So a knowledgeable dealer in Porsches suggests not to drive under 3000 rpm on the road. What is accepted practice, and why?

If my signature change took, you will know this is for a 2010 C2S (Cab) with 36k miles. (Yes, I know there are no SAI ports on the DTI engine, which was a big pain in my 993 cab, but since rectified I hear with larger ports on the water cooled, pre-DTI engines. In any case, not a factor for my DTI engine.)

Thanks.
Charlie

 

I have never heard of that.

 

Me neither. Why? Oil pressure? Or oil lubrication from crankshafts?

 

That's something left over from the olden days. In fact, many years ago, when I started driving 911s (in the 1970s) you routinely kept things up in the power band--from 4,000 to 6,000 RPM. Today's higher displacement engines and thus higher torque engines simply do not need to be driven in such a fashion. I have noticed that in top gear mine runs along at about 75 mph at 3,000. It has excellent pulling power down to even 2,000 rpm. One should never "lug" an engine, but today's engines are not susceptible to that down at 2,000 rpms.

Things have changed a lot in the 911 world. It's really not your father's 911.

 

get that. The dealer's argument seemed to be oriented around some sort of carbon build up, but I am not sure.

 

I have heard of carbon buildup on other cars, but the 911 9A1 motor (to date) does not seem to fall victim to this. One thing Porsche engineers did was direct the high pressure injectors onto the back of the intake valve to assist in cleaning. While this does not take care of cleaning the intake manifold, it does deal with the more critical valve seat. Another plus MAY BE that the stream gets broken up reducing its force against the opposite side of the cylinder to minimize bore scoring.



As for rpm ...

With my PDK in Lexus mode (daily freeway commute) I don't pass 2K rpm until I pass 75. Here I get over 30 mpg. Yes, I know, mpg is not the purpose of the 911, and I do have weekly (or more) drives where the mpg drops below 15. I maintain 4K+ rpm on those drives for a quarter to a half tank and will admit the motor seems non responsive below those rpms when I revert to "normal" drive mode.

Yet, there is plenty of normal day torque at 2K to pass another vehicle, and on the too frequent right lane pass when I don't trust the other car's lane use or language the 911 kicks down to 6th, 5th, 4th, 3rd instantly.

 

One of the directives for the M96/97 engined 996s and 997s was to avoid engine speed at or below the 2,400 RPM range for an extended period of time.

Reason being, at 2,400 RPM and below, the VarioCam system puts a lot of strain on the timing chains and tensioners.

 

Where was that info documented?

 

I seem to recall feeling the variocam kick in almost exactly at 3K, almost like a turbo boost. At least that's what I figured it was.

I also remember reading that keeping the revs above 2500 puts less load on the IMSB. On the interstate I think I downshift from 6-5 around 63mph to keep the revs above 2500, it hits 3K around 70 I think. (.1, 3.6L, 6sp stick).

 

I received it in a document that Mr. Raby provided to the previous owner of my 997.

 

OP doesn't have an IMS based engine and the 3k rpm advice from the dealer is misplaced.

 

Interesting responses. Would someone point out if the DTI engine is different in this regard (rpm at cruise speeds) than the pre-2009 engine? And if owners can identify the model year of their 911 in responses, this could help.

Thanks.
Charlie

 

You shouldn't "lug" any engine - your engine speed should be matched to the proper gear to avoid placing too much stress on the drivetrain components.

But, never letting the revs drop below 3,000 RPM? That's absurd.

If I recall, 3,000 RPM in first gear is around 15-16 MPH. How do you deal with a traffic jam?

 

the practical effect of the dealer (not a Porsche new car dealer, but well-informed) recommendation is that you cruise at 3200 rpm at 68, which means 5th gear, instead of 2800 rpm in 6th gear, as an example (if my numbers are a tad off, humor me, but you get the idea). Seems silly to me, hence this thread.
Mine is a DTI, 2010 S.
Charlie

 

Silly dealer. Don't lug the engine. That's all.