Login
02212013, 02:10 AM  #221  
Grease Monkey
42
Rep 2,347
Posts
Drives: 2011 E90 M3,1994 Euro E36 M3/4
Join Date: Apr 2006
Location: Fort McMurray, Alberta, Canada

Quote:
Even in my world of 60120 Litre turbo diesel engines, torque ratings are never quoted it is always HORSEPOWER or KW. The reason for this is because the horsepower rating is what determines how much work can be done by that engine, not the torque rating! 

Appreciate
0

02252013, 05:06 PM  #222  
Captain
23
Rep 846
Posts
Drives: '69 GT3, 1M, 912, R32
Join Date: Nov 2010
Location: SF Bay Area, Shenzhen, Oman

Quote:
Quote:
At the risk of exacerbating the whole 1M vs M3 debate, I'm going to use realworld numbers to illustrate, 1M vs M3 convertible, both 6MT at 95 MPH in 4th, the best starting gear for either MT car at that speed. I'm going to walk through this so you guys can calculate this yourselves to better understand it. You want to estimate the car's thrust first, which is essentially how much torque it puts to the ground including gearing, etc. The equation: Wheel torque (ft lbs) x final drive ratio x 4th gear ratio / tire radius (in feet, ie 25.5 / 12 / 2) Let's say the M3 makes 255 ft lbs at the wheels on a dynojet. We'd do 255 x 3.85 x 1.19 / 1.06 = 1102 lbs of thrust. Pretend this is moving a 4200 lb car (with driver, and yes convertibles are heavy), so 1102/ 4200 = .26, or basically .26 Gs ignoring aero, wheelspin and rotational inertia. Take the 1M in the same gear: 350 x 3.15 x 1.18 / 1.06 = 1227 lbs of thrust, 3700 lb car = .33 Gs. So 27% better acceleration for our example 1M. The next step, however, is to calculate acceleration at a specific speed. Speed in MPH is: RPM x tire radius x pi x 2 x 60 / final drive ratio / 4th gear ratio / 5280 feet So 5800 rpm in the M3 is 5800 x 1.06 x 3.1415 x 2 x 60 / 3.85 / 1.19 / 5280, or 96 mph. Take thrust using torque from the dyno curve at that specific RPM, and you get thrust to weight at that speed I already used the ~255 ft lbs the M3 makes at 5800. Same thing for the 1M: 4700 x 1.06 x 3.1415 x 2 x 60 / 3.15/ 1.18 / 5280 = 96 mph. And again, the 1M makes about 350 at the wheels at that rpm depending on the dyno. So you now know how to calculate thrust to weight ratio for a particular speed. All you need are the gear ratios, weights, plus the dynos, such as: And And you can calculate which car will accelerate harder in any gear at any speed (again, ignoring aero, rotational inertia, etc). Now to one of the reasons I chose these particular cars and dynos for comparison. Using the dynos shown above plus the weights, the 1M and M3 have near identical power to weight ratios. So 4200 lbs / 375 whp = 11.2:1, plays 3700 lbs/ 330 whp, also 11.2:1. Now if torque really doesn't matter the numbers say the cars should accelerate be very close to identically. As we calculated above, however, this is not the case at most speeds. In fact, using these weights and dynos (and identical power to weights), the 1M in this example would pull an average of about ~10% harder if both cars were shifted perfectly. That looks like the graph below the 1M is pulling harder from any starting speed until 125 mph, at which point they are equal: Now this is not supposed to be a 1M vs M3 argument. This is to illustrate that power to weight is not the only thing that matters. Area under the power curve is what matters, and all else being equal, more torque gives you that. You're welcome to do the actual math with any numbers you like, but any time you put power to weight equal and raise the torque the results are likely to be similar. Bottom line for me: The extra 100 ft/lbs from the M4 will probably give it the equivalent of ~10% more hp in the from of more area under the horsepower curve, which will have a bigger effect on realworld acceleration than the roughly 8% less weight it will be carrying around. So from that point of view, even at a rated 415 hp, the M4 is shaping up rather well. Now I'm as big a fan of normally aspirated motors as the next guy, but I clearly understand there will be gains other than fuel economy from forced induction. And I certainly understand that torque can be fun too.
__________________
1M, 1969 Porsche 911 w/ 997 GT3 Cup Motor (435hp & 2,100 lbs)
Last edited by Pete_vB; 02252013 at 09:51 PM. 

Appreciate
0

02262013, 04:09 AM  #223  
Lieutenant General
222
Rep 10,201
Posts 
Quote:
Let me start with this correction by rearranging your words a bit... If a lazy driver who won't properly put the car in the gear which maximizes acceleration and at the same time "requests" maximum acceleration cares (continue reading on with the quote...) Quote:
Now that we have that straight let's continue.


Appreciate
0

02262013, 05:28 AM  #224 
Lieutenant Colonel
67
Rep 1,829
Posts 
^,^^ The advantage of higher torque at low rpm (=higher power at low rpm) only matters when you are at low revs, which only happens once from idle, afterwards you are shifting at higher rpm so it becomes irrelevant.
This advantage of turbo is negated by the time penalty of turbo lag, when you get only the power of 6 instead of 8 cylinders at zero boost. Area under Power curve, hp/weight, and drag at high speed, you guys have mentioned are completely accurate as I can see it. 
Appreciate
0

02262013, 11:12 AM  #225  
Captain
23
Rep 846
Posts
Drives: '69 GT3, 1M, 912, R32
Join Date: Nov 2010
Location: SF Bay Area, Shenzhen, Oman

Quote:
So, we now have the formula. Gearing we have. So let's look at how much HP the examples are putting down, both peak and at different speeds in 4th, and compare it to your statement above: At 105 mph, per the formula above, the M3 is turning 6350 RPM. We go to the blue line on the M3 dyno above and see it's making about 255 tq, or 308 hp as you'd prefer. 4150 lbs / 308 hp = 13.5 lbs per hp. The 1M turns 5150, makes 335 tq/ 328 hp per the graph, and again I'm using a heavy 3700 lbs to make peak power to weight equal. So 3700 / 328= 11.3:1. Per your statement above, the best power to weight at that speed will accelerate harder, so the 1M is ahead at that speed. Now look at 110 mph and so on. 105 MPH: M3 13.5, 1M 11.3 110 MPH: M3 12.9, 1M 11.2 115 MPH: M3 12.3, 1M 11.2 120 MPH: M3 11.9, 1M 11.4 (11.3 in 5th) 125 MPH: M3 11.6, 1M 11.5 (11.2 in 5th) 130 MPH: M3 11.4, 1M 11.6 (11.2 in 5th) 135 MPH: M3 11.2, 1M 11.7 (11.2 in 5th) Now even without shifting, the 1M is averaging 11.4 lbs per hp over this speed range with these example numbers. The M3 matches its peak of 11.2, but it averages 12.1. So it's averaging 6% lower power to weight. 8% less power to weight if the 1M shifts. The M3 can't shift to a better gear, 3rd ends before 105. So per your statement, two cars with equal peak power to weight ratios, but the one with more torque is accelerating harder almost everywhere. Again, shifted perfectly, no lazy driver. 8% that's the equivalent of going from 415 to 448 hp. This is the advantage the M4 is going to have in acceleration due to area under the power curve, and why you should care how much torque the car has. Even if you know how to shift. Or drive a car that shifts for you.
__________________
1M, 1969 Porsche 911 w/ 997 GT3 Cup Motor (435hp & 2,100 lbs)
Last edited by Pete_vB; 02262013 at 11:43 PM. 

Appreciate
0

02272013, 01:00 AM  #226  
Lieutenant General
222
Rep 10,201
Posts 
Quote:
Since, we've already pretty well determined that it is impossible for the next M3/4 to have a 7k+ rpm redline, 400 ft lb of torque and only 415 hp, we should examine a known case. What gives a car like an M3 a better overall performance gain: a 10% increase in peak power to weight ratio (which will realistically probably mean a 5% increase in power at an rpm of redline/2) or a 10% increase in torque, likely at an rpm much lower than redline? Some initial simulations showed these cars would perform very closely in most drag racing related competitions. My simulations were actually surprisingly closer than I suspected they would be. Of course then I immediately recalled the use of the M3 in the way it really "should" be used. On more of a road coarse / track type setting (of course corner to corner in a canyon, as well, not necessarily on a track per se). Taking into account the mostly correct statement just below: Quote:
Again nothing particularly wrong with BMW giving us more torque. It is particularly great for drivers who simultaneously demand peak acceleration but will not choose the best gear for obtaining it . I'd simply prefer, for a somewhat more real world speed x to speed y performance (i.e. nondrag race performance gains) more peak hp. With more peak power you do get the near equity in drag racing type of results but get a clear advantage in more canyon/track type of results. I certainly can not guarantee the universality of such a result but I strongly suspect that for most cars the same general trend will hold on this point. 

Appreciate
0

03012013, 07:06 PM  #227 
Banned
0
Rep 4
Posts 
I just cannot believe that they expect people to give up on the 414hp V8 over 1 horse power, that's just ridiculous. I don't think the improvements over E9X is anywhere NEAR as those back in the day were for the E46. 300 lb in weight reduction (and that's optimistic)? Come on. Who gives a crap about weight reduction of a few hundred pounds, I, among many people, will chose super charging the E9X for 1020k (for an amazing ESS supercharger) over buying into the turbo campaign. At the end of the day, it's the engine that makes an M3 an M3. I just don't have that special feeling towards the F80 M3.
And please don't compare the new M5 vs the old one, the new M5 has had a massive torque improvement over the old one, and the difference between the old V10 and the new V8 in terms of the sound, feel, etc is much less than that of the new proposed I6 and the old V8 in the old M3. I think once you hit the V8 category, anything above is a marginal gain in terms of that special sports car feeling. This I6 feels nothing but a japanese turbo charged engine. Who cares about efficiency, I can pay 80 grand for a car do you think I'll even think about $20/week more for the gas? What are these guys thinking about? 
Appreciate
0

03012013, 07:08 PM  #228 
Banned
0
Rep 4
Posts 
I also dare everyone who is showing favoritism toward the new car to get in a E9X M3 and go for a 3rd gear roll from 40 mph to 120 all the way to 8400 rpm and tell me how that feels. Probably one of the best feelings I have ever had in my life.

Appreciate
0

03012013, 10:08 PM  #231 
Banned
0
Rep 4
Posts 
Come on now, you know I'm right. Most of us aren't going to go for drag racing or tracking this car at a competitive level. Who cares if it's lighter, 200 lbs here and there "on spec" means nothing. Once you start adding features one after another, the improvement will be negligible (it's like having another passenger in the car, do you really feel the difference?). I'd pick the V8 over any 415hp I6 turbo, I'm sure a big majority of the existing M3 owners will either do the same or look at other options.

Appreciate
0

03022013, 06:36 AM  #232 
Moderator
214
Rep 13,937
Posts 
^^^ Consider power to weight.
It sure sounds to me like you've already reached the conclusion that the new M3/M4 will not see an incremental improvement in performance over the E9x M3 as its predecessors have over their respective outgoing models, or indeed as the new M5/M6 did vs. the E6x. When you factor in your demonstrably cocky attitude, it seems like a recipe for egg on face to me. Just my opinion.
__________________
A genuine BMW effeightzero with them tandem clutches in the transmission and that dad gum sun roof on the topa da cawr.

Appreciate
0

03022013, 07:54 AM  #233  
Brigadier General
44
Rep 3,156
Posts 
Quote:
People hardly track their M3's, the new one will fit a daily driver mentality better since you'll gain so much off the line performance.
__________________
2012 335i Mineral Gray
M Performance Whore: PPKExhaustBrakesPerformance Suspension Struts & SpringsLSDBlack Kidney GrillesCF Spoiler and Mirror CapsBav Stage 1400MsBMWF30.com 

Appreciate
0

03022013, 08:16 AM  #234  
Major
25
Rep 1,073
Posts 
Quote:
Can we now please stop whining over the loss of cylinders. It's the world we live in today, and that's how it's going to be. Deal with it, or become an oldtimer fanatic. 

Appreciate
0

03032013, 05:53 PM  #235 
Captain
10
Rep 946
Posts 
Do you really drive around like that all day? More often then not, when I want to pass someone I prefer to do it in a high gear (and at lowrpm) to avoid giving them an earful of exhaust. That's why I absolutely love the overboost on the 335is, of course going to lower gears will always be faster but it's nice to also have the flexibility to accelerate hard in the low and midrange. I can accelerate from 40 in 2nd, but I could also do it in 5th or even 6th quickly enough to pass whoever I want unless they're going full throttle (for some reason haha). I once raced my buddy's E46 330ci in my 135i, him shifting at redline and me upshifting at 3,000rpm in each gear, and we were dead even. These turbo motors have tons of power all over the place which can be entertaining in its own way.

Appreciate
0

03032013, 06:27 PM  #236 
Moderator
214
Rep 13,937
Posts 
Not at all. I think you may have inadvertently failed to consider the context of my post as established by the one I replied to. If you have a chance, you may wish to go back and reread.
Neither an M3 nor a 335is will accelerate well from 40mph in 5th or 6th gears. It can be done in either car (or any car, really), but its not the most effective use of the engine and gearbox.
__________________
A genuine BMW effeightzero with them tandem clutches in the transmission and that dad gum sun roof on the topa da cawr.

Appreciate
0

03032013, 08:52 PM  #237  
Lieutenant General
222
Rep 10,201
Posts 
Quote:
Do I drive around at 7 or 8k+ rpm all the time, no. Do I consistently use 60007000 rpm, you bet. Similarly, when I do want maximum acceleration I have absolutely no reservations/qualms/misgivings/hesitations, etc. about using the best gear and using the full 8400 rpm. I think the debate can also be looked at this way. Is there anything wrong with gobs of torque down low in the rpm range? Absolutely not. The key thing is that in nearly all real world motors a strong low end torque curve is accompanied by both a low redline as well as a strongly falling torque curve some significant rpm below redline (another way to say this is you end up with a power curve having a peak with hump, again well below redline. You can really feel this type of power curve. It is the classic "nothing left up top" type of feel. For me personally, if I had to choose between the two, I prefer the linear power curve and high redline. It's more fun and better on the track or in the twisties. Should you choose to push the motor and transmission, you get a big reward, both acoustically, in the vibration and in the visceral sense of acceleration at high rpms, not to mention the performance itself. 

Appreciate
0

03032013, 09:01 PM  #238  
Banned
8
Rep 426
Posts 
Quote:
Keep in mind 415 hp will be clearly underrated given every single other turbo motor is. Probably realistically looking at 440hp and a couple hundred pounds less which is good for an equivelent of 25hp in acceleration/power or so given their power to weight. So realistically 50hp equivelent is realistica if you consider weight factored in 

Appreciate
0

03042013, 03:10 AM  #239  
Lieutenant General
222
Rep 10,201
Posts 
Quote:
E9X M3 power curve  nearly perfectly linear F10 M5 power curve  a big hockey stick (totally flat in power for the entire top 1500 rpm) Do I really need to paste in images of these stark differences for you to see them? Now that being said, up to about 5700 rpm the torque and power curves are very similar and will feel so. 

Appreciate
0

04212013, 08:02 AM  #240 
Major
19
Rep 1,360
Posts 
I hope it gets at least 450hp. For me, 415hp even with the weight reduction and increase in torque, is not gonna do it.
__________________
2014 E63 AMGS
2012 C63 AMG (P31)  gone 2011 E90 M3 FBO  gone 
Appreciate
0

04212013, 08:35 AM  #241  
Moderator
214
Rep 13,937
Posts 
Quote:
Well, that's completely speculative on my part with not even a hint that I am on the right track from any source. But, given the latest M5 news, I'd give myself pretty decent odds. What do you think?
__________________
A genuine BMW effeightzero with them tandem clutches in the transmission and that dad gum sun roof on the topa da cawr.


Appreciate
0

04212013, 10:33 AM  #242  
Major
19
Rep 1,360
Posts 
Quote:
But, why not start at ~440450hp, and then offer a comp package increasing power up to 460470? You and I both know that with the numbers I'm suggesting this car will be an absolute BEAST and will sell even better, without hurting the M5/M6 sales. But, I'm only a car enthusiast with no knowledge of what these numbers mean to BMW. We'll see...
__________________
2014 E63 AMGS
2012 C63 AMG (P31)  gone 2011 E90 M3 FBO  gone 

Appreciate
0

Post Reply 
Bookmarks 
Thread Tools  Search this Thread 

