Removing scratches/marks from Car

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I wanted to know
1. How to remove scratches from the car body.
2. what type of paint to use to disgiuse any scratches
3. how to clean the parts inside the hood without using a lots of water.

Please advise.

4. It will be great if someone can tell what's the relation between the speed of a CAR and the RPM dsiplayed on the dashboard. What is the ideal RPM and how should it chnage when the car is accelerated / de-accelerated.

posted by  amitverma0101

1) Touch up paint - or - may be rubbed out with compound.
2) Touch up paint.
3) A rag and elbow grease.

posted by  DodgeRida67

Blah, you do know for #4 you coulda gave him a quick short answer verse making him read a novel :wink2:

Paint scratches can never be completely disguised, you will always be able to tell that the scratches were once present, the only way to get rid of them, is to paint the car (or entire body panel). But if you don't care, what he said.

As for RPM being relavent to car speed, this depends. Are you driving an Auto or Standard. I won't get deep into this, I'll make it as simple as I can for you. RPM's are not completely relavent to a cars output speed on an automatic for there is no solid connection between the engine and the transmission. All that's between your engine and transmission with an auto is a hydraulic pump (engine turns a fan type object, and it has tranny fluid inside of it, and the fluid the fan presses, hits a fan on the other side, the tranny side and makes it turn (This is all within something called a torque converter)).

For a Standard trans, the clutch makes a solid link between the engine and trans with the clutch. That is why if you don't get the car moving before you completely let off the clutch, you can stall the car, which you can't do in an auto.

As for how the RPM's should change as the car is accelerated, well, this can vary also. If you're driving hard, you want to get your car up to peak horse then drop it into next gear (let's say peak is 4500RPM). Now, if you're driving normally, you'd want your car to shift much earlier, as early as 2500RPM-3000RPM, and your cruising speed may be at about 1500RPM for best economy. Here's an example of how this is accomplished with gear ratios that I took from an 05 standard mustang.

1st - 3.370
2nd - 1.990
3rd - 1.330
4th - 1.000 (almost always is 1 on 5 speeds)
5th - .68
Reverse - 3.150 (This is usually lower than 1st gear, not in this case)

What all those numbers mean is each of them represents the input of the tranny when the trannys output is 1 full turn. So for first gear, the engine needs to rotate 3.370 times for each complete output turn (the driveshaft) of the tranny. For 4th, it's even, for every 1 engine rotation, there's 1 output rotation. For 5th, the engine only needs to rotate .68 times for 1 output rotation.. etc. So you see how 5th gear can be very economical at highway speeds.

So the ideal RPM for cruising speeds vary's a lot, in the city it may be 1500 or so, but on the highway, depending if you have 5th (a.k.a. Over-Drive) you may be looking at anywhere between 1800 and about 2500 (engine size also changes your RPM, if you have a 4cyl, usually the ratios are different than that of a V8 because it doesn't have the power, so it needs to run at higher RPMs to compensate)

Hope that helped....

posted by  88GrandPrixSE

1. Assume clutch lockup on modern transmissions

2. I think initial shift points are best found like the truckies method: Get vehicle up to a reasonable speed in 2nd and kick down to first, the revs/speed where the lower gear just accelerates the vehicle is your shift point. Ditto procedure for subsequent gears. This puts the shifting just under the max torque curve intersections and as we all know acceleration follows the torque curve.

posted by  Wally

Sorry, I didn't include enough information.
I need this for my Nissan Altima 1994 GXE Automatic transmission.
I think there is something wrong with the car.
When I first start the car, the RPM hovers around 1200.

From gear 1 to 2 : 2500-3500 RPM. On 2, it remains between 1500-2000 if the speed is not increased.
It does the same (RPM rises upto some level) everytime the gear goes up.

Then, after driving for 15-20 minutes, when I am stading on a RedLight, it drops to 600-800.

If, I switch the A/C on, the RPM increases by 300-400.

What is lowest RPM a car in good condition should have?

posted by  amitverma0101

That's all normal, The car idles easier when in park or neutral because the tranny is freewheeling with the motor, but when you're stopped at a red light the tranny is locked solid so the engine has to work harder, so it idles slower. A/C will increase engine RPMs because it takes a good amount of power to turn the A/C unit, so again, the motor has to work harder, and when the compressor cuts off, the RPM's will jump. Car's idle usually about 700-800ish with the trans locked up, but they can idle as low as 500, depends on the car.

Your car sounds normal

posted by  88GrandPrixSE

Thanks a lot !
Makes me feel comfortable.

posted by  amitverma0101

Many scratches can be completely removed through Cut-polishing with an aggressive cutting compound (with a powerpolisher and wool pad.)
If the scratches are really deep and through all layers of the Clearcoat-then wet-sanding ,followed by cut-polishing is reqiured.If the scratches are through to the metal -then a touch-up paint stick($6)-from the car dealership will cover them up well.Or there's the more expensive option of repainting the scratched area.
As a detail department manager,I have successfully removed thousands of scratches for cutomers.It might be worth getting an estimate from a detail shop for (just cut-polishing the scratched area-not the whole car)-If it was just several deep sratches ,it would take me 10 minutes to remove them and I would charge less than $20. If your not experienced at "scratch removal"-It might be a bit risky to try it yourself.Good luck,and I would be happy to answer any Detail/Appearance questions you or anyone else may have.

posted by  Nicktheguy

Does this include when your drunk friend draws on your car? I took the car in for a normal wash and wax but I can still see the outline of what she drew, is there anything else that I can do?

posted by  element driver

Have you tried to buff it out yourself? What did she use to draw on it with?

posted by  97Talonchik

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