Changing from 5th to 1st gear at 100kph

whomitconcerns

Was just reading about the people aking about changing gears but skipping 4th to 2nd etc, etc while slowing and stopping.

It got me thinking, if you go from 5th to 1st while doing 100kph what actually happens? I mean I know your engine would pretty much blow up and you would lose any and all control, but would it actually blow up???????????? I remember going from 4th to 2nd one time when i started driving and not breaking hard..it wasnt much fun..but 5th to 1st for instance?

But in reality anyone, just curious?

P.C.

I don't think you would get it to go into first gear.

homer simpson

Is it not imposable to do this? I know any car I've drove will refuse to go into first unless you almost stopped. Only know that from when coming to a stop at junctions ect, never actually tried to force the car into first though.

theteal

not many cars will let you into 1st if doing anything other than a few kmph

whomitconcerns

well lets say 2nd then? Or is this not posible either. But this is interesting, I never realised it wouldn't actually allow you go to 1st gear.

Fiona

My car is hard to get into first gear at the best of times!

2 stroke

Gearboxes are designed to stop idiots doing this, but if you did manage to slip it into first and declutch on a regular basis, you could have more metal in your gearbox oil than on the gears.

String

You should be presented with that horrible gearbox crunching sound :eek:

com1

To see what would happen going from 5th to 1st at 100kph... Lets suppose the following gear ratios (the figures are not taken from any particular gearbox) (the ratio is <turns of the engine> : <turns of the transmission>)

1st - 3.0:1
2nd - 2.4:1
3rd - 1.8:1
4th - 1.3:1
5th - 1.0:1

So jumping from 5th to 1st will immediately try to multiply the engine revs by 3 in order to synchronise the engine revs with the wheel revs to try and keep the car going at a constant speed.

Say that 5th gear is revving the engine at 4000rpm at 100kph, if you managed to change to 1st the engine will immediately try to jump the revs to 12,000rpm... should be interesting in a normal car.

The rev limiter will go mental
The clutch will probably burn out
It would not suprise me if the timing went to hell crashing valves into pistons and all that good stuff
You would probably also get a lot of friction welding going on...
Bits would probably start shooting out of the engine through the bonnet

in other words 'it would be bad', probably,

Bohrio

whomitconcerns wrote: »

Was just reading about the people aking about changing gears but skipping 4th to 2nd etc, etc while slowing and stopping.

It got me thinking, if you go from 5th to 1st while doing 100kph what actually happens? I mean I know your engine would pretty much blow up and you would lose any and all control, but would it actually blow up???????????? I remember going from 4th to 2nd one time when i started driving and not breaking hard..it wasnt much fun..but 5th to 1st for instance?

But in reality anyone, just curious?

Most cars wont allow you to go from 5th gear to 1st gear, some might but you will need to force 1st gear by pushing really hard and is not easy to do.

Second gear will me more feasible although unless you are a novice driver you should realize you are on the wrong gear before you release the clutch completely, what will happen, well, 100 km/h should be ok as most cars can reach 100-110 km/h in second gear. You will experience a sudden loss of speed and probably that will be it, wheels might lock momentarily, if the car is rwd the car might oversteer a bit, if your speed is higher than the maximum speed the gear can handle you risk the chance of blowing the engine too, but this will have to be very extreeme as it will be more likely the car will slow down before the engine blows up.

Henry Ford III

I recall someone (a learner driver) who actually did this in a Fiat Ritmo years ago.

The gearbox made a break for freedom, and ended up on the tarmac.

whomitconcerns

So we need a test volunteer :P

bbam

Since it was a Ritmo are you suere it didn't rust so badly that the gearbox fell out. I'm pretty sure they were rusting as the last wheel was put on in the factory.

I'm of the era when they were new and I honestly don't remember seeing one without bubbling on either the arches or round the windscreen.

knifey_spoonie

Mr Valve will get a prompt and short lived introduction into Mr Piston. Its not a pretty sight or sound.

padd b1975

bbam wrote: »

Since it was a Ritmo are you suere it didn't rust so badly that the gearbox fell out. I'm pretty sure they were rusting as the last wheel was put on in the factory.

I'm of the era when they were new and I honestly don't remember seeing one without bubbling on either the arches or round the windscreen.

Ritmos had the coolest wheels.

Elvis_Presley

well OP thats why they invented rental cars!give it a go and report back with photos! and maybe have a good cover story for the rental agency ;-)

homer simpson

whomitconcerns wrote: »

So we need a test volunteer :P

I know someone who is bringing a car that is running to one of them end of life vehicle places next week, I'm half tempted to try it in the field behind us and record it on camera and see what happens :pac:

MrDerp

whomitconcerns wrote: »

So we need a test volunteer :P

I'll pledge 20 euro towards a banger on donedeal

We need some mics to record the sound in the engine and the gearbox.

Anyone got a good video camera? We could do a boards.ie motors automobile mythbusters

b318isp

Assuming you could get the synchro on the gearbox to engage, the biggest worry would be the big ends. Normal high forces on a con-rod are downwards - the piston pushing down on the crank during the ignition stroke.

High loading in the reverse direction risks shearing or stretching the big end bolts, causing a breakage or a loss of oil pressure on the bearing shells.

Anan1

Given some really sh1tty tyres and a wet & greasy road you might just get away with it!

Gary ITR

15 damaged valves, a forged rod bent, piston with holes in it, cylinder wall smashed, head destroyed.

That was the end result when it happened to our race car

cjt156

Anan1 wrote: »

Given some really sh1tty tyres and a wet & greasy road you might just get away with it!

So, pretty much the typical Irish car on the typical Irish road then?

DanWall

As the timing will not go out, the valves will not hit the piston. The con rods are well able to take it. You cannot do it on a field because the wheels will act as a clutch on the earth. Your will simply take teeth of the gears and possibly destroy the clutch

matt-dublin

I would say in a newer car with a rev limiter you might be lucky and it might cut out as the rev limiter kicks in.

on an older car with no rev limiter id suggest the gearbox would explode and you might see a piston fly through your bonnet.

Gary ITR

DanWall wrote: »

As the timing will not go out, the valves will not hit the piston. The con rods are well able to take it. You cannot do it on a field because the wheels will act as a clutch on the earth. Your will simply take teeth of the gears and possibly destroy the clutch

I beg to differ. I've seen it a few times on race cars and what I posted above is usually the end result

Anan1

Even if the timing gear remained intact, when you rev an engine beyond a certain point the valve springs simply can't get the valves out of the way of the pistons fast enough.

b318isp

matt-dublin wrote: »

I would say in a newer car with a rev limiter you might be lucky and it might cut out as the rev limiter kicks in.

A rev limiter is a bit of a misnomer - all that happens is that the fuel is cut off after a set maximum rpm, there is no mechanical limitation of engine speed.

Matt Simis

FWIW my 850CSi has a warning in the manual about not dropping to 4th from redlined 6th due to serious damage via engine overspin. Redlined 6th is 180mph+ in an E31.

Northern Monkey

I was in an RX8 that was dropped into 2nd at 60mph when they first came out. The sales man did it to show me how high the engine can rev.

"you drive it like a motorbike" I think was the quote from him at the time.

matt-dublin

b318isp wrote: »

A rev limiter is a bit of a misnomer - all that happens is that the fuel is cut off after a set maximum rpm, there is no mechanical limitation of engine speed.

yeah but when that happens it will cut out because of the gear, ie kangaroo juice. (in theory if it doesn't explode first :P)

lostboy

Northern Monkey wrote: »

"you drive it like a motorbike" I think was the quote from him at the time.

LOL

ive actually accidentally shifted down a gear too low on one of my bikes before. back wheel locks up until the bike slows down to where the gearing of the wheel can turn the engine over again and wheel unlocks and the engine jumps up to somewhere around the redline, i wouldnt recommend it.

thankfully coming from the 2 stroke way of life i was smart enough to grab the clutch the moment the wheel locked allowing everything normal turning

ShadowHearth

I doubt you will be able to shift from 5th to 1st, but check YouTube, there are tons of miss shifts on tracks. Instead of 4th puts in to second and then it goes boom.
Nasty expensive sound.

Roselonda

I usually just lurk in the background here but since I have a bit of experience in this area I thought I'd share it.

I was back from the the UK for a wedding at home last summer, rented a car while I was back...a brand spankin new Kia Venga (piece of sh1t IMO) with only delivery miles on the clock.

I gave a few friends of mine a lift back from the wedding the following day and got a bit lost at one stage. My mate who was still a bit still pissed from the night before decided he this was very funny and started cracking jokes about my sense of direction. To get him back I decided an impression of his old lady driving style was in order. Part of this involved revving the engine quite a bit so put it in to first when I was doing roughly 100kph and quickly let out the clutch.

Engine revved wildly on the limiter for second or two and then the engine management light came on and it lost all power. I pulled in and turned off the ignition. When I tried to restart it turned over but there didn't seem to be any compression at all. Rental company sent out a mechanic, I didn't exactly tell him what happened but he reckoned it was probably a snapped timing chain/belt.

I did feel a small bit guilty but taking Kia Venga's off the road is doing society a service!

guil

nasty

https://www.youtube.com/watch?v=BJQXlwr0H1A

Fiona

knifey_spoonie wrote: »

Mr Valve will get a prompt and short lived introduction into Mr Piston.

But why can't Mr Valve and Mr Piston be frwenndssss

Wossack

Fiona wrote: »

But why can't Mr Valve and Mr Piston be frwenndssss

they become a bit too close if you ask me - have a bit of a wham-bam affair, till one f's off (sometimes making a new exit for themselves), leaving the other one irreparably damaged

b318isp

matt-dublin wrote: »

yeah but when that happens it will cut out because of the gear, ie kangaroo juice. (in theory if it doesn't explode first :P)

I don't follow you?

deandean

It happened with, what's the name of the Jag supercar from the 90's, XJ220 or summit, a journalist from the Guardian newspaper did an incorrect gear change and dropped it from 4th or 2nd to 1st, made complete $hit of the engine, tens of thousands worth of damage. Any good searchers here might be able to find the article.

You'll get a severe engine over-rev, valve bounce, crank & rods rotating well above design RPM, t/belt slip or break, usually results in catastrophic top end damage.

But hey, do try it and report back. Here's a challenge: they say Civic VVTI engines are bulletproof.....

Gary ITR

LIGHTNING wrote: »

Have seen many of them drop their guts on the track. Its not a nice noise at all!

Mine went at turn 3 *sob*

matt-dublin

if you managed to get it into first gear and release the clutch the rev limiter would kick in restricting fuel to the engine. This would force the revs to drop quickly and likely the car would judder to a halt because the engine's power has been taken away to move the gear.

Similar if you're driving in first gear and take your foot off the accerator the car starts to jump when you put your foot back down on the accelerator.

Gary ITR

LIGHTNING wrote: »

Turn 3 claims another victim :pac:

To be fair I wasn't driving and it wasn't a missed shift. The miss happened at turn 4 in the race car

b318isp

matt-dublin wrote: »

if you managed to get it into first gear and release the clutch the rev limiter would kick in restricting fuel to the engine. This would force the revs to drop quickly and likely the car would judder to a halt because the engine's power has been taken away to move the gear.

Similar if you're driving in first gear and take your foot off the accerator the car starts to jump when you put your foot back down on the accelerator.

No, although the fuel supply will be cut, what is being discussed here is that the car is now driving the engine.

Wossack

know of a guy, who went down instead of up on the gearbox of a turbo'd hayabusa, and bent the swingarm (and threw a conrod out the side of the engine, for good measure)

b318isp

Gary ITR wrote: »

To be fair I wasn't driving and it wasn't a missed shift. The miss happened at turn 4 in the race car

I found that it is tempting to drop a gear prior to first part of turn 3, but for stability reasons just feathered the throttle and waited to brake, H&T and drop (from fourth) into 2nd gear just prior to turning in for the second part, even though there is precious little time to do so.

dr.fuzzenstein

Once tried to kill a Toyota Avensis ('98 or thereabouts).
Booted it to 120 km/h or so in 5th and went to 3rd.
Engine roaring, rev counter hit the end stop, revs dying down and engine continuing as normal.
You just can't kill a Toyota.

dgt

dr.fuzzenstein wrote: »

You just can't kill a Toyota.

I'm sure I could I have a story about a Corolla trying to jump start a lorrey that died in the process and what was called in to start it when it failed? A Bravo :cool: and it jump started the lorrey too

Aaaaanyways... My dad often spoke about cars from the 60s and 70s that would allow you to do this. "There's nothing to stop you putting it into first" he said, "mind you, it would probably be the only time you would do it..."

I took that to mean the gearbag would go into shíte, possibly throw the prop shaft into the ground and spin all around... Messy either way!

kirving

Well, it would be ok if you came off the clutch slowly enough to not break the engine. (Would proabably need a new clutch tho).

I did something along the lines of this in college a few weeks back. Now there were no exact figures, but gear ratio's, masses, and speeds were all ballpark. Worked out that in first gear, the rotational components had an effective linear inertia of about 600kg. This reduces substantially as you move up through the gears.

Not sure if it would work in reverse, but it would be like having a force of 600kg pulling the car backwards.

b318isp

Kevin Irving wrote: »

Well, it would be ok if you came off the clutch slowly enough to not break the engine. (Would proabably need a new clutch tho).

I did something along the lines of this in college a few weeks back. Now there were no exact figures, but gear ratio's, masses, and speeds were all ballpark. Worked out that in first gear, the rotational components had an effective linear inertia of about 600kg. This reduces substantially as you move up through the gears.

Not sure if it would work in reverse, but it would be like having a force of 600kg pulling the car backwards.

The next step is to work out the torque presented to the engine!

Tea 1000

dr.fuzzenstein wrote: »

Once tried to kill a Toyota Avensis ('98 or thereabouts).
Booted it to 120 km/h or so in 5th and went to 3rd.
Engine roaring, rev counter hit the end stop, revs dying down and engine continuing as normal.
You just can't kill a Toyota.

That's nothing, I'm struggling to think of any car that you couldn't do that in.

scholar007

P.C. wrote: »

I don't think you would get it to go into first gear.

You aint been in a car with my wife so! She will ram any gearstick into first long before the car has stopped or slowed down sufficiently.

Sesshoumaru

A lot of modern motorbikes get up to 150kph in 1st gear. What happens really depends on the machine!