[Outlaw 06]

Okay, see attached .jpg for the R&T spec sheet on the 2007 E90 335i with 6MT and ZSP. Here are my calculations based on the overall 4th gear ratio @ an average engine speed of 4,000 RPM and an average tire circumference of 78.7 inches (approximately 6.56 feet) for the Sport Package’s 255/35/ZR-18 rear tires.

The 335i sedan has a 4th gear ratio of 1.19:1 and a final drive of 3.08:1

1.19 x 3.08 = 3.67:1 overall gear ratio (from the engine and driveline to the road).

Divide 4,000 rpm by the 4th gear ratio of 3.67 and you get 1,090 tire RPM (tire rotations per minute in 4th gear at 4,000 RPM engine speed).

The (new) ZSP tires have a circumference of about 6.56 feet, so the car will travel approximately 1,090 tire RPM x 6.56 feet/rotation = 7,150 feet in one minute.

Divide 7,150 feet / 5,280 feet per mile = 1.354 miles in one minute in 4th gear.

Multiply 1.354 miles per minute x 60 minutes per hour = 81.2 mph in 4th gear at 4,000 RPM (which is less than 60% of the N54’s max rated engine RPM).

81.2 MPH is a fairly comfortable highway speed at a moderate engine speed of only 4,000 RPM. Someone please check my math, but if my calculations are correct it’s pretty clear that driving 80 MPH in 4th gear certainly isn’t putting any undue stress on the N54 engine.

[Baldur Abendroth]

Originally Posted by TJDiCandido

Okay, see attached .jpg for the R&T spec sheet on the 2007 E90 335i with 6MT and ZSP. Here are my calculations based on the overall 4th gear ratio @ an average engine speed of 4,000 RPM and an average tire circumference of 78.7 inches (approximately 6.56 feet) for the Sport Package’s 225/40/ZR-18 front and 255/35/ZR-18 rear tires.

The 335i sedan has a 4th gear ratio of 1.19:1 and a final drive of 3.08:1

1.19 x 3.08 = 3.67:1 overall gear ratio (from the engine and driveline to the road).

Divide 4,000 rpm by the 4th gear ratio of 3.67 and you get 1,090 tire RPM (tire rotations per minute in 4th gear at 4,000 RPM engine speed).

The (new) ZSP tires have a circumference of about 6.56 feet, so the car will travel approximately 1,090 tire RPM x 6.56 feet/rotation = 7,150 feet in one minute.

Divide 7,150 feet / 5,280 feet/mile = 1.354 miles in one minute in 4th gear.

Multiply 1.354 miles per minute x 60 minutes per hour = 81.2 mph in 4th gear at 4,000 RPM (which is less than 60% of the N54’s max rated engine RPM).

81.2 MPH is a fairly comfortable highway speed at a moderate engine speed of only 4,000 RPM. Someone please check my math, but if my calculations are correct it’s pretty clear that driving 80 MPH in 4th gear certainly isn’t putting any undue stress on the N54 engine.

We get what you are trying to say and if you are only keeping the car for 2 years i'm sure it wont matter. But if you want to keep your car awhile and give it the best chance of not breaking right out of warranty this is not the way to go. Bmw is never ever going to give us a chart on estimated engine life based on average day to day rpm speed. The arguement I am hearing here is that from 4k to 5k or 6k there is no stress issues unless you go beyond that. The fact is that 1k is less stress than 2k and 2k is less than 3k and so on an so forth. This stress compounds on up the chain but you won't see a result right away and most everyone here has 50k or less on their cars. But really what is the F-ing point on being in sprint position at 4k all the time? This isn't a mad max movie.

[Aija]

i hope this is not how u are breaking in your car for the first 1.4k miles

[Outlaw 06]

Originally Posted by Baldur Abendroth

We get what you are trying to say and if you are only keeping the car for 2 years i'm sure it wont matter. But if you want to keep your car awhile and give it the best chance of not breaking right out of warranty this is not the way to go. Bmw is never ever going to give us a chart on estimated engine life based on average day to day rpm speed. The arguement I am hearing here is that from 4k to 5k or 6k there is no stress issues unless you go beyond that. The fact is that 1k is less stress than 2k and 2k is less than 3k and so on an so forth. This stress compounds on up the chain but you won't see a result right away and most everyone here has 50k or less on their cars. But really what is the F-ing point on being in sprint position at 4k all the time? This isn't a mad max movie.

BMW 335i's are high performance cars. If I wanted to putt around at 2,500 RPM all day I would have bought a Yaris...

[IN54NITY]

TJDiCandido, I'm with you. Although breaking in a car with constant rpm of 4000 rpm wouldn't be good (I know you never said that) I don't see anything wrong with it after break in. I see 125mph in 4th gear on the track ~regularly~ (I try to make it once a month - but I also change my oil every 3k miles). I guess some peoples experience is with Buicks and expect the same engine problems with BMWs, not realizing their electric components on their BMWs will fail much sooner. I think 5th or 6th is good enough for highways with low to very low traffic, but I'll use 4th where there is a lot of traffic - I think this increases my safety margin, as the ability to accelerate out of a problem is just as good as braking to avoid a problem.

[Tom K.]

Originally Posted by TJDiCandido

BMW 335i's are high performance cars. If I wanted to putt around at 2,500 RPM all day I would have bought a Yaris...

If it is a high performance car, why is it tuned so that the torque peak begins at 1,400 rpm?

And if you were reading R&T back in the '60's, you'd recall that they complained about the Euro mini cars (Dauphine, Fiat 600, BMW 700, etc.) which were geared to turn 4,000 revs @ 60 mph in 4th (top gear) and were burning up exhaust valves within 30k miles.

BTW, has anyone compared the n35i gas mileage in 4th vs. 6th above 60 mph?

Tom

[Outlaw 06]

Originally Posted by aleckzandr

TJDiCandido, I'm with you. Although breaking in a car with constant rpm of 4000 rpm wouldn't be good (I know you never said that) I don't see anything wrong with it after break in. I see 125mph in 4th gear on the track ~regularly~ (I try to make it once a month - but I also change my oil every 3k miles). I guess some peoples experience is with Buicks and expect the same engine problems with BMWs, not realizing their electric components on their BMWs will fail much sooner. I think 5th or 6th is good enough for highways with low to very low traffic, but I'll use 4th where there is a lot of traffic - I think this increases my safety margin, as the ability to accelerate out of a problem is just as good as braking to avoid a problem.

A voice of reason...

Originally Posted by Tom K.

If it is a high performance car, why is it tuned so that the torque peak begins at 1,400 rpm?

And if you were reading R&T back in the '60's, you'd recall that they complained about the Euro mini cars (Dauphine, Fiat 600, BMW 700, etc.) which were geared to turn 4,000 revs @ 60 mph in 4th (top gear) and were burning up exhaust valves within 30k miles...

This is 2010 not 1960, and engine technology has come a LONG way in 50 years...

The optimal torque AND horsepower in the N54 occurs between 4,000 and 5,000 RPM (see attached).

[IN54NITY]

Originally Posted by Tom K.

If it is a high performance car, why is it tuned so that the torque peak begins at 1,400 rpm?

Again (look at one of my previous thread posts last page), don't get too caught up with torque. Power - the ability to do work (Force through distance) in a given amount of time, is what's going to get the passing done safely and quickly. I don't mean blowing by the car you're passing either, but being ~able~ to do so on seconds notice. This is the whole point of this particular discussion. (Quote: "IMO, both 5th and 6th gears are virtually unusable on American highways")

Originally Posted by Tom K.

And if you were reading R&T back in the '60's, you'd recall that they complained about the Euro mini cars (Dauphine, Fiat 600, BMW 700, etc.) which were geared to turn 4,000 revs @ 60 mph in 4th (top gear) and were burning up exhaust valves within 30k miles.

You're getting dangerously close to comparing a N54 to a motor made by Fiat almost 50 years ago.

Originally Posted by Tom K.

BTW, has anyone compared the n35i gas mileage in 4th vs. 6th above 60 mph?

I would estimate (no hills, no strong ambient headwind) it's 19-20mpg vs 27-29mpg.

[Baldur Abendroth]

Originally Posted by TJDiCandido

BMW 335i's are high performance cars. If I wanted to putt around at 2,500 RPM all day I would have bought a Yaris...

I'm not saying its bad to punch it now and then all day, im saying it's not good to stay punched all day. I take my car right up to redline a few times a week and I'm often in the 4-6k range at various times throught the day. But all the fucking time? If you cruise anywhere in 4th at 80mph for more than 30 min you're decreasing the life span of the engine, period. The smart thing to do is be in 5th or 6th at 80, if you need to past some folks, shiift down to 4th or 3rd and hammer it, then back to cruising gear, who doesn't get this? I guess if you drive a stick this makes more sense.

[CarForHire]

It's also wasting gas. Maybe with the S65, but not with the N54. When I'm cruising, I'm trying to save gas and give my engine a break.

[Outlaw 06]

Originally Posted by Baldur Abendroth

I'm not saying its bad to punch it now and then all day, im saying it's not good to stay punched all day. I take my car right up to redline a few times a week and I'm often in the 4-6k range at various times throught the day. But all the fucking time? If you cruise anywhere in 4th at 80mph for more than 30 min you're decreasing the life span of the engine, period. The smart thing to do is be in 5th or 6th at 80, if you need to past some folks, shiift down to 4th or 3rd and hammer it, then back to cruising gear, who doesn't get this?

4,000 RPM is "punched"???

I didn't say I'm in 4th gear "all the time" either. I said that I occasionally shift into 5th gear when I’m feeling lazy enough to put the car in cruise control (on an open, uncongested highway). I also try out 6th gear about once a month to make sure it’s still there…

Other than that, I pretty much keep the car in 4th gear and below. As shown earlier in this thread, 4th gear in a 335i is suitable for sustained triple-digit speeds, so it’s more than adequate for American highway speeds below that.

When I push down my right foot I want immediate and noticeable throttle response, and I'm willing to sacrifice fuel economy for that.

[stuntman314]

Originally Posted by cstavaru

Is this a joke ?

this has to be.... lmao why stay in 4th and lose mpg when you could stay in 6th and downshift when power is needed in a split second.

[SmoothStyle1]

Originally Posted by kootz

just got 2011 e90 335i and I find myself staying in 4th gear running at 80-90 mph. RPM between 3.5/4K RPM. So it's not screaming and seems to be in the sweet spot RPM wise. I'm sure my mpg will suffer, but I really don't care... Curious if anyone else runs mostly in 4th on the highway...

6th gear for me. With the torque we have in the 335i why not save gas?

[Alexander]

Originally Posted by stuntman314

this has to be.... lmao why stay in 4th and lose mpg when you could stay in 6th and downshift when power is needed in a split second.

I still think that this is one gigantic joke. Apparently people are unaware of down shifting.

[Outlaw 06]

Originally Posted by jayely1

40+ im in 6th..Not accelerating at 40, but just steady is fine. 50+ 6th.

^ This is the real joke.

At 50 MPH in 6th gear, the N54 engine is operating at under 1,800 RPM and is producing under 100 HP (at 40 MPH it's 1,450 RPM and 80 HP). The N54 engine idles at 1,000 RPM for crying out loud, and at idle it doesn't have to move a 3,800 pound car...

[PeteW84]

So which gear do you use during regular city/road drive? 2nd?

[galahad05]

4k rpm is not bad. With proper cooling and oiling, no real ill effects. (old-school engine builder here)

Yes, technically there is more wear, but the difference is so slight that it basically doesn't matter.

Fuel economy is the big deal here-you're wasting a bit more fuel just cruising down the highway when your RPMs are up. It's totally unnecessary. If you really want to pass someone, drop a gear or two from the cruising gears.

[Alexander]

Originally Posted by galahad05

4k rpm is not bad. With proper cooling and oiling, no real ill effects. (old-school engine builder here)

Yes, technically there is more wear, but the difference is so slight that it basically doesn't matter.

Fuel economy is the big deal here-you're wasting a bit more fuel just cruising down the highway when your RPMs are up. It's totally unnecessary. If you really want to pass someone, drop a gear or two from the cruising gears.

[xtac]

idk I'm in 6th at 55-60+, if I wanna zoom I bring it down to 4th, and than when im good ill put it back in 6th. Only time im in 4th is there is some traffic and im at 40+

Than again im a newb MT driver, but i listen to my engine and at 6th its at 2500rpm

[advocado]

Check out a high performance driving school. There are a number of good ones in Texas.

[ruxp]

A lot of people seem to think that higher gear automatically = better fuel consumption, but I've found that I get better mileage when I keep the RPMs at around 3k. That means at 60mph, I'm cruising in 4th. 80mph is where I start to see the benefit of using 6th gear.

[galahad05]

Hmmm. That's an interesting observation.

I'll give it a test today, checked using the instant MPG measurement screen.