hit you in the head with your car. Your a brave man. The car does look rather nice on the table cloth.

Don't know if brave is the right word.. crazy or stupid may be better. She puts up with me and the cars so I really cannot complain. placing the cars on the table right before dinner for a couple of pictures wasn't the brightest thing 've ever done.. Oh and thanks for the compliment on the Table Cloth.. Its one of her favorites..LOL

Kitchen table is best place to work, IMO. That's where I have mine, along with a soldering iron, spare parts, shock oil, etc.

But my wife guaranteed me that if I didnt move it by this weekend, I would 'pay for it in other areas.'


I'm thinking of just grabbing a cheap HK ESC/Motor to play with for now.. cost wise nothing even comes close, but is it worth the wait from China? hmm

Originally Posted by Conundrum4000

Kitchen table is best place to work, IMO. That's where I have mine, along with a soldering iron, spare parts, shock oil, etc.

But my wife guaranteed me that if I didnt move it by this weekend, I would 'pay for it in other areas.'


I'm thinking of just grabbing a cheap HK ESC/Motor to play with for now.. cost wise nothing even comes close, but is it worth the wait from China? hmm

I know a couple of guys who run them and they are hard to beat for the money. They don't seem to last as long as the Castle systems or some of the other brands, but for the price and if you are not abusing them they will be fine. Unfortunately, Castle seems to be making only 4pole motors now and they are too much for the touring cars, They will work, but you have to be careful with the power.. They will cause havok with the belts.

I have a shop that I do all my work in. Its fully decked out for r/c including my planes and helicopters. but I was upstairs in the dining room when I decided to take the picture. Not the best plan but I survived. I don't work on the table with my cars.. that would be pushing it with the wife.