Auto vs Manual Transmission

[renfield90]

Originally Posted by strat61caster

MT, never spend any time at 4k rpm.

The only reason to do that is to make noise.

...or you're going faster than 90.

[strat61caster]

Originally Posted by renfield90

...or you're going faster than 90.

If I'm doing over 90 I'm in 4th gear over 5k rpm thankyouverymuch.

But I suppose those that live in flyover states with 90 mph speed limits probably do hang out at that rpm.

[LS1M]

The only problem is if you're cruising at 2.5K rpm, and you accelerate, then lugging the engine will cause knock and that's bad. Your automatic transmission will automatically downshift if you need to pass someone. Us MT guys have to do that ourselves.

There ain't no power below 3K so I save that for long steady stretches, to save gas.

-Mark

[shiumai]

Originally Posted by humfrz

No.
humfrz

Let's rephrase the question to:

Is it advisable/advantageous to cruise at 4k rpm instead 3k rpm for normal street driving, or on the highway/freeway?

[humfrz]

Originally Posted by shiumai

Let's rephrase the question to:

Is it advisable/advantageous to cruise at 4k rpm instead 3k rpm for normal street driving, or on the highway/freeway?

My short answer is NO ......

One of the few times that I "cruised" at over 4,000 RPMs, in a low torque, low HP car, was at 14,000 feet in a loaded down miata.

Why? Because just in case I needed every bit of power that puppy had to pull (push) me through a curve ....... especially on what were the gravel sections.

Do you see the guardrails to save you ...... ?? You don't, because there weren't any.

Yep, your machine will be happier cruising at 3,000 rather than 4,000 rpms .....and you will save gas ........


humfrz

[shiumai]

Originally Posted by Icecreamtruk

Pull it thru that torque valley baby!

My car is supercharged -> no torque valley

OP - just because you can, doesn't mean you should. Don't focus on a number or specific RPM (except redline); just pick the gear that provides what you need at that time. Choose your gear by feel and engine sound. If you need more acceleration, downshift. If you need to save gas, stick to 2500 to 3000 rpm. There's no need to buzz up and down streets or the freeway at a constantly higher rpm unless you just want to make noise, run at a higher oil temp or waste fuel unnecessarily. With the AT (which I have as well), I shift manually or keep it in sport mode , which keeps the revs about 500 rpm higher than normal mode. normal mode tends to bog the engine in stop and go traffic, and is more suited to freeway cruising.

Like @humfrz illustrated, there are times when you would drive at higher revs, like in the canyons or on the track, when you want to keep in a certain power band. But not typically needed for every day normal driving.

[guybo]

Listen to your engine, it'll tell you where it wants to be for an RPM range.

If you are going at a steady speed for a long stretch, keep your RPMs under 3000 to save some gas. As for the autobox, it'll automatically keep to a safe and fuel conscious RPM range. If you want to cruise at 4k RPM 1) you should have gotten a MT 2) Watch your transmission temps and make sure it's in a happy range. 3) (Q for for those with a slushbox) Does Torque Pro have tranny temps and what is a happy tranny temp for this car?

[Yal]

I've got the AT and the only time that I'm up around 4k is in the mountain portion of my commute. I don't worry about overheating the headlight fluid as I ponied up for the optional headlight fluid cooler.

[MuseChaser]

I can't think of a single good reason why you'd want to drive around "cruising" with your engine at 4000 rpm. If you were climbing an incredibly steep hill with a car loaded w/ cinderblocks and that was the only way to keep the car up to the speed you wanted, then OK. Otherwise... why?!?

Think of riding your bicycle. Would you want to pedal furiously w/ very little resistance in the pedals to go a certain speed, or at a comfortable 60-70 rpm cadence (what most casual bicyclists use, including myself) w/ a bit of resistance felt to work against? On a bicycle, you choose the gear that gets the job done most efficiently and with the least amount of effort/wear from/on the rider (the engine) in a given scenario. Cruising around at 4000 rpm is like riding a bike on a flat smooth road in the lowest gear, requiring you to pedal like mad. Even worse, unlike on a bike, when you take your foot OFF the gas in your car, the engine will create a lot MORE resistance and slow the car down faster than it would in a higher gear. Going down a steep hill, that's desirable.. OK, that may be an another instance where "cruising" at 4000 rpm might be a good idea; going down a steep hill and using engine braking instead of overheating your brakes.

Otherwise, I'm stymied by the original question. Why would you want to? The upper ranges are for acceleration and power. I routinely cruise flat roads between 2000 and 2500 rpm, and downshift when I need more power.

Still confused by the desire to stay in the upper ranges....

Barry

[c4lvinnn]

Originally Posted by MuseChaser

I can't think of a single good reason why you'd want to drive around "cruising" with your engine at 4000 rpm. If you were climbing an incredibly steep hill with a car loaded w/ cinderblocks and that was the only way to keep the car up to the speed you wanted, then OK. Otherwise... why?!?

Think of riding your bicycle. Would you want to pedal furiously w/ very little resistance in the pedals to go a certain speed, or at a comfortable 60-70 rpm cadence (what most casual bicyclists use, including myself) w/ a bit of resistance felt to work against? On a bicycle, you choose the gear that gets the job done most efficiently and with the least amount of effort/wear from/on the rider (the engine) in a given scenario. Cruising around at 4000 rpm is like riding a bike on a flat smooth road in the lowest gear, requiring you to pedal like mad. Even worse, unlike on a bike, when you take your foot OFF the gas in your car, the engine will create a lot MORE resistance and slow the car down faster than it would in a higher gear. Going down a steep hill, that's desirable.. OK, that may be an another instance where "cruising" at 4000 rpm might be a good idea; going down a steep hill and using engine braking instead of overheating your brakes.

Otherwise, I'm stymied by the original question. Why would you want to? The upper ranges are for acceleration and power. I routinely cruise flat roads between 2000 and 2500 rpm, and downshift when I need more power.

Still confused by the desire to stay in the upper ranges....

Barry

Um, because cruising sometimes means (Texas highways for me specifically) going 80+ and 80 is right at 4000 RPMs? Nothing you can really do about it except change the final drive ratio and I don't care that much.

[shiumai]

Originally Posted by c4lvinnn

Um, because cruising sometimes means (Texas highways for me specifically) going 80+ and 80 is right at 4000 RPMs? Nothing you can really do about it except change the final drive ratio and I don't care that much.

That's a specific situation where you don't have the choice to upshift any more as you're mechanically limited. Then of course, it makes sense to do so.
I wish socal cruising speeds were 80+ (without drawing attention).

[c4lvinnn]

Originally Posted by shiumai

That's a specific situation where you don't have the choice to upshift any more as you're mechanically limited. Then of course, it makes sense to do so.
I wish socal cruising speeds were 80+ (without drawing attention).

Just making a point to say cruising at 4k RPMs isn't going to kill your car or anything like that. And sometimes that cruising at 4k RPMs is just that, you're cruising at 4k RPMs, lol. Just seems like a lot of replies here are like "WHY?!!?!" um because that's the gear ratios they put in the car and I'm going at a normal rate of speed?

[wparsons]

I drive around the city with rpm's really low, cruising at high rpm is just making noise and wasting gas. You can easily drive around town in 5th (MT) at 60km/h+ without lugging the engine, just don't floor it and expect it to accelerate.

[strat61caster]

Originally Posted by LS1M

The only problem is if you're cruising at 2.5K rpm, and you accelerate, then lugging the engine will cause knock and that's bad.

This engine doesn't lug until you're well under 2k rpm, makes no power below ~2.5k, sure, but it's not lugging.

Or you're putting in shittier gas than California gets...

Originally Posted by shiumai

I wish socal cruising speeds were 80+ (without drawing attention).

About 80% of Socal has cruising speeds of 80 mph, you just live in the 20% where cruising speed is 20 mph