Maximum revs at idle...

[renault12ts]

...as we all know is restricted to 3000.

So, the question is, why does mine rev right up to the maximum 4500 and beyond when the engine is cold, but eventually is restricted to 3000 as the motor gets warm?

 

[jaymanek]

something wrong with it! Needs plugging in..

Could be an air leak at intercooler pipes maybe.

 

[Dieselman]

All diesels should rev to the governor in any situation.

 

[renault12ts]

All diesels should rev to the governor in any situation.

I'm not sure I understand Will.

When sitting still, car in neutral, these cars will not rev beyond 3000 rpm usually...but mine does when cold. But when it gets warm it will not go beyond 3000rpm.

So...why is the restrictor (or whatever it is) not working when cold?

 

[whitenemesis]

I'm not sure I understand Will.

When sitting still, car in neutral, these cars will not rev beyond 3000 rpm usually...but mine does when cold. But when it gets warm it will not go beyond 3000rpm.

So...why is the restrictor (or whatever it is) not working when cold?

CAT warm-up?

 

[Dieselman]

I'm not sure I understand Will.

When sitting still, car in neutral, these cars will not rev beyond 3000 rpm usually...but mine does when cold. But when it gets warm it will not go beyond 3000rpm.

So...why is the restrictor (or whatever it is) not working when cold?

It should rev to the red line in any situation, if not it's faulty.

 

[renault12ts]

It should rev to the red line in any situation, if not it's faulty.

Not when sitting still out of gear surely?

 

[Dieselman]

Then it will fail an MOT smoke test.

It has to rev to the governor in all situations.

 

[Paul/]

So combining DM's & WN's points, is it that yours upshifts at max 3000rpm unless cold? My CLS320cdi goes to redline (4500?) from kickdown and I imagine it would if I hold gears. Aside from kickdown, it also upshifts at higher rpm when cold.

 

[renault12ts]

So combining DM's & WN's points, is it that yours upshifts at max 3000rpm unless cold? My CLS320cdi goes to redline (4500?) from kickdown and I imagine it would if I hold gears. Aside from kickdown, it also upshifts at higher rpm when cold.

If you are sitting in your driveway, car out of gear...will the engine rev to the red line? Try it please...I always thought they were protected from going beyond 3000 rpm in neutral.

 

[Paul/]

If you are sitting in your driveway, car out of gear...will the engine rev to the red line? Try it please...I always thought they were protected from going beyond 3000 rpm in neutral.

Sure, will do when Wife brings it back shortly.

In meantime though, I'm 99% sure it redlined when I accidentally braced myself against accelerator when reaching back to get something off back seat and forgot the engine was still running (perhaps that was in P rather than N). Nearly wet myself.

 

[Paul/]

Yep, I've just confirmed that mine redlines in N.

 

[Dieselman]

Yep, I've just confirmed that mine redlines in N.

As ALL diesels have to.

 

[renault12ts]

Yep, I've just confirmed that mine redlines in N.

As ALL diesels have to.

Thanks guys.

 

[Paul/]

Might it be some special mode enabled (towing, winter)? Though I thought they only restricted shiftpoints rather than max revs.

 

[Paul/]

Or if you're unlucky it might be emergency mode, which apparently limits to 3000rpm...

320 CDI engine...... - Benzworld.org - Mercedes-Benz Discussion Forum

 

[markjay]

Not familiar with diesels in particular, but I would be surprised if engines were differently rev-limited when not in gear than when in gear (manual or auto)?

Said that, I was always told that reving engines in neutral is bad for them - something about increased wear due to lack of load on the crankshaft and rods? Or overfueling? Can't remember what it was now...

 

[BigSilverEstate]

http://www.mbclub.co.uk/forums/engine/129997-silly-q-revving-tunnel-engine-tranny-damage.html

There is reference on this thread to a feature preventing over revving when in P or N. Would this only apply to petrol engine cars?

 

[Aoraki]

Both mine and my dad's C250cdi's will red line in N, we've tried, however, the W212 350cdi I had last year would only ever rev to 3000rpm when in N