|
|
|
Post Reply |
|
Thread Tools | Search this Thread |
07-19-2008, 07:44 AM | #1 |
Captain
55
Rep 780
Posts |
M3 vs Competition - factoring in Torque, Weight and Gearing
Following on from some of the information posted in this thread (see http://www.m3post.com/forums/showpos...3&postcount=50), I decided to capture some of the dyno test data from Rototest Research Institute (http://www.rri.se/) and compare the performance of the M3 with its competitors, taking into account not only dyno performance but also gearing and weight.
All performance data is based upon the "at the hubs" measurements from RRI. Weight is based upon the kerb weight measurement performed by RRI, plus 75kg for the driver. These results don't incorporate other factors such as drag, which obviously becomes more of a factor at higher speeds and favours cars with more power, regardless of weight. The vertical axis in each comparison represents torque @ wheels per tonne (derived by taking the actual torque @ wheels in each gear and dividing by weight in metric tonnes). The horizontal axis represents vehicle speed in km/h. Each graph shows the weight scaled torque output for a number of gears, and gives a good indication of how the cars would perform against each other. The results are quite interesting... Round 1: M3 Manual vs M3 DCT Test Data: M3 MT Weight - 1686kg M3 DCT Kerb Weight - 1711kg (added 25kg to MT weight) Redline - 8250RPM (used for both cars) Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=793 (used for both cars) Comparison: Interestingly the manual transmission has shorter gearing for 1st gear, which in theory should see it launch quicker off the line if executed correctly. 2nd gear is very even between the two, but once the DCT hits third gear it has a clear advantage. The DCT has the MT in 3rd and 4th gears - the MT has a brief period of respite between 155km/h and 170km/h, but otherwise between 115km/h and 195km/h, the DCT has a clear advantage due to its shorter gearing. Past 195km/h it is pretty close, the MT has a slight advantage with its taller gearing, but I suspect the effect of the instantaneous changes of the DCT have a much greater impact here, where losing a few km/h in speed between gear changes be much more noticeable in terms of a performance comparison. BMW state the DCT is faster than the manual, and apart from the initial launch off the line, the figures tend to back up factory claim. DCT wins Round 1. Round 2: M3 Manual vs C63 Test Data: M3 MT Weight - 1686kg M3 Redline - 8250RPM M3 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=793 C63 Weight - 1903kg (much higher than the factory quoted EC weight of 1730kg!) C63 Redline - 7000RPM C63 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=795 Comparison: The lighter weight and short 1st gear of the M3 MT effectively negates any advantage the more powerful C63 engine has initially off the line. The C63 however has a much stronger 2nd gear, the huge mid range torque should help the C63 to a quicker 0-100km/h time. The C63 still has an advantage in 3rd gear which will see it quicker through the 1/4 mile with a faster trap speed, but the high RPM power of the M3 is starting to take effect. By 4th gear, the M3 should actually be quicker, however a steadily increasing amount of drag will work in the C63's favour with its stronger power output. The C63's torque advantage is too much for the M3 manual to overcome, C63 takes Round 2. Round 3: M3 DCT vs C63 Test Data: M3 DCT Weight - 1711kg M3 Redline - 8250RPM M3 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=793 C63 Weight - 1903kg (much higher that the factory quoted EC weight of 1730kg!) C63 Redline - 7000RPM C63 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=795 Comparison: This is the comparison we are all waiting for in real life. The taller 1st gear of the DCT (as compared with the manual) means the C63 should get off the line a bit quicker assuming traction is controlled appropriately, and even with a shorter 2nd gear, the DCT will not be able to match the C63 to 100km/h. Once passed 90km/h though, the DCT is on top of the C63 thanks to its shorter gearing, which should see it match the C63 down the quarter mile. This comparison is pretty tight, but the faster gear changes of the DCT might just give it the edge. Round 3 is a points decision to the DCT! Round 4: M3 DCT vs RS4 Test Data: M3 DCT Weight - 1711kg M3 Redline - 8250RPM M3 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=793 RS4 Weight - 1811kg RS4 Redline - 8000RPM RS4 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=281 Comparison: So the M3 DCT has just managed to see of the stiff competition from AMG, so what about its Audi competitors? First up it's the aging RS4. Unfortunately for the RS4, it looks like its age really has caught up with it and it has no chance whatsoever against the M3 DCT. The RS4 only has a low RPM torque advantage, but where it counts it falls well behind. Round 4 is a KO win to the DCT! Round 5: M3 DCT vs R8 Test Data: M3 DCT Weight - 1711kg M3 Redline - 8250RPM M3 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=793 R8 Weight - 1703kg R8 Redline - 8000RPM R8 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=778 Comparison: The M3 DCT has trounced the RS4, but what about the much revered R8? The R8 is over 100kg lighter than the RS4, and performs better in both the mid-range and high-RPM than its RS4 sibling, despite sharing the same powerplant. Combine this with slight shorter gearing, and the R8 is fares much better against M3 DCT. The R8 has a clear advantage off the line, with stronger 1st and 2nd gears. Combine this with its Quattro AWD transmission, and the R8 should be able to lay down considerably quicker 0-100km/h times than the M3 DCT. 3rd gear is much closer, but the R8 still has a slight advantage, which should see it run a quicker quarter mile than the M3 DCT. Round 5 goes to the R8, and so it should given the price tag on the R8 Round 6: M3 DCT vs M5 SMG Test Data: M3 DCT Weight - 1711kg M3 Redline - 8250RPM M3 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=793 M5 Weight - 1919kg M5 Redline - 8000RPM M5 Dyno Data - http://www.rri.se/popup/performanceg...p?ChartsID=153 Comparison: So the M3 DCT has seen off its main current rival the C63, and even given the R8 a good go. Things are looking good for the M3 DCT, so how will it fare against big brother M5 with the more antiquated SMG transmission. Well as good as the M3 DCT is, the M5's peaky 500HP engine is just too much for the M3 DCT (and all of the other cars discussed here) in a drag race. Although the M3's power band looks much nicer for daily driving, once that M5 engine gets spinning, it is all over. Round 6 is a KO to big brother M5. |
07-19-2008, 09:21 AM | #2 | |
Colonel
99
Rep 2,000
Posts |
Quote:
I used to do this for hours at a time, comparing various cars, plus same car with different gearing, etc, etc. I called the results the "Dunderbex Numbers", which meant nothing in particular but sounded vaguely technical. The one thing I found problematical (as you do ) is that I could never effectively show graphical results of automatic cars with any accuracy. There just isn't enough published data generally available in regard to torque converter stall points, slip rates and actual torque multiplication to come up with anything meaningful. Bruce |
|
Appreciate
0
|
07-19-2008, 09:40 AM | #3 |
Major General
382
Rep 8,033
Posts |
Nice graphs. Swamp and TBone are using a simulation tool called CarTest, which pretty much does this kind of comparison for you automatically after you supply the torque curves and some other specs for the different cars.
On thing: as I mentioned in the thread where jm1234 posted his graphs, the RRI torque data are for steady-state tests. A real drivetrain under acceleration would produce less torque at the wheels due to rotational inertia effects and other dynamic variables. Also, different engines might respond slightly differently to the acceleration pulls. DCT gearing in 3rd looks good!
__________________
|
Appreciate
0
|
07-19-2008, 11:04 AM | #4 |
Captain
43
Rep 644
Posts |
Great data!!!!
I figured the R8 would be a close run, with the M3 loosing..... Interesting that the 6MT has a "lower" 1st gear, which of course gives it a serious advantage...but with a 3.85 rear end vs the 3.15 in the DCT....that has to count quite a bit....
__________________
Brian
2008 E92 M3, MR, DCT, extended BB leather, loaded! 1988 Porsche 928S4, Guards red/Champagne leather 1989 Porsche 928S4 track beast!!! |
Appreciate
0
|
07-19-2008, 11:12 AM | #5 |
Major General
1208
Rep 8,034
Posts |
I'm surprised to see the R8 being quicker than either M3 because all of the data in Europe put the M3 manual ahead of the R8. Maybe the R8 isn't as light as the quoted figures suggest.
|
Appreciate
0
|
07-19-2008, 11:40 AM | #6 |
Captain
146
Rep 795
Posts |
|
Appreciate
0
|
07-19-2008, 07:34 PM | #8 |
Lieutenant General
634
Rep 10,407
Posts |
Nice work, very interesting. This give so much more information than silly single figures like peak hp or peak torque. Although as a single number peak hp/weight is still quite a good figure.
|
Appreciate
0
|
07-19-2008, 07:37 PM | #9 | |
Captain
146
Rep 795
Posts |
Quote:
George |
|
Appreciate
0
|
07-19-2008, 10:10 PM | #10 | |
Captain
55
Rep 780
Posts |
Quote:
Yeah using gear ratios and final drive to calculate number of wheel revolutions per engine revolution, and then the wheel circumference to derive speed. I didn't put in the other C63 gears as they aren't really relevant (I'm surprised at how tall the C63 gearing is). Fully agree in a drag race much of each curve is not used - my comments were based around shifting at redline since this is the ideal shift point for all of the cars shown and moving to the next gear torque curve at the same speed as redline in the previous gear... |
|
Appreciate
0
|
07-20-2008, 04:55 AM | #12 |
Lieutenant General
634
Rep 10,407
Posts |
The radius of the drive wheel is part of the torque multiplication just as gear ratios are. They belong in that calculation as well as the one to get vehicle speed. Probably not a big correction but a small error if you left it out.
|
Appreciate
0
|
07-20-2008, 06:43 AM | #13 |
Major General
1208
Rep 8,034
Posts |
Audi RS4 and R8 peak power is 420ps @ 7800rpm, RED LINE 8250rpm. (difference 450rpm)
Mercedes C63 peak power is 457ps @ 6800rpm, RED LINE 7200rpm. (difference 400rpm) BMW M3 peak power is 420ps @ 8300rpm, RED LINE 8400rpm. (difference 100rpm) BMW M5 peak power is 507ps @ 7750rpm, RED LINE 8???rpm (difference ???rpm) please fill in the blanks. Working on the opinion that maximum revs is the ideal point of shifting in all of these cars is wrong, peak power revs is the point, nothing before it and nothing after. Whether is would make that much of a difference to your findings I don't know but I thought I should correct the point in question. |
Appreciate
0
|
07-20-2008, 11:28 AM | #14 | |
Colonel
99
Rep 2,000
Posts |
Quote:
Bruce |
|
Appreciate
0
|
07-20-2008, 07:39 PM | #15 | |
Captain
55
Rep 780
Posts |
Quote:
I would have thought the radius of the drive wheel determines the actual horizontal force applied at the contact point of the wheel? Force at the wheels (as opposed to torque) is probably the better parameter to graph anyway, as it directly relates to acceleration... |
|
Appreciate
0
|
07-20-2008, 09:32 PM | #16 | |
Lieutenant
19
Rep 431
Posts |
Quote:
|
|
Appreciate
0
|
07-21-2008, 01:22 AM | #17 |
Lieutenant General
634
Rep 10,407
Posts |
jm, mixja: I misspoke. Linear accelerative force is indeed what matters and thus torque should be divided by wheel radius (and by weight as already done). Either way you want to look at it the overall wheel OD does act just like gears, same torque, larger wheel, less force.
Last edited by swamp2; 07-21-2008 at 04:01 AM.. |
Appreciate
0
|
07-21-2008, 02:23 AM | #18 | |
Major General
1208
Rep 8,034
Posts |
Quote:
You want to be shifting into that thick torque band and until your torque is also far up the rev range then there is no benefit holding on to the gear. I can only gauge from experience and that is what I have found on every occasion. |
|
Appreciate
0
|
07-21-2008, 03:12 AM | #19 | |
Captain
55
Rep 780
Posts |
Quote:
In all of the cars looked at in this topic though, there is no benefit in shifting before redline, the closest that breaks this rule is the RS4 in third gear going to fourth gear... |
|
Appreciate
0
|
07-21-2008, 06:01 AM | #20 |
Major General
1208
Rep 8,034
Posts |
The S5 I had was the exact same, peak power was at 7000rpm but redline was 7500rpm. I found no benefit shifting at redline though because of the shortness of 1st gear it was always harder to shift at the 7000rpm but all other gears definitely felt better to shift below the redline.
The RS4 and R8 have peak torque from 3000~5600rpm so shifting at 7800rpm puts you back into that torque curve. There is no doubt that the M3 is designed to redline in every gear to get the best from it but the others including the C63 work best working between the torque band and peak power. |
Appreciate
0
|
07-21-2008, 06:14 AM | #21 | |
Captain
55
Rep 780
Posts |
Quote:
|
|
Appreciate
0
|
07-21-2008, 06:17 AM | #22 |
Major General
1208
Rep 8,034
Posts |
Very possible, as swamp and bruce can confirm I am not as technical as they are and base everything I know on expereince. AWD may be play it's part in this but I still feel the torque curve is more important than anything else.
|
Appreciate
0
|
Post Reply |
Bookmarks |
|
|