# 6th gear argument rehashed



## allaboutme (Dec 22, 2003)

I just read the link to a thread titled "ZHP & SMG" from a while back. There was an argument that the 6th gear does save gas while others believed it was useless and had no power.

When I was crusing between 65 and 70 miles per house in 6th gear, there was a noticeable "weakness" when accelerating to maintain the speed. I agree that it has enough to slowly push me forward, but it wasn't a lot. I feel much more comfortable at 5th since it has more grunt to plow ahead if I need to.

Now, that brings me to the controversy over whether it saves gas or not. I FIGURE that it probably would save gas assuming it was CRUISING; however, there's a chance it will waste more than it can save. I think it's best to compare it to a multi speed bicycle. When you start off on a low gear you get plenty of power like the low gears on a car. If you were crusing at a fast speed and you were utilizing a higher gear you would notice that it takes considerably more energy to add speed to the bike. Whereas, a lower speed would push you faster with less expenditure of my precious human power. 

As always, I'm probably wrong hahaha.. that piece was my best attempt at trying to add tot he overdrive gear argument.


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## Emission (Dec 19, 2001)

The 6th is an overdrive, and it will save you fuel. With that in mind, 5th will have more power as the engine is spinning faster. Better yet, try 4th - you'll fly!


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## bavarian19 (May 11, 2003)

the conclusion of these arguments was that the gear was strictly for high speed cruising. The gear is mainly used above 70-75. By no means was it to drive uphill or accelerate, but more so to conserve gas on long straight flat highway roads... that and going waaaaaay over the speed limit :eeps:


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## allaboutme (Dec 22, 2003)

Emission said:


> The 6th is an overdrive, and it will save you fuel. With that in mind, 5th will have more power as the engine is spinning faster. Better yet, try 4th - you'll fly!


Well, yes.. That's obvious enough.
I don't think my statements were clear enough. I think speeding up in 6th gear will waste more fuel than it can conserve. Does that seem valid to you with my bike analogy?


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## Plaz (Dec 19, 2001)

allaboutme said:


> Well, yes.. That's obvious enough.
> I don't think my statements were clear enough. I think speeding up in 6th gear will waste more fuel than it can conserve. Does that seem valid to you with my bike analogy?


Yes. In my limited unscientifically controlled experiments, it seems my car does just as well, if not better, on gas mileage when I shift at high rpms vs. low rpms.

:dunno:


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## MysticBlue (Jun 20, 2003)

As I said in the previous thread you mentioned, it most definitely is for cruising, not passing, no doubt about that. But if I am on the freeway I use it if there isn't a lot of traffic. It makes for a quieter drive and I have not ever had to shift down due to going up a hill. This includes a 6 mile 7% grade; one of those kind of hills that has a bunch of warning signs on the downhill side and run-away truck ramps filled with gravel. 75 mph all the way up, 6th gear, in cruise control, no problem. And yes, it gets better gas mileage. Probably not a huge diff; like 1 or 2 mpg but that's not the real reason I use it. Just seems more relaxed.


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## hugh1850 (Jun 20, 2003)

MysticBlue said:


> As I said in the previous thread you mentioned, it most definitely is for cruising, not passing, no doubt about that. But if I am on the freeway I use it if there isn't a lot of traffic. It makes for a quieter drive and I have not ever had to shift down due to going up a hill. This includes a 6 mile 7% grade; one of those kind of hills that has a bunch of warning signs on the downhill side and run-away truck ramps filled with gravel. 75 mph all the way up, 6th gear, in cruise control, no problem. And yes, it gets better gas mileage. Probably not a huge diff; like 1 or 2 mpg but that's not the real reason I use it. Just seems more relaxed.


Exactly.


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## mtbscott (Jul 16, 2003)

I use 6th gear in my car pretty much anytime I'm on the highway at speeds of 60 or better. If I need quick acceleration for some reason, I shift down to 5th or 4th as needed. I commute over 50 miles daily and am able to cruise around 70 to 75 for most of that. My car averages around 23-24 mpg overall. On extended trips, where I have been able to reset the trip computer after a gas stop, the car will get as much as 28 mpg cruising at 75-80 in 6th gear. I have no doubt that it saves gas, is quieter, and saves wear and tear on things. That said, there's a reason for the car having 6 gears, all of them have their need and place in the grand scheme of things.


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## BradS (Aug 27, 2003)

Over here, in the land of rational speed limits (130kph or higher), 6th gear is great. On the 120 kph stretches, I leave it 5th, as 6th seems to have no positive mpg effect. 

In the states, shifting into 6th would seem, uh, well, I guess it's something else to do once you get to 70 mph to occupy your time. 

If I bring this car back to the states I may have to swap in a 3.46 or better rear diff to just keep 6th relevant.


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## Tanning machine (Feb 21, 2002)

mtbscott said:


> That said, there's a reason for the car having 6 gears, all of them have their need and place in the grand scheme of things.


Yes, particularly for that occasional jaunt to Germany.


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## Emission (Dec 19, 2001)

allaboutme said:


> Well, yes.. That's obvious enough.
> I don't think my statements were clear enough. I think speeding up in 6th gear will waste more fuel than it can conserve. Does that seem valid to you with my bike analogy?


Are you thinking full throttle of 6th gear is going to use more gas than partial throttle at 5th gear (assuming you are doing 60 and want to get to 80)?

Even though there is more fuel going into each injector at full throttle in 6th, I think that is outweighed by the fact the engine is turning a few hundred times less every minute compared to 5th. I'd imagine those few hundred extra injections of fuel (for the higher RPM) use more gas.


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## richard (Apr 3, 2002)

I can see where having a 6th gear on the autobahn would be beneficial, but living in a large metropolitan area it's a complete waste. I'm lucky to see 5th gear in Chicago. Even a trip to the suburbs I wouldn't use it. For people that travel cross country maybe. I really think it's pure marketing.


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## The HACK (Dec 19, 2001)

Guess how many RPM is there between 5th and 6th at 75mph? 180. A measly 180 revolutions a minute.

It's all a marketing ploy. The drivetrain loss from a direct 1:1 gear and an overdrive gear is larger than whatever fuel you're going to save from turning the engine 180 times less a minute. 6th gear is worthless.


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## Emission (Dec 19, 2001)

The HACK said:


> Guess how many RPM is there between 5th and 6th at 75mph? 180. A measly 180 revolutions a minute.


180 or 1800?

180 seems WAY TOO low.


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## Kaz (Dec 21, 2001)

The way E46s are laid out, I think it's a really fine line, and depends quite a bit on the car's final ratio. It seems pretty pointless on a 2.93 in a normal 330, but it would really be useful in my car with a 3.46. Naturally, for ///marketing purposes, BMW is going to have to include it in every model, but it would make even more sense if it was properly matched to the proper overall ratio.


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## hugh1850 (Jun 20, 2003)

At constant speed of 70 mph, on level grade, in 5th gear I am running about 3000-3100 rpm. In 6th a the same speed the engine is running at 2500-2600 rpm. I can usually gain 2-5 more mpg than in 5th.


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## BradS (Aug 27, 2003)

The HACK said:


> Guess how many RPM is there between 5th and 6th at 75mph? 180. A measly 180 revolutions a minute. QUOTE]
> 
> Hack,
> 
> ...


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## Tanning machine (Feb 21, 2002)

allaboutme said:


> I think it's best to compare it to a multi speed bicycle. When you start off on a low gear you get plenty of power like the low gears on a car. If you were crusing at a fast speed and you were utilizing a higher gear you would notice that it takes considerably more energy to add speed to the bike. Whereas, a lower speed would push you faster with less expenditure of my precious human power.
> 
> .


I don't think the analogy works completely. The reason the big gears are tougher on a bike is because they're, well, bigger. So you need to exert more energy for one turn. But you also get more for that one turn in terms of drive.

Here's where the issue is: at what turning rate are you most efficiently exerting force? Depending on your strength, it's a certain number of pedal cranks per minute. If you're in too low a gear, then you have to spin the pedals faster than you're capable. Sure, they're easy to turn, but you burn out your lungs. If you're in too big a gear, you have to use too much muscle, while your lungs are okay--it's like lifting too heavy a weight. Your muscles get burned, while your lungs aren't fully exerted. You want a happy medium.

Same thing with an engine: you want to be at the most efficient running point in terms of power/fuel consumption. Obviously, you don't drive in 6th speed around town, because the engine isn't powerful enough at 20mph to turn the wheels. At highway speeds, the engine goes too fast and blows out.

So, to answer the question, you have to figure out a) what's the most efficient point for the engine to be operating, which is generally the highest gear in which it's not lugging at the speed you're going. IF that's 6th, use 6th. If not, use a lower gear. If you have to go up hills regularly, and the engine lugs, well, you need to shift down. BUt you're not going to waste gas by shifting down, because you're using a more efficient gear.


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## rumratt (Feb 22, 2003)

Emission said:


> The 6th is an overdrive, and it will save you fuel.


How are you so sure? This is an awfully general statement. Despite seeming intuitive, the statement is not guaranteed tob e true. Would a 7th, 8th, and 9th save gas? How can you be certain that 5th gear isn't the sweet spot for certain cruising speeds in the E46?

I don't use 6th unless I'm using the cruise control and driving over 75mph (I have the 2.93 diff).


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## rumratt (Feb 22, 2003)

Tanning machine said:


> So, to answer the question, you have to figure out a) what's the most efficient point for the engine to be operating,


Agreed. :thumbup:



> which is generally the highest gear in which it's not lugging at the speed you're going.


Hmmm. You sure? Is this based on intuition, or data? I can imagine it's possible for there to be some gap between "ideal efficiency" and "lugging".


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## ff (Dec 19, 2001)

allaboutme said:


> Now, that brings me to the controversy over whether it saves gas or not.


When cruising to Florida last month, our first stretch of the trip we received 33 MPG using 6th gear. And that was with the perf. pkg.'s shorter rear end gearing. Averaged over 30 MPG for the entire trip. Average speed was about 77 MPH.

But at lower speeds, and more typical in-town driving, I doubt that 6th will do anything but make your mileage worse. Too tall a gear for frequently changing speeds.


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## BradS (Aug 27, 2003)

In an ideal world, that rpm at which the engine produces exactly the horsepower required, after drivetrain and aerodynamic losses, to maintain a given velocity is the optimum rpm for economy, as the engine is using precisely the minimum amount of burned fuel required to produce that horsepower with no excess fuel or HP created. 

But, the real world has variables in driving, requiring acceleration. An engine accelerates most effeciently (fuel required to achieve desired HP) at the peak of it torque band--that point at which the engine most effeciently produces power. The fat part of the torque band is rarely down at that minimum rpm needed for steady state driving.

So, driving through Florida, very flat, near sea level with lots of air density, and few variations, you'll get higher mileage. So ff can pop 33mpg. But, if he goes to Northern Alabama, the constant acceleration required to go up hills and avoid pick-up trucks loaded with hunting gear (no flames--I used to own one!) means his mpg will drop since periodic acceleration is required.


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## Moderato (Nov 24, 2003)

Not to change the subject...well it's sort of the subject....but anyway I have a 2004 330i on order with the 6speed. Based on what I've read the first 5 gears are the same as any other E46 up to 2003 right? So in another words, my driving experience with the 6speed is going to be exactly the same as anyother E46 with the 5speed except that I have one more overdrive gear right? My last car was an 04 STi and that had a 6speed. It was my first 6speed as all my other cars had 5speeds. With the STi there were plenty of times when by force of habit I wanted to go to 2nd, but as I got used to the 6speed I was using 3rd instead. So in this case the 6speed was a completely different experience from the 5speeds I had been used to, but with my 04 330i the first 5 gears will be the same as the other E46 5speeds, but I will simply have an extra overdrive gear?


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## Plaz (Dec 19, 2001)

Moderato said:


> I have a 2004 330i on order with the 6speed. Based on what I've read the first 5 gears are the same as any other E46 up to 2003 right? So in another words, my driving experience with the 6speed is going to be exactly the same as anyother E46 with the 5speed except that I have one more overdrive gear right?


Correct, unless you got the Performance Package, which includes a slightly shorter final drive.


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## The RedShift (Dec 31, 2002)

Oh come on guys. Don't you think that if the 6 speed got better mileage that BMW would say so to up their overall mileage rating with the US Govt? The five speed 330s and six speed 330s are still both rated at 30 highway and 24 city. My guess is that there is no difference. I just drove from Seattle to LA, with an average of 73 MPH at 29.5 MPG. Not bad for a five speed. I truly doubt that the six speed is anything but a marketing ploy.


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## GeoMystic (Aug 21, 2002)

I love the 6th gear. I just drove down to Florida as well and was averaging around 33 mpg riding 6th gear. 

It also pulls pretty well incomparison to 5th. Sure it is not as peppy, but when you're in 6th at that high speed it is plenty enough. After all you chose a manual transmission for a reason, when you want more passing power, downshift that sucka! Don't be lazy. 

Also the difference between 5th and 6th gear is WAY more than 180rpm's!


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## Moderato (Nov 24, 2003)

Plaz said:


> Correct, unless you got the Performance Package, which includes a slightly shorter final drive.


I got the standard 330i sport pacakage. After my experience with the STi I wanted something a little more relaxed. It's interesting that the 1st 5 gears have stayed the same, and just the 6th overdrive gear was added. I wonder why they did it that way instead of altering all of the 6 gear ratios. My only guess was that the 1st 5 gears were perfect for the car and if it aint broke don't try to fix it :thumbup: Either way having the 6th gear is nice and won't hurt anything.


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## rumratt (Feb 22, 2003)

Moderato said:


> Either way having the 6th gear is nice and won't hurt anything.


It doesn't hurt, but it isn't as useful as it could have (and should have) been.


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## BradS (Aug 27, 2003)

IMHO, it would be much more useful, especially in the US, with a 15% steeper rear screw, say about 3.36:1, or even 3.46:1. Actually, as I sit here and think about it, it would be nice if BMW gave some options on final drive. I know its a PITA for CAFE purposes, but a range between 2.93 and somewhere in the high 3's, say 3.90, would be nice. 

And a real limited slip, to pick that scab.


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## SergioK (Aug 14, 2002)

Emission said:


> The 6th is an overdrive, and it will save you fuel. With that in mind, 5th will have more power as the engine is spinning faster. Better yet, try 4th - you'll fly!


I wish I had a 6th OD in my car!  I need the extra fuel economy when cruising at warp speeds. :rofl:


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## calvol (May 15, 2003)

*6th won't save gas*

6th won't save gas because their is a power loss conversion through the 0.85 gear, which reduces the efficiency, as opposed to the 5th gear, which is a direct 1:1 gear, with no gearing losses. 6th gear will lower RPMs, and that's about it. Gas mileage will be the same.


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## wrwicky (Jan 17, 2003)

calvol said:


> 6th won't save gas because their is a power loss conversion through the 0.85 gear, which reduces the efficiency, as opposed to the 5th gear, which is a direct 1:1 gear, with no gearing losses. 6th gear will lower RPMs, and that's about it. Gas mileage will be the same.


On my car at highway speed and above it saves a couple of mpg. Of course YMMV, literally.


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## calvol (May 15, 2003)

*Ok, with the ZHP 6th will save gas*



wrwicky said:


> On my car at highway speed and above it saves a couple of mpg. Of course YMMV, literally.


because of the taller final drive... However, the 5th gear/2.93 ratio will get better gas mileage than the 6th/3.08, because the former will not have gearing losses with the 1:1 direct drive.


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## BradS (Aug 27, 2003)

calvol said:


> 6th won't save gas because their is a power loss conversion through the 0.85 gear, which reduces the efficiency, as opposed to the 5th gear, which is a direct 1:1 gear, with no gearing losses. 6th gear will lower RPMs, and that's about it. Gas mileage will be the same.


Huh? Please explain this power loss conversion theory.


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## Optimus Prime (Nov 11, 2003)

calvol said:


> 6th won't save gas because their is a power loss conversion through the 0.85 gear, which reduces the efficiency, as opposed to the 5th gear, which is a direct 1:1 gear, with no gearing losses. 6th gear will lower RPMs, and that's about it. Gas mileage will be the same.


This is probably the most retarded post I've read in a long time.

So by your assumptions 4th would be even more fuel efficeint, since you get a ratio better than 1:1, you actually have more power at the wheels. By this way of thinking, your car is most efficeint when running at redline, since you are going fastest in the lowest gear possible.

What it really comes down to is the thermal efficeincy of the engine, and the efficeincy of the drive train. Most engines overall efficeincy is best at low RPM's. You want to get a certain amount of power to the wheels, with the least amount of fuel being sprayed into the engine.

If no, or little, acceleration is required. It is most efficient to be in the highest gear possible, allowing the engine run at a low RPM. However, when acceleration is needed, it is often best to drop a gear or two. This allows better acceleration for the given fuel used, and allows you to quickly get up to speed and then return to cruising.

Example:

It may take 20 seconds to accelerate from 50-70 at 3/4's throttle in 6th gear, after which time you return to 1/4 throttle for cruising. However, it may take 10 seconds to accelerate from 50-70 at 3/4's throttle in 4th gear, after which time you return to 1/2 throttle for "cruising" in 4th gear.

In this example, 4th gear is much more efficient in acceleration because it requires half the fuel for the exact same acceleration. However, 6th gear is more efficient in cruising because it requires 1/2 the fuel for a given speed.

In Short:
If you know how to drive, the 6 speed will always get more MPG.


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## calvol (May 15, 2003)

*Go buy yourself an education...*

Anytime you have other than a 1:1 ratio there are conversion losses... 5th is direct 1:1, which is zero conversion losses, and still within a RPM range for cruising.... 4th gives you more torque, but is outside the optimum RPM range for cruising.... maybe you should have done your homework in ME 101.


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## rumratt (Feb 22, 2003)

hittinlike54 said:


> If you know how to drive, the 6 speed will always get more MPG.


This is based on your intuition, and it is not necessarily a true statement. I will quote my own text that I have already written once in this thread (and nobody answered)



rumratt said:


> How are you so sure? This is an awfully general statement. Despite seeming intuitive, the statement is not guaranteed to be true. Would a 7th, 8th, and 9th save gas? How can you be certain that 5th gear isn't the sweet spot for certain cruising speeds in the E46?


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## eelnoraa (Oct 13, 2003)

I give my thought.

I think anytime you have a conversion, there is a lost, whether it is 1:1 or 1:anything. They may have diffrerent lost, but the difference should be small enough. So 1:1 5th should have about the same lost as 1:0.85 6th.

In general, the lower rpm, the less fuel the engine use. But at low rpm, the engine may not have enough torque. I tend to agree with someone above. The most efficient would be running the engine with lowest rpm which have enought torgue to sustain the speed you are traveling. So at any situation which you can run 6th gear without lugging the engine, you are most efficient.

eel


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## Optimus Prime (Nov 11, 2003)

rumratt said:


> This is based on your intuition, and it is not necessarily a true statement. I will quote my own text that I have already written once in this thread (and nobody answered)


Actually this is based on my masters degree in Mechanical engineering. A 7th gear would make the car more efficeint, as would an 8th, 9th, etc. Why do you think CVT's are so efficeint. The reason you don't see many 7,8 or 9 speeds is practicallity. a 7th gear might only yield a .2 mpg advantage, thus making it impracticall so spend a lot of money on it. Also, only recently have manufacturing methods allowed relatively light and small 6 speed transmissions. Back in the day, a 6 speed would have been 7 feet long and 1000 lbs. (maybe a slight overstatement  )

Basically, at any given speed. There is an exact engine speed, and thus gear ratio that will yield the best MPG. The more ratios you have to choose from, the more likely you are to hit that sweet spot.


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## rumratt (Feb 22, 2003)

As impressed as I am with your Masters degree  , I think you have made some over-general statements that can not be defended.



hittinlike54 said:


> A 7th gear would make the car more efficeint, as would an 8th, 9th, etc.


First, lower gears doesn't automatically make anything more efficient. All it does is bring the engine into a different RPM range. If you bring the RPM's BELOW the optimum range, than you are not improving efficiency.

Second, there are issues of efficiency losses in gearing. So even if bring the RPMs into a SLIGHTLY more efficient range, it could be possible that you don't realize this efficiency due to increased drivetrain losses.



> The more ratios you have to choose from, the more likely you are to hit that sweet spot.


So if you're admitting there is a sweet spot. So this gets back to my original question. How do you know that 6th gear is closer to the "sweet spot" than 5th? You can't argue this definitively without a LOT of extra information that you don't have. :dunno:


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## FenPhen (Jan 13, 2004)

calvol said:


> With a 1:1 gear, you have less friction because the strike angle is exactly 90deg between teeth, and there is minimal churning because of equivalent tooth sizes. That ideal condition doesn't occur with ANY GEAR RATIO other than a 1:1... SO, given the final ratios for the ZHP & 330i are the same, the added inefficiency of the 0.85 gear lowers the MPG.


I'm not a MechE, but is strike angle relevant since car transmissions use helical gears?


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## calvol (May 15, 2003)

BradS said:


> No I don't think I'm missing anything. .


Really? I just proved your earlier post was wrong...



BradS said:


> Originally Posted by BradS
> Please pull out that ME101 text and explain how a mechanical link, such as the gears in a manual transmission, have any "conversion loss." Other than the small amounts of energy lost in bearing friction, I fail to see how any mechanical gear, regardless of ratio, would have a "conversion loss" that was measurably different than another. .


Excuse me, "bearing friction"? I just cited ME101 that shows gearing efficiency is related to friction and churning. Your saying it's insignificant, when you didn't even know it mattered. Now YOU tell me I'm wrong? Haha.


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## daihard (Feb 15, 2004)

calvol said:


> Excuse me, "bearing friction"? I just cited ME101 that shows gearing efficiency is related to friction and churning. Your saying it's insignificant, when you didn't even know it mattered. Now YOU tell me I'm wrong? Haha.


From my earlier post which you may have missed...

----------------------
Not to take sides, but the only thing that the direct gear (1:1) doesn't have is "gear reduction" within the transmission. Gear reduction (and internal power loss) still occurs within the final gear. Besides, in the typical manual transmission, all gears are spinning no matter which gear you are in. Therefore, my conclusion is that the direct 5th gear does not offer any more efficiency than the other, indirect gears.


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## wrwicky (Jan 17, 2003)

Man o man. A guy gets busy at work for a few weeks and the most inocuous thread just goes ballistic. 

1:1 is more efficient? Probably, assuming gears of a similar radius, width, material, gear oil, machining technology, face design, yaddy, yaddy,yaddy. In the real world with the two transmissions in question I would be suprised if there was a full percent difference in efficiency.

For all of the folks who mentioned they wish we could test this. WTF are you guys talking about? Don't all of our cars come equipped fuel consumption "energy" guages? I put my car in sixth steady at 75mph - I get 31ish, I put my car in fifth at 75 mph I get a little less than 29. Done. Sure that guage is not that accurate. But I'm sure the difference produced under identical conditions is pretty accurate.

For those who think the ratios should be tighter; I dont know. I've got a ZHP which is a little "cammier" than std. and it still has a VERY broad torque band. I think a fairly wide set of ratios really suits the engine beautifully. 

Sixth gear is a big deal to me. As an early ZHP buyer, when I put down my deposit, the ability to obtain a six speed was a deal-maker for me. As an ex miata owner, I can't tell you how many times I wanted to shift that 5 spd into sixth.


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## FenPhen (Jan 13, 2004)

wrwicky said:


> For all of the folks who mentioned they wish we could test this. WTF are you guys talking about? Don't all of our cars come equipped fuel consumption "energy" guages? I put my car in sixth steady at 75mph - I get 31ish, I put my car in fifth at 75 mph I get a little less than 29. Done.


Yeah, that was eating away at me too, seeing how I can't conduct that experiment myself till April.


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## SergioK (Aug 14, 2002)

wrwicky said:


> For all of the folks who mentioned they wish we could test this. WTF are you guys talking about? Don't all of our cars come equipped fuel consumption "energy" guages? I put my car in sixth steady at 75mph - I get 31ish, I put my car in fifth at 75 mph I get a little less than 29.


Ah! but the naysayers would have us believe that what you really saw/ or what really happened, was that you were in 4th at a steady 75mph getting 41MPG and when you went to 6th you were getting a crappy 31ishMPG.


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## Moderato (Nov 24, 2003)

Moderato said:


> Threads like this are what I love about good forums. If we were all having this disscusion in person it wouldn't be this productive. Emotions get in the way, and effect one's statements. On a board like this you read a post, think about it, and then collect your own thoughts in writing. In 4 weeks I'll have my 330i 6 speed, and when I get it I will compare my mpg with constant factors in 5th vs. 6th and put an end to this debate with the results of my testing.


Ok, I've had my car for about 1600 miles now and the 6th gear does give better fuel economy, but here's the key: If you use it in the proper situation.


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## Mr. E (Dec 19, 2001)

Here we go again! Let me settle in...

So Moderato, what is the "proper situation" where 6th gear gives you better fuel economy?

: popcorn:


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## Moderato (Nov 24, 2003)

Mr. E said:


> Here we go again! Let me settle in...
> 
> So Moderato, what is the "proper situation" where 6th gear gives you better fuel economy?
> 
> : popcorn:


Easy, just pay attention to the MPG gauge. If you cruising in 6th and you think that you might be getting better mileage in 5th or 4th depending, drop it down to 5th or 4th and see if it goes up or down, based on your experiences with that you will get an idea what the "proper situations" are. Wash, Rinse and Repeat. :drink:


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## allaboutme (Dec 22, 2003)

Uh... I started this thread? :eeps:


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## grayghost (Jan 10, 2003)

Moderato said:


> Easy, just pay attention to the MPG gauge. If you cruising in 6th and you think that you might be getting better mileage in 5th or 4th depending, drop it down to 5th or 4th and see if it goes up or down, based on your experiences with that you will get an idea what the "proper situations" are. Wash, Rinse and Repeat. :drink:


If by "MPG guage" you mean the little dial/pointer indicator (not the computer), then I'm afraid that will be very misleading.  That guage is basically just a Mainfold Vacumn guage and you have to understand what it is really telling you. (To much to try to explain here.) But, in a number of circumstances, especially slight acceleration, the MPG guage will show better mileage in a lower gear, while just the opposite is true.
Don't get me wrong, I'm a believer in having/using 6th gear and have been testing the results of various gears using the computer based MPG numbers. I'm convinced that 6th gear saves gas at about any speed over around 50 MPH. Not much though, until you get around 70 MPH at which point the savings are around 2 MPG. On my 2004 330Ci I get about 31 - 32 MPG (computer reading) at 70 - 75 MPH steady speeds (interstate) using 6th gear.


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## SergioK (Aug 14, 2002)

Should we merge this thread and the 'DSC' thread together? :angel:


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## Salsero2 (Mar 10, 2004)

This thread is painful -- I hope you 6 spd haters have finally seen the light. I have a 5 spd but there is no doubt the 6 spd will be more efficient properly driven. You can go round and round with the technical differences but, they are small in the big picture.

Get over your comparison of the ZHP to the 5 spd as they are not valid as the ZHP has a different DME, camshafts and differential gears. The overdrive allowed the ZHP to obtain a 30 MPG rating like the 5 spd but what would it have been w/o the overdrive? Unquestionably worse.

The 6 spd allows BMW to offer a slightly more agressive setup while minimizing economy loss and reducing cruising RPM, noise, wear etc. Bottom line: as employed in the ZHP it is better than the 5 spd. PERIOD.

For the non believers -- the earth is flat.


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## MA330CIC (Mar 13, 2004)

Salsero2 said:


> This thread is painful -- I hope you 6 spd haters have finally seen the light. I have a 5 spd but there is no doubt the 6 spd will be more efficient properly driven. You can go round and round with the technical differences but, they are small in the big picture.
> 
> Get over your comparison of the ZHP to the 5 spd as they are not valid as the ZHP has a different DME, camshafts and differential gears. The overdrive allowed the ZHP to obtain a 30 MPG rating like the 5 spd but what would it have been w/o the overdrive? Unquestionably worse.
> 
> ...


 :stupid: :stupid:


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## Hou330izhp (May 25, 2004)

wrwicky said:
 

> Sixth gear is a big deal to me. As an early ZHP buyer, when I put down my deposit, the ability to obtain a six speed was a deal-maker for me. As an ex miata owner, I can't tell you how many times I wanted to shift that 5 spd into sixth.


I don't even use 5th anymore; I do a straight shift from 4th - 6th. I see no need to strech my arm all the way up to 5th for a few seconds before I shift it into 6th.


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## SergioK (Aug 14, 2002)

Hou330izhp said:


> I don't even use 5th anymore; I do a straight shift from 4th - 6th. I see no need to strech my arm all the way up to 5th for a few seconds before I shift it into 6th.


I get lazy too... sometimes I just like using odd numbered gears. :rofl:


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## swchang (Oct 5, 2003)

6th saved me a couple mpg over 5th the other day. Even made my hair grow back in. Thank you 6th gear!


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## Mapman (May 26, 2003)

swchang said:


> 6th saved me a couple mpg over 5th the other day. Even made my hair grow back in. Thank you 6th gear!


What?!? 6th gear hasn't helped me yet with this. Maybe the Performance Package comes equipped with a Rogaine (tm) soaked headliner. :dunno:

Can any of you follically-challenged ZHP owners confirm this?


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## SergioK (Aug 14, 2002)

Mapman said:


> What?!? 6th gear hasn't helped me yet with this. Maybe the Performance Package comes equipped with a Rogaine (tm) soaked headliner. :dunno:
> 
> Can any of you follically-challenged ZHP owners confirm this?


No no, I think you are confused. It's the addition of the 6th gear which, in studies, has actually proved to reduce RPM. Since this is done with the shifter, you must use your hand. Any interaction thereof would affect this area. (Note: increase in folicle stimulation in the hand may be indicative of other 'issues', please see your doctor immediately)


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## jm8571 (Mar 3, 2002)

The HACK said:


> Okay, some rudimentary Physics here...
> 
> Horse power is an equation of ENERGY. That's why how it's calculated is always engine torqueXconstantXRPM. It doesn't matter how much LOAD is in the engine, what your throttle input is, or if you're going up hill or down hill. If your RPM is X,XXX, then your HP output is XXX, period. It's a measurement of energy and it's a simple formulation of mass times velocity (in this case, rotational velocity). If your object is travelling at a constant XXX velocity then it's carrying YYY energy, period. As you accelerate you gain more energy, but at any given speed (RPM) your energy is constant.
> 
> ...


Power varys as the load varies. With speed a constant (and hence RPM a constant) if you tow a trailer, you will consume more gas than if you do not tow a trailer. This is because the frictional forces have increased, and hence the energy delivered, to keep speed constant, will increase.


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