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      01-20-2008, 05:44 AM   #155
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In the real world these numbers mean nothing!!!! I have a e46 M3 and I live in the Northern NJ. 15 mins away from NYC.. All I can say 0 to 35 is the new 0 to 60 these days. 1st and 2nd gear are used the most!!! The new M3 will not be such a great car near city limits. Dont get me wrong I like my M3 but with all this traffic I cannot reach its full potential as a DD. I drive my Jeep Cherokee more than my M3. Only time I enjoy my M3 is to drive 1 hour away on the weekends. The 335i with steptronic would be the better car for DD in my area anyway. Heck a 335xi will beat a 335i and E92 M3 from 0 to 35mph LOL. The M3 will always be a sports car and will be great on a track. The 335i will be a sporty 3 series and be great for daily driving.
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      01-20-2008, 05:51 AM   #156
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Quote:
Originally Posted by hwelvaar View Post
I currently drive a E92 335i (since 8 months) and I recently did a 1-hour test-drive with the E92 M3.

My opinion:
- I prefer the torque of 335i for daily driving (and my 335i is still stock) - it makes your car real fast in daily traffic
- when you're not revving, the M3 feels slow ; I was *really* disappointed. I was *hoping* that the M3 would blow me away, so I could convince my own brain to drop the extra bucks to get an M3. But it didn't. Not on normal roads.
- the sound of M3 engine is fantastic in high revs, but not noticable in low and mid RPMs
- the sound of 335i is very nice in both mid and high RPMs
- I prefer the suspension of the M3 for daily driving (with EDC in comfort) and the fact that you can switch to sport when needed;
- It felt good to drive around in a car labeled "M3"
- I prefer the looks of stock M3 over stock 335i (no-brainer)
- LSD is a must-have for occasional fun drifting !
- 1 hour-drive on normal roads, and 1/4th of the M3 fuel tank is empty -> M3 really drinks alot !
- the brakes on the M3 are definitely good (and noticably better than stock 335i)


So yes I can modify the 335i, throw in PROcede, an LSD, Bilstein suspension with electronic comfort and sport setting, some carbon for the external, and a big brake kit. I would not need to fear to pull up next to a stock M3 at the lights, and certainly not when doing rolling starts.

But I'd still not have an M3 badge. And I must admit that saying 'I drive an M3" would make me feel better than "I drive a 335i"

Also, I'm afraid to tune my 335i. Basically I never had any tuning done on any of my previous cars either.

Conclusion for me personal: Today's turbo engines is what you want if you'll be driving +95% of the time on normal roads. I want an E92, with all the tech options of the M3, but with a modded 400HP 500Nml torque 3L twin-turbo engine of the 335i.

That car would rock. Even better, if some tuner would come out with a reliable turbo-kit for the E92 M3, which would deliver low-rev torque, that would be heavon on earth for me.


Any thoughts ?

thanks for your review it was helpful to decide my next car from BMW!
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      01-20-2008, 03:13 PM   #157
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Quote:
Originally Posted by lucid View Post
...Please allow me to reiterate that almost everyone who has participated in this discussion so far is aware that rotational inertia related loses of the drivetrain will reduce the torque at the wheels for both cars under acceleration. As you can see above, I have acknowledged that before, so I am not sure that there was really a need for a detailed explanation. The issue is if the rotational inertia for the two drivetrains are significantly different from each other—to the extent that they would factor into the relative acceleration performance of the cars above 2000 rpm.
I'm not sure you're correct about the level of knowledge in terms of how rotational acceleration actually affects acceleration by gear, but if you are, sorry I bored the multitudes.


Quote:
Originally Posted by lucid View Post
...Yes, at lower gears, the angular accelerations will be higher, therefore the torque loss will be higher as well. However, that relationship, as can be seen above, scales up linearly. So, there is no square term there.
OK, perhaps my bad. Not sure how 1/2 the square actually turns out to be linear, but I barely scraped thru higher math courses, so I defer to you and Swamp in this regard.

By the way, glad you cleaned up that section. I was preparing myself to be involved in a bunch of additional discussion about those details - something which I find unrewarding, both on general terms and because it's ancillary stuff.

Quote:
Originally Posted by lucid View Post
First of all, please note that the measured vs. expected performance is somewhat small, so small differences in a variety of factors can be influential...
I beg to differ. There is a significant variation between expected and actual, particularly in the 50-70 test, where I'd personally expect the M3 to best the 335 by somewhere in the seven or eight tenths area, instead of the meager tenth it actually managed.

Quote:
Originally Posted by lucid View Post
1. You are operating under the assumption that the moment of inertia, “I”, for both cars are the same, or that it is more for the M3. That is a significant assumption. You say a few things about the engine layout, but that is far from being convincing. At this point, we don’t know anything about the mass of the rotating components, but one would think, given the M3 engine revs up to 8400rpms, BMW engineers would have busted their asses to bring those weights down by using different more expensive materials. We need the “I” numbers to be conclusive.
I agree with you in general terms, which is exactly why I called it an approximate draw. Normally, you'd think the M3 engine would have significantly more rotational inertia than the 335, by a facter of four over three, using the old shade tree rule of thumb of overall displacement affecting rotational inertia in a more or less linear fashion.

Quote:
Originally Posted by lucid View Post
2. Regardless of all this, even if we assume the M3 has a higher “I” figure, the M3 still comes out to be faster in the 2000rpm+ comparison. This whole debate got kicked off because I started arguing against the 335 being faster above that range. I am ignoring the other comparison which starts around 1100rpms since, from the very beginning, I acknowledged that the 335 would have the upper hand there as that is what the data I posted also demonstrate. So, I am not sure about what your point is exactly. Are you saying that if the test was done in 2nd or 3rd gear instead of 6th gear, the rotational inertia related losses would be higher for the M3 because of the higher angular accelerations experienced in those gears (it will pick up even more revs per unit time than the 335 during that race), and the M3 would be slower? If that's what you are getting at, keep in mind that the M3 picking up more revs would also mean that its average torque would also go up significantly, whereas the average tq for the 335 would stay the same, relatively speaking.
My pretty firm impression is that the debate got started because you and Swamp felt that there is no way the 335 will be more lively than the 335 in general everyday driving (plus the tone you guys took, which you later apologized for to a couple of guys), and I felt that the chart you showed as evidence (in note 17) was way too simplistic. My major points (in note 42) were around rotational inertia and part-throttle performance, and the latter was mistakenly (and unfortunately) misinterpreted as throttle mapping differences. What I was really talking about in terms of part throttle performance was the bulgy nature of the resultant 335 torque curve, caused by part throttle resulting in more than a linear boost map - typical of today's turbo cars.

I later remembered about the C & D data, and typed that novelette. The major point there was that due to increased rotational inertia, you don't get what you think you're going to get from aggressive gearing.

Quote:
Originally Posted by lucid View Post
...3. Weight might be a significant factor...

...In your most recent post, you are now saying that the weight is almost identical...

...I am not sure about what is going on with these numbers. Were these measurments obtained on the same day and issue, with exactly the same method? The M3 number is definitely unladen DIN...

This is where the waters get really murky, and the difference between the measured vs. expected performance you reported might actually be explained by the weight difference these cars have.

If the above C&D numbers are correct, the 335 might be about 7% lighter, and the weight difference alone can explain a significant portion of the difference between the measured vs. expected performance you reported.

Because of the several points I raised above, I stick to my original position.
Car & Driver weighed their 335 in a standard road test, and since that weight coincided with weights published in other road tests by other publications (plus BMW's published weight for the car), that seems to be correct. I don't know what the issues were around the Lightning Lap weight, but assume they were using corner by corner weighing at the track, and screwed up.

Their number for the M3 seems to be a little light considering what I've read from BMW elsewhere, but the car was in fact a European version, and based on that it may in fact been a little heavy, since C & D weighs cars empty with all liquids topped off, American style. The difference between American and Euro standard weights seems to be in the neighborhood of 150 pounds or so, meaning the car would've come in at roughly 3500 pounds under U.S. terms. Why heavy? Options, maybe.

As far as comparing cars based on road tests a year or so apart, C & D "zeroes" their test results to a C & D standard day, which seems to be roughly equivalent to the old SAE Gross Standard Day. Not perfect, but as close as they can manage.

The gorilla in the room may be the supposed under rating of the 335 by BMW, but even if I assume 325 HP and a like amount of torque for the 335, the M3 still comes up a little short when you factor in turbo lag, which I think accounts for at least two or three tenths in such a low speed roll on. Figure around maybe 180 pound feet for the 335 the instant you mat the throttle, soaring to 300 (or possibly 325) pound feet after around a second or so - but not less than that.

If you factor in, say, a 12% rotational inertia penalty for the M3 based on more aggressive gearing (per my novelette), the numbers start to work out pretty well.

Bruce

Edit: PS - Assuming the 335 really is under rated, that's yet another reason why it seems to be a killer car in everyday driving compared to the M3.
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      01-20-2008, 03:25 PM   #158
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Quote:
Originally Posted by gmund1948 View Post
The trolling, you are doing must be entertaining to you
it is almost like an M3 is out of your reach or you are in
a self jusification mode.
Nobody is trolling here (except maybe for you). Money is not the issue. Spending $50K or $70K on a car is not gonna make much of a difference. As I said to somebody else before on these forums "just becasue you have the money it doesn't mean you MUST give it away". The M3 has to "earn" my business if you get my drift.


Quote:
Originally Posted by gmund1948 View Post
You have taken a position without a comparison, and keep shouting about badges as justification.
Unlike you, I have NOT yet taken a position or else I would no still be driving my E46. I am waiting for the M3 just like a few others here to see it its worth my money. I am not the type of person who would get on the M3 waiting list without knowing if the car is for me.

Quote:
Originally Posted by gmund1948 View Post
Drive the M on a track if you can and you will see the differences that cannot show up in a magazine.
I hardly drive the car to the track. I just need a really snappy car merging in and out of traffic around the city. Sometimes I let it rip out on the desert roards.

Quote:
Originally Posted by gmund1948 View Post
Thanks for the compliment, however it is futile to argue any point unless
you have experienced both, which you have not.
It wasn't a complement but you knew that already. You obviously have not experienced both either. I suggest you do unless of course you have already made up your mind. I have nothing to do with Vishnu, I only test-drove a friend's car with the tune.
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      01-20-2008, 03:41 PM   #159
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Quote:
Originally Posted by coaster View Post
It wasn't a complement but you knew that already. You obviously have not experienced both either.
Quote:
Originally Posted by gmund1948 View Post
After 2 days of driving the M3 at the Nurburgring, and also lapping in the 335
(convertable) It is obvious which car BMW has built for the upper end of performance driving.



Best regards, south
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      01-20-2008, 05:44 PM   #160
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
Edit: PS - Assuming the 335 really is under rated, that's yet another reason why it seems to be a killer car in everyday driving compared to the M3.
Assume 325-335 HP and TQ.

Signed,
Someone whose has read about every 335i dyno put up on e90post.com
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      01-20-2008, 06:28 PM   #161
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Actually you are correct

I have not driven the vishnu? car but I have driven the AC Schnitzer tuned 335 with about 350 HP, lowered, with exhaust and modded suspension, done by the Germans who have a lot more experience than the procede boys. but hey we have the autobahn over here and a few more open roads and tracks close by.

I own a 335 convert and an 08 Corvette C-6 and will be getting an M3 in March/April but I do track the car and we have areas of the Autobahn with no speed limit so It is a different world

I reread your post(s) and since you do not drive the car at the track, and only need it for traffic, a 335 would be a fine car for you. The 328 would easily meet your needs as well.

It really is not a badge thing, however the M-3 is not a car to weave in and out of traffic, it is snappy alright, but you will never use the car so you are right, no need to spend the extra bucks.

I like you, dislike car buyers who buy performance only to be a poser. You say only need snappy. The vishu 335 will give you bragging rights and additional boost. The voiding of warranty is disconcerting, because most of the other more established tuners cover you.

Glad to hear you dont work for them, I detest trolls

good luck in your choice









Quote:
Originally Posted by coaster View Post
Nobody is trolling here (except maybe for you). Money is not the issue. Spending $50K or $70K on a car is not gonna make much of a difference. As I said to somebody else before on these forums "just becasue you have the money it doesn't mean you MUST give it away". The M3 has to "earn" my business if you get my drift.




Unlike you, I have NOT yet taken a position or else I would no still be driving my E46. I am waiting for the M3 just like a few others here to see it its worth my money. I am not the type of person who would get on the M3 waiting list without knowing if the car is for me.



I hardly drive the car to the track. I just need a really snappy car merging in and out of traffic around the city. Sometimes I let it rip out on the desert roards.



It wasn't a complement but you knew that already. You obviously have not experienced both either. I suggest you do unless of course you have already made up your mind. I have nothing to do with Vishnu, I only test-drove a friend's car with the tune.
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      01-20-2008, 06:31 PM   #162
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Quote:
Originally Posted by sdiver68 View Post
Assume 325-335 HP and TQ.

Signed,
Someone whose has read about every 335i dyno put up on e90post.com
Ok, so you prefer the 335. Why do 335 owners feel like they have to justify the car to everyone?

There is already a big discussion on this in the "M3 vs" forum. Go there and try to convert people.
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      01-20-2008, 06:50 PM   #163
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Quote:
Originally Posted by Epacy View Post
Ok, so you prefer the 335. Why do 335 owners feel like they have to justify the car to everyone?

There is already a big discussion on this in the "M3 vs" forum. Go there and try to convert people.
Because there's definitely some 335i drivers who furtively covet the M!

Human behaviour.... (as he puts on his flame retardant suit)
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      01-20-2008, 09:04 PM   #164
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Enjoy your 335i's.
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      01-20-2008, 09:10 PM   #165
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Quote:
Originally Posted by Epacy View Post
Ok, so you prefer the 335. Why do 335 owners feel like they have to justify the car to everyone?

There is already a big discussion on this in the "M3 vs" forum. Go there and try to convert people.
Seriously, the same issue keeps coming back. Remember when that V2 chipped 335 beat a M3 in a drag race and 100 posts were made in 4 different forums here.
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      01-20-2008, 09:58 PM   #166
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Quote:
Originally Posted by gmund1948 View Post
I reread your post(s) and since you do not drive the car at the track, and only need it for traffic, a 335 would be a fine car for you. The 328 would easily meet your needs as well.
Actually that's not right. The 328 is not a car for me at all. I haven't even bothered to drive one it's waaay underpowered for how I like to drive. Infact the stock 335 is actually marginal for my taste and would not have considered it either had it not been for its tuned performance. The Vishnu 360 WHP car I drove actually impressed me. Excellent driver for long trips and really quick in acceleration. Pretty good handling as well but probably far less "raw" than the M3. I still need more reasons to justify the extra money for the M3 and I hope to find them when I drive it.

Quote:
Originally Posted by gmund1948 View Post
... however the M-3 is not a car to weave in and out of traffic, it is snappy alright, but you will never use the car so you are right, no need to spend the extra bucks.

good luck in your choice
I might take the car to the track once a year (or even less frequently) but that's not enough to justify the M3 purchase.

Good luck to you as well ... I guess each of us has his own interests and it's good to be able share information without necessarily having to agree with each other's car opinions.
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      01-20-2008, 11:25 PM   #167
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
I'm not sure you're correct about the level of knowledge in terms of how rotational acceleration actually affects acceleration by gear, but if you are, sorry I bored the multitudes.
Just to make sure we are on the same page here. Rotational inertia can affect acceleration in two ways:

1. The rotational inertia of the two drivetrains can be different.
2. Even if the rotational inertia of the two driven trains are the same, it is true that since the M3 has a more aggressive final drive ratio, the rotating masses in front of its differential will experience higher angular accelerations (rpm gains per unit time) during WOT acceleration.

Speaking to 1, we don’t really agree that there is a difference. You are saying 335’s I is lower. Swamp and I seem to be saying it is either the same as the M3’s or higher. We don’t have the numbers, and we most likely never will.

Speaking to 2, we all seem to agree it is true, but we don’t seem to be able to agree on the magnitude of the effect.

Also, if M3’s I happens to be lower than 335’s I, than the effect of 1 might cancel out the effect of 2.

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
OK, perhaps my bad. Not sure how 1/2 the square actually turns out to be linear, but I barely scraped thru higher math courses, so I defer to you and Swamp in this regard.
The kinetic energy formula needs to be differentiated with respect to time since we are interested in what it takes to change the energy per unit time.

If we look at the right side of the equation:

1/2 * I * w^2

and differentiate with respect to time, we get (by using the power rule):

1/2 * I * w^2 * d/dx = 1/2 * I * 2 * w * dw/dt = I * w * dw/dt

since dw/dt is alpha, which is angular acceleration, we get:

I * w * alpha

When the left side of the equation is differentiated, you simply end up with power, which is T * w (the same way P = F * v in linear motion), so the whole thing becomes:

T * w = I * w * alpha

w cancels out, which brings us back to

T = I * alpha

So, one can consider the rotational inertia related loss either in terms of power or torque. Since we are dealing with the torque curve and acceleration in this discussion, we naturally stick to the torque equation.

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
I beg to differ. There is a significant variation between expected and actual, particularly in the 50-70 test, where I'd personally expect the M3 to best the 335 by somewhere in the seven or eight tenths area, instead of the meager tenth it actually managed.
Well, according to your calculation, the difference between expected vs. actual is 0.4 seconds. This could be attributed to the point Swamp was making regarding the average torque method you used in the comparison. Or, to the point I was making about the weight difference (see below for more), or something else that we are not taking into account here. It is a bit of a stretch to conclude it is because of the rotational inertia differences I think.

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
I agree with you in general terms, which is exactly why I called it an approximate draw. Normally, you'd think the M3 engine would have significantly more rotational inertia than the 335, by a facter of four over three, using the old shade tree rule of thumb of overall displacement affecting rotational inertia in a more or less linear fashion.
Well, if it is indeed a draw, then why are we debating? My point was NOT that the M3 was faster at low revs; it was that the 335 was not faster above 2000 rpms.

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
My pretty firm impression is that the debate got started because you and Swamp felt that there is no way the 335 will be more lively than the 335 in general everyday driving (plus the tone you guys took, which you later apologized for to a couple of guys), and I felt that the chart you showed as evidence (in note 17) was way too simplistic. My major points (in note 42) were around rotational inertia and part-throttle performance, and the latter was mistakenly (and unfortunately) misinterpreted as throttle mapping differences. What I was really talking about in terms of part throttle performance was the bulgy nature of the resultant 335 torque curve, caused by part throttle resulting in more than a linear boost map - typical of today's turbo cars.
Again, my objection was to statement that the 335 was faster because it has more torque. With the assumption that daily driving happens above 2000rpms, I said that wasn’t the case at the wheels. Yes, you are absolutely right that the steady-state torque at the wheels chart does not tell the whole story, but it is a great place to start depending on how much of a difference in the rotational inertia related torque losses there will be in between the two cars. Swamp and I assumed that there would not be too much of a difference, if any, and therefore treated the steady state torque at the wheel charts as a pretty good approximation.

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
I later remembered about the C & D data, and typed that novelette. The major point there was that due to increased rotational inertia, you don't get what you think you're going to get from aggressive gearing.
I agree, but again, it depends on how big that effect is compared to total torque generated at the shaft, which we still have not nailed down. Also, keep in mind the aggressive gearing allows the M3 to climb up the rev band much quicker at a given gear, and since its torque curve rises sharply at low rpms, allows it to reach its peak torque levels (~350 Nm / total reduction) much faster. If the M3 had a flat curve at low rpms like the 335, I would be inclined to say the effect can be significant.

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
Car & Driver weighed their 335 in a standard road test, and since that weight coincided with weights published in other road tests by other publications (plus BMW's published weight for the car), that seems to be correct. I don't know what the issues were around the Lightning Lap weight, but assume they were using corner by corner weighing at the track, and screwed up.
Yes, C&D’s 335 number is matching BMW’s EU spec number (with driver and luggage). The problem is that C&D’s M3 number is not matching BMW’s EU spec number.

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
The gorilla in the room may be the supposed under rating of the 335 by BMW
The steady state torque at the wheel curves are not based on BMW data. They are measured independently. I am not sure if you checked the link I posted or not.

These posts are getting longer and not shorter, so maybe time to let it go unless one of us comes up with some definitive numbers?
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      01-21-2008, 12:52 AM   #168
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Quote:
Originally Posted by lucid View Post
Just to make sure we are on the same page here. Rotational inertia can affect acceleration in two ways:

1. The rotational inertia of the two drivetrains can be different.
2. Even if the rotational inertia of the two driven trains are the same, it is true that since the M3 has a more aggressive final drive ratio, the rotating masses in front of its differential will experience higher angular accelerations (rpm gains per unit time) during WOT acceleration.

Speaking to 1, we don’t really agree that there is a difference. You are saying 335’s I is lower. Swamp and I seem to be saying it is either the same as the M3’s or higher. We don’t have the numbers, and we most likely never will.

Speaking to 2, we all seem to agree it is true, but we don’t seem to be able to agree on the magnitude of the effect.
In regard to 1, I have been saying that the inherent engine and drivetrain inertia in both cars is a wash, but the M3 suffers more because of aggressive gearing.

In regard to 2, the magnitude of the effect is that you get between 81 and 88 percent of what you think you get (mechanically speaking) in terms of increased acceleration, with an average of about 85%. The data is from testing approximately thirty cars over the years - with German cars, on average, below 85%.

Bruce
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      01-21-2008, 10:19 AM   #169
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Quote:
Originally Posted by bruce.augenstein@comcast. View Post
In regard to 2, the magnitude of the effect is that you get between 81 and 88 percent of what you think you get (mechanically speaking) in terms of increased acceleration, with an average of about 85%. The data is from testing approximately thirty cars over the years - with German cars, on average, below 85%.
Leaving the other points I made aside on weight, M3's climbing T curve, and Swamps point about the ave T method, what exactly are the above data you are referencing indicate? In other words, what is being measured exactly? I want to make sure I understand this before responding.
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      01-21-2008, 10:19 AM   #170
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Quote:
Originally Posted by Epacy View Post
Ok, so you prefer the 335. Why do 335 owners feel like they have to justify the car to everyone?

There is already a big discussion on this in the "M3 vs" forum. Go there and try to convert people.
It's the other way round.

A 335i owner posted his impressions of the M3 and protests resulted.

I have no dog in this fight, by the time the M3 is available my lease is up. But you don't want to hear that, you'd rather assume bias, justification, or any other ad hominem reason as opposed to talking about the cars.
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      01-21-2008, 10:46 AM   #171
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Originally Posted by sdiver68 View Post
It's the other way round.
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Originally Posted by sdiver68 View Post
Respect? From whom? Poseurs? Badge-whores? Ignoramuses?

No thanks.



Best regards, south
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      01-21-2008, 11:08 AM   #172
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Best regards, south
Exactly.

Another way to say remove the purely subjective bias of a badge.
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      01-21-2008, 11:42 AM   #173
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Quote:
Originally Posted by lucid View Post
Leaving the other points I made aside on weight, M3's climbing T curve, and Swamps point about the ave T method, what exactly are the above data you are referencing indicate? In other words, what is being measured exactly? I want to make sure I understand this before responding.
Quote from note 133 in this string:

"...If you've stuck it out to this point, let me offer a single example.

In three passes with a Vericom on board (same stretch of level road, same technique, within a few minutes of each other, etc.), my 3 liter M3 showed an average peak acceleration of .463 G in second gear (at peak torque, obviously). The G peaks were measured at .465, .462 and .463 G, first to last.

In *first* gear (same stretch of road, same day and approximate time as the second gear runs, etc. etc.), the car pulled an average acceleration peak of .644 G, averaged from three runs at .649, .638 and .646 G.

So what?

OK, here's what. According to BMW, my car had a first gear ratio of 4.20:1, and a second gear ratio of 2.49:1. Assuming truth in BMW publishing , the car should've been able to pull .781 G in first gear, based on the .463 G average obtained in second. (The .781 figure is from multiplying the second gear results by a ratio of 4.20/2.49.)

In fact, if I had tested the car on a chassis dyno at, say, a static 4250 rpm (peak torque), the car would've demonstrated a drive wheel force differential that would very closely approximate the difference in gear ratios between first and second gears. There would be slightly more wheel slip in first gear, and first gear is generally slightly less efficient than second gear (by generally less than a percent), but this is small potatoes. Furthermore, in my test out on the road, I was obviously contending with more rolling and wind resistance in second gear than in first gear, so these factors would tend to cancel out the tire slip and transmission efficiency differences. Drive wheel torque would vary, as I said, pretty much equal to the difference in gear ratios.

So why the discrepancy in acceleration values?

The shortfall of about 17.5% out on the road (.644 observed over .781theoretical) is due almost entirely to rotational inertia - "flywheel
effect", which only comes about when you are accelerating (or, in fact, decelerating). In first gear, that M3 gained about 189 engine rpm for each mile per hour gained, while in second, it was down to 112 rpm. It takes energy to accelerate these rotating parts, and this energy is then unavailable to accelerate the car. The parts affected are basically every rotating thingy forward of the transmission tailshaft. This obviously includes the engine, flywheel and all engine driven accessories, as well as the clutch, pressure plate, transmission input shaft, various gear clusters, etc.

In the gospel according to Sir Isaac, these parts don't like to change their speed, and the only thing that will make them do that is engine power - which is then not available to accelerate the car. Proportionally more power is lost in first gear than in second gear, etc, etc. The same effect occurs when you change final drive ratios. You'll get higher peak acceleration in each gear - but not proportionally as high as the difference between the ratios would suggest.

I've done testing on many, many cars over the years, and the smallest shortfall I've ever measured was on an '85 stick Vette (with a lightweight Borg Warner Super T10 transmission and a fairly light flywheel at about 18 pounds). That shortfall was about 12%, but most cars had a shortfall typically around 15%. German cars (with flywheels apparently liberated from old U-boats) often were in the low 80s, meaning an acceleration loss getting uncomfortably close to 20%..."


Moreover, my experience with cars over the decades leads me to believe that rotational inertia tends to have a very significant effect in terms of how lively a car feels in everyday driving. I don't know how to quantify this, but, starting way back when we hurled a set of 4.56s into a '57 Chevy to replace the "slow" 3.55s, I noticed that even though the car was quicker in a drag race, in everyday driving, it seemed to be noticeably slower. In that scenario, you needed to work a little harder to stay with traffic. That is to say, it felt as if it needed a little more effort. My belief is the difference was for two reasons. The first is that you'd shift earlier, interrupting power earlier, which we all know means something in terms of drag race ET. (Yeah, I know it's everyday driving, but the principle is exactly the same.) The second is rotational inertia, which grows with gearing, and is omnipresent regardless of throttle setting. My theory is that rotational inertia plays a bigger role in everyday driving than it does in a drag race simply because it's 100% with you all the time, and if you're at light power settings, it plays a bigger role.

I admit I have no way to back this up, and some help would be wonderful.

For this and other reasons I've documented (interminably) in this string, I believe the OP when he says the 335 feels quicker than the M3 in everyday driving. Furthermore, my belief is that not only does it feel quicker, it is quicker.

I can't back that up in a quantifiable way, either, but this matches my firmly held belief that good automatics are measurably quicker than good sticks in everyday driving, even though most of them are slower on track.

Bruce
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      01-21-2008, 11:49 AM   #174
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As a side note to the technical discussion on this thread, I think the choice between these cars entails more than a real-life performance per dollar consideration. I personally have a deep appreciation for well designed and built machinery. So, even if I'll get to drive the M3 on a track only 3-4 times a year, I would still would like to own one the way some people like to own fine works of art. There is no question that its engine and transmission are innovative, and its handling is special in its class. We can debate the meaning of that for daily driving, but that doesn’t change the fact that the artifact itself is superior in terms of the engineering rigor that created it; that is what the M division does.
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      01-21-2008, 12:22 PM   #175
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Quote:
Originally Posted by sdiver68 View Post
It's the other way round.

A 335i owner posted his impressions of the M3 and protests resulted.

I have no dog in this fight, by the time the M3 is available my lease is up. But you don't want to hear that, you'd rather assume bias, justification, or any other ad hominem reason as opposed to talking about the cars.
It's not the other way around. The OP isn't the one in here fighting the same old battle.
I don't have to assume anything. It is all over your posts and everyone knows it.
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      01-21-2008, 01:46 PM   #176
sdiver68
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Quote:
Originally Posted by Epacy View Post
It's not the other way around. The OP isn't the one in here fighting the same old battle.
I don't have to assume anything. It is all over your posts and everyone knows it.
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