dockt

Sorry if this has been debated before but looks like there's new info out re: APR's ECU upgrade for the 2.0T. For real-world, day-day, but spirited driving, which is the better value/car -- chipped A4 or S4?

Points:
- The ECU upgrade gives impressive gains in hp/torque; torque is now on par w/ the stock 3.0T in the new S4, and I'll guess that the A4 weighs less. Again, for daily driving, how much does the hp difference matter?
- In terms of cosmetics, the S-line A4 looks exactly the same as the S4, save for the exhaust treatment; wheels will even be the same. Inside, the S4 seats look sweeter but the S-line seats are no joke either. I believe steering wheels are the same.
- The S4 will likely cost towards $10k more than an S-line A4; on paper
- The S4 has a new sport differential, but how much difference will it make on the streets above quattro?
- S-tronic in the S4; A4's tip is much slower.
- '10 A4 will have rear LEDs as well (fwiw).

I'm not saying that the A4 is better than the S4 -- these types of debates go on and on over in the BMW boards (335 vs. M3). Just wondering if I could afford an S4, would it be "smarter" to get the S-line A4 chipped?

Bada Bing

I had a chance to drive the 3.0T A6 (300-hp. 310 lb-ft) at the Audi Driving Experience this past weekend. That's a sweet engine. There is no way the 2.0T can match the smoothness and linear power delivery of a supercharged V6.

Mobilehavoc

You're looking at just pure max torque numbers. Did you see the dyno readings? The torque with APR ECU flash is above 300lb/ft only between 2000-3000 RPM after which it falls pretty steeply. I'd guess even a straight inline V6 would have smoother power delivery. If you can afford an S4, why wouldn't you get one?

Mobilehavoc

Sorry forgot to add, notice that on stock B8 A4 2.0T the power curve is pretty flat until about 4400rpm which I believe adds to the smooth and fun day-to-day driving. I know how the B8 A4 feels after you get to 5000rpm and the loss of power is noticeable so I would imagine you'd notice it on a chipped A4 after 3000rpm.

I guess maybe just shift very very early!!

Bada Bing

I am a little surprised that the big gain with the APR chip is in peak torque, not horsepower. The hp gain appears to be about 25 on the average across the rpm band. Also, the torque drop after 3000 rpm with the APR chip will make the car feel like the stock 2.0T after 5000 rpm (out of breath). I am sure the S4 3.0T will have a more linear and natural looking torque curve. But these power curves are only half the battle. The V6 will sound and feel much better than a chipped 2.0T.

need_TQM

I got curious as to where the additional torque/gear ratio cross over would be...

The gear ratios of the Tip Trans are lower by 44% (1st to 2nd), then 35% (2-3), then 25% (3-4), and then 24% (4-5) so until you lose over 24% of engine torque, you are better off not shifting. Even then, the gear change has to put you in a RPM range where the engine produces at least 24% higher torque to get any advantage.

For this engine+transmission combination, the torque*gear ratio product (which determines how much acceleration you get) only overlaps right out near redline (6100+ for 2/3 shift, and 5600+ for 3/4, and 5600+ for 4/5 for the stock ECU, and it looks like about 6200, 5800, 5800 for APR). Only where these overlap would early downshifting be beneficial. So shifting "very very early" isn't going to help. "A bit early" will, but it's also true for both APR's tune and the stock ECU.

The resulting acceleration from shifting to stay within that 2-3k RPM high torque (~300 ft-lbs) band will be worse than just letting the RPM climb to ~5800 before shifting.

Jacon

just get the chip and slap on a K04, then upgrade to a K04 program. Thats what I plan on doing

Mobilehavoc

Wow, can you translate that into something a bit more simple. I read it about 3 times and still don't quite get it.

need_TQM

Sorry... I'm not very good at explaining things, but I'll try...

In the end you really don't care about torque from the engine, you care about the acceleration it provides to the car. The acceleration is, in the end, a bunch of constant things multiplied by the engine torque multiplied by the gear ratio. 1st gear is obviously the highest (4.171 in this case) and gives the largest acceleration.
2nd gear is quite a bit lower -- 2.34, so you have to have a lot more engine torque to make up for the loss in gear ratio to give you the same acceleration. If the engine torque has fallen off (like the 2.0T does at high RPM) and the shift takes you back into a lot higher torque RPM band it might be beneficial, but...

For the 2.0T with the gear ratios Audi put in the tip you won't get better acceleration from the car by shifting very early -- best acceleration will be by shifting at redline for from 1-2, about 6100 RPM for 2-3, and ~5700 for 3-4 etc.

The 6MT is very similar -- slightly lower ratios for 1,2,3,4 about equal 5, and higher 6th) but the "cross-over" points are only about 100 RPM different -- still above 5500 RPM.

So... If you are doing 0-60 runs at WOT, the 2000-3000 RPM APR 300 ft-lb peak torque will only be seen once -- during the pass through it in 1st gear, since you wouldn't shift until > 5600 RPM and the shift would bring you back to an RPM > 3000 for the next gear. If you are cruising at some other speed in the 2000-3000 RPM range and nail the throttle, you will see higher acceleration than stock, but the trans will likely shift down to give you overall better acceleration and move the engine out of the 2000-3000 RPM range.

Did that make (more) sense?

Arin@APR

Get the S4... Do you have any idea how much HP we'll get out of that beast with just a stage 1 ecu upgrade?