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View Full Version : Is it really possible to "disable" a car with a banana?


KarlGauss
02-27-2011, 03:19 PM
In the original Beverly Hills Cop (http://www.imdb.com/title/tt0086960/), Axel Foley sabotages an unmarked police car by inserting a banana into its tailpipe. According to what happens in the movie, it looks like doing so causes the car to stall as soon as it starts.

Does that really happen? Does the banana truly "disable the unit" (to use the phrasing spoken by the frustrated Police Chief). I'd think it would be more likely that you'd kill the occupants by carbon monoxide poisoning.

Thanks!

running coach
02-27-2011, 03:26 PM
Mythbusters did this (http://mythbustersresults.com/episode15). Didn't work, everything they tried to plug the pipe with got blown right out.

engineer_comp_geek
02-27-2011, 03:29 PM
Theoretically, if you block the exhaust you can stop a car from running. Car engines need to "breathe". They suck in air, combine it with gasoline, and blow the burnt gases out the exhaust. If the exhaust is blocked, the gases can't vent, and the combustion chamber will still be full during the suck part of the cycle and the engine won't be able to shove more air and gas into the cylinder. In short, blocking the exhaust will stop the engine from running.

The problem with a banana is that the pressure that builds up inside the exhaust is sufficient to simply blast the banana out the tailpipe. Your banana plug won't stop a car from running.

Cecil's take on the subject:
http://www.straightdope.com/columns/read/769/if-you-shove-a-potato-in-a-cars-tailpipe-will-the-car-explode

thelabdude
02-27-2011, 03:31 PM
Good work pat. I think if you could get something to stick, it would work.

yabob
02-27-2011, 03:38 PM
Even if you managed to plug it up with something that didn't get blown out, the exhaust system could leak, or you could blow apart a joint somewhere in it, and the pressure wouldn't build up enough.

Fubaya
02-27-2011, 03:47 PM
It still seems doubtful, but in Axel Foley's defense, he does stick three (http://movieclips.com/Tp5Uy-beverly-hills-cop-movie-a-couple-of-bananas/) up the tailpipe (video link).

CalMeacham
02-27-2011, 04:20 PM
And once you've caught the potential car-staller, you eat the banana, thereby disarmin' him.

RaftPeople
02-27-2011, 04:29 PM
Can't say about a car, but I have seen it done with a motorcycle.

In high school one of the younger neighbor kids was sitting on his 80cc yamaha dirt bike and talking to us as it idled. The tail pipe on this was about as narrow as a finger. My older brother stuck his finger in the tailpipe to plug it and it died pretty quickly (note: the bike had not been running long enough for the pipe to be very hot).

Arkcon
02-27-2011, 04:32 PM
My sister's Honda Accord did once stall from a tailpipe obstruction. Years ago, the snow plow buried her car, when we finally dug the car out and she drove it away, I saw icy snow firmly wedged into the exhaust pipe.* I thought, "If Beverly Hill's Cop is accurate, she should be stalling right about -- *chugga* *chugga* *sputter* -- yep, right about now." I had to melt it free with boiling water before the car would start again. `Course, between Mythbusters and Cecil, no one believes that you can stop a car by plugging the tailpipe, but firmly packed frozen snow will do it, if you have some handy.

*I am not interested in any similarity between the described scenario and a porno anyone has seen -- this is my sister we're talking about here.

running coach
02-27-2011, 04:35 PM
And once you've caught the potential car-staller, you eat the banana, thereby disarmin' him.

What if he has a pointed stick?

Czarcasm
02-27-2011, 04:39 PM
It can be done with a hard rubber buttplug and a rubber mallet.



Or so I've been told.

Lemur866
02-27-2011, 04:55 PM
It can be done with a hard rubber buttplug and a rubber mallet.


Just fix the damn thing and leave my private life out of it.

KarlGauss
02-27-2011, 06:37 PM
Thanks to all.

I guess I missed that Mythbusters (and Cecil's take on it, too).

Heyoka13
02-27-2011, 06:42 PM
This brings up something about bananas.

I have seen a video of a LN2 dipped banana be used to hammer a nail. I have also seen LN2 dipped flowers shatter like glass when struck. Are the 'vegetable tissues', ie. the banana flesh and the flower all that much different from each other (moisture content, fibrous matter, etc.) to have such differing mechanical properties?

Philster
02-27-2011, 07:29 PM
In the world of R/C, to shut down engines, we block the tailpipe with our fingers (some guys pinch the fuel line, but this starves 2-strokers of the oil and they run lean. This parentheses comment was added because the SDMB is full of all types).

So, blocking a tailpipe will shut 'er down, but I guess it takes more than some bananas.

LouisB
02-27-2011, 10:38 PM
I've always heard that a potato is the way to go, providing the potato is of a size that will permit its insertion in the tail pipe. I've never seen it done, by the way.

thelabdude
02-27-2011, 11:27 PM
Must cars now come from the factory with a solid, welded exhaust system. Don't think they are going to blow apart. Once clamped replacement parts are added, maybe, maybe not.

fifty-six
02-27-2011, 11:33 PM
I'm not gonna fall for the bannana in the tailpipe.

Siam Sam
02-27-2011, 11:45 PM
I've always heard that a potato is the way to go, providing the potato is of a size that will permit its insertion in the tail pipe. I've never seen it done, by the way.

A potato is what we used in high school. Being too big was not a problem, but rather in fact was preferable, because you could cram it in tight and the excess area just trimmed away.

It seemed to work. We did it to the shop teacher's pickup, and the next day it was at the mechanic's, because it had died and he couldn't figure out what was wrong with it. Then the next day after that, he seemed in a piss-poor mood. We did it to the car of a student at a rival high school, and I heard that it worked. However, in both cases, I did not actually see it work with my own eyes.

Rick
02-27-2011, 11:51 PM
Must cars now come from the factory with a solid, welded exhaust system. Don't think they are going to blow apart. Once clamped replacement parts are added, maybe, maybe not.Umm no. Welding costs money. Cars are built as cheap as possible. Factory systems are always clamped in my experience, replacements may be welded.

thelabdude
02-28-2011, 12:10 AM
Actually welding is cheap. Not a clamp in sight in the last few cars I have bought.

Elendil's Heir
02-28-2011, 12:13 AM
What if he has a pointed stick?

Shaddap!

Anaglyph
02-28-2011, 02:13 AM
This brings up something about bananas.

I have seen a video of a LN2 dipped banana be used to hammer a nail. I have also seen LN2 dipped flowers shatter like glass when struck. Are the 'vegetable tissues', ie. the banana flesh and the flower all that much different from each other (moisture content, fibrous matter, etc.) to have such differing mechanical properties?

J've seen both in real demonstrations: I think it is more a question of geometry: Flower petals are thin sheets that shatter easily, while a banana is a solid junk. Think of the the mechanical properties of a solid block of ice compared to a thin sheet of ice

Dog80
02-28-2011, 03:04 AM
Diesel trucks provide additional braking by blocking the exhaust path. This is what an exhaust brake looks like: http://nl.wikipedia.org/wiki/Bestand:Exhaust_brake_governor.jpg

The exhaust brake is also used to turn off the engine. If you just turn the key the engine will keep running, since there's no electric ignition system in diesels. The exhaust brake is operated via a button on the floor with the heel of the left foot.

Mangetout
02-28-2011, 05:48 AM
This brings up something about bananas.

I have seen a video of a LN2 dipped banana be used to hammer a nail. I have also seen LN2 dipped flowers shatter like glass when struck. Are the 'vegetable tissues', ie. the banana flesh and the flower all that much different from each other (moisture content, fibrous matter, etc.) to have such differing mechanical properties?

The notion that things (and especially parts of people) will shatter into fragments when frozen is something that happens in the movies a lot, but not nearly so much in real life. Things that were fragile in the first place (such as flower petals) are the exception.

Machine Elf
02-28-2011, 07:54 AM
Diesel trucks provide additional braking by blocking the exhaust path. This is what an exhaust brake looks like: http://nl.wikipedia.org/wiki/Bestand:Exhaust_brake_governor.jpg

The exhaust brake is also used to turn off the engine. If you just turn the key the engine will keep running, since there's no electric ignition system in diesels. The exhaust brake is operated via a button on the floor with the heel of the left foot.

This may have been true on older diesels with mechanical fuel injection, but modern diesels all have computer-controlled injection; turn the key off, and the computer stops injecting fuel.


Can't say about a car, but I have seen it done with a motorcycle.

In high school one of the younger neighbor kids was sitting on his 80cc yamaha dirt bike and talking to us as it idled. The tail pipe on this was about as narrow as a finger. My older brother stuck his finger in the tailpipe to plug it and it died pretty quickly (note: the bike had not been running long enough for the pipe to be very hot).

The difference is that this bike probably had a two-stroke engine. Whereas a four-stroke engine is a positive-displacement air pump that can build up a lot of pressure in the exhaust system (i.e. typically enough to blast out any fruity obstruction) before suffocating itself, a two-stroke engine relies on a dynamic gas exchange process; even a slight excess pressure in the exhaust system will inhibit air flow through the engine and kill it.

I saw the same thing as you with a 250cc motocross bike, also with a two-stroke engine. A friend had loaned us the bike for a day, and although he had reminded us to remove the rain cork from the tail pipe before riding, we forgot about it. The bike of course ran like shit for several minutes, until we realized the problem.

BwanaBob
02-28-2011, 10:57 AM
Some punks in my old neighborhood did this to an old guy's car. He had trouble starting it; on the third try, the potato flew out of the exhaust pipe.

TriPolar
02-28-2011, 11:02 AM
A banana may not be effective in the exhaust pipe, but it will make a mess of things if introduced into the air inlet, especially in a carburertor. It would also be effective in the fuel line, and you might be able to cram enough banana into the ignition keyhole to stop a car from working. If you smear it all over the windshield it will slow things down for a while. You could also use the hard part at the tip to force open a tire valve releasing all the air. Introduced into the brake lines it might make the car disable itself at the bottom of a steep incline. And of course, the peel left on the driveway could disable the driver.

I've heard of a truck that couldn't start after backing into a pile of dirt that clogged the tailpipe. Didn't see it myself though.

Siam Sam
02-28-2011, 11:08 AM
Back in Texas, they sold fireworks twice a year -- in the two weeks leading up to the 4th of July and the two weeks before New Year's. There was one type called a Texas Twister, sort of a long cigar shape, and it would shoot around along the ground while whistling and sparking, then explode in a loud pop. The whistling was LOUD. They had a version with two wires instead of a fuse, and you wound the wires onto a couple of spark plugs. Then when the driver started the engine, it sounded like all hell was breaking loose undeneath the hood. I used to pull that on my father. It didn't exactly disable the car, but he claimed it was as sluggish as a tank until I took the wires off the plugs.

yabob
02-28-2011, 11:56 AM
I'll admit that I seem to have seen far fewer cars with bits of the exhaust system falling off or dragging on the ground in the last several years. Hasn't happened to anything I've owned since about the early 90s. And I remember repairing a few by clamping a soup can around the break in the tailpipe. I'll stand by the remark that if you have an exhaust system in that kind of shape, it may leak, or the back pressure will simply finish the job of making it fall apart.

RedSwinglineOne
02-28-2011, 02:44 PM
Demolition derby cars often route the exhaust straight up and out to avoid killing the motor with a crushed exhaust pipe.

Cugel
03-01-2011, 07:46 AM
My sister's Honda Accord did once stall from a tailpipe obstruction.

Happened to me once too. Doing a three point turn on a dirt road, the shoulder sloped off more steeply than I'd realised. I braked too late on the reversing part and embedded the exhaust pipe into the dirt embankment. Had to dig out space behind it with a stick to get the car to start again.

ducati
03-01-2011, 11:55 AM
Potato. Preferably 2.

Jam them up in there solid & you've got a stranded enemy or cute girl that now needs a ride home...

Ahhh, high school. Good times.