Could someone explain the '4k rev limit' in neutral?

[doversole]

Hi all, DoverSole again.

Been browsing the forums as you do, came across various references to the above. I guess it seems logical but i'd welcome an explanation. Strikes me several of us may be a touch relieved to know there's no fault. Certainly no mention of it in the Haynes.

Thanks, Dover

 

[television]

Most MBs will not rev over 4k in neutral, this is purely a safety device as it is not good to go over that RPM without a load,,its un natural

 

[doversole]

Thanks, Malcolm - I sort of surmised it would be something along those lines.

 

[carnut13]

Most MBs will not rev over 4k in neutral, this is purely a safety device as it is not good to go over that RPM without a load,,its un natural

In fact most modern engines wont rev much over 3k.. my Jaguar for instance. The Engine Management stops it. Used to give the MOT guys kittens at one time :-D

 

[recycledjuvenile]

Forget haynes. It is in the merc handbook. fuel cut off steps in at 4k

 

[dragon]

Remember during MOT a couple of years ago to warm up the catalyst, they revved it up to 4K for a couple of minutes made me sick. I complained though and they stopped doing it. They still do it if it not warm enough to fail the emission.

 

[kth286]

Is it on the autos only and to protect the torque converter ?

 

[recycledjuvenile]

it is on auto or not and it is to protect the engine

 

[moosehead]

I thought this was due to torque convertor stall speed. Probably needs someone with a more technical understnding to explain.

 

[hardtop]

what we need is someone to volunteer to overide it then knock it into drive at 7k to see what fails first ? i think the box

 

[doversole]

I think the nut behind the steering wheel might fail first - have a hunch.

DoverSole

 

[recycledjuvenile]

I have a manual and it does exactly the same thing. Does not matter if it is an auto or not

 

[rich599]

by pressing the brake pedal at the same time this overides it

 

[recycledjuvenile]

it does not in mine

 

[television]

it does not in mine

On many cars in the range if you touch the brake pedal this kills the throttle,,I thought that something was wrong when I first bought it and use the heel and toe technique