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Old 12-29-2014, 03:28 AM   #1
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Default Problems going straight with Colt Porsche 962 body

I am having trouble keeping my Team Associatd TC4 basher going straight with my new Colt Porsche 962 body. My friend at my LHS said the Porsche body has too much downforce and that I will have to cut slits and vents into the shell to allow some air to flow through.

Here is a pic of the Colt Porsche 962 body and where I was suggested to cut.
Will cutting these slits help to keep the car straight? Anyone have any other ideas or suggestions?
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Old 12-29-2014, 07:05 AM   #2
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Originally Posted by tc4basher View Post
I am having trouble keeping my Team Associatd TC4 basher going straight with my new Colt Porsche 962 body. My friend at my LHS said the Porsche body has too much downforce and that I will have to cut slits and vents into the shell to allow some air to flow through.

Here is a pic of the Colt Porsche 962 body and where I was suggested to cut.
Will cutting these slits help to keep the car straight? Anyone have any other ideas or suggestions?
Is this happening at high(er) speeds, or during low speeds?

The car should run pretty straight without cutting holes in the body. Did it run straight before switching to this body shell?

I would check things like your steering trim, front alignment, toe in and camber. Make sure the bearings are running free, and nothing is dragging on the road or the tires are not rubbing the body. Does the car do the same thing with out the body....
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Old 12-29-2014, 08:19 AM   #3
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Yeah, your friend probably watched too much Simpsons. They used speed holes.

Get the steering geometry, suspension and some rear toe in right and your car should run straight as an arrow even with a poorly inflated used condom for a body.

Hopefully you're not running some stupid turn motor either, seeing you have a shaft drive car otherwise it'll torque steer like a pig and you'll never make it go straight.
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Old 12-29-2014, 08:36 AM   #4
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How is the car not running straight? Is it always pulling one way, or is it erratic and wandering either way? Is it only at high speed, or even while cruising around at partial throttle?

TC3s and TC4s were notorious for torque steer; if this is happening while accelerating and braking, then that's likely your problem and you'll mostly just have to learn how to drive it. Usually it will turn one way on acceleration and the other during braking. If the only thing you changed was the body and it was running true before, or if it runs true with a different body (try an old one) then there could be some asymmetrical aerodynamic issues with the body itself. If it feels skittish, has significant understeer at speed and wanders randomly then it's possible you have too much rear downforce and the front wheels are getting light. I wouldn't cut those holes suggested as it will weaken the body and cause drag. I would trim the rear "wing" (whale-tail) down.
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Old 12-29-2014, 12:07 PM   #5
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My tc4 does not go straight at low speeds and high speed with this body. It is kinda eratic and wants to go left or right and not straight. I switched back to my hpi f1 Mcclaren body and it goes straight again so I know its because of the porsche body. Im thinking maybe the rear wing has to much diagonal angle in it and slits need to be cut back there?

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Old 12-29-2014, 12:28 PM   #6
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4wd sedans aren't really meant to use lemans style bodies; they usually have too much rear downforce and not enough front downforce; this will cause the erratic steering and wandering that you describe. Sedan bodies utilize the windshield and nose for a significant amount of downforce which is localized more toward the front. That Porsche body is likely to be used on 200mm pan cars; but still probably wouldn't handle very well anyways.

You could try reducing the rear downforce by trimming down the "wing" or adding slots, but you'd be better served by using a propper sedan body.
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Old 12-29-2014, 12:37 PM   #7
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I was planning to use this body for speed runs on my other TC4 which has gone 111 mph and should be faster now. I've seen some people use "le mans" type bodies for speed cars. I was hoping this body would make my car less prone to lifting off the ground at high speeds with its increased downforce.
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Old 12-29-2014, 12:44 PM   #8
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If your car handles fine with one body but poorly with another, taking all body related variables into account (body not badly out of shape, etc, and assuming the body is perfectly symmetrical and there's no idiotic mistakes on your part such as body rubbing on wheels and such) I would suggest your car has some handling problems exacerbated by the body that gives more downforce. Reducing downforce is just masking the issue.
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Old 12-29-2014, 12:46 PM   #9
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The downforce on that body looks poorly distributed.

Also, more downforce = more drag. You likely won't be much faster with that body and possibly slower. Cutting slots will cause even more drag.

First thing I would do is trim down the wing.
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Old 12-29-2014, 12:50 PM   #10
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too much motor not enough traction will do that...
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Old 12-29-2014, 12:59 PM   #11
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I think I will try cutting holes near the rear wing to try decreasing downforce back there. If that does not work I will try trimming the rear wing down as you guys suggest.

It does go very straight even at over 100 mph with my F1 McClaren body.

Here is a video of a TC3 that goes pretty straight with the Porsche 962 body without trimming:

http://youtu.be/cAT2plpLu8M
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