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A6 (C7 Platform) Discussion Discussion forum for the C7 Audi A6 produced from 2011

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Old 01-09-2014, 04:13 PM   #1
q5q7
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Default Lets talk about quattro

so the design of quattro makes some Audi nose heavy, A6 included.


why can't they move the engine/transmission backward OR move the front wheels forward a little and make the shaft driving the front wheels longer? I am trying to educate myself and also those who tells me my Audi is a nose heavy car.

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Old 01-09-2014, 04:21 PM   #2
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I believe it's because the transfer case is built into the transmission, so placing the power train further back means less cabin space and a very large transmission tunnel. Also, their platforms are made for both transverse and longitudinal engine placement, so placing more space between the axle and the firewall might inhibit the design.
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Old 01-09-2014, 05:39 PM   #3
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Quote:
Originally Posted by q5q7 View Post
why can't they move the engine/transmission backward OR move the front wheels forward a little and make the shaft driving the front wheels longer? I am trying to educate myself and also those who tells me my Audi is a nose heavy car.
The Audi front half shafts come out of the transmission. They have to be a straight shot to reduce stress on the CV joints. If the transmission was moved to the rear, the half shafts would have to be at a greater angle to join to the front wheels. That would add more load to the CV joints and they would fail at a higher rate than they do now.

Four wheel drive trucks have a front and rear differential, a transfer case and two drive shafts to send power to the wheels. The additional equipment adds weight and places the engine higher.

Audi's engine placement is a compromise to achieve a lower center of gravity. They also make the engines shorter and lighter to reduce the weight in the front.
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Old 01-09-2014, 10:12 PM   #4
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One of the improvements from the C6 to C7 A6 was moving the entire engine/tranny rearward a bit, not that anyone would notice it looking at the long front overhang on the C7's. Also, the A6 is set up only for longitudinal engines. Other Audis (A3 and TT here in the States for example) have transverse engines that take up less room front to rear.
I firmly believe that the longitudinal orientation of the A6ís engines is one of the reasons every cheapo Japanese rental I get seems to idle more smoothly than my A6. Back in the 1970ís when automakers started moving to FWD and transverse engines in their lower end models a major reason was less vibration transmitted to the interior (not necessarily NVH, since they still made tinny sounds). When I drive my brotherís Honda Fit I donít feel anything in terms of vibration from the engine, certainly much less than from any of my last 4 Audiís since 2005.
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Old 01-10-2014, 02:45 AM   #5
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Quote:
Originally Posted by irenesbob View Post
I firmly believe that the longitudinal orientation of the A6ís engines is one of the reasons every cheapo Japanese rental I get seems to idle more smoothly than my A6. Back in the 1970ís when automakers started moving to FWD and transverse engines in their lower end models a major reason was less vibration transmitted to the interior (not necessarily NVH, since they still made tinny sounds). When I drive my brotherís Honda Fit I donít feel anything in terms of vibration from the engine, certainly much less than from any of my last 4 Audiís since 2005.
Shocked to hear this I feel my At is silky smooth I never know the car is running.
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Old 01-10-2014, 08:06 AM   #6
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From a post above: "I firmly believe that the longitudinal orientation of the A6ís engines is one of the reasons every cheapo Japanese rental I get seems to idle more smoothly than my A6."

Interesting-- I also was surprised while sitting at a stop-light I could notice a small vibration in my 3.0 A6. I wonder if others have noticed this as well?
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Old 01-10-2014, 08:53 AM   #7
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I never noticed that my A6 didn't idle smoothly until one day when I threw a hoodie in the passenger seat. I noticed at stoplights that edges of it would vibrate.
I can't feel it or hear it, but if you have something that moves easily, you can see it.
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Old 01-10-2014, 09:14 AM   #8
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A somewhat related discussion on a VW blog:
http://www.luxury4play.com/automotiv...al-engine.html
A bit of history: I am 72 and I remember many years ago when (primarily Japanese) cars started going FWD and having transverse engine packaging.
One of the advantages was economy of assembly and a resulting negative was difficulty in repair as the engine bay became jammed with engine, transmission, everything all in a smaller space. Prior to that most straight fours had huge amounts of space around the engine itself and the tranny was well back almost under the front of the cabin Ė easy to work on.
As is pointed out in the link I provided, there are torsion forces generated as the engine accelerates and decelerates. When the engine and tranny are longitudinally oriented (front to rear) as the engine torques, it shakes (for lack of a better word) from left to right, sort of. The force of this torsion-ing is spread out over the width of the front sub frame Ė limited to perhaps 60Ē to 75Ē. When the engine/tranny are transversely mounted (side to side) the same torsion forces are spread out over the entire front to rear length of the car. With all that steel to absorb the torsion/torqueing/twisting power, so less is felt in the driverís seat.
I recall my brother had a 1967 GTO stick shift. When in neutral and gunning the engine the entire car would lift an inch or two on one side, then settle and repeat as he played with the throttle. The torsion forces were that powerful. With a lot of today's cars with transverse engines, even the powerful ones, blipping the gas at idle does not make the car move like that because the forces are being absorbed and dissipated over the longer front to rear dimension. Anyway, that is my two cents. That's my stroy and I'm sticking to it
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Old 01-10-2014, 09:29 AM   #9
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Perhaps it would be better to get back to Quattro-Cause-Nose Heavy topic.

Would that be safe to say that most Quattro Audis are built on front wheel drive platform therefore understeer/nose heavy characteristics are inevitable regardless of giving Quattro drivetrain 60/40 torque distribution where 60% sent to rear and 40% to front, respectively?

BMW builds 5 series on rear wheel drive platform and giving it all wheel drive powertrain does not necessary make it nose heavy, now does it?
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Old 01-10-2014, 09:31 AM   #10
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Actually, I had a Jetta TDI and it had gobs of torque. However, on the highway, it had a rocking chair effect because of the transverse mount. Essentially, on long drives, you'd get sleepy because the torque would rock the car fore and aft, like a rocking chair. Torque steer was minimal because of the e-diff, but there was some definite squat and dive going on thanks to the transverse engine.

Also, the direction of the pistons and rotation of the flywheel in a transverse would be smoother, but there are some very smooth BMW engines out there. When I compared the A6 to the E-class and 5-series, I got a definite hint that Audi was letting the engine introduce itself into the cabin as a way to make the car sportier. I know that ever since Lexus came out, BMW and MB have worked harder to isolate the engine from the rest of the car, essentially creating tombs. This must explain why BMW now pipes in engine noise through the stereo system on the M5. This is where the A6 comes across to me as honest... in the 90's, a 7-series had some vibrations but the 3.5L inline 6 was mighty smooth. That slight engine creep into the cabin was the sporting credentials the BMW's used to have - and now Audi has it. Strictly my opinion, of course, but definitely fact because I say so
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Old 01-10-2014, 09:31 AM
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