Best Shift Points

[K. Roman]

I live in SF, there are many hills, small streets and lots of traffic.
If suppose I shift at 6000, and 2000 is a definite no no, am I supposed to stay in first gear the whole time?
I usually get to shift to second and that's about it until I find an excuse to hit a freeway.
I would probably spill my girlfriends cappucino if I stayed in first.

[porschenut]

Originally posted by rick-l
He asked for "best" shift points. To me (and someone who would buy a 911) that would be max acceleration.

Well, since everyone on this board bought a 911, and there is widespread disagreement on this, then your assumption is incorrect. "Best" does NOT necessarily mean "fastest".

Best could also mean "least engine wear", or "best compromise between performance and fuel economy".

I shake my head every day when I read posts from you speed demons who are under the impression that these cars are made to be driven hard. They are not. They are made to WITHSTAND hard driving, but that does not mean that it is GOOD FOR THEM.

A Porsche engine and drivetrain has no special magic. The rules are the same as for all other cars. The harder you drive them and the higher you rev them, the more stress you put on them and the sooner they wear out as a result. FULL STOP.

Do I shift at 5-6k occasionally? Sure I do, because I'm willing to trade a little engine life for some fun. But 90% of the time I shift at 3.5-4k because I want my car to last many years and keep its value without spending an arm and a leg maintaining it. I am also perfectly happy with that level of acceleration. For me, the fun of the car is more in its handling than its speed, and I get a tremendous amount of enjoyment just leisurely cruising through the twisties at 3k rpm.

Do whatever you want with your car, but try not to assume that all 911 drivers are just like you. They aren't, thank god, or there would be far fewer 911s on the road today.

[Zeke]

Originally posted by Thack
"I would never sfift into a gear while intending to go anywhere that would put the engine at 2000 rpm. That's just lugging it and that will wear out an engine."

You are kidding right?

"FWIW, race cars are set up track by track to shift at the max torque rpm and into the next gear at the max hp rpm "

How much racing have you done? If you shift at max torque then you are missing some high torque on the other side of the curve. You would be wasting torque considering when you shift to the next gear you will definitely have less torque at a lower rpm. I shift when I feel the power fall "off".

Racing? Enough. 2nd mechanic on a formula team, a stint at Mickey Thompson when they were in 3-4 types of racng simultaneously and karts for 30 years. Now, with karts especially, I understand torque and hp because there really is so little to work with and yet the things would regularly top 100mph at Willow with 16hp.

BeepBeep, clear as mud? Nope, I'm with you on that. We are sayin the same thing essentially.

Who would have thought so much discussion on shifting? You never know what is gonna take here and what will slide.

[porschenut]

Originally posted by Thack
When I cruise on the freeway its around 3200 rpm at 70 mph. Thats 5th gear. My 79 SC is stock and doesn't have big power so I don't "race" people. When necessary I will have it in 4th and pull away from most people or pass cars with ease.
When tooling around the neighborhood I regularly see 2000 rpm. I don't want to attract attention and be seen as a racer through the hood. Lugging it is when you are in 5th gear at 1500 rpm. You can physically feel the motor and trans "shake". If you shift above 3000 rpm you won't have that problem. but I can't see running my car to 6000 every time I jump in it.

You and I will still be enjoying our original engines when the rest of these power junkies are on their second rebuild.

[nostatic]

Originally posted by porschenut
You and I will still be enjoying our original engines when the rest of these power junkies are on their second rebuild.

No, you'll just be praying that the B12 treatment clears up the carbon buildup.

From everyone I've talked to and everything I've read, going *slow* with these engines is just as hard on them as going fast. Will constant redline shorten the life of the engine? Probably, but I think that spending most of your time loping along at 2K will result in an unhappy engine, and is a waste of the car. I don't think babying these cars does them any favors...and frankly I don't enjoy my car at 2K.

ymbermv
(your mileage between engine rebuilds may vary)

[tsuter]

If you have that "white mystery gunk" in your oil cap you shift at 2500-3000.

If you have powder painted or polished Fuchs you shift at 3000-3500.

If you have a powder painted fan you shift at 4000+

If you have 300HP then you shift when you see the other guy in the rear view.

[porschenut]

Originally posted by nostatic
No, you'll just be praying that the B12 treatment clears up the carbon buildup.

From everyone I've talked to and everything I've read, going *slow* with these engines is just as hard on them as going fast. Will constant redline shorten the life of the engine? Probably, but I think that spending most of your time loping along at 2K will result in an unhappy engine, and is a waste of the car. I don't think babying these cars does them any favors...and frankly I don't enjoy my car at 2K.

ymbermv
(your mileage between engine rebuilds may vary)

Oh, what a load of crap you've been listening to. Can you provide a logical explanation why going slow is just as hard on the engine as going fast? You have to be careful who you listen to and what you believe. There's way too much snake oil mythology surrounding this cars. The rules of engine wear are governed by reason and common sense, not by German engineering or lead-footed hot shots who will believe anything that justifies their need for speed.

Secondly, I never lope along at 2k, nor did I ever encourage it in any of my posts. I merely stated that there's no reason to keep the RPM's above 3k unless you are accelerating or cruising at high speed. At cruise speed, you should be in a gear that is easy on the engine (want to maximize cooling don't you?) while still providing enough available torque to handle an emergency. I find that sweet spot to be between 2500 and 3000.

p.s. Sorry for the rant. I'm having a rare day.

[tsuter]

Another "newb" probably with "white mystery gunk.

Same guy looking for his "performance springs"?? LOL

[Formerly Steve Wilkinson]

"Lugging" is a myth. It's in fact a very efficient way to run an engine. Our dads all told us not to lug the engine, but none of them who did were mechanical engineers.

Stephan

[Jack Olsen]

It depends on what you consider lugging. I'll quote a post by John Colasante:

In the manual, it says:

"Never lug the engine in high gear at low speeds. This rule applies all the time, not just during the break-in period", page 12

Lugging is when you are under load, like going up a hill, and at low RPM and you have it in a high gear.

[84porsche]

I am definitely learning alot - please continue - I am the first in my family to even own a sports car so this is great. I added the short shifter in the car - but does it enhance better shifting points? I hope so. I started shifting with the light to learn and then pushed it a few rpms higher.

[Thack]

"I think that spending most of your time loping along at 2K will result in an unhappy engine, and is a waste of the car. I don't think babying these cars does them any favors...and frankly I don't enjoy my car at 2K."

I don't spend most of my time at 2K. I just get through the neighborhood that slow. When I get to a main road I go to about 2.5 or 3K, maybe more. When I enter the freeway I'll see 4K or faster. I look at my plugs and they look fine, no carbon build up. Do you suggest I go to Wal-Mart at 6K or 5K?

[amk]

I've read that for best acceleration you should keep the RMP between peak torque and peak power. In theory on my car that's 4200 RPM (peak torque) to 6000 RMP (peak power). Seat of the pants it certainly seems to pull strongest over 4000 RPM. I haven't dynoed the car yet so I'm not sure how flat the torque curve is.

On the track (which I'm very new to) I'm changing at a little over 6000RMP (red line is 6800) and the revs drop to just under 5000RMP before I'm accelerating again. Around town I typically change around 3000-4000RMP, unless I'm having a little fun, in which case I keep it over 4000.

Those are the shift points my car seems happiest with, I'll know more once I get it dynoed.

[nostatic]

I will never claim to be a mechanic (nor play one on tv), so I'll defer to those "in the know". I thought there were plenty of examples of engines not being run hard, and having the valves/etc get carbon build up. Isn't this part of the 993 OBDII issue?

[nostatic]

Originally posted by Thack
Do you suggest I go to Wal-Mart at 6K or 5K?

I would suggest you don't go there at all (I've never set foot in one and never will), but that's another rant/thread entirely...

hey, drive your car however you like.

[911pcars]

As suggested by several listers, lugging is not just an engine speed-related phenomenon. I can drive at 1500 rpm without lugging the engine. Of course, I may be in 1st or 2nd gear, have very small throttle openings and the car speed might be only 12 mph, but the engine is not being lugged.

To put undue load on an engine by lugging, you must have a combination of relatively low engine speed with relatively wide throttle opening. Operating the engine like this puts the engine on the edge of detonation and creates excess heat.

As for the term "best", I think you should define what this means to you in order to arrive at the "best" answer.

Sherwood
http://members.rennlist.org/911pcars

[GrindingGears]

I posted regarding this question not very long ago...

How to drive a 911?

My answer: Turn key, warm up oil, flog if you want, cruise if you choose, either way, enjoy.

[nostatic]

As Sherwood said (and I asked early on), "best for what?" The Carreras have a shift indicator light that must be telling you the "best" shift point, but I believe that is calibrated to maximize fuel economy, as opposed to fun economy.

I'm interested to see what the experts say with regards to "best" for engine longevity. I thought that most of the wear takes place when first started. So I'll pose a specific question: assuming an engine in proper tune and properly cooled will running it at 3K make for a longer lasting engine than running at 6K? Is there a plot of engine life v. rpm? Assuming that 6K is harder on the engine, how significant?

Not that I'm going to quit spanking her regularly. But just for the record I don't race anybody, nor do I speed recklessly. I just tend to run at higher revs (staying in second as opposed to third around town) and like to get up to speed quickly. And as I said, being at 3500 vs. 2500 allows for quicker avoidance of latte-laden suvs or cigarettes tossed from careless cars ahead

[911pcars]

Todd,
Running at a constant, steady speed will always produce longer engine life (as well as better fuel mileage) compared to accelerating and decelerating. That probably doesn't answer your question.

Not an expert, but lower engine revs is relative, but that equates to lower load on engine parts and bearings. To qualify that; as long as the engine is not being lugged, carbon buildup is kept to a minimum and the engine is at operating temperature, lower than max. engine revs should result in longer engine life. How much longer? Don't know. Putting miles on any engine will increase overall wear. However, if engine longevity at the expense of driving enjoyment is one's priority, then just park it and look at it. Plenty of owners do just that - saves the engine revs for the next owner.

Sherwood

[real550A]

High RPM's cause higher temperatures and higher gas pressures, which equal
poor fuel economy, higher bearing loads, and expensive rebuilds sooner.

There is a price for all this fun!