What kind of damage would we be looking at if any, from a motor being spun backwards...say by a 100+mph spin backwards , without the clutch being disengaged?
What would most likely be effected? valvetrain wise and engine wise.

 

Thats gonna be tranny damage.

 

the timing belt assembly was only designed to spin one way as well. If spun the other way there is a chance of it jumping time, and if it jumps too much then the pistons hit the valves, and if this was done for more than a split second, it is a high chance the whole engine is destroyed.

 

Evil! Any more details?

 

I've had an Evo traveling the opposite way at around 75 MPH with it in a forward moving gear while the car was moving backward. The car was totaled when it was all said and done, but even after the crash, the motor started up just fine.

My advice if you ever get into a situation like that on a closed course (drifting attempt or something) is to just stay WOT so that you make enough power to keep the wheels spinning, or mash the clutch to the floor. I wouldn't want to tear up the drivetrain.

 

Sorry, was more theoretical than anything....although I have been in a situation like that at close to 120mph, I stood on the gas all the way through the spin, until I started rolling and bouncing off various immovable objects, when I came to a stop on my side ,minus left front suspension and wheel assembly and left rear wheel and suspension somewhere crammed up under the car into the body, for what ever reason I decided to see if the motor would fire back up , I turned the key and it started no problem... but with 21,000 dollars worth of damage it was deemed a total loss.

 

uhm... the motor is not affected by the rearward driving gear. the motor still runs "forward"

and you shouldn't go starting cars that just got ****ed up... that's called electrical fire... and it can easily cost you your life.

 

What he is meaning is....

Drive forward, get up to around 100 MPH, spin the car 180 degrees, keep the car in a forward gear, will the motor be damaged when the wheels stop rotating the "right" direction for that gear and start going the direction of travel. The answer is yes.

 

in a spin....two feet in

 

So the wheels will spin the other way? They won't just lock up and slide to a stop? I see cars going backwards a lot in racing and even on some car shows when they spin, so if the wheels stopped spinning forwards during that they would start to spin backwards?

I hadn't really thought about it before. That rule ^ sounds good but if you try to catch the car you might spin nearly 180 degrees before you actually "loose" it so then I guess you have to get the clutch pedal down really quick.

Aston

 

Interesting topic...

At ~100mph you will be in one of the higher gears. In mid-spin the wheels will need to slow down to zero rotation before spinning the other way... if you're still in gear by then the engine will stall... then when the wheels start spinning the other way the engine will not be under any sort of power which is okay to spin backwards, but...

...just remember it nearly impossible to maintain going backwards. With the engine stalled and you still being in a forward gear just the compression alone (engine braking/slowing you now) will most likely cause you to continue spinning in one direction or another.

...but if for some odd reason you maintained going backwards and was too dazed to have the smarts of putting in the clutch... the oil pump would now be working backwards... damage to the engine would result due to whatever amount of time you left the engine spinning (but not combusting) without oil... this is a candidate for spun bearings and all sorts of other bad stuff which might not be immediately apparent in a subsequent start-up and running.

In race conditions when something bad happens such as this; the first priority is to get the car stable again... taking it out of gear should be second nature to an experienced driver since it takes the engine and transmission dynamics out of the equation. Once the car is under control you can then use the power as a tool to get you straight and back on track.

 

the best thing to do. taught that at the track. and heard all HPDE say that too. light grip on the wheel, thumbs up, clutch in, brake in and ride it out.

 

But with the car out of gear you have less control and then you have to worry about getting it in to the right gear for the speed your traveling and engaging the clutch smoothly once you get it under control to make sure you don't cause it to spin again. Also, like you said, you can use the power to control the car if it is still in gear. I know a lot of experienced rally drivers that would recommend staying in gear and on the power. It all depends on where you are and the type of spin though, something you have to learn from experience probably.

Aston

 

it's just spinning out. worst thing that could happen is your engine stalling out.

560 is common on other cars like vette, nsx, etc.

I would be more worried about the differential then anything else, but i still wouldn't worry about that.

 

key words: "experinced rally drivers" which none of us are close to.