Scenario:

If you are in 4th gear and your rpm is say 5500 and you accidentally shifted to 2nd, would there be a mechanism that would prevent you from shifting into a lower gear so that you won't kill your engine?

 

In the '03 there is a rev limiter...so it will cut off fuel for 2 reasons.

1. Your at a standstill and rev engine
2. You rev much higher then redline

A friend drove my car and downshifted too early...the car slowed down quickly, but the fuel was cut until below redline...in a normal car, he would have blown the engine.

Either way, its not good for the car, don't do it on purpose.

Erik

 

I mean is there a mechanism that will not allow you to downshift? Something like a lock that prevents you from shifting the shifter down until the computer senses the it won't over rev the engine.

 

No, there's nothing like that except of course for the lockout preventing you from putting it in reverse when you're going forward. That's why we enthusiasts love manuals - if they were idiot proof there would be no fun! Besides, like tifosiv122 said, why would you need one as long as you've got your rev-limiter? Both the '02 and '03 models have them (as do almost all cars with a manual gearbox these days).

 

Yes, there is a mechanism of some sort....I dont think you can shift into 1st over a certain speed...or its really hard to the point where you would really have to force it into gear.

I suppose it would be useful if the electric device failed, having a mechanical backup, but I don't know of any such system.

Erik

 

There is no such mechanism on any gear. If you do what your scenario suggests, you will over rev the engine. A fuel shut of or ignition based rev limiter won't help. The engine is mechanically connected to the wheels. When you down shift to the wrong gear, the wheels will force the engine to turns the revs that match that gear. There is absolutely nothing on the car that can prevent this and the damage that may result.

A rev limiter is only useful if you forget to shift or if you miss an upshift.

 

No doubt someone will find a way to blame MB for this 'oversight'.

 

Late response, but I think you'd be more likely to accidentally shift from 4th to 3rd, rather than into 2nd. It would take a more concentrated effort to move over to the left gate and down, assuming you meant to go into 5th anyway??? Also, you might be saved since the synchros would be very hard to overcome at that rpm -- you might realize what you're doing when you feel more resistance than normal...

 

Imagine you intended to shift from 6th to 5th but forgot to push right, and ended up shifting to 3rd. Ouch!

 

And every other Manufacturer out there. Most of the time when you downshift to too low a gear the rear end will be forced to lock up momentarilly to slow the wheels down enough to not do damage. The amount of traction at speed of the driving wheels will normally be less than the engine braking potential. Hence the rear end of the Benz will lock for a second thus slowing the vehicle down enough to not damage anything. This is not any safety feature it is physics. I had heard a dealer in a brand new Viper when they first came out missed the 3rd to 4th shift while accelerating at about 80MPH and hit 2nd instead of 4th. He was not quick enough to mash the clutch back in so the rear end decelerated very rapidly causing the Viper to spin. He did $30,000+ damage to the car as a result. The car spun out of control accross the median and into the other set of lanes and bounced off gaurd rails on every body panel, then spun to a stop in the median. Not fun for the dealership owner who was driving at the time showing the car off to a client. Let's just say he did not make the sale.

If you want to drive stick you need to learn how to push that clutch back down if you need to and do it quickly to not hurt the engine or your car. If you do not know at what speed you can downshift to a certain gear then you need to either not downshift or you need to get an automatic. My wife did not know how to drive stick until 3 weeks ago and she has picked it up quite well. She even downshifts to stop now and she knows what gear she can hit and when she can hit it. And it has only been 3 weeks and she learned on the Benz. It is not rocket science but if you need protection from damaging the engine on a downshift then I am sorry to say that you may have made the wrong transmission choice.

 

Im not sure if its the same for the 2.3l '02 engine, but for the 1.8l '03;

Standstill - Fuel Cuts at 4,000 rpms.
While Driving - Fuel Cuts at 6,250 rpms.

Redband is 6,000-7,000rpms.

Erik

 

As someone mentioned before I am pretty sure there is a locking mechanism for first gear that does not allow you to down shift into it above a certain speed.

 

No. You can't get into first when you're moving b/c of the issue of synchronizing with such a small gear when you're moving. It may end up behaving like a lockout feature, but it's not a "feature." Anyone who's ever driven a farm tractor will know what I mean.

 

Can't say that I have!

Erik

 

i remember a couple months ago i was with my friend in his celica and he was trying to show me it was fast and he was floring it but accidently shifted into 1st gear instead of 3rd. Well anyway all i heard was a LOUD noise and i saw the RPM go into 7 or 8k? what ever the highest # on the tach is. Well suprisingly nothing happend to his car.

 

Luckily, the Celica and handle 8000-9000 RPM. No such luck in my 1984 Subaru. I want a quick 5-3 down shift to pass, but got 1st instead. Yes, the wheels locked momentarily, but when traction was restored, I peg my tack, so I don't know how fast the engine was spinning. Luckily, it was under warranty and the dealer didn't realized I over-rev'd it, so they replaced the crankcase, and all main bearing.

 

My wife and I both learned how to drive on manual transmission cars...something that later in life we both appreciate. She wouldn't get a car with an auto if you could get it with a manual instead.

Automatics are pretty boring.