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Old 06-22-2011, 01:54 PM   #31
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Originally Posted by JJBinks View Post
You got a pretty good car then. haha. In my 6 years working at a hobby store when someone switched to a faster more powerful motor... an .18tz we will say based on what we sold. That transmission and drivetrain had a hard time keeping up. Just based on repairs that came into our shop.
What parts were you seeing failing on the drivetrain? The most notorious issues were either spur gears (usually from improper gear mesh), differential outdrives (which do wear and just wear faster with higher powered engines), and differential ring gear wear but that was more of an issue with the Nitro MT than the RS4 Nitro 3...and that was usually traced back to an issue with the spacers on the drive shaft gears.

You can see some chassis flex due to more power but that's fairly minimal compared to other factors. The average Joe Drive wouldn't be able to detect the chassis flex changes seen in an RS4 Nitro 3 with all other factors being equal. Higher speeds will exacerbate the situation but still not to the point where anyone other than an expert driver would feel the difference.

In many cases, a flexible chassis can be a GOOD thing for a novice driver or if racing on very bumpy conditions as it keeps the car more stable and feel less twitchy. A very ridged car can be very precise but may almost feel "too responsive" for most drivers by reacting to every little input or imperfection in the surface.
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Old 06-22-2011, 02:24 PM   #32
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Thanks all, really appreciate the respond...
Yes I do agree that changes will alter the car characteristic in various section..
My son is an average driver and we are working on his driving skills...currently we put 50wt on all for shocks with the black springs...any suggestions...thanks
Is he running the stock kit black springs or the progressive black springs? 50 wt sounds about on par but what is he running for pistons inside the shocks? The stock pistons, IIRC, are #2s and that's where he should be too.

Let's get down to some other, possibly more critical questions. How's the drivetrain? Is is clean, rotating freely, and are the diffs set up with thick grease inside? Is he running a front spool or one-way differential?

What is his ride height front and rear? What kind of surface are you racing on, asphualt? I remember you mentioning you are running foams...are you adjusting ride hieght for tire wear?

How are you setting your camber? Do you have a camber gauge? What are you running for camber settings? Measuring upper links will only get you in the ballpark as variations in material during the molding process of the plastic gives slightly different deminsions to the ball cups and thus will cause different camber angles even if the links measure the same. It may only be .5 degrees but it's enough of a difference.

Then are you setting the car's tweak? A car that is not properly tweaked will be a handful to drive. This is a criticle step in getting the car set up and if you have access to a tweak board, even better but you can do this without one.

What's your front toe at? Are you toe-in or toe-out? How much?

To give you an idea of how critical these steps are let me share with you a story. I was at a track one day and saw a young boy and his father at the track. The young boy was driving and had a box stock Super Nitro. The car would run for a while then flame out and the father was trying to get it restarted. I walked over and offered to help explaining that the reason his son's car kept dying is that it was overheating. I richened up the needle a quarter turn and the car didn't flame out duirng the qualifier. However, he finished dead last multiple laps down. I could see the car was all over the place and not handling well at all.

After the race I asked the boy and his father what tires they were running...their answer was the stock M compound slicks. I then asked if they had set the car up and made all the checks I just asked you about. They hadn't. So I told them that after the boy turnmarshled to come and see me.

When they did I handed them a set of 33R slicks with the molded inserts in them and put them on his car. I then took their car and went through all those steps. Checked ride height then put it on my Hudy setup board. After getting all that squared I put it on my MIP tweak board and set the tweak. I then handed the car back to the boy and when it was his turn to race again, I went and watched him race.

He won the race by a lap and set a new TQ pace. He then went on to win the main too. We didn't touch his shocks or add any aftermarket parts other than the tires and inserts. Next time I saw them at the track Dad told me they went out and bought the tires I had let them use that week.

So if you haven't got the right tires for your track and haven't made sure your setup settings are spot on then anything else you do to the car won't help all that much as they'll just be better parts on a still weak setup.

For the Nitro 3 I would reccomend the following basic setup numbers.

Ride Height: 3.5 to 5.5mm with the rear riding level or .5mm higher than the front.

Camber: 1-2 degrees positive camber (top of the tires leaning in towards the car) front and rear. The goal is to have the tire wear evenly. If when you bring the car back into the pits your foam tires look "cone" shaped, you may need to adjust camber from the current setting. Usually 1.5 degrees is a good starting point.

Front Toe: Set this to either 0 toe (tires pointing straight ahead | | ) to 1 degree toe in (tires looking like / \ ) when viewed from above and the car pointed away from you. If you would like a more aggressive feel to the steering when entering a corner, you can set it to 1 degree toe out (\ /). This will make the car feel very twitchy though. I'd start at 0 and see how that feels.

Tweak: NOTE: it is important to make sure your shocks are the same overall length BEFORE you do this step. ALL FOUR should be the EXACT same length. Use a set of calipers to measure.

Threaded shock bodies are a BIG help if you don't have them. You can use spacers but they're really a pain. To set tweak fill your gas tank to about half full, put the car on a totally flat AND LEVEL surface (the level part is very important), and compress the suspension a few times. Then, using an hobby knife, lift the car from the very centerline of the chassis between the left and right side tires on either the front or back. Both tires SHOULD come off the ground at the same time. If one comes up before the other, you need to adjust the oposite shock. So if you're checking tweak on the rear and the right rear tire comes up before the left rear you will need to increase the preload (add more spacers or move the spring collar down) to the LEFT FRONT shock. If the left lifts before the right on the rear, you would increase the preload on the RIGHT FRONT shock. After you make the adjustment, put the car back down, compress the suspension again, and repeat until both tires come off the ground at the same time.

Once you're done with one end of the car, flip it around and repeat the process with the other end remembering to compress the suspension before each test. ALSO it is important to do this adjustment AFTER you have checked your ride height since you use your preload to alter your ride height too...this means that if you change your ride height you'll need to re-tweak the car.

Hope this helps. Best part about this is, with the exception of the tires and tools, it's all free.
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Old 06-22-2011, 08:32 PM   #33
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You got a pretty good car then. haha. In my 6 years working at a hobby store when someone switched to a faster more powerful motor... an .18tz we will say based on what we sold. That transmission and drivetrain had a hard time keeping up. Just based on repairs that came into our shop. I agree with you HPI did use some pretty decent parts..... haha
Possibly got a good one, or just got lucky, or...

When i decided to go big block, i tore down the entire car, and rebuilt checking and setting all gear mesh tolerances and dogbone loads to my liking, and everything was a little loose for my liking straight from HPI.. so maybe this is why some are breaking drivetrain parts when going to engines with more torque.


I wish the parts on my Firestorm would have taken the abuse as good though, cause it couldnt handle the power for squat. Thats why it has a Duratrax diff and OFNA dogbones
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Old 06-23-2011, 10:23 AM   #34
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Possibly got a good one, or just got lucky, or...

When i decided to go big block, i tore down the entire car, and rebuilt checking and setting all gear mesh tolerances and dogbone loads to my liking, and everything was a little loose for my liking straight from HPI.. so maybe this is why some are breaking drivetrain parts when going to engines with more torque.
Whoa...big block power is a lot different than a .12 racing style engines or even an 18 small block. The Nitro 3 was never designed with big block power in mind. The Nitro and Nitro 2 were better able to take big block power than the Nitro 3 was.
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Old 06-23-2011, 10:29 AM   #35
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Whoa...big block power is a lot different than a .12 racing style engines or even an 18 small block. The Nitro 3 was never designed with big block power in mind. The Nitro and Nitro 2 were better able to take big block power than the Nitro 3 was.

I agree haha. When I was talking drivetrain weakness I was speaking about putting an os .18 tz motor in it. .12 it does pretty well from the one person I have seen put one in. The store I was at was mostly bashers, no one cared about a race legal .12 haha
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Old 06-24-2011, 06:00 AM   #36
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Whoa...big block power is a lot different than a .12 racing style engines or even an 18 small block. The Nitro 3 was never designed with big block power in mind. The Nitro and Nitro 2 were better able to take big block power than the Nitro 3 was.
most cars/trucks that come with .12 or .15's were never designed with big block power in mind. Is that supose to stop those of us that do it?

But like i said....sofar with almost a gallon of beating on it, i have yet to break ANYTHING with the bigblock in the car. And im not easy on my stuff...
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Old 06-25-2011, 04:33 PM   #37
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most cars/trucks that come with .12 or .15's were never designed with big block power in mind. Is that supose to stop those of us that do it?

But like i said....sofar with almost a gallon of beating on it, i have yet to break ANYTHING with the bigblock in the car. And im not easy on my stuff...
Well of course not. LOL But you were claiming people were having breakage problems with small block engines...and saying it was due to the slop in the system from HPI. Except for pinion to spur mesh, there were no major issues with the gear train in the Nitro 3 (The Nitro MT was a whole different story). I'm saying that so long as maintenance is done, the stock Nitro 3 is good for any small block engine. The fact that it is handling the power of a .21 with nothing more than proper shimming shows that the parts are more than enough for a small block's power. They were engineered with the idea of mass production, and the flaws associated with it, in mind.

After all, I put a .21 in a Super Nitro and it had few issues with the power other than accelerated wear.

Last edited by Robotech; 06-25-2011 at 04:44 PM.
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Old 12-07-2017, 01:39 AM   #38
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Default Question on hpi rs4 rtr 3 evo

Having a problem wmy hpi rs4 looking for carburator factory setting and also wondering on whats the best glow plug to run in it what number thanks new to nitro
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