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      01-24-2013, 06:21 PM   #89
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Quote:
Originally Posted by pbonsalb View Post
I have a turbo E36M3. In 4th gear on a Dynojet in SAE, it makes 170 lbs rwtq and 80 rwhp at 2500 rpm, 517 lbs and 400 rwhp at 4000 rpm, 440 lbs and 500 rwhp at 6000 rpm, and 360 lbs and 480 rwhp at the 7200 rpm redline. The tires are 255/40/17. I find that in 2nd and 3rd gears, where the torque multiplication is higher, the torque comes in so hard and fast that I often lose traction and that once I lose traction, I do not regain it (maybe because the car is going sideways and I back off. From 3300 to 4000, it gains about 225 lbs rwtq, and this is usually the window in which the traction disappears. I have often wondered whether a more gradual power torque delivery would help with traction, and have considered the idea of running a bigger turbo to shift power higher while also increasing top end power and torque. I view more "linear" as more "gradual."
That sums it up well with a real world example, thank you. Ultimately, its how linear is the power increased as revs increase. More linear = more predictable/smooth = easier to keep traction.
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      01-24-2013, 06:22 PM   #90
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Originally Posted by Goat Rodeo View Post
I'm accusing you of feigning ignorance of one of the most repeated characteristics of this car in order to be in the position to provide a lesson. Please don't take offense.

I'll play. Everyone (sans yourself) talks about the "linear power delivery" of the M3. This exact phrase used by BMW themselves in their press release for the M3 CRT: "the high-revving unit provides the linear power delivery you expect from an M car." It is easy to control the amount of power to the wheels because the engine responds linearly to throttle response. A little bit of throttle, a little bit of power. A lot of throttle, a lot of power. Yet seemingly the ratio is constant; there seems to be a 1:1 ratio between your foot and how fast the car accelerates.

This is different to a car with a large peak throughout its rev range. No power, no power, no power, POWER!!! The sudden inconsistency of power application to the wheels from one moment to the other overloads available traction and the car becomes difficult to control.

The E9X is extremely easy to drive around town and in inclement weather due to this behavior. In fact to some it feels deceptively underpowered and underwhelming during test drives for this reason.

Or another way: If you smoothly and linearly accelerate, you don't spin the tires. If you smoothly accelerate and then stomp the accelerator (non-linear), you spin the tires. Isn't this obvious?

I enjoy reading your posts and find them educational. I hope you're not insulted that I think you're being purposely disingenuous -- I find it hard to believe you're not. I am hoping you will now translate my attempt into whatever the proper technical explanation may be.
Well said. I always enjoy reading Bruce's posts as well, even though he chooses to always take the opposing view of this forum and go against the grain by praising Audi and Mercedes while seldom giving the M3 its due. I suppose he does so in order to keep egoes in check around here and remind everybody that the e9x M3 is not the greatest car ever created in every respect, even though many of us choose to believe that.

I agree he might be taking his role as the devilís advocate to a bit of an extreme here to chastise MKE_M3. It seems fairly simple to me that a linear power delivery is the smooth buildup of power across an RPM range. This is the product of a flat torque curve that increases horsepower at a linear rate across the RPM band in question, as contrasted with a rising torque curve that would result in power building in a curvilinear fashion (i.e. exponentially). Thatís the best way I can describe what weíre talking about here, but perhaps Bruce can correct my mistakes.
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      01-24-2013, 06:35 PM   #91
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
Assuming he meant "flat torque curve", then I particularly want to know how that improves traction.
A flat torque curve (at a given throttle position, for simplicity's sake) means constant acceleration. The jerk (derivative of acceleration over time, da/dt) is 0.

A peaky torque curve will have non-zero jerk. Due to hysteris of the tire carcass, it can only tolerate so much jerk before the static coefficient of friction is overcome and the tires spin. While tires do have an outright torque maximum for given conditions, inducing enough jerk would be enough to spin tires that otherwise wouldn't from torque alone.

Example: If I apply 100% throttle in my supercharged S2000 from 2000 RPM to redline in 3rd gear, I won't break traction. If I punch it at 6k, I will. The amount of torque applied at 6k is no different. The jerk is.

Last edited by urBan_dK; 01-24-2013 at 06:41 PM.
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      01-24-2013, 06:50 PM   #92
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
Assuming he meant "flat torque curve", then I particularly want to know how that improves traction.
As you mention in an earlier post, tires deliver peak traction at certain slip angles, maintaining that slip angle is made easier when power is delivered in a predictable fashion (no significant or unpredictable lumps in the torque curve).

You were right about torque, no HP, being multiplied by gearing. Out of genuine curiosity, can you explain why, if gearing doesn't matter, a car can increase speed by 30mph faster in 1st gear (traction not an issue)than at any point in 3rd gear? If power is all that matters, is the only difference wind resistance? It seems like gearing must be playing a role here, as well.

p.s. since you may ask, an unpredictable lump in torque could be due to turbo lag where different throttle input patterns can lead to peak torque being built at different speeds/rpm's in real world driving, say if you have to lift when getting cut off or as traction breaks coming out of a corner then roll back on to the throttle vs. flooring it from 2500 RPM.
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      01-24-2013, 08:29 PM   #93
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Originally Posted by Mr.Metak2you View Post
Those all seem on the 'light' side. Not sure what they are including in this weight. It is well documented even on BMWUSA website that the S65 weight is 202 kg (445 lb) like I mentioned in my previous post. In browsing online I found weights for the S85 and S62 in a comparison that CAR magazine did.

S54: 478 lbs, 217 kg
S65: 445 lbs, 202 kg
S62: 527 lbs, 239 kg
S85: 529 lbs, 240 kg

Good Read! http://www.europeancarweb.com/featur...e60_m5_engine/
It looks like the bimmerforums link uses the short engine weight, which excludes accessories, cylinder heads and whatever else.
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      01-24-2013, 10:11 PM   #94
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Quote:
Originally Posted by urBan_dK View Post
A flat torque curve (at a given throttle position, for simplicity's sake) means constant acceleration. The jerk (derivative of acceleration over time, da/dt) is 0.

A peaky torque curve will have non-zero jerk. Due to hysteris of the tire carcass, it can only tolerate so much jerk before the static coefficient of friction is overcome and the tires spin. While tires do have an outright torque maximum for given conditions, inducing enough jerk would be enough to spin tires that otherwise wouldn't from torque alone.

Example: If I apply 100% throttle in my supercharged S2000 from 2000 RPM to redline in 3rd gear, I won't break traction. If I punch it at 6k, I will. The amount of torque applied at 6k is no different. The jerk is.
The S62 has a pretty kickass torque curve.

S62 vs s85, stock vs stock:

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      01-24-2013, 11:22 PM   #95
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It appears that BMW could have went with the AMG philosophy and shoved the S62 - as Mercedes has done with the M156 (6.2L V8) and numerous models - into the M3. By basing the S65 V8 on its bigger brother the S85 V10 we are the recipients of the newer techhnology (for the time) a higher revving, higher horsepower, lower displacement masterpiece.

That being said the S62 is no slouch, and still very much relevant - http://www.e90post.com/forums/showthread.php?t=795884

3 S62 engined DP cars took the top three starting positions for this years Rolex 24.
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      01-25-2013, 04:25 PM   #96
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Quote:
Originally Posted by urBan_dK View Post
A flat torque curve (at a given throttle position, for simplicity's sake) means constant acceleration. The jerk (derivative of acceleration over time, da/dt) is 0.

A peaky torque curve will have non-zero jerk. Due to hysteris of the tire carcass, it can only tolerate so much jerk before the static coefficient of friction is overcome and the tires spin. While tires do have an outright torque maximum for given conditions, inducing enough jerk would be enough to spin tires that otherwise wouldn't from torque alone.

Example: If I apply 100% throttle in my supercharged S2000 from 2000 RPM to redline in 3rd gear, I won't break traction. If I punch it at 6k, I will. The amount of torque applied at 6k is no different. The jerk is.
Good post.

But listen, an engine with a building torque curve, even a steeply building torque curve, will create next to zero actual "jerk", as you say. I am not familiar with any engine on the planet that will gain significant torque within, say 25 or 50 rpm. Even a car gaining an outrageous 347 pound feet of torque over 1500 rpm (in the example given by pbonsalb) cannot be called a "jerk" in second and third gear.

Your example of punching it from cruise in third gear at 6000 rpm is an example of jerk from the takeup of driveline lash when going from light-loading cruise to full power.

Look, I'm not saying that the jerk factor is immaterial. What I am saying is that it's of little consequence in terms of a building torque curve.

Of course, saying it's of little consequence is not the same as saying it's of zero consequence, so I guess, point made, at least to some extent.

Bruce

PS - Just got back from the auto show in Harrisburg. It ain't a big deal like Detroit, L.A. and new York, but I'm still a happy guy.
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      01-25-2013, 04:33 PM   #97
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
Your example of punching it from cruise in third gear at 6000 rpm is an example of jerk from the takeup of driveline lash when going from light-loading cruise to full power.

Look, I'm not saying that the jerk factor is immaterial. What I am saying is that it's of little consequence in terms of a building torque curve.
I would tend to agree that more of the jerk comes from drivetrain lash in this case. The nice thing about the M3 is there is almost no jerk from a changing torque curve over the RPM band, and the torque management parameters used to tune the ITB openings at various RPMs and throttle position (drive-by-wire makes this possible) allows a predictable amount of torque at any RPM for a given throttle position. It's really quite amazing.
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      01-25-2013, 05:41 PM   #98
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Quote:
Originally Posted by MKE_M3 View Post
...Out of genuine curiosity, can you explain why, if gearing doesn't matter, a car can increase speed by 30mph faster in 1st gear (traction not an issue)than at any point in 3rd gear? If power is all that matters, is the only difference wind resistance? It seems like gearing must be playing a role here, as well...
The simple explanation is that speed eats power in a completely linear way.

Fleshing that out is made simpler by going back to that trusty old torque-at-the-drive-wheels thing.

Let's say we have a CVT in an M3 that allows power to peak at 40 MPH, which is (not altogether coincidentally) where power peaks in a stock 6-speed car. At that point (and discounting rotational inertia and driveline friction), the drive wheels are getting about 4095 pound feet of torque thrown at them (4.06 CVT ratio X 3.85 final drive ratio = 15.63 overall gearing, times 262 pound feet of torque at 8300 rpm = 4095 pound feet). Of course, from now on the CVT keeps changing its gearing so that the car stays at the power peak as speeds increase.

At 100 mph, the CVT, still faithfully keeping the engine at the power peak, is now down to about a 1.62 ratio, times the final drive ratio of 3.85, giving a 6.24 total ratio, times 262 pound feet gives us 1635 pound feet at the drive wheels, which is (and what are the odds?) just 40% of the pound feet thrown at the drive wheels at 40 MPH.

So, ignoring increased wind and rolling resistance at 100 MPH, we will need 250% of the torque (and of course power) to achieve the same acceleration at 100 mph as we enjoyed at 40 mph. Boys and girls, we'll need 1035 HP at 100 MPH to achieve the same acceleration that 414 HP gave us at 40.

So, just as with a linear power curve , we will need linear increases in power with linear increases in speed in order to maintain acceleration.

Therefore, since power doesn't vary gear to gear, but power needs increase with speed, first gear pulls your face off, and third doesn't.

Bruce

Edit: PS - All numbers rounded off on a 20 year old calculator that I got free with a bowl of soup.

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      01-25-2013, 08:14 PM   #99
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I own both and they are flat out different. Not a great comparo as both are fantastic and never went head to head in the market. I do thank the S62 for being a distant parent to the S65 though. Remember when BMW knocked the S62 down to 4.0l for racing purpose? And sitting on pole for 24hr Daytona is the Telmex BMW dp, which power-plant is under the hood?
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      01-25-2013, 10:57 PM   #100
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
The simple explanation is that speed eats power in a completely linear way.

Fleshing that out is made simpler by going back to that trusty old torque-at-the-drive-wheels thing.

Let's say we have a CVT in an M3 that allows power to peak at 40 MPH, which is (not altogether coincidentally) where power peaks in a stock 6-speed car. At that point (and discounting rotational inertia and driveline friction), the drive wheels are getting about 4095 pound feet of torque thrown at them (4.06 CVT ratio X 3.85 final drive ratio = 15.63 overall gearing, times 262 pound feet of torque at 8300 rpm = 4095 pound feet). Of course, from now on the CVT keeps changing its gearing so that the car stays at the power peak as speeds increase.

At 100 mph, the CVT, still faithfully keeping the engine at the power peak, is now down to about a 1.62 ratio, times the final drive ratio of 3.85, giving a 6.24 total ratio, times 262 pound feet gives us 1635 pound feet at the drive wheels, which is (and what are the odds?) just 40% of the pound feet thrown at the drive wheels at 40 MPH.

So, ignoring increased wind and rolling resistance at 100 MPH, we will need 250% of the torque (and of course power) to achieve the same acceleration at 100 mph as we enjoyed at 40 mph. Boys and girls, we'll need 1035 HP at 100 MPH to achieve the same acceleration that 414 HP gave us at 40.

So, just as with a linear power curve , we will need linear increases in power with linear increases in speed in order to maintain acceleration.

Therefore, since power doesn't vary gear to gear, but power needs increase with speed, first gear pulls your face off, and third doesn't.

Bruce

Edit: PS - All numbers rounded off on a 20 year old calculator that I got free with a bowl of soup.
nice bruce.
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      01-26-2013, 11:15 PM   #101
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
Good post.



Your example of punching it from cruise in third gear at 6000 rpm is an example of jerk from the takeup of driveline lash when going from light-loading cruise to full power.


Bruce
I think I will dare ask for a small clarification. How much driveline lash is there from a lightly loaded cruise to full power? I would say none.

Also, I would use for an example of a peaky power curve, the old Yamaha two stroke engines we use to ride. They would lift the front wheel when they came " on the pipe". Really something for an inexperenced rider.
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      01-27-2013, 01:42 AM   #102
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Quote:
Originally Posted by White 13 View Post
I think I will dare ask for a small clarification. How much driveline lash is there from a lightly loaded cruise to full power? I would say none...
You shouldn't be thinking of driveline lash as the takeup of the sum of individual clearances. It's that, of course, but it's also the "twist" or deflection of individual driveline components, plus the tire carcasses. That's why urBan_dK's S2000 will accelerate uneventfully through 6000 rpm in third gear, but break the tires loose from there while coming off cruise. Yes, the jerk is much less than if he were decelerating against engine compression in third just before punching it, but it's still a sudden jerk.

Bruce
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      01-27-2013, 02:27 AM   #103
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
You shouldn't be thinking of driveline lash as the takeup of the sum of individual clearances. It's that, of course, but it's also the "twist" or deflection of individual driveline components, plus the tire carcasses. That's why urBan_dK's S2000 will accelerate uneventfully through 6000 rpm in third gear, but break the tires loose from there while coming off cruise. Yes, the jerk is much less than if he were decelerating against engine compression in third just before punching it, but it's still a sudden jerk.

Bruce
I can see a little in the tire carcass that I had not considered but driveline gotta be pretty small. Might even absorb a little power and spread it out a little. I will need to consider it somemore.

I like your: The simple explanation is that speed eats power in a completely linear way.

Very nice. Horsepower and torque are very interesting and cause much confusion. I need that beer klinking smilie here.
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      01-27-2013, 01:50 PM   #104
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Quote:
Originally Posted by White 13 View Post
I think I will dare ask for a small clarification. How much driveline lash is there from a lightly loaded cruise to full power? I would say none.

Also, I would use for an example of a peaky power curve, the old Yamaha two stroke engines we use to ride. They would lift the front wheel when they came " on the pipe". Really something for an inexperenced rider.
Are you referring to those old RZ series Yamaha's? if so you went waay back LOL
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      01-27-2013, 01:59 PM   #105
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Quote:
Originally Posted by VCMpower View Post
I own both and they are flat out different. Not a great comparo as both are fantastic and never went head to head in the market. I do thank the S62 for being a distant parent to the S65 though. Remember when BMW knocked the S62 down to 4.0l for racing purpose? And sitting on pole for 24hr Daytona is the Telmex BMW dp, which power-plant is under the hood?
The comparison was raised as the S62 and S65 are the only 2 n/a production ///M V8 engines ever created. Specs, HP, Torque and power delivery is the general comparison and talking points.
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      01-27-2013, 04:08 PM   #106
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Quote:
Originally Posted by car_fan View Post
Are you referring to those old RZ series Yamaha's? if so you went waay back LOL
im guessing just any 2 stroke yamaha like yz250 i had. amazed at how it wanted to kill you at certain rpms all of the sudden. And it was my first bike and quite an experience.
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      01-27-2013, 08:08 PM   #107
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Quote:
Originally Posted by White 13 View Post
I can see a little in the tire carcass that I had not considered but driveline gotta be pretty small. Might even absorb a little power and spread it out a little. I will need to consider it somemore.
I would postulate that the driveshaft, for instance, will twist if you throw a single foot pound its way. OK, perhaps not enough to measure without astoundingly sophisticated instrumentation - but it will still twist.

Now figure about 1200 foot pounds thrown at it in first gear at the torque peak. Twist will likely be eyeball-measurement obvious. How about the half shafts getting around 4600 foot pounds thrown at them. Still say they won't twist?

How about the sprung clutch hub? The dual mass flywheel?

Hell, even the cranshaft will twist with each cylinder firing. I remember reading an SAE paper about that decades ago.

My intent is not to rag on you, but did you ever hear about "Gallopin' Gertie"? "She" was a supension bridge in Washington State, video'd here. Hey, what's some wind compared to massive steel girders?

Even stout things will deflect under load.

Bruce

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      01-28-2013, 01:13 AM   #108
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I do know that drivelines twist. I am at least a little familiar with the failure rates of twisting driveline from repeted stress. I know of at least one Sikorsky helicopter (S 64) that measures power by driveline twist. But all in all very small amounts we are talking about here.
I thank you for not ragging on me and my intention is not to antagonize anyone here but what about the idea that the twist may absorb some of the shock and spread it out?
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      01-28-2013, 01:16 AM   #109
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Quote:
Originally Posted by 1MOREMOD View Post
im guessing just any 2 stroke yamaha like yz250 i had. amazed at how it wanted to kill you at certain rpms all of the sudden. And it was my first bike and quite an experience.
Yea, the YZ250. That silly thing almost ended my young learning cruve. And, yes, that was quite a while ago.

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      01-28-2013, 01:41 AM   #110
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Quote:
Originally Posted by White 13 View Post
I do know that drivelines twist. I am at least a little familiar with the failure rates of twisting driveline from repeted stress. I know of at least one Sikorsky helicopter (S 64) that measures power by driveline twist. But all in all very small amounts we are talking about here.
I thank you for not ragging on me and my intention is not to antagonize anyone here but what about the idea that the twist may absorb some of the shock and spread it out?
That it does, I would say - until the twisting slows down and stops. As it stops, that's the jerk.
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