SLOW RS4 Rally???

[mexican_speed]

Wuz up, I recently bought a RS4 Rally, when I completed building the kit I was amazed to realize that it was fairly sluggish on take-off. I'm runnig a Reedy Rage Pulse-R 13x2, with a Novak Cyclone. I swappedd this setup from my Traxxas Bandit, BTW, the Bandit is fast. But on my RS4 it seems it that someting is holding back on it. My buddy has the same car with a 15x2 on his and that car screams. My gear ratio is 20t pinion and 96t spur, 48pitch. Any and all suggestions are highly appreciated.

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You have a good memory, remember what the back of my car looks like everytime I WIN!!!

[JP]

Try going to an 17-18 tooth pinion.

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[SubaruTiburon]

Uhh...JP...get your gearing right. I run a 31t pinion and an 83t spur with a 19x2 motor in my rally and it flies...i think maybe you have a backwards part somewhere, check your gear mesh, maybe thats your problem.

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Lets state the obvious, HPI rally cars rule.

[hpiguy]

UHHH I agree with JP on this.

If you want more punch off line, drop a tooth or three on the pinion.

If you want more top end go up a tooth or two.

Subaru: Your nineteen turn motor has more torque, so your gearing may be right for your 19 turn motor, but it is WAY off for a 13 turn motor.

[rcracer28]

ARE YOUR BELTS TO TIGHT? ARE THEY LINED UP RIGHT? CHECK IN SEE BECOUSE THATS A BIG THING WITH BELT DRIVEN CARS!

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ask me anything

[mexican_speed]

Hey guys, I checked my belts and they are straight an tensioned accordingly, but I have noticed that on the lay shaft the rear belt pulley looks frayed. Normally on a 4WD car, when you turn either the front or back wheels all of the wheels should turn. So i tried this on the front wheels, all wheels turn, the catch is the rear wheels, the diff turns the belt and the pulley on the layshaft but not the front
http://www.rccaraction.com/ubb/confused.gif. This is my first HPI product, is this or is this not normal. I was also considering an aftermarket layshaft with oneway pulleys.

[easttex75]

How can a 20 tooth pinion with a 96 tooth spur be way off guys, if the manual suggests a 22-23tooth pinion for a 13T motor? A 20tooth is a little undergeared. Most likely there is some binding somewhere. Gear mesh too tight, belts rubbing. As crazy as it sounds, make sure there's not a rock wedged under the rear assembly. This happened to me, and my rear belt was frayed as well. Loosen the motor mount screws, take the mesh apart and roll the truck on the ground. It should move very easily..

[mexican_speed]

I checked for any rocks and/or debris, but did not find anything. It was the layshaft pulley for the rear wheels that looked frayed. I know Robinson Racing Products makes an aluminum layshaft with oneway pulleys. I'll just invest my money on one of those and replace the composite plastic pieces. Can anyone tell me if these are any good.

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You have a good memory, remember what the back of my car looks like everytime I WIN!!!

[This message has been edited by mexican_speed (edited 10-12-2000).]

[Top End]

Maybe your motor's comm needs to be turned. Try swapping your motor with your buddy's, you already know his is fast, if your car is suddenly fast with his motor, you know the problem. A 13turn motor is going to need to have the comm turned at least every 5 runs or so to maintain like new performance.

Just a thought.

[dc racer]

Check the eccentric cams in the which hold the rear diff bearing. Make sure they both point to the same number. Try starting with number 4, if the belt skips move up to number 5. Also make sure nothing is rubbing against the diff.

[This message has been edited by dc racer (edited 10-12-2000).]

[dc racer]

The robinson lay shaft is not really necessary. It will add rotational mass which slows acceleration. It can also wear more quickly than the stock nylon pieces. As for the one ways, they are a matter of preference, adding a one way may make the car faster in the corners but the car will only brake with the rear wheels when brakes are applied, thus making it very easy for the car to spin out under braking.