|
|
02-23-2011, 08:31 PM | #243 | |
Lieutenant General
611
Rep 10,407
Posts |
Quote:
Also complicating things is that the 335i is most likely underrated buy about 20-30 hp. For a true 300 hp 300 ft lb 335i the advantage is almost universally with the M3 (again assuming you are driving in the right gear for the best acceleration at WOT). For a real 335i there are some points in a drag race where it will put down more wheel force than the M3. Have a look at the very last graph in this post. This removes the any possible overrating issue since it used actual dyno results (as does the post linked below). You will also like this one. The M3 vs. close competitors factoring in actual dyno data, gearing and weight. Link. Unfortunately the 335i was not included. The only problems here with displaying the information in this fashion are: 1. Way too much data to look at, and, 2. What you probably really want are graphs vs. time like the ones I posted in post #213 in this thread. In the end, the key take away is simply this: Power to weight rules. And of course I mean peak power...
__________________
E92 M3 | Space Gray on Fox Red | M-DCT | CF Roof | RAC RG63 Wheels | Brembo 380mm BBK | | Vorsteiner Ti Exhaust | Matte Black Grilles/Side Gills/Rear Emblem/Mirrors | | Alekshop Back up Camera | GP Thunders | BMW Aluminum Pedals | Elite Angels | | XPEL Full Front Wrap | Hardwired V1 | Interior Xenon Light Kit | Last edited by swamp2; 02-24-2011 at 03:22 AM.. |
|
Appreciate
0
|
02-23-2011, 09:01 PM | #244 | |||||
Lieutenant General
611
Rep 10,407
Posts |
Quote:
Quote:
Quote:
Quote:
Quote:
Please let's try to get back on topic. Everyone. This is not another 335i nor modded 335i vs. M3 thread.
__________________
E92 M3 | Space Gray on Fox Red | M-DCT | CF Roof | RAC RG63 Wheels | Brembo 380mm BBK | | Vorsteiner Ti Exhaust | Matte Black Grilles/Side Gills/Rear Emblem/Mirrors | | Alekshop Back up Camera | GP Thunders | BMW Aluminum Pedals | Elite Angels | | XPEL Full Front Wrap | Hardwired V1 | Interior Xenon Light Kit | |
|||||
Appreciate
0
|
02-24-2011, 06:35 AM | #245 | |
Lieutenant General
5234
Rep 10,616
Posts |
Quote:
Put a $250 to $500 tune in the 135/335 and the M3 gearing torque advantage is all gone except at very high rpm. The 335is with a slightly uprated factory tune is putting out 340 lbs at the rear wheels. Most M3 put out 250-260 lbs while most 135/335 are doing 275-285 lbs at the rear wheels. Add your 25% advantage to that and you have 312-325, but remember the M3 torque peak is 3900 and the 135/335 torque peak is half that (less according to BMW), which really helps in daily driving though not on the dragstrip. I'd do a spreadsheet/simulation, but I'd rather go drive one of my cars -- maybe the one with the high horsepower low torque S65, maybe the one with the high torque moderate horsepower N54 or maybe the one with the massive torque and horsepower turbo S52. |
|
Appreciate
0
|
02-24-2011, 07:58 AM | #246 | |
Moderator
7515
Rep 19,368
Posts |
Quote:
So, let me see how that effects my example. So, then, we start with two identical M3s. We then modify one of them with a power adder such that it now makes as much power in second gear at 25mph (@ whatever RPM that happens to be - I don't know off the top of my head, and it would differ between 6MT to DCT anyway) as the still-stock one does in 1st gear at 25mph (again, whatever RPM that happens to be - it will definitely be a higher RPM than the other car though). Now, if we put them next to each other traveling at 25mph, and punch it, they will accelerate at the same speed. Well, this is true only for the initial instant the throttle is pushed. After that, presumably, the power curves no longer mirror each other @ the respective engine RPMs so one car will start to pull. But if the curves somehow matched up identically throughout the rest of the rev range, until the car in first gear hits redline, then indeed they would be neck and neck the whole time to that point. This I am more apt to accept. It does make you shake your head a little though. |
|
Appreciate
0
|
02-24-2011, 09:51 AM | #247 | |
Law Enforcer
25100
Rep 22,288
Posts
Drives: '22 Chalk Gray Porsche C2S
Join Date: Jun 2006
Location: ..in your rearview!!!
|
Quote:
How much "power" does a car really need to make a great daily driver? <--That was a rhetorical question! Like I stated in an earlier post, claiming one is better than the other sounds silly to me. Both the 335i and the M3 have MORE than enough power (...MORE power than a car needs). |
|
Appreciate
0
|
02-24-2011, 09:55 AM | #248 |
Colonel
87
Rep 2,464
Posts |
I have one question. We always say high revving engine is better. This way we can have shorter gear ratios and take advantage of torque multiplication.
BUT, let say we have two cars with perfectly flat torque curves. Car1 has 200lb-ft torque, 305hp, and revvs to 8000rpm. Car2 on the other hand has 400lb-ft torque, 305hp, and revvs to 4000rpm. For the sake of example, assume the engines idle at 0rpm. The cars weigh same, use same tires etc. They have the same gearbox, but the differentials are 2x different (or differentials are same but the gear ratios are 2x different) such that they put the same torque to the wheels. Are these cars will have the same acceleration?
__________________
2011 MINI Cooper S
previous cars: E92 M3, Z4MC, Z4 Roadster, E36 328 Sedan |
Appreciate
0
|
02-24-2011, 09:56 AM | #249 | |
Colonel
87
Rep 2,464
Posts |
Quote:
__________________
2011 MINI Cooper S
previous cars: E92 M3, Z4MC, Z4 Roadster, E36 328 Sedan |
|
Appreciate
0
|
02-24-2011, 10:35 AM | #250 | |
Moderator
7515
Rep 19,368
Posts |
Well, if you buy into what Bruce has said above (I do since I think he's correct ), then the answer to your question depends on the power curves. So I don't believe there's enough information here to make a conclusion. Power and torque curves do inter-relate, however, I still believe you need to supply an actual power curve here to reach an answer. You've only given a peak power spec (not even a peak power RPM), or so it seems if I've understood you properly.
Quote:
|
|
Appreciate
0
|
02-24-2011, 10:40 AM | #251 | |
Colonel
87
Rep 2,464
Posts |
Quote:
__________________
2011 MINI Cooper S
previous cars: E92 M3, Z4MC, Z4 Roadster, E36 328 Sedan |
|
Appreciate
0
|
02-24-2011, 10:42 AM | #252 |
Moderator
7515
Rep 19,368
Posts |
Well, you see, it is another example of the contradictory logic that seems to win a lot of mindshare on automotive forums.
On the one hand, people want a manual gearbox because they insist on very finite control over the gear ratios that their transmission provides. But on the other hand, they want a car that doesn't really need those ratios to provide a good sensation of speed an performance to begin with. Of course, the irony here is that, even with a 335i, obviously the car accelerates best when in the lowest gear fro the current speed (below 100 mph anyway). And, as a corollary you need to wind the thing to 7000 RPM to get the best acceleration anyway (in lower gears). I suppose what it comes down to the fact is that, people care most about how the car feels, not how it actually performs. Low end torque makes a car feel faster, even when it isn't. Similarly having a manual gearbox makes a person feel like they are driving fast, even if they are not (in fact, even if they aren't even using it effectively). |
Appreciate
0
|
02-24-2011, 10:42 AM | #253 |
Moderator
7515
Rep 19,368
Posts |
|
Appreciate
0
|
02-24-2011, 10:44 AM | #254 |
Colonel
87
Rep 2,464
Posts |
What is a power curve then? Power is hp, right? If so, then the power will increase from 0 (@ 0rpm) to 305hp at redline. Since one of the cars have redline at 4krpm, its power curve will be steeper.
__________________
2011 MINI Cooper S
previous cars: E92 M3, Z4MC, Z4 Roadster, E36 328 Sedan |
Appreciate
0
|
02-24-2011, 10:45 AM | #255 | |
Colonel
87
Rep 2,464
Posts |
Quote:
__________________
2011 MINI Cooper S
previous cars: E92 M3, Z4MC, Z4 Roadster, E36 328 Sedan |
|
Appreciate
0
|
02-24-2011, 10:53 AM | #256 | |
Moderator
7515
Rep 19,368
Posts |
Quote:
Also, you didn't say initially that the cars made maximum power at redline. Not all cars do, you know. In fact most don't. The M3 doesn't (though it's close @8300 RPM, IIRC). |
|
Appreciate
0
|
02-24-2011, 10:56 AM | #257 | |
Colonel
87
Rep 2,464
Posts |
Quote:
So again, the cars weigh same, use same tires etc. They have the same gearbox, but the differentials are 2x different (or differentials are same but the gear ratios are 2x different) such that they put the same torque to the wheels. Are these cars will have the same acceleration? ------ And yes, you're right that M3 has its max power at 100rpm shy of redline. I believe same was true for S54 engine.
__________________
2011 MINI Cooper S
previous cars: E92 M3, Z4MC, Z4 Roadster, E36 328 Sedan Last edited by Erhan; 02-24-2011 at 11:10 AM.. |
|
Appreciate
0
|
02-24-2011, 11:49 AM | #258 | ||
Moderator
7515
Rep 19,368
Posts |
Quote:
So I recalled correctly that power and torque are interrelated earlier, but I forgot that the above formula makes it explicit. Quote:
|
||
Appreciate
0
|
02-24-2011, 11:55 AM | #259 |
Colonel
87
Rep 2,464
Posts |
I'm guessing they'll have same acceleration too, but than the "high revving engine is better because you can take advantage of gearing" argument is gone now...
__________________
2011 MINI Cooper S
previous cars: E92 M3, Z4MC, Z4 Roadster, E36 328 Sedan |
Appreciate
0
|
02-24-2011, 12:01 PM | #260 |
Moderator
7515
Rep 19,368
Posts |
I believe that counter-argument only holds if you have a transmission with zero shift time. Don't quote me on that.
|
Appreciate
0
|
02-24-2011, 12:04 PM | #261 |
Colonel
87
Rep 2,464
Posts |
Ok I see what you're saying, but let's assume shift times are 0ms. Because the argument says high revving engine takes advantage of gearing, not shift times. Also, the engine with more torque that is using smaller ratio gears will have to shift less number of times than the high revving engine anyways.
__________________
2011 MINI Cooper S
previous cars: E92 M3, Z4MC, Z4 Roadster, E36 328 Sedan |
Appreciate
0
|
02-24-2011, 01:41 PM | #262 | |
Moderator
7515
Rep 19,368
Posts |
Quote:
I suspect they are the same performance. The thing is, as noted in this thread, I think it is tough to develop an engine with FI that has a flat torque curve like that. Typically it peaks early and then falls. You could just set the redline really low like your example, but then you are not taking advantage of the power that could be made a higher RPM. |
|
Appreciate
0
|
02-24-2011, 01:55 PM | #263 | |
Colonel
87
Rep 2,464
Posts |
Quote:
Hold'on though... both cars have the same torque at the wheel because I adjusted the diffs/gearing that way. Which means, the car with more torque will have half the power at the wheels. So it will be slower. What do you think? |
|
Appreciate
0
|
02-24-2011, 02:39 PM | #264 | |
Moderator
7515
Rep 19,368
Posts |
Quote:
In your example, the two cars will have the same power at a given speed because their power curves are the same except one is multiplied by two (on the RPM axis), while at the same time their gearing differs by exactly a factor of two. Remember, while gearing multiplies torque, "power at the wheels" is the same as power at the engine, less parasitic losses of course. IOW, gearing does not multiply power like it does torque. |
|
Appreciate
0
|
Post Reply |
Bookmarks |
|
|