swdotc

Hi
What rpm do you guys shift from 1st to 2nd gear in hard acceleration?
I am trying to find an optimal up-shifting point at 1st gear where it minimizes that "jerk" moment and still makes the quickest 0-60.
It seems 7000 rpm just before the redline is the quickest 0-60 but still I experience some shift shock.
I am seeking some racing experts advice!

helix139

If you've got it in dynamic and are driving hard, you're going to get some shift shock. If you want smooth shifts, put it in comfort, Let off the gas gradually rather than suddenly before disengaging the clutch, and apply a little gas while re-engaging the clutch. Lower RPMs are better as the revs won't fall as fast.

NWS4Guy

If you are stock, you might as well shift around 5,500 to 6K, that is where boost and HP/TQ will be bleeding off, so this will keep you in the meat of the powerband.

need_TQM

I've heard this kind of reasoning a lot before and I'm a bit confused by it. Can you explain?

According to the Audiusa website 2nd gear is 2.158 where 1st is 3.667. To get the same acceleration from the car you have to have about 70% more torque when you shift down. At no (reasonable) point in the 3.0T curve is redline 70% lower.

Shouldn't redline 1-2 shifts result in the fastest 0-60 time?

NWS4Guy

The dashed lines are stock HP (red) and TQ (white).




If you shift at redline, you will go from 7K in 1st down to just over 4K in 2nd. That gives you about 1 to 1.4K of RPM's in the power before it starts giving out. If you take a stock car and floor it throught the gears, you might notice it giving up a little after 5K, if you drive one back to back with an APR car, you will suddenly notice that it REALLY obviously runs out of steam aroudn 5K and wonder how you didn't notice this before.

The video is a stock vs APR stage 1 car. You will notice the pull at the high RPM's on the tuned car.

http://www.youtube.com/watch?v=WMZvP8u-0do

need_TQM

No doubt it falls off. But what I'm not understanding is this : in the end what actually accelerates the car is torque*gear ratio*(other stuff which is fixed - tire diameter/weight...). If your goal is to get to 60 the quickest - the lower torque even at 7100 rpm * first gear ratio is still better than torque at any point on that power curve * 2nd gear ratio (you would need 348ft-lbs to beat the 205 at 7100 for a stock ECU). At some point at higher gears this probably doesn't hold - but you reach 60 in 2nd...

What am I missing?

swdotc

The more I read, the more I get confused.(--_--);;;
Please someone explains it in easier way

4SIDUA

WOW! 327HP at wheel!
Considering transmission loss around 15-20%, the stock engine output is 380-400hp

http://wiki.answers.com/Q/How_do_you...ine_Horsepower

Any reason why Audi down played the engine numbers?

need_TQM

Imagine an engine that produced the same torque at any RPM - to make things easy let's say it produces 100 ft-lbs. Using 1st gear in the 6MT would give you 367 ft-lbs at the transmission output shaft. Using 2nd gear would give you 216 ft-lbs.

I'd think you would want to use that highest gear ratio as long as the engine torque doesn't fall off so much that 2nd gear * engine torque is higher.

Now look at the curves APR produced that NWS4Guy posted, for the stock 3.0T it looks like torque is down to about 205 at 7100 rpm. 205*3.667 = about 751 at the transmission output shaft. To beat that using the 2nd gear ratio (2.158) you would need 348 ft-lbs (751/2.158=348) available - but peak torque is "only" 327.

I think the fastest 0-60 will mean shifting at redline, even though torque is dropping off and you are not in the "power band" - the gearing makes up for it.

Unless I've got this wrong ... NWS4Guy?

2nd to 3rd is a different story - the closer gearing makes it overlap before redline - in 2nd gear at 7100 the 205 ft-lbs would be 442 at the trans output (205*2.158). You need 291 ft-lbs to match that in 3rd.

Do I have this wrong?

LeadToRome

The most common theory revolves around the S5 and its 340 HP 4.2L V8, asking essentially who would buy a car with two less doors that puts out less horsepower and burns more gas at the same time. It seems like a reasonable question.