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07-16-2012, 08:58 PM | #45 | |
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mods: track ready stuff
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07-17-2012, 02:44 AM | #47 | ||||||
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Testing is not more accurate than simulation. Anyone who believes this does not understand either. PERIOD. Have a look at the fairly large performance database of M3's performance here on the forum. For any given contest there is a very large range of values obtained. Variables contributing to test (i.e. "REAL" world) testing include but are not limited to: driver, weather, road condition, road slope, tires, tire wear state, tire inflation, level of vehicle break in, fuel variability and on and on and on. Unfortunately with almost all "REAL" testing that you've done yourself and even that is reported by the media too many of these factors are random and uncontrolled leading to large variations. With simulation you remove EVERY variation expect the one or ones the user wishes to control. This is true cause and effect isolation along with control of the size of the input change/difference. Basically not even practically possible in the "real" world. This was a 6MT to 6MT simulation comparison. The stock FD ratio is 3.846. Oh and do you know how OEMs figure out how fast or efficient any given car will be long long before prototypes are built? Physics based simulation. Do you know how all mechanical systems are tested virtually for a wide range of loads like structural thermal, aero, acoustic, etc. long before the prototypes are built - physics based simulation. Do you know how cars are successfully manufactured today taking into account things like stamping, welding, casting, and other manufacturing processes - physics based simulation. Get with the 1980's dude! Quote:
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I do agree that diff ratio changes come with compromises. Highway rpm may be higher, MPG may be less, traction may be worse off the line, acceleration will be slower or faster to certain arbitrary target speeds or through certain arbitrary speed ranges. The factory's compromise is usually good for the average driver.[/quot] More or less correct as the simulations indicate. Although prior work done my another M3post.com member showed that the existing M3 FD ratio were pretty close to optimal for some common performance metrics (may have been ET, don't quite recall). Quote:
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I'll bet that a pre and post "geared" MT E9X M3 car will not show STATISTICALLY significant 1/4 improvements with a 3.85 -> 4.10 FD mod. In fact I'd bet pinks (if you car has a comparable value...). Money where your mouth is. The app does provide 60 foot times. Quote:
Dinan and other FD folks are selling FEEL and peak and average in gear acceleration (which is what you feel). Any sophisticated seller will realize that for most cars FD mods do not appreciably improve numbers across the board. There is no such thing as a free lunch. Without more power or less weight (or perhaps less losses or improved aero) you simply DO NOT, CAN NOT get an overall improvement in performance. Those that say otherwise are not better than snake oil peddlers. I really tire of this debate somewhat but feel strongly enough about it to continue to try to promote a wider understanding of it. Next? ...
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07-17-2012, 12:03 PM | #48 | |
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stay in the lab buddy, "real-life" data will always prevail.. Any yes, car manufacturers are still acutally racing cars, 1/4 mile, road racing, etc. I used to drag race ALOT, and I can't listen to someone who is posting statistics versus real world information.. One last Q... Have you ever even drag raced a car?? Or do you just like to read? Schnell has gears and first hand info.. My last car picked up like 2/10 from gears. Keep in mind every .1 in the 60 ft equates to about .2 upstairs.. There's so many factors that a simulator cannot depict. Hence why people start w/ sims and move to the real thing. |
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07-17-2012, 12:08 PM | #49 |
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A neat little article on gears that if read correctly helps to understand why BMW chose the rear gears they did..
http://www.carcraft.com/techarticles...rks/index.html |
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07-17-2012, 12:52 PM | #50 | ||
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One other last point to make here is that a larger FD will get you rowing through the gears faster. This aspect of the change will almost for sure make one feel that the car is better/faster. However, the effect is actually positively harming performance. A bit like a nice throaty/racy exhaust, it will absolutely sound faster but wont be. Be cautious of your ability to really feel the true result! Quote:
Just to humor you I have been the drag's both to watch and to drive my own car. I've also been to the track many times and autox as well. If you do not understand the need for statistics for concrete proof when measurement error and/or random error are larger than the effects of many modifications themselves then the entire conversation is pretty well lost on you. Although there are some factors not adequately captured by simulation those factors for street cars, even exotics at the 1/4 mi track are very few and can be almost entirely eliminated since we are doing an A-B comparison. Again since you don't understand this the point is pretty well lost.
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07-17-2012, 01:10 PM | #51 | |
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ok, I guess as you say I don't get it. Keep resorting to "statistics" and I will keep testing in the "real world" racing.. Good day! |
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07-17-2012, 07:58 PM | #52 | |
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I agree that how you "feel" your car should count as well.
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07-17-2012, 09:16 PM | #53 |
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Again, BMW chose the 3.85 from a range of reasonable choices, as the best choice for the average driver given performance and fuel economy targets. The choice was a compromise. It was not the choice that made the car the fastest or that gave it the best fuel economy. There are good reasons why people may want to accent one or the other more, and change the ratio to achieve that.
Each car will have to make 5 shifts to reach its top speed, so shift time ends up being equal. The only difference is that the shorter geared car will have a slightly lower top speed and will have a slightly reduced maximum speed in each gear. It will go through the speed range of that gear faster, however, because torque is being multiplied better. Sure, pick some speed range that requires the shorter geared car to have to change more gears than the longer geared car, and the longer geared car will likely be faster (though DCT dramatically reduces any gear change time advantage). Having run 4 different diffs on my E36M3, I have experienced what ratio changes do in the real world. Even your own simulation in Post #48 shows that one knocks a second off one's 60-130 time with the shorter diff, and people routinely do other mods that you probably agree make a performance difference in order to knock that same second off their 60-130 time. |
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07-17-2012, 10:29 PM | #54 | |
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I am relying on physics based simulation. I contend that far too many make rash and even incorrect conclusion from "real world" test data due to lack of statistics and uncontrolled influences.
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07-17-2012, 10:48 PM | #55 | ||
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The diff ratio was chosen almost entirely for performance. It is very close to the best ratio to maximize 1/4 mi times. A slightly LOWER ratio would actually produce a better 1/4 mi time. Generally in gear results are improved by going with a large ratio. CarTest allows a cool parameter exploration/optimization tool. Obviously neither in simulation nor in the real world can you optimize for diverse performance metrics simultaneously. See chart below. Quote:
You misread the data. By changing the starting gear the 4.10 geared car can gain a maximum of 0.4 seconds improvement for 60-130. Make an arbitrary change though to perhaps 50-120 or 70-140 and there would probably be a loss of 0.4 seconds. Now if all you care about is ONE particular contest then indeed some very minor benefits can be gained. It seems abundantly clear here you are painfully proud of all of you diff swapping exercises and will go to any measure to prove they have large benefits. Almost any other mod that simply provides some speck of broadband power gains (pulley, tune, high flow cat, etc.) is a far better mod than ANY final drive mod. Why, it adds power and that improves results ACROSS the board.
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07-18-2012, 12:44 AM | #56 | |
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07-18-2012, 07:14 AM | #58 | |
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On the street in daily driving, we are not always doing our computer simulation. Sometimes we accelerate without having the computer simulate the best possible gear changes. We actually drive the cars. I have run from 60-130 starting in 4th, for example. And the 4.10 would be a second faster. Not being in the computer chosen perfect gear making computer perfect shifts is the real world and the torque multiplication shows up there. Even in your computer perfect world, the 4.10 diff is faster from 60-130 regardless of what gear you start in. Why is that? Because torque is multiplied better. And where do you see the most dramatic difference? Where there is a long pull in the same gear, like running 60-130 iin 6th. You see a 1.5 second improvement because the torque multiplication is better. Why don't you run some simulations to debunk the underdrive pulley? Let's say it adds 10 rwhp. Go run your computer. You will come back and tell us not to do it because on the computer the gains show up as little or nothing in the quarter mile. You could play this game for any minor mod. Do it for a tune that adds 10-15 rwhp. Then tell people that tunes are all in your head and that there is no point because your computer simulation of maximum acceleration only with perfect and ideal shifts only shows minimal gains. The 4.10 diff is multiplying torque better by 5% in every gear at every rpm. The tune that adds 10-15 rwhp is adding most of that power from 5000 rpm and next to nothing from 750-5000 rpm where I drive 99% of the time. I'll stay in the real world. Simulations have their value, but the real world has much more value to me. |
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07-18-2012, 09:06 AM | #59 | |||
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to your second point, no again.. The OP asked for a good mod for torque. For the best bang for buck, rear gears are a great mod. You are not gaining power, we know that. Quote:
BTW, people use real world data, just for that reason. Any race team will actually race the car (drag, road race, etc.) b/c as you stated, your simulators are for perfect situations and does not allow for variables or "uncontrolled instances" as you said which are not "realistic" Keep playing w/ apps; the rest of us will stick to trial and error! |
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07-18-2012, 03:05 PM | #60 | ||
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The best band for the buck is actually M-DCT. Depending on the contest and shift speed of a MT driver is can be good for an equivalent 20-50 hp over the 6MT. That's a whole other discussion though... Dig around for those threads if interested. Lat but not least if you spend 99% of your time driving a high reving car like an M3 below 5000 you clearly have no interest in actually making the car go and the entire discussion is pretty well moot.
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07-18-2012, 03:23 PM | #61 | |
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Engineering and science are measurement based activities. No disagreement whatsoever on that. However, the devil is in the details and race team and professionals (say the OEMs). Have the time and money for very high quality testing under controlled circumstances. What do they do BEFORE and AFTER they test - THEY SIMULATE!!! What is THE 1/4 mi time for the E9X M3? If you consult the"database" link I provided prior you will find not a number but a pretty wide range of numbers: 12.6 s - 13.3 s Similar ranges exist for all contests. Due to uncontrolled circumstances natural variations in results will occur. For each time reported by these sources how many runs do you think they took to get their best times? I'd guess around 10. Each of those runs probably showed a couple tenths of variation. Let's imagine a "12.7" second M3 showed runs ranging from 12.7 up to 13.1 (we always report bests). If you then turned around and immediately added a pulley and did one run at 12.8 would you imagine the pulley did not add power? You would probably have to take ANOTHER 5-10 runs and average them to see the actual difference. Heck maybe from heat soak even with the pulley you could not best the 12.7 time. "Real world" testing sort of tells us that the pulley IS NOT MAKING MORE POWER (well less losses technically but basically the same thing). That is absolutely, positively THE WRONG CONCLUSION. With simulation ALL of these natural variations are AUTOMATICALLY equalized and with ONE run you can ISOLATE the effect you are looking for. Are we making any progress here? It does not take statistics to verify significant mods say such as adding a blower to an M3. It most likely WILL take statistics and some effort at environmental control to see the effect of low power modifications (or zero power modifications such as the FD as being discussed here). Physics based simulation can effectively shortcut the arduous and perhaps expensive testing process through natural and perfect control of potentially confounding or uncontrollable inputs. Get it?
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07-18-2012, 04:01 PM | #62 | |
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My sole enjoyment from my car is not dragstrip runs through the quarter mile. The vast majority of the 30-50 mph, 50-70 mph and 60-130 mph runs in your simulation show the 4.10 gears are best. What do you do most in daily driving? 1/4 mile runs, 30-50 mph accelerations, 50-70 mph accelerations, 60-130 mph accelerations? I do a lot more 30-50s and 50-70s than I do 1/4 mile runs in my daily driving. And life is not a perfect computer simulation. I am not always in the perfect gear. Last edited by pbonsalb; 07-18-2012 at 04:07 PM.. |
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07-18-2012, 07:03 PM | #63 |
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Well if this is going to continue, I'm gonna grab some
Intresting discussion, though. Nice to see that this data supports that a pulley works that well. Probably the best bang for the buck in our cars, IMO.
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07-18-2012, 07:05 PM | #64 |
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I've seen enough. I mean there's a reason dynos (specifically mustang) replicate real world data w/ load bearing rollers; there's a reason why street tuning is still great; there's a reason b/c countless variables not observed from a sim program. For 1/4 mile I will still bet, two cars, stock for stock, one w/ 4: 10 or lower gear (shorter gear (higher #) ) will be faster in the 1/4 mile. Shit, the OP was looking for best bang for the buck to increase torque?? And you still would spend 3x amount for a pulley?? OK, good advice.
One last question though chief; you use a sex simulator before you do the real thing? Last edited by m3an; 07-18-2012 at 07:17 PM.. |
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07-18-2012, 07:12 PM | #65 | |
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