01-22-2013, 09:49 AM | #45 |
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This is key in the handling department...and the reason I wanted a RWD.
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01-22-2013, 10:25 AM | #46 | |
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But the 335ix drive is only 200lbs lighter than the S4, and with the weight balance thrown off with the heavier engine/x drive equipment, I would think there won't be too big of a difference between them. I've actually read some complaints about xdrive understeer when exiting corners, since the xdrive will clutch power towards the front when applying heavy throttle at moderate speeds. The ZF rear torque vectoring on the S4 is the star in this situation, which is designed specifically to combat the understeer without applying brakes on the inner wheels. The sensation of RWD vs AWD is what really distinguishes the two. The vehicle pitch due to RWD acceleration is awesome, you can't argue with how satisfying it is. The S4 feels more like a pull, and while it is probably overall harsher and faster, it doesn't cause you to lean back like the 3 series (but it definitely puts a smile on my face ).
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01-22-2013, 10:36 AM | #47 |
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I owned a 2011 S4, MT,
I now have a F30 335iX, MT S4 was faster (stock vs stock) 335iX is more fun to drive (less understeer, more RWD bias) 335iX look&feel is a little better (interior, visibility, feel...) Both great cars to me Try them both and decide |
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01-22-2013, 11:03 AM | #48 | |
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http://www.bmw.com/com/en/insights/t...echnology.html |
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01-22-2013, 11:05 AM | #49 |
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01-22-2013, 11:09 AM | #50 |
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01-22-2013, 12:10 PM | #51 | |
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I'll look for a good source on this, but seem to remember it from these forums, if I'm wrong I'll retract my statement - keep in mind marketing documents are not always accurate. Edit - The most objective source I can find is here: http://www.awdwiki.com/en/xdrive/ Notice that it says torque can shift from 50-50 to 0-100. I'll look for the thread where some very informed BMW owners debunked the myth that xdrive can split torque 0-100 to 100-0. |
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01-22-2013, 12:35 PM | #52 |
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While I have little experience in interpreting transmissions, if the rear wheels are spinning frictionlessly on ice, how can they have any torque? Torque is a force applied, not a rotational velocity. No friction = no torque, at least in physics.
Perhaps the rear wheels remain engaged, and turning as fast as the front wheels, but at times they are applying no torque, and all the torque is coming from the front wheels? |
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01-22-2013, 12:51 PM | #53 | |
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In the scenario you present, assume the front wheels have good traction while the rear wheels are on ice (somewhat academic example I suppose). In this case, you do not want any torque to be transferred to the rear wheels. Ideally, the center differential would route all torque to the front wheels and the rear wheels would roll without slippage. In the case of xdrive, this is not possible and thus the rear wheels will start spinning regardless because the rear-axle is connected to the drivetrain at all times. Obviously, torque transferred to the ground is all at the front wheels (called torque appropriation according to this), but the inertia of the rear-axle will always be engaged.
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01-22-2013, 12:59 PM | #54 | |
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It would be preferable to have the back wheels spinning at just the point of slipping, although if the front wheels have traction, the back wheels likely should be rotating at a similar speed, not much slower. In fact, spinning at a similar rate to the front wheels offers the best chance to gain traction. I read the linked section on "torque split ratio". It seems to be defined as the ratio of the rotation rate of the front and rear axles, which is NOT the apportioning of the torque between the axles. So maybe the "torque split ratio" is at most 50/50, but that does not mean the slipping rear wheels are doing less than the optimum thing. Last edited by JohnVidale; 01-22-2013 at 01:14 PM.. Reason: adding detail |
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01-22-2013, 01:17 PM | #55 | ||
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I'm no expert on drivetrains, so take my answer with a grain of salt. I don't think that the wheel speeds are coupled from the front and back - that would be the purpose of a locking differential. I understand that torque can be routed backwards through the drivetrain - ie engine braking - but I don't think your hypothesis holds. You will likely see lots of wheel spin from the back wheels in our example, which is not the ideal solution. In practice, the rear wheels will never be on a frictionless surface - thus the purpose of the center differential (or clutch) is to route power in a manner that prevents any wheel from slipping. XDrive has less authority to do this since the front wheels can never be turned with a mechanical advantage greater than the rear wheels. Crap...I really need to get back to work
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01-22-2013, 01:23 PM | #56 | |
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Last edited by drob23; 01-22-2013 at 01:30 PM.. |
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01-22-2013, 07:36 PM | #57 | |
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This is what I am wondering. I am a skier, I do not need AWD for daily use, but I do not want to switch cars with my wife who drives the X5. I actually bought the X5 for me, but I am just a manual car guy I neeed a sports car feel in a practical AWD sedan IN MANUAL ONLY. Eliminating the need for me to have two cars, one for play one for driving. |
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01-22-2013, 07:37 PM | #58 | |
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Since you have had both cars, do you notice the weight? Does the Audi feel sporty to you, is it nimble, do you have a manual? Thanks. |
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01-22-2013, 08:35 PM | #59 | |
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Based on what you've said, if you want to track and have the faster car, the S4 would be the choice. Else, if you don't need AWD then I'd go with a 328i/335i because it'll be the sportier feeling car day to day (RWD of course being the culprit). You will not realize the shortcomings of the drivetrain until after you take it to a track - which a stiffer suspension + rear LSD should solve your problems (at which point you're encroaching on the M3). The 3 series will also get you better fuel economy if that matters. Just borrow the wife's car for your ski trips... Hell...you could even wait for a 55k 3200 lb C7 corvette with a rev matching 7MT. Thing is supposed to be 0-60 in high 3 seconds?!?!
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01-22-2013, 09:04 PM | #60 | |
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The door panels felt cheap, the dealer wouldn't budge on the price...quite frankly they were a bunch of know it alls. Plus BMW is better quality and the f30 looks 10 times better.
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01-22-2013, 09:30 PM | #61 |
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I have a 2011 S4 as well as a 2013 F30 328i M-Sport. I initially went into Audi North Scottsdale to look at either a 2013 S4 or S5 but 36mo lease was $150/mo more than my current lease payment with FEWER options (buying at invoice). North Scottsdale BMW occupies the same piece of real estate and a line of F30's was 10ft away so I wandered over on my way out. I ended up with a 2013 F30 M-Sport in EBII w/premium/heated seats/paddles/EBT AND a significantly lower payment (at invoice minus 5% of holdback). I decided on the 328i vs 335i because a quick call to Dynocomp confirmed stage 2 tune of 325hp and 70fps torque AT THE WHEELS would run me $1200. 335i performance with a but over $10k saved
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01-22-2013, 09:42 PM | #62 | |
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No tracking, it is a DD, will not switch with the wife. Hahaha. I will get AWD rather than switch. |
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01-22-2013, 10:12 PM | #63 | |
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But ultimately, assuming your local dealership has some S4's with sports differential, you need to test drive each one and decide which one will be more viable for DD duty. The idrive blows away the MMI and the HUD is really cool, but I think the Audi interior is much nicer with alcantara (I also swapped LED's inside) and the DRL's look straight nasty from head on. I really like the individual setting for drive select - you can tailor specifically the cars feel - I prefer stiff suspension, nominal shift maps/throttle response, aggressive sports diff, nominal steering and conservative engine noise (silly speaker I think). I also prefer the more subtle styling of the Audi. The F30 has more rear seat room if that matters. If you go BMW and you're picky with options, chances are you'll need to custom order. BMW offers more competitive pricing and lots of incentives if you qualify (check out the ordering/pricing section). Audi cars have their trim levels - in this case only 2 - and from there not much optioning can be done. But if you have to order an Audi it could take a looooonnnngggg time, so be prepared to drive to a distant dealership if you want a specific S4.
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01-22-2013, 11:30 PM | #64 |
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At the time I was looking at the S4 Audi Drive Select was only an option on the Prestige model and was a $4k+ option on top of that. Talk about sticker shock! It could have just been a configurator bug at the time because now it appears the adaptive suspension and sports diff are now available on any S4 at a more reasonable price. If the car I wanted was under $60k at the time I was looking I might have put more effort into negotiating but it was so far out of the ballpark of an equally equipped F30 that it wasn't an option. It does appear that Audi has adjusted to be more competitive.
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01-23-2013, 07:25 AM | #65 | |
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Now you get audi drive select when you order the sports differential at 1.2k. The adaptive suspension is an additional 1.2k which requires the differential. In fact, many of the bare bones offerings have simply 6MT and sports differential bringing the price just south of 50k msrp. Most of the other options are luxury in function with the exception of 19" rims.
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01-24-2013, 06:43 PM | #66 |
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My S4 and 335xi
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