16 replies to this topic

[timtulip]

Ok, so we've had this Porsche 997 for a long time http://www.slotforum.com/forums/index.php?...page=Porsche997 But we've had the red car with all the racing livery.
It's always been a great basher of a car. Quick, strong, low maintenance, grippy on the track like nothing else.
So I got the blue car with the racing livery and also the green GT3.

I haven't opened the green GT3 yet.

But the blue one got a little treatment: MJK tyres like the first red car that we have. The super glue in the standard plastic bushes trick. That's it.

The car behaves like a dog.
It rolls out of the slot. It doesn't accelerate very well at all. It doesn't brake well at all. Absolutely nothing like the red car (which is exactly the same chassis, motor, body etc).

On the track we have set up at the moment, the red car is consistent with a 5.9 sec lap time, occasionally doing the 5.8.

The blue car (the dog) does 6.8's and 6.9's. Once it did a 6.5

I took the body off the blue car (the dog) and it did 5.7 on numerous runs. As does the chassis of the red car.

So i know it's not the chassis of the blue car, or the motor, or the tyres, or anything like that. It's just the body is doing something stupid on the chassis.

The body rubbing on the tyres would explain the slow acceleration, but it doesn't explain the extremely poor braking. The body doesn't rub on the tyres anyway.

Nothing is rubbing.

I just don't get why there are so many problems with the body on: slow, no braking, pops out of the slot.

Does anyone have any idea what the heck is going on????

[Ember]

How many mounting points on the car? Could the body be causing the chassis to twist?

Not claiming to know what's going on. It was just the first question that came to mind after reading your post.

Interested to see what is suggeseted as the cause.

Embs

[FLY in the wall]

Like Ember I cannot think of the actual cause may I suggest swapping the bodies over that will confirm or eliminate that.
It is the lack of braking that baffles me. You could be just unlucky and have a bad motor but without the body it seems to do OK.

[manimmal]

on a general handling note for these porsches, open the holes the led's fit into the headlight cluster for improved body roll. mine both responded very well to gram or two of weight as far forward as possible. on a second read of your post i'd be taking the guide spring out as well, this will improve your lap times significantly, and doesn't really reduce the 'marshalability' of the car much at all.

the body and chassis were revised pretty early in the piece too, so you may have two identical cars that aren't quite identical.

[timtulip]

Yeah, I swapped the bodies. The red car body on the chassis does exactly the same same, behaves badly. So now i know it's a chassis thing.
It's not twisted as far as i can see.

I would add weight to the car, but when the body is off the chassis performs brilliantly.

I have a suspicion that the body mount holes on the chassis are not lined up properly with the body mounts themselves, causing chassis some trouble. This is the only thing i can think of.

So i'm going to shave off the standard body mounts and make my own out of wall plugs. We'll see how that goes!

Other than that, I'm still baffled to why the car is behaving so dreadfully.

[timtulip]

Oh, sorry Ember. There's 4 mounting points on the car.

Edited by timtulip, 25 June 2010 - 10:47 AM.

[Dreamer]

inverting one chassis on top of the other would give you an indication on whether the mounting holes are the same on both chasis. And how does that chasis work in the other body?

[rick1776]

Take the traction magnet out of the "good" car and put it in the "bad" car. Then get back to me and say what happened.

[timtulip]

Dreamer: the chassis still behaves like a dog with the good body on it, so that's why i'm thinking it's something funny with the chassis.

Rick: I added some magnets to the bad car. Still the same result. Goes like crazy with the body off, but as soon as the body (or either of the bodies) goes back on then the problems start.

Edited by timtulip, 25 June 2010 - 12:44 PM.

[rick1776]

Have a very close look at the wiring from the guide through to the motor. I suspect that the boby is interferring with the wiring or perhaps binding up the guide. You may even have a partial break in the wire that makes the problem known only when it is stressed in some manner when the body is put on. Place the body on the car but only use two screws to hold the body on. One at the front and one at the diagonal opposite rear. Just do up the screws so that the body is still very loose on the chassis. Do the wheels turn freely, front and rear ones? Does the guide rotate freely? Do a couple of laps and see what times it does. Repeat with the good car set up the same? Still no joy? Throw car in bin and buy a Pioneer.

[timtulip]

Hahahaha... it nearly went in the bin last night!

Will definitely look at the wiring. I didn't even think of that.

[FLY in the wall]

Don't bin it send it to me

What throws me is the lack of brakes. If there is a tab on the body that rests on the motor that could upset the gear mesh if it is binding but it doesn't explain the lack or brakes. To me that can only be electrical (famous last words)

Is the Spur gear loose? Just grasping.
Give the wires a damn good tug.

Last ditch bin all the DPR ready stuff and run new wires direct to the motor.

[timtulip]

Ok. So after everyones suggestions on here, (man, i tried SO many different things with this car, i've never taken the body off a car so many times!!!) and I thank you all so very much for your help, it was the simplest of solutions in the end.

I tried the wiring, the possibility of the chassis being twisted, the guide doing something funny, the body tabs rubbing on the spur or something like that. It the end it was...... tires.

We use the MJK rubber on a lot of our cars, they're fantastic on the plastic track. On the old red porsche (the good one), we used MJK rubber but we don't know what size. All we know is that the profile of the rubber was meant for one of the old dodgy Lambo's we had (very wide rear tires, extremely low profile).
So when we got these new Porsche we also ordered some MJK rubber but it ended up having a much taller side wall (it fills the guards totally).
I had some old Slot.It silicone things, extremely low profile, that fit the Porsche. Instant improvement.
They take a bit to warm up, but they brought the car down into the lap times of 6.0 - 5.9 consistantly (the fastest lap time is now the Marice Carter #88 Camaro at 5.5 running MJK's).

So the rolling diameter of the large sidewall MJK's that we used on the dog Porsche ended up playing with everything.

Lesson learned.

[timtulip]

I got the MJK's that we've been using on the first Porsche (the red one). Another big improvement. But the car just still wasn't running as well as it should have been, at least not as good as the other couple of Porsche that we have.

Earlier in this thread, Fly In The Wall briefly mentioning something about the possibility of the car having a dud motor. So i pulled an old motor out of a very trashed Camaro that was in the box of parts. And wow. The blue Porsche with all of the fiddly things i've now done to it (float the body by trimming the chassis, shaving the body posts so they are no longer recessed into the chassis, re-wiring to bypass the DPR business, glueing the rear bushes in, small spacers to take out rear axle play, MJK rubber) performs better than any of the other cars, except my Camaro (Camaro will always be King on my track hahahaha)

Thanks Fly In The Wall and everyone else! I've learnt a heck of a lot from this one little car. From tuning cars to rebuilding cars!

I hope this thread helps someone else one day too!

[grandtorino92]

i have the exact same problem with these two cars but its the other way around the red car is the dog and the blue flys. very confusing

[lenny broke]

grandtorino92, on Jul 21 2010, 04:20 PM, said:

i have the exact same problem with these two cars but its the other way around the red car is the dog and the blue flys. very confusing

Why don't you swap the bodies over then you have exactly the same problem. might be less confusing

I'll get out ya way now

LB

[timtulip]

grandtorino92, on Jul 21 2010, 04:50 PM, said:

i have the exact same problem with these two cars but its the other way around the red car is the dog and the blue flys. very confusing

If you have a spare SP motor the same as the blue car, put the spare motor in the red car.
I wish i did this as the first thing, because i think that's where most of my troubles were in the first place! As soon as i swapped the motor, everything made sense.