BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > M3 (E90 / E92 / E93) > M3 vs....
 
INDustry distribution
Post Reply
 
Thread Tools Search this Thread
      12-12-2007, 12:41 AM   #221
bruce.augenstein@comcast.
Lieutenant Colonel
21

 
Drives: Legacy GT - 13.704@99.39
Join Date: Jul 2007
Location: Manheim, PA


Posts: 1,907
iTrader: (0)

Quote:
Originally Posted by swamp2 View Post
...Excellent work Bruce (sarcasm)! You have matched a SINGLE TEST case of the E46 M3 1/4 mi time within 1/100th of a seconds for the 1/4 mi time. That is great, but like I keep saying fairly meaningless. The range of times reported by different magazines probably looks something like this (13.0, 13.2, 13.5, 12.9, 13.3). Actually I totally made that up, but I'd bet digging through the data it would be very similar. [b]NOW AGAIN, FOR THE MILLIONTH TIME, WHY IS 13.10 vs. 13.1 A BETTER COMPARISON THAN 13.10 vs. 13.5 (OR WHATEVER THE WORST REPORTED MAG TIME WAS). IT ISN'T! YOU HAVE CHERRY PICKED YOUR SINGLE TEST DATA POINT VS. THIS SIMULATION.
Here is why. When asked to run a simulation to see how close you would be to gbb357's C & D's results in note 107, you came up with that way the hell off nonsense in note 110. The time was 13.1 107, and you were at 13.5 103 and change. gbb357 was not asking you to come up with averaged test results from Death Valley to the Everest summit. He just asked you to model those numbers. You seemed proud of the very bad results, and mentioned that you had done just as well with the C63! (Your exclamation point.)

When I (rather politely, I thought) mentioned that the numbers were well off, but the only thing I could put my finger on was something at the top end, you did your normal ego protection attack, including this gem:

"Why are these numbers “reasonable”? Simply because they are typically within the average numbers reported from tests plus or minus the variation in the reported test numbers. This is the hallmark of an acceptable/reasonable simulation." Your bolding, by the way.

Down here at the track, though, four tenths is four car lengths, and you just got your ass kicked.

Quote:
Originally Posted by swamp2 View Post
Although I definitely appreciate your humor about being a pain in the ass, I'd also say resorting to insulting someone parents and genes (sarcastic or not) is stooping pretty low and grasping at straws.
I don't think lucid is as humor-impaired as you are, and understood the compliment both to himself and his parents. Jeez, Swamp. Ever see "Good Morning Vietnam"? "You are in more dire need of a blow job..."

Bruce
Appreciate 0
      12-12-2007, 04:49 AM   #222
swamp2
Lieutenant General
United_States
213

 
swamp2's Avatar
 
Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA


Posts: 10,201
iTrader: (1)

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
Here is why. When asked to run a simulation to see how close you would be to gbb357's C & D's results in note 107, you came up with that way the hell off nonsense in note 110. The time was 13.1 107, and you were at 13.5 103 and change. gbb357 was not asking you to come up with averaged test results from Death Valley to the Everest summit. He just asked you to model those numbers. You seemed proud of the very bad results, and mentioned that you had done just as well with the C63! (Your exclamation point.)
Thanks for all the personal advice Bruce, but no thanks. I don't care for your quotes nor you advice. If you spout your insulting drivel from a movie I'll spout my opinion on what you need - reading and comprehension ability and a freaking brain.

Any monkey can tune a simulation to match results. You can tune the data entries for an Enzo to match performance numbers for a Hugo. Ever heard of "garbage in garbage out" a classic expression in the world of simulation. There is no skill nor magic in that. Other than weight, shift times, transmission losses and some basic launch optimization, the numbers I used for the input E46 M3 simulations were blind/default and completely un-tuned. Do you know what that means? NO OTHER DATA ABOUT THAT PARTICULAR CAR NOR TEST THAT YEILDED THAT PARTICULAR SUBSET OF RESULTS WAS KNOWN. In these circumstances the results I obtained are again within the accuracy of the variability of known tests. I just can not say that enough times. I am seriously tiring of trying to help you understand. I actually think this will be my last exchange with you on this topic. I've simply run out of energy, explanations, analogies, logic, patience, etc. You have missed the boat.

If I recall correctly gbb357 did not ask me to engage in a curve fitting exercise i.e. to "model" a single set of test results. That is about as contradictory and nonsensical as you can get - to "model" a single set of results. You do not model one test case unless you are modeling a process that is highly repeatable. I am honestly begining to loose all hope of getting the basics concepts of simulation, accuracy, random and systematic errors and predictability across to you. If gbb357 did in fact want to test my curve fitting abilities (rather than my ability or the quality of CarTest) I can whip out a CarTest simulation pretty quickly to match those exact test results. What then happens when friendly forum user X presents me with his test results or the results from magazine Y that are drastically different????? Well I could go tweak the simulation to match those results as well but you simply must see the logical consequence of this repeated ad infinitum. The real problem with that process would simply be the lack of justification for changing the parameters to tune to the results each time. In simulation you should either have a justification for your parameters or bracket/envelope them as I demonstrated quite effectively in my use of simulation to prove the C63 AMG is under-rated. You did see this exchange in the "Top Gear..." thread, right? Did you notice how incredibly close one data point on how over-rated the CLK63 AMG is corresponded to my power prediction of the C63 AMG required to get the performance it does (note almost identical engine)? This is a much better use of simulation than trying to obtain a very highly accurate absolute measurement of any particular single metric or groups of metrics for a single car.

Not sure how many times I have to repeat this as well but simulation (esp. as I am using it, to try to match a "moving target" of varying magazine results) is actually much more accurate in relative predictions rather than absolute predictions. Specifically, the time difference between two cars in the 0-100 or trap difference in the quarter, etc. This is because a relative simulation comparison removes some of the systematic errors present in both results. Almost magic! Even with this ranking of relative over absolute, and of bracketing/enveloping over absolute, I am still happy with the absolute results I have obtained and they are reasonable compared to the spread of test results.

Indeed the accuracy I have obtained thus far in my efforts are not suitable to predict with absolute accuracy results for a drag racing team. Like I explained many posts ago that is a fairly different goal, process and simulation strategy. You simply never read nor understand (nor rarely reply directly to) what I post.

All of this being said I do think that 1/4 mi trap speed may be the worst results for my absolute predictions from my use of CarTest. Like enigma mentioned this appears to be related to some air drag effects or other higher speed dominated effects. Bruce, neither CarTest nor my simulations are perfect, but at least I understand the limitations of both and the entire concept of predictability. You have a lot of homework and learning to do here.

Get busy dusting off the TRS-80. I am truly done with you on this topic. Adios.
Appreciate 0
      12-12-2007, 05:18 AM   #223
footie
Major General
No_Country
149

 
footie's Avatar
 
Drives: ????????????
Join Date: Oct 2007
Location: BMW M3 will get a V6TT


Posts: 7,507
iTrader: (0)

Garage List
2008 E92 M3  [0.00]
Quote:
Originally Posted by enigma View Post
Um, who thought the RS4 was a better car? A lot of people didn't want an RS4 because its AWD which takes away a lot of the drivers experience.
I was only highlighting that is the majority of the reviews between the E46 M3 and the RS4 the Audi came out on top and in quite a few of reviews between the RS4 and the E92 M3 the same has being true. What you or I think is irrelevant, my comments where directed at roadtesters opinions not ours.
Appreciate 0
      12-12-2007, 05:40 AM   #224
footie
Major General
No_Country
149

 
footie's Avatar
 
Drives: ????????????
Join Date: Oct 2007
Location: BMW M3 will get a V6TT


Posts: 7,507
iTrader: (0)

Garage List
2008 E92 M3  [0.00]
Quote:
Originally Posted by gbb357 View Post
I agree, drivers that don't have much skills or don't have experience when it comes to racing or just driving hard and fast, a car like the RS4 would be more appropriate. The M3 in the other hand, you gotta have skills. The same goes with Porsches and other true hard core sports cars.
Actually that statement isn't totally accurate, the Boxster and Cayman don't require anything like the skill to drive as a 911 does or even an M3 for that matter.

But I do agree that the RS4 is much easier to drive quickly and I have said as much on numerous occasions, the same applies to all AWD cars and not just Audis.
Appreciate 0
      12-12-2007, 05:12 PM   #225
gbb357
Captain
23

 
Drives: IS300
Join Date: Oct 2007
Location: New York


Posts: 707
iTrader: (0)

I thought this was funny too Bruce.

Quote:
Originally Posted by Bruce
When I (rather politely, I thought) mentioned that the numbers were well off, but the only thing I could put my finger on was something at the top end, you did your normal ego protection attack, including this gem:

Quote:
Originally Posted by Swamp
"Why are these numbers “reasonable”? Simply because they are typically within the average numbers reported from tests plus or minus the variation in the reported test numbers. This is the hallmark of an acceptable/reasonable simulation
."
The original average number that the magazines got of 0-60 for the ISF is 4.5. They where 4.2, 4.4, 4.7 and 4.8. Your (Swamp) original simulation data of 0-60 was 5.1 seconds. Now how is 5.1 even remotely close to the average number that the magazines have gotten of 4.5 if what your saying on your statement above is true? Please don't use the newly corrected data to justify your statement. You would've have known it in the first place if it wasn't corrected by another member.
Appreciate 0
      12-12-2007, 05:35 PM   #226
footie
Major General
No_Country
149

 
footie's Avatar
 
Drives: ????????????
Join Date: Oct 2007
Location: BMW M3 will get a V6TT


Posts: 7,507
iTrader: (0)

Garage List
2008 E92 M3  [0.00]
Quote:
Originally Posted by gbb357 View Post
The original average number that the magazines got of 0-60 for the ISF is 4.5. They where 4.2, 4.4, 4.7 and 4.8. Your (Swamp) original simulation data of 0-60 was 5.1 seconds. Now how is 5.1 even remotely close to the average number that the magazines have gotten of 4.5 if what your saying on your statement above is true? Please don't use the newly corrected data to justify your statement. You would've have known it in the first place if it wasn't corrected by another member.
Am I to assume your opinion is that simulation aren't as accurate as swamp is leading us to believe.

I don't think that will go down to well, best stay out of the firing line.

As for the times listed above for the IS-F, in Europe I believe the average for the M3 is something like 4.7s to 100km/h so if you re-adjust back to 60mph that will probably end up at 4.6s, based on that the two cars are all but equal though this just up to speeds of 60mph, the Lexus should pull harder after this speed what with it's eight speed gearbox. Has anyone an opinion on what the gap would be between the two at say 150mph ............. (no simulators required).
Appreciate 0
      12-12-2007, 06:01 PM   #227
swamp2
Lieutenant General
United_States
213

 
swamp2's Avatar
 
Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA


Posts: 10,201
iTrader: (1)

Quote:
Originally Posted by gbb357 View Post
The original average number that the magazines got of 0-60 for the ISF is 4.5. They where 4.2, 4.4, 4.7 and 4.8. Your (Swamp) original simulation data of 0-60 was 5.1 seconds. Now how is 5.1 even remotely close to the average number that the magazines have gotten of 4.5 if what your saying on your statement above is true? Please don't use the newly corrected data to justify your statement. You would've have known it in the first place if it wasn't corrected by another member.
Someone provided me with an incorrect final drive ratio. It has a huge impact on simulation results and on real world results as well (obviously). I accepted the error and thanked toothdoc for the correction and sighting. If you can not accept that no one is perfect all of the time they you have a lot of waking up to do.

It is simply ludicrous to believe that one update of one input parameter from a known incorrect value to a known correct one is not the best course of action. toothdoc was nice enough to point out the error, I fixed it and the results are now nearly perfect considering the average of the 0-60 figures as you have reported them vs. the blind simulation with std. transmission loss parameters.

I can not believe how badly and desperately you guys are struggling to find something to nitpick at here. The results are what they are and they continue to validation the tool and my applicaiton of it. Have fun - your petty nitpicking seems childish, boring and entirely non-productive to me.
Appreciate 0
      12-12-2007, 06:17 PM   #228
swamp2
Lieutenant General
United_States
213

 
swamp2's Avatar
 
Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA


Posts: 10,201
iTrader: (1)

Quote:
Originally Posted by footie View Post
Has anyone an opinion on what the gap would be between the two at say 150mph ............. (no simulators required).
Of course I do. My "guess" is between the three cars, M3 6MT, M3 M-DCT and IS-F there will be a distance difference between the leader and furthest back at 150 mph of about 50'-100' or about 4-8 car lengths. Very close IMHO.

Very curious as to how others come up with their "guesses" or "opinions".
Appreciate 0
      12-12-2007, 06:27 PM   #229
footie
Major General
No_Country
149

 
footie's Avatar
 
Drives: ????????????
Join Date: Oct 2007
Location: BMW M3 will get a V6TT


Posts: 7,507
iTrader: (0)

Garage List
2008 E92 M3  [0.00]
Quote:
Originally Posted by swamp2 View Post
Of course I do. My "guess" is between the three cars, M3 6MT, M3 M-DCT and IS-F there will be a distance difference between the leader and furthest back at 150 mph of about 50'-100' or about 4-8 car lengths. Very close IMHO.

Very curious as to how others come up with their "guesses" or "opinions".
I reckon I know the order this will be in but I was disregarding the M-DCT out of the equation at it's an unknown quantity at the minute and we are only really playing guess work to how the gearbox etc will be setup.

What I wanted to know was between the IS-F and the current M3 in manual form.

Quote:
Originally Posted by Footie
Am I to assume your opinion is that simulation aren't as accurate as swamp is leading us to believe.

I don't think that will go down to well, best stay out of the firing line.
Notice the nice side step there, out of harm's way.
Appreciate 0
      12-12-2007, 06:44 PM   #230
swamp2
Lieutenant General
United_States
213

 
swamp2's Avatar
 
Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA


Posts: 10,201
iTrader: (1)

Quote:
Originally Posted by footie View Post
What I wanted to know was between the IS-F and the current M3 in manual form.
My "guess" is that these two will be within 0-4 car lengths at 150. Very close. Launch will be critical.
Appreciate 0
      12-12-2007, 06:52 PM   #231
footie
Major General
No_Country
149

 
footie's Avatar
 
Drives: ????????????
Join Date: Oct 2007
Location: BMW M3 will get a V6TT


Posts: 7,507
iTrader: (0)

Garage List
2008 E92 M3  [0.00]
That is indeed quite close. In fact when you calculate how much a car would have travelled in one second at this speed, four lengths of either of these cars would mean the difference between the two times would only be 0.2~0.3s.

That is even closer than I would have thought.

Unless my calculation are way off, of so can someone explain what I am doing wrong.
Appreciate 0
      12-12-2007, 07:47 PM   #232
swamp2
Lieutenant General
United_States
213

 
swamp2's Avatar
 
Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA


Posts: 10,201
iTrader: (1)

Quote:
Originally Posted by footie View Post
That is indeed quite close. In fact when you calculate how much a car would have travelled in one second at this speed, four lengths of either of these cars would mean the difference between the two times would only be 0.2~0.3s.

That is even closer than I would have thought.

Unless my calculation are way off, of so can someone explain what I am doing wrong.
Need to correct my guesses. I was reading something wrong. With DCT in the mix the max separation should be about 180 ft/15 car lengths, 6MT M3 vs IS-F again 1/2 that, 90ft/8 car lengths. Again this is an upper limit estimate, may be much closer. 8 cl's at 150 mph corresponds to about 0.4 s. Again just my guesses, no simulation involved .
Appreciate 0
      12-13-2007, 12:38 AM   #233
bruce.augenstein@comcast.
Lieutenant Colonel
21

 
Drives: Legacy GT - 13.704@99.39
Join Date: Jul 2007
Location: Manheim, PA


Posts: 1,907
iTrader: (0)

An update on the IS-F quarter mile

Since I've been one of the principal hijackers of this thread (sorry, folks), I thought perhaps I could take the opportunity to post something on topic.

Figuring what the heck, I have "Quarter, Jr.", and since it seemed to do so well when tracking the E46 M3, I thought I'd hurl in the IS-F data from the current Car & Driver test and see what it hurled back out at me. Here's the result:

60' 2.06
330' 5.53
660' 8.33
MPH 88.6
1000' 10.71
1/4 12.72
MPH 112.3

Pretty good stuff. C & D got 12.7 @ 114, so even though my calculated MPH is a little low, that discrepancy represents only about a 2% power differential (about eight horsepower), since C & D calculates finsh line speed as far as I know, which Quarter, Jr. shows at 113.2. In addition, the model shows an 0-60 time of 4.39 seconds, and an 0-100 time of 10 seconds flat, each of which is two tenths of a second off the C & D numbers.

I used a car weight of 3970 pounds assuming driver and their hot-damn test gear, and again used the SAE (gross) Standard Day weather conditions, which is approximately what they use.

Combined with the dyno results quoted long ago and far away in this string, I'd say a case could be made that although the Lexus is a healthy runner, it is probably not significantly under rated in terms of power, contrary to previous testimony by He Who Must Not Be Named.

OK, that's not fair, since Swamp has sworn to be mute. Fun, though.

Just as an additional check, I entered the BMW 328 data from the same issue, and got a 14.83 @ 95.4, against their 14.8 at 95. Hm-m. Now I'm a bit high on MPH, with a finsh line speed of 96.1. That represents about a 3.5% increase in calculated power vs what C & D got, which is also around eight horsepower.

Results seem very close to a more or less known quantity like C & D, but not necessarily against other publications who's test methods are unknown to me. Edit: Note that there isn't any real tuning to be done with this very simple product.

When I get ShiftMaster working, I'll try a couple of passes as well.

Bruce
Appreciate 0
      12-13-2007, 04:13 AM   #234
swamp2
Lieutenant General
United_States
213

 
swamp2's Avatar
 
Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA


Posts: 10,201
iTrader: (1)

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
Since I've been one of the principal hijackers of this thread (sorry, folks), I thought perhaps I could take the opportunity to post something on topic.
...
I opted out of the discussion of why my results and the software I am using are so grossly in error. AS well I opted out of trying to explain some of the finer points of simulation. I did not opt out of all discussion on the thread. Now that you have made a very nice post I feel like chiming in again. A couple tenths here a couple tenths there, a couple tenths vs. my best run (#4 in post #145). Great job Bruce. See how easy it is for me to admit someone else did a nice job? You have however misrepresented my statements about potential under-rating of the IS-F. What I said was, "It is most likely that car has a combinaton of a very advanced, low loss automatic transmission and some under-rating, maybe as much as 20 hp." That is not all that much differnt than your potential discrepancy of 8 hp is it (compared to out of 416 total)? Sure 8 is less than half of 20 but I did state 20 as a max/upper limit estimation!

I am curious about a few key parameters that you used in your sim, namely:
-Automatic transmission losses
-Torque converter losses, if any
-Shift times
-Did you input a torque or hp curve or just peaks

Also why are you quoting two simulation results for trap speeds?

Lastly do you really have any reason to believe your sims should match C&D better than any other magazines results or is it simply convenient?
Appreciate 0
      12-13-2007, 06:33 AM   #235
footie
Major General
No_Country
149

 
footie's Avatar
 
Drives: ????????????
Join Date: Oct 2007
Location: BMW M3 will get a V6TT


Posts: 7,507
iTrader: (0)

Garage List
2008 E92 M3  [0.00]
I am very curious as to how exact these can be, like do they allow the input of surface types, awd transmissions etc. or is this too much to expect.

P.S.

Autocar have driven the IS-F and it's in this week's magazine, their belief time with the left them feeling it's not the equal dynamically of the RS4, M3 or C63 but like the engine and it's performance is very impressive..........not so the interior or the UK's suggested retail price.

Also in same issue they did a proper roadtest on the C63 on UK roads and rate it now No1 ahead of the M3. When I get to read in full will give full run down of points, that's if someone hasn't beaten me to it.
Appreciate 0
      12-13-2007, 11:16 AM   #236
bruce.augenstein@comcast.
Lieutenant Colonel
21

 
Drives: Legacy GT - 13.704@99.39
Join Date: Jul 2007
Location: Manheim, PA


Posts: 1,907
iTrader: (0)

Quote:
Originally Posted by swamp2 View Post
...I am curious about a few key parameters that you used in your sim, namely:
-Automatic transmission losses
-Torque converter losses, if any
-Shift times
-Did you input a torque or hp curve or just peaks
Swamp, there are no inputs for these items other than for power, and for that, you enter the peak power @ rpm, along with engine size and the shift point. No other power figures, and no torque figures at all. None.

This is either infuriating or amazing, depending on your point of view.

I would say in addition that Patrick Hale of RSA was one of those resident geniuses at the time we were messing about with this stuff, and "Quarter" was pretty much a legendary package. If memory serves, Quarter demands a good deal more input than Quarter, Jr., but I'd guess that the Jr. package still uses much of that magical original code, with obvious defaults for necessary parameters.

Quote:
Originally Posted by swamp2 View Post
Also why are you quoting two simulation results for trap speeds?
I'm quoting trap speed and speed at the finish line, and these have been somewhat different since around 1990, I think. That's when the NHRA got nervous about Top Fuelers getting to be too damned fast, and thus ending up in the boondocks before they could get the things stopped on tracks with shorter shutdown areas. They changed the speed trap from a 132 foot block bracketing the finish line to a 66 foot block ending at the finish line. At the time, I remember analyzing over 100 published road tests before coming up with the idea that the difference averages about seven tenths of one percent (.007) for most cars. Anal? Who me?

In any event, Quarter, Jr. gives you both speeds.

Quote:
Originally Posted by swamp2 View Post
Lastly do you really have any reason to believe your sims should match C&D better than any other magazines results or is it simply convenient?
It's convenient, but I also simply don't know about matching anybody else's results. C & D mentions their test methods from time to time, including adjustments for weather, so I'm a little more sanguine about looking at their stuff, compared to, say, Road & Track as an example. R & T doesn't do any weather adjustments, and they don't (fully) publish the local conditions at time of test. Other nutbooks may tell you even less.

Bruce

PS - While we're sort of locked into the "She don't idle too good but she's hell in the quarter" mindset, everybody should get themselves to a drag strip at least once in their lives to watch the Top Fuelers run. I hadn't been to a strip in perhaps thirty years or so to actually watch an event (just attending for time trials for whatever I was driving at the time), but my bride and I went to watch a national NHRA event a couple of years ago.

My theory is that you don't actually watch the Top Fuelers run. They happen to you.
Appreciate 0
      12-13-2007, 01:29 PM   #237
swamp2
Lieutenant General
United_States
213

 
swamp2's Avatar
 
Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA


Posts: 10,201
iTrader: (1)

Quote:
Originally Posted by bruce.augenstein@comcast. View Post

PS - While we're sort of locked into the "She don't idle too good but she's hell in the quarter" mindset, everybody should get themselves to a drag strip at least once in their lives to watch the Top Fuelers run. I hadn't been to a strip in perhaps thirty years or so to actually watch an event (just attending for time trials for whatever I was driving at the time), but my bride and I went to watch a national NHRA event a couple of years ago.

My theory is that you don't actually watch the Top Fuelers run. They happen to you.
Cool. Thanks. I will have to give it a look.

+1 on watching top fuelers, esp. the rails. Even just the acoustics is enough to raise every hair on your neck and give you goosebumps. The pits are quite a hoot as well with the nuts wearing gas masks and industrial ear protection getting within feel of flame throwing headers belching noxious yellow nitro-methane.
Appreciate 0
      12-13-2007, 07:08 PM   #238
bruce.augenstein@comcast.
Lieutenant Colonel
21

 
Drives: Legacy GT - 13.704@99.39
Join Date: Jul 2007
Location: Manheim, PA


Posts: 1,907
iTrader: (0)

Footie, sorry I'm so late with this reply.

Quote:
Originally Posted by footie View Post
Bruce,

Myself not being a technical man are you saying that changing the gears makes really very little difference on the overall result. Like you said in the first few hundreds it's more noticeable but this advantage doesn't grow to anything like the advantage some here believe it can be.
That's what I'm trying to convey, but it's important to understand that this is in the fairly narrow context of a drag race, with emphasis on a traditional run from a standing start. In other contexts, a final-drive change can offer quite a nice payoff.

As a for instance, I personally believe that on an E46 M3, a change in final drive ratio to a 4.10 from a 3.62 would be a good one. In everyday driving out on the highways, it would be a more responsive and enjoyable beast, answering your right foot with more eagerness. Cruise rpm would jump up from, say, 3000 to about 3400 (at around 80 mph), so the car would be making that much more power. The change would come at the cost of some extra fuel consumption and possibly noise, although these engines are very smooth at cruise, so noise won't be much of an issue.

Quote:
Originally Posted by footie View Post
Take two cars for example the E63 and the M5, both have 7 gears and both roughly produce the same power but their really difference is in the amount of torque and at what revs. From what you are saying would I be right in thinking that the E63 should be able to pulls daylight between it and the M5 based on the fact it has more torque regardless of where it is produced.
We all have massive areas of ignorance, so just to display a little of mine, I had to go look up what the hell an E63 was.

That said, are we talking about M5 vs M6? I thought that they had identical engines and drivetrains, with the M5 having a minor weight penalty. Obviously I've got it wrong, so let me know what we actually *are* comparing.

Quote:
Originally Posted by footie View Post
I have always had a problem understanding what some more technical guys here have said that it not the amount that is important but where it's produced. Surely that is determined by the gearbox and gearing as each car roughly makes the same speed in each gear or there abouts.

Please can someone explain this in to layman terms for us thickies.
OK, you're speaking about torque here, and that's important, but horsepower is really what you're after. Back in '93 or '94, I wrote one of my stupendously long replies in a notes string about power and torque, and unbeknownst to me, that reply got picked up on the Vettenet site, and then here and there on the 'Net, until now it's out there on maybe a hundred sites or so, and has been translated into four languages. Most of the sites have the original, which was very torque centric (important in the context of the discussion I had entered), but some have later versions which even further flesh out how power is really what we're after.

In any event, I used the example of a waterwheel I observed way back when, making around 2600 foot pounds of torque according to the folks in the old-timey flour mill (and tourist attraction) that the wheel served. Now, there's no way your M3, or C63, S4 or S5 is going to be making anywhere near that amount of torque, but the rest of the story is that the wheel was rotating at about 12 rpm.

If you hooked that wheel to the drive wheels of a car, that car would lurch up to 12 rpm of the drive wheels in an instant, and the waterwheel would hardly notice. However, 12 rpm of the drive wheels is about one mile per hour for the average car, and what if you wanted to go faster?

Well, you'd have to gear it up. If you wanted to go 60 miles per hour, you'd need to gear it up by 60 times, and returning to the topic of simple machines you studied as a kid, you'd have one 1/60th of the torque you had without gearing, meaning you'd have about 43 foot pounds of torque to keep the car at 60. Ain't enough, as we English majors say, and if you do your HP/Torque sums, 12 times 2600, over 5252 gives you......6 HP.

Horsepower is essentially torque at speed, and as speed increases, so does the need for power, in a completely linear way. Remember how that water wheel booted you up to one mph? Well, if you're addicted to our Lord God of Acceleration, you're going to need 360 HP if you want to be booted just as hard at 60 - and that's not even including increased air and rolling resistance.

What causes some confusion is that, in any given gear, the car will accelerate in a way that exactly matches it's torque curve, so it's not accelerating as hard at the power peak as at the torque peak. At 7900 rpm, the M3 is down to 221 foot pounds of torque, so it's accelerating only 84% as hard as it did at the torque peak in that gear. However, even though torque is what is actually accelerating the car, making more power at any given car speed is the key.

As an example, an E46 M3 is doing something around 40 miles per hour in second gear at its 4900 rpm torque peak, so in order to get a feel for acceleration potential at that speed in second gear, you'd multiply 263 foot pounds of torque by the second gear ratio of 2.53, times the final drive ratio of 3.62, which gives you 2408 foot pounds of torque at the drive wheels - enough to sock you in the back pretty hard. In fact, as mentioned, that's as hard as you're going to accelerate in second gear. At that point, by the way, you're making 245 horsepower.

However, what if the car was making max power at that point instead of max torque?

In order to do that, you'd need to re-gear the car in order to get to its 7900 rpm power peak at 40 in second gear, so you'd need a 5.84 final drive ratio. There, you'd have about 221 foot pounds of torque (in the U.S., at 333 HP) times the second gear ratio of 2.53, times 5.84, giving you TA DA! 3265 foot pounds at the drive wheels - or about a 36% harder boot in the back. Just doubling back here, 333 horsepower is about 36% more than 245 horsepower. What're the odds?

Torque is what you feel, but horsepower rules.

My dad once told me (quite truthfully, I think) that the way you could tell who was a true expert in something is that he or she could relate fairly complex ideas in simple terms, using relatively few words. By that standard, I'm more or less an idiot - but, did all that rambling actually add anything to your knowledge?

Bruce

PS - All this said, if you have two cars with pretty even power to weight ratios, the car with better torque to weight will win, because it'll be making more power to weight on its way up to the power range off the line, and also after each shift.
Appreciate 0
      12-13-2007, 07:20 PM   #239
enigma
Captain
6

 
Drives: E92 M3 and Elise
Join Date: Oct 2006
Location: Land of the Microchip


Posts: 689
iTrader: (0)

Quote:
Originally Posted by bruce.augenstein@comcast. View Post
As a for instance, I personally believe that on an E46 M3, a change in final drive ratio to a 4.10 from a 3.62 would be a good one. In everyday driving out on the highways, it would be a more responsive and enjoyable beast, answering your right foot with more eagerness. Cruise rpm would jump up from, say, 3000 to about 3400 (at around 80 mph), so the car would be making that much more power. The change would come at the cost of some extra fuel consumption and possibly noise, although these engines are very smooth at cruise, so noise won't be much of an issue.
I never understood this line of thinking. If you want to maintain more power at cruise speed, why not just leave the car in 5th? You get the same effect without having to take anything apart.

On a road course gear changes can be a win by keeping the car in the ideal power band and avoiding having to shift at all the wrong places. I swear in my car I ht the rev limiter about 300' before 3 diffrent brake zones at Laguna. Only in issue in a MT car, in the DCT you would go ahead and do the shifts.
Appreciate 0
      12-14-2007, 05:22 AM   #240
footie
Major General
No_Country
149

 
footie's Avatar
 
Drives: ????????????
Join Date: Oct 2007
Location: BMW M3 will get a V6TT


Posts: 7,507
iTrader: (0)

Garage List
2008 E92 M3  [0.00]
Bruce,

I roughly get it but what happens when you come across a car like the new RS6, it's peak power of 580HP @ 6250~6750rpm and torque of 650Nm @ 1750~6250rpm (a peak which is higher than even the M5's 6100rpm). Surely figures like these it has to be accelerating hard than the M5 or is it a case that at this point the gearbox choices come into play.

It just I have read on numerous sites that the debate seem to be split pretty evenly on which will be the quickest. I too would love an opinion from someone with knowledgeable experience on this, because my heart says (being a power hungry mother) that surely the RS6 will be way quicker what with it's extra power and torque but then my head (capt sensible) chimes in saying things like weight, 7 gears and higher peak power etc.

Some Bruce, what do you think?
Appreciate 0
      12-14-2007, 09:21 AM   #241
bruce.augenstein@comcast.
Lieutenant Colonel
21

 
Drives: Legacy GT - 13.704@99.39
Join Date: Jul 2007
Location: Manheim, PA


Posts: 1,907
iTrader: (0)

Quote:
Originally Posted by footie View Post
Bruce,

I roughly get it but what happens when you come across a car like the new RS6, it's peak power of 580HP @ 6250~6750rpm and torque of 650Nm @ 1750~6250rpm (a peak which is higher than even the M5's 6100rpm). Surely figures like these it has to be accelerating hard than the M5 or is it a case that at this point the gearbox choices come into play.

It just I have read on numerous sites that the debate seem to be split pretty evenly on which will be the quickest. I too would love an opinion from someone with knowledgeable experience on this, because my heart says (being a power hungry mother) that surely the RS6 will be way quicker what with it's extra power and torque but then my head (capt sensible) chimes in saying things like weight, 7 gears and higher peak power etc.

Some Bruce, what do you think?
My money would be on the Audi. If I assume power to weight is close, then the Audi has better torque to weight, and with that very broad curve, will have the power to weight advantage after each shift, even with the slightly closer ratios in the BMW.

The BMW has a more efficient and "better" gearbox (I assume it will shift more quickly than the Audi), but assuming Audi will allow pre-loading off the line (and they will), the RS6 will launch like a ball bearing out of a slingshot, leaving the M5 for dead.

At speed, it'll be closer, I think. I'd still give the Audi the nod, though. Way up there into triple digits, power over net frontal area gets more important than power to weight, and the Audi will get the nod there as well.

Bruce

PS - I have no axe to grind, here. I don't give a damn about either of the companies, nor any other auto manufacturer, for that matter.

On second thought, that may not be correct. I'm actually pretty much a badge whore for all of them. Right now, for instance, I'm pretty excited about what Hyundai is doing, and watching everybody else sweat.

Who said promiscuity is wrong?
Appreciate 0
      12-14-2007, 11:30 AM   #242
gbb357
Captain
23

 
Drives: IS300
Join Date: Oct 2007
Location: New York


Posts: 707
iTrader: (0)

I'm with you on this one Bruce.

Quote:
Originally Posted by Bruce
PS - I have no axe to grind, here. I don't give a damn about either of the companies, nor any other auto manufacturer, for that matter.

On second thought, that may not be correct. I'm actually pretty much a badge whore for all of them. Right now, for instance, I'm pretty excited about what Hyundai is doing, and watching everybody else sweat.

Who said promiscuity is wrong?
I'm almost in the same boat. There's almost no car out there that i don't like. Especially when it comes to European cars, specifically Germans. If there is one brand that i am a fanboy of, it's Mercedes. Specially AMG models, there's just something about them that really gets me excited everytime i see one or read about them.
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 07:36 PM.




m3post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST