Healthy Driving

[Aebous]

I've been curious about this as well since I drive a stick. I'm always wondering what is the optimum RPM for the engine.

I tend to keep the rpm around 2k once i'm at a steady speed (whichever gear), i've often wondered if it would be better for the engine to be at a lower rpm if possible for simple steady driving. As CJ hinted at, the people with the Auto's should tell us what their cars rpm is at when they are just sitting at a steady speed. I would think the auto box is going to pick the optimum RPM for cruising.

 

[csmith319]

It's not really just about RPM - an engine will happily sit at any RPM within it's permitted range - though obviously the higher the revs the more likely the internal wear. But sitting anywhere between 1200 and 3000 is fine. Our ears tend to be more sensitive than the metal in the engine!

However, there is a problem is the engine is labouring - i.e. struggling to maintain an RPM because you're in too higher a gear and need to change down. I've only ever driven my own Z4 enough to be able to tell, but with the 3.0si, there's so much power across the rev range it would rarely be in a position to labour unless I was on a very steep hill at low speed in 5th or 6th gear.

It's rea.lly something you should be able to feel - oes the engine sound like it's struggling; on the other hand, are you having to use excessive throttle inputs to make little or no difference to the speed?

 

[oo7ml]

I would think the auto box is going to pick the optimum RPM for cruising

good point...

 

[cj10jeeper]

I would think the auto box is going to pick the optimum RPM for cruising

good point...

Yep - that's why I posted details on it as you can be sure that a standard mapped engine, not in sport mode, is going to pick the ideal point to settle on once the torque converter is locked, to max fuel economy, without causing any undue strain on the engine.

I should however have been much clearer and said that whenever I wanted to 'cruise', regardless of speed the gear would change, such that the car settled to 1800 revs. or in some cases a little less. Obviously beyond a certain speed and once in top the revs continue to rise. It will of course be slightly different to a manual with different ratios and also varies based upon final ratio wheels and tyres, but I would suggest any would be happy at 1800

IMHO forget about sports car for a moment and 'pressing on' and any critique of driving styles, but I would suggest that most people drive at too high a revs for too long, with the exception of the odd 'dad' who holds fith until it near stalls..

Someone with a manual stick it in a gear and see how low it will go on a flat smooth road and hold speed comfortably - interested.

 

[Rama]

FYI - the speeds I gave in my last post for each gear land the rpm's around the 2,000 mark give or take, so we are not far apart.

And 3.0 is the smallest engine I've ever owned. One was the Z4 with the 6 cyl., and one was a e34 530 with a 3.0l V8 - loved that engine!

Other cars were a Firebird I used to have that was 5.0, the 540 that was 4.4, and the Jag VDP that was a 5.3 V12.

Generally a 3.0 is not considered big here....at least for people of my general age.

3.0 is fairly big by UK standards as we've historically run smaller cars on smaller engines, but it's all relative - My 4 current cars are 3, 3, 4 and 6 litre so no friend of the planet...lol

This thread is intriguing and driving to the next city and back today caused me to watch the rev counter. In steady drive it would change up every time it hit 2000 rpm to the next gear. Ask a bit more of rapid acceleration and it would hold onto it to 2500 to 3000 and full throttle of course right over to the redline. It sat on the urban motorway in top at 1800 rpm so being an auto if anything was strained it would have just changed down.