I have not noticed anything in the manual which tells me what revs I should be driving at before the engine warms up. Anyone knows what I should limit to in order not to wear the engine out?

Its a E320 CDi.

 

I don't know if the specs on the CDI, but all MB gas engines have rev limiters when they are in neutral and oil pressure dependant limiters. I also think that there is a safety built in for when the car is cold. However, I never wait to warm up my car but I never rev my engine past 2k rpms until I get a couple of bars on the temp gage. I don't have the desire to test if there is a limiter on MY car, maybe someone want to volunteer :-).

After driving my Audi for years and years. It is interesting to note that just because the engine is warm and at operating temp. The oil can still be cold! What is important thing is the OIL temp not the engine temp. Unfortunately, the MBs don't have an oil temp gage. I kind of got used to the Audi's oil temperature gage. It's nice to have.

Steve

 

Me too!

I think Steve's personal cold engine 2K rpm limit is very reasonable, along with the proviso of using only light throttle openings. It's what I instinctively use myself. 2,000 rpm insures low piston speeds with abundant torque available in a CDI, and will allow a vehicle speed of ~70 mph.

 

This is how BMWs usually go, so maybe it will work on the mercs too. I also like to do this with the E-and the C. Usually shifting at around 3-4 RPMs. What is the CDIs redline?

 

Without going outside to look at the rev counter, I think red starts at 4000 rpm.

So do you wait for the temperature to reach optimum to go beyond 2000 rpm or do you like Steve wait for just a few bars to go up? I normally wait for optimum temperature but that just takes ages to reach.

 

The absolute redline on the 320 CDI is 4600 rpms. Full-throttle upshifts occur at about 43-4400. But the CDI has much more torque than the gas engine- some 60% more than the 320 - and at much lower rpms. There's no real need to exceed 2,000 rpms on a cold engine, unless it's some sort of an emergency.

 

You know, this is a very debatable issue. Now that we have synthetic oil of "0" W something. Engines get good lubrications in cold temperatures. I always get going right away so I dont stink up the garage with fumes.

My 2000 RPM limit is with a red line of 6000+ on both my cars. Like said above, I do not punch it either. I just let it roll and rev softly up to 2k and the car runs very smoothly. Once the engine is a few bars up I might let it get up to 4k, but no higher until it is totally warm.

On a diesel however. I think it is a bit more complicated. I think (this is my opinion) that since you got a turbo and turbos need very good lubrication to last long good oil is crucial! I bet that by 2k RPMs your turbo is ready to boost if your throttle is pressed enough. (I might be wrong, but I would imagine so) If you do rev the CDI to 2 K don't make the turbo start boosting too much and take off, that should be OK. I think that is the real key on a diesel. Also, I would not give it full throttle and have fun until it is at normal operating temp. (again my opinion). I have only driven diesels ( a bunch) but never owned one).

I like to keep cars for at least 10 years. I truly believe that idling to warm up the engine is not good (terrible for the old oils). I do it once or twice a year if I have to dig my car out of the snow and it is freezing. However, I know idiots that rev the crap out of cold engines and the cars take it. Hard to believe.

After 262,000 miles (or 424,440 Kms) my Audi's engine has never had the block opened! All originally built in Dec of 1985. Pretty impressive, I think! My family has always warmed the engine up while driving and revving the engine slowly. (I was 12 when we bought the car, so I obviously did not have it as a new car) The engine has just now started to consume .2 quarts of oil between oil changes. We also only used and still use Castrol CTX 10 W40.

How you run the engine at the cold start is crucial once it gets old. It will determine if you have a piece of S or a solid reliable engine!

Don;t take this as fact, this is opinion!

Steve

 

Again good points by Steve, IMHO.

I'd add that the issue that really concerns me about cold engines is loose internal clearances causing piston scuffing and other problems. To illustrate how much engines can change dimensionally, a Porsche 944 I previously owned was said to grow one inch in engine height from cold to fully warmed up! The CDI has a cast iron block, so probably doesn't grow that much, but still has an aluminum head, and I like to insure that things are as dimensionally stable as possible before flogging the car.

Steve, I strongly suspect (no boost gauge, darn it) that CDIs are making lots of boost by 2 grand, as the 369 lb/ft torque peak begins at 1800 rpm. Probably yet one more reason to do gentle warm-ups.

BTW, Audi should give you a gold dash plaque!

 

Yes its usually half of your redline, so 2000 rpms would be right.

 

It is not only when you start a cold engine you should be aware that you drive a car with turbo charger

The turbo chargers hang directly on the exhaust manifold and become very hot by the hot exhaust gases and the engine proximity. That is however its operating temperature. If it is still cold, and under load it still becomes hotter than the engine.

The ball bearings in the turbocharger are supplied with oil. After sharp travelling during a longer period, the charger and of course the ball bearings naturally gets very hot. Now, without "cooling phase" if the engine is switched off immediately, brings the hot oil to crystallize and the oil circulation is interrupted.