Optimal shifting points? At what RPM? Need help!

[DC135i]

Hey guys,

I did a search for this topic, but I couldn't find anything, so I'm posting this question, as it's driving me batty:

For everyday driving, is there an optimal shifting point, in terms of RPM, for each gear? For example, should I shift up at 2500 RPM? I know I can just listen to the engine, but my concern is "over-doing it" or shifting wrong, and how that could negatively affect my car (engine, transmission, clutch, the works). I'm very new to high-performance engines, so I might be worrying for no reason, but that's why I posted this question, to get some opinions/facts/feedback, etc... I'm guessing that these cars can take it, so to speak....day in and day out driving semi-hard...perhaps I'm just still in a "baby my new toy" mindset, so I'm probably just being over cautious.

Also, what RPM should you start downshifting? If the RPMs go below 2k, should I downshift? What's recommended here?

I'm fairly new to the manual transmission (it's been 7+ years since I last drove stick!), and I just want to make sure I'm doing it right for my new 135i.

I appreciate any assistance!!

[KCRich]

I would imagine that any fuel efficiency benefits gained by shifting at a precise point would be negligible. The overall style of driving seems to be the overriding factor, whether the cars under hard acceleration or not. I wouldn't concern myself with finding an exact up or downshift point.

[mistermojorizin]

what do you mean by "optimal for everyday driving"?

i mean i know what the shift is to achieve max acceleration - redline 1st and 2nd, 6800 in 3rd and 6400 in 4th and 5th.

what are you trying to achieve? upshift as quick as you can without lugging the engine to get best gas milage, accelerate smoothly. downshift as late as possible before the engine starts to lug.

[driftdriven]

Okay, I may be wrong but since you have gotten no straight answers I will tell you what I do. If I feel like saving gas I will shift as soon as I can into the next gear as long as the next gear has enough torque to just slightly keep the car moving (this is normally just above 1,000 rpm). Otherwise I leave it in neutral to cruise down a slope. For acceleration I would do a search on the optimum shift point for best acceleration. It is not redline for our cars, it is the point where the next gear has more torque then the gear you are in.

Another way to drive......DRIVE IT LIKE YOU STOLE IT!!! It will always put a grin on your face


Again, I could be wrong, but if I am let me know! :iono:

[spudw]

If the aim is to save fuel, shift short and drive slow, no? Although, it's really unclear why this would be a top-of-mind issue for someone who has chosen a twin-turbo, 300hp sports coupe.

[Heinzftw]

Keep the shift around 3k rpm's max. If you really want to save gas. Did you purchase the wrong car?

[Boosted_N54]

just watch how much... mpg ...gas you are wasting in your dislpay and then by that you will figure it out on your own

[mistermojorizin]

another trick for saving gas is this - on the flats keep it on cruise, on the hills turn the cruise off and let it decelerate a bit, especially towards the peak of the hill, then on the way down accelerate (gently) and try to keep as much momentum as possible going into the next hill.

[DC135i]

Originally Posted by Heinzftw

Keep the shift around 3k rpm's max. If you really want to save gas. Did you purchase the wrong car?

Ok, let me clarify, as after re-reading my post, I did notice that it read like I was concerned about gas mileage, which I'm not (or I wouldn't have bought this car, despite "efficient dynamics.")

What I was trying to relay was my concern for "over-doing it" or shifting wrong, and how that could negatively affect my car (engine, transmission, clutch, the works). I'm very new to high-performance engines, so I might be worrying for no reason, but that's why I posted this question, to get some opinions/facts/feedback, etc... I'm guessing that these cars can take it, so to speak....day in and day out driving semi-hard...perhaps I'm just still in a "baby my new toy" mindset, so I'm probably just being over cautious.

Please don't crucify me for my post, though...as this forum was designed for questions like mine (however dumb), to get feedback from peers (hopefully constructive feedback)

[mistermojorizin]

Originally Posted by DC135i

Ok, let me clarify, ... What I was trying to relay was my concern for "over-doing it" or shifting wrong, and how that could negatively affect my car (engine, transmission, clutch, the works)....

so i understand what you're saying, you're main concern is damageing the car?

you can shift it at redline without hurting anything. don't force the shifter though. don't shift too early or it will lug the engine. don't let the rpms drop below say 1,000 rpm in general, don't lug the engine. lugging the engine will hurt it.

otherwise, you can shift anywhere where it feels right. the sweet spot for me is usually 3,500 when i'm just cruising around. that's where it feels like the shifter goes into the next gear the easiest.

[Thud]

Originally Posted by mistermojorizin

another trick for saving gas is this - on the flats keep it on cruise, on the hills turn the cruise off and let it decelerate a bit, especially towards the peak of the hill, then on the way down accelerate (gently) and try to keep as much momentum as possible going into the next hill.

Also, avoid using the brakes at all costs. Brakes do nothing but convert motion into wasted heat. :thumbup:

[Qube]

You really want to do that? Just shift JUST as you hear the psssft from the DV.

[4wheelcycle]

I am a pretty sedate driver, but I generally don't drive my 135i below below 2,000 RPM. I know the turbo-enhanced torque is supposed to be strong above 1,400, and I'm sure lower RPM levels are fine for 1st and 2nd gear. However, for 3rd gear and above I downshift if the RPMs hit 2,000.

For upshifts, I usually shift around 3,000 RPM for sedate, around town driving and around 5,000 for spirited country road driving. The torque is so strong, you really don't have to take it to the high RPMs for higher HP - it pulls great on just the torque.

Around town, most of my driving is in the 2,300 to 2,700 RPM range.

[atr_hugo]

Ha - I've been short shifting to keep the revs in town under 2K. And then I watch the instantaneous mileage numbers. It's like driving a Prius. (NOT; -)

[mistermojorizin]

Originally Posted by Qube

You really want to do that? Just shift JUST as you hear the psssft from the DV.

what does the pssft mean? that the turbo is kicking in? what rpm's do you usually hear it at, i'll have to listen carefully.

[x97Melbourne]

i think the may have gotten the wrong car if you're trying to save gas.....

[mistermojorizin]

135 is great for performance driving gas milage

for example check out this comparison in mpg between the M3 and the prius. (m3 wins)

[ML]

In general, turbo motors can be a little deceptive about maximizing gas mileage. The computer's fuel curve is actually a surface, or maybe more appropriately, a family of curves. It is typically a function of both throttle position and boost pressure. So, a turbo motor like the N54 can pretty easily drive in 5th or 6th gear at a low rpm up a hill. However, what you may not realize is that the turbos are producing a lot of boost to allow the engine to run in that condition in a manner that you think is effortless and, because the boost is high, be using a lot of gas. So, to maximize fuel efficiency, the goal is to run the engine in vacuum as much as possible as opposed to boost, which may not occur at the bottom end of the rpm band depending on speed and what gear you are in.

Now with all of that said, the N54 may not really play by these rules since the turbos are supposed to be making full boost all the way down at 1400 rpm (as opposed to other large single turbo motors where the boost starts to come in around 2500 rpm). It just kind of makes it hard to drive this car in vacuum. I guess the bottom line is to use you instantaneous gas mileage readout from the computer and learn the best way to drive your car.

Mike

[DC135i]

Originally Posted by ML

In general, turbo motors can be a little deceptive about maximizing gas mileage. The computer's fuel curve is actually a surface, or maybe more appropriately, a family of curves. It is typically a function of both throttle position and boost pressure. So, a turbo motor like the N54 can pretty easily drive in 5th or 6th gear at a low rpm up a hill. However, what you may not realize is that the turbos are producing a lot of boost to allow the engine to run in that condition in a manner that you think is effortless and, because the boost is high, be using a lot of gas. So, to maximize fuel efficiency, the goal is to run the engine in vacuum as much as possible as opposed to boost, which may not occur at the bottom end of the rpm band depending on speed and what gear you are in.

Now with all of that said, the N54 may not really play by these rules since the turbos are supposed to be making full boost all the way down at 1400 rpm (as opposed to other large single turbo motors where the boost starts to come in around 2500 rpm). It just kind of makes it hard to drive this car in vacuum. I guess the bottom line is to use you instantaneous gas mileage readout from the computer and learn the best way to drive your car.

Mike

Thanks...i edited my question to reflect that gas mileage wasn't my actual concern.

[Guran]

Originally Posted by ML

In general, turbo motors can be a little deceptive about maximizing gas mileage. The computer's fuel curve is actually a surface, or maybe more appropriately, a family of curves. It is typically a function of both throttle position and boost pressure. So, a turbo motor like the N54 can pretty easily drive in 5th or 6th gear at a low rpm up a hill. However, what you may not realize is that the turbos are producing a lot of boost to allow the engine to run in that condition in a manner that you think is effortless and, because the boost is high, be using a lot of gas. So, to maximize fuel efficiency, the goal is to run the engine in vacuum as much as possible as opposed to boost, which may not occur at the bottom end of the rpm band depending on speed and what gear you are in.

Now with all of that said, the N54 may not really play by these rules since the turbos are supposed to be making full boost all the way down at 1400 rpm (as opposed to other large single turbo motors where the boost starts to come in around 2500 rpm). It just kind of makes it hard to drive this car in vacuum. I guess the bottom line is to use you instantaneous gas mileage readout from the computer and learn the best way to drive your car.

Mike

Well said.

Here's another fuel economy tip. When you're coasting down a long hill, drop it down to a lower gear (yes for autos too). The engine will spin to higher rpms but the fuel consumption will actually be zero. This is because at high engine speeds, the ECU stops feeding fuel to the engine and you rely on compression braking to maintain your speed. You'll also lengthen the life of your brakes. On the other hand, if you coast down in a high gear or neutral, you will need to use the brakes to slow down and the engine will still be consuming fuel all the time (not much though). It's easy to prove this to yourself using the instantaneous fuel consumption reading. Works regardless of whether you have a turbo or not.

OR you can say rats to fuel economy and play Fangio down the damn hill! :roundel:

[jeremyc74]

Originally Posted by DC135i

Thanks...i edited my question to reflect that gas mileage wasn't my actual concern.

As far as damaging the engine, you' just not going to unless you're constantly in the redline day in and day out. Shift where it's the smoothest for the type of driving you're doing, and don't worry too much about it.

For example, If I'm in a turn lane at a redlight, I'll just stay in 1st gear even though I'm past the point I would normally shift up at, just to avoid a downshift a couple of seconds later. Just do what comes natural and you won't hurt anything.

[mistermojorizin]

oh, i just remembered what you shouldn't do with the enginge- the money shift.