[Hoooper]

Can you tell that it resulted in better times? More power in 3rd gear isn't necessarily faster than less in second, due to gearing. In this case I don't doubt it but do you have a time difference?

[Puerto Rican 335d]

TDi were you shifting or was the gearbox on DS mode. Anyhow WOW!! sounds impressive and awesome, you need to do the 1/2 run Im guessing close 150 mph on the 1/2 mile cuase I did 129.68 only with RENNtech flash and OEM IC

[DbLog]

TDI,
Congrats!! Glad all your hard work is paying off

[TDIwyse]

Originally Posted by Hoooper

Can you tell that it resulted in better times? More power in 3rd gear isn't necessarily faster than less in second, due to gearing. In this case I don't doubt it but do you have a time difference?

Here's some old Gtech data I found that I re-studied before this weekend. You need to account for wind resistance increasing as the speed goes up. This and other data I had taken convinced me to shift out of 2nd early.

[Puerto Rican 335d]

I thought you were always pulling out on 2nd gear?

[TDIwyse]

Originally Posted by Puerto Rican 335d

I thought you were always pulling out on 2nd gear?

correct. those plots are with 2nd gear launches.

[Hoooper]

I must not be reading those charts right, it looks like you were pulling more Gs right up to the shift point than after. The way im looking at it even if you factor in wind resistance it looks like shifting anywhere before at least 4k would hurt you. Do you still have the Gtech? A comparison of each using the Gtech would make it obvious

[TDIwyse]

Originally Posted by Hoooper

I must not be reading those charts right, it looks like you were pulling more Gs right up to the shift point than after. The way im looking at it even if you factor in wind resistance it looks like shifting anywhere before at least 4k would hurt you. Do you still have the Gtech? A comparison of each using the Gtech would make it obvious

Well, let's go over it together and double check my thought process. A little more description on the data. All 4 of these are in DS mode and letting the car shift itself, and with my old PSS tires at different combinations of pressure and DCT vs "no nannies". The comments with lines tell you if DCT is on and where it kicked in, or "no nannies" and rpm flare when traction broke. Only the black line (all nannies off and no slippage) gave a good launch without slippage or pwr reduction from traction control. Let's focus on that one.

So at ~3.4 seconds the car is still in 2nd gear and the G's have fallen to < 0.4. The car shifts out of 2nd at ~ 3.7 sec (see the rpm drop on the other plot). In 3rd gear the G's are > 0.4 (even with more wind loss) all the way out to ~5.5 seconds. Would this not indicate better acceleration (more G's) by shifting out of 2nd a bit before the car does by itself?

Now, this data is specific to my car, so it may not apply to others.

[Hoooper]

it looks to me like if you initiate the shift at 4000 RPM and the shift initiates within 0.5s you would come out ahead. I guess this depends on how long the wait is between telling it to shift and when it actually starts shifting. Looks like based on the Gs you would want the shift to be happening before 4400 RPM or maybe a bit earlier. By that I mean if you watched the tach it would peak at 4400 RPM as opposed to the 4750 it appears to hit. Best bet would probably be to take two readings, one in 2nd all the way to redline, and then another starting in 3rd somewhere around 2500 (early enough to get the turbo fully spooled before too deep into the gear) and compare the two G charts. You would want to tell it to shift just enough before the crossover point so that you put yourself into the next gear at a point in the G chart that isnt lower than you would have been holding the gear. Tough to tell off of just those charts since there isnt enough range on the 3rd gear chart

[TDIwyse]

Originally Posted by Hoooper

...Best bet would probably be to take two readings, one in 2nd all the way to redline, and then another starting in 3rd somewhere around 2500 (early enough to get the turbo fully spooled before too deep into the gear) and compare the two G charts. You would want to tell it to shift just enough before the crossover point so that you put yourself into the next gear at a point in the G chart that isnt lower than you would have been holding the gear. Tough to tell off of just those charts since there isnt enough range on the 3rd gear chart

I don't have access to that data now, but I do have it (most of my on-road testing with the Gtech and the Android Torque app are in 3rd gear). 3rd gear has more G's than 2nd close to where you are talking.

Basically with my drag tires on I looked for what the speedometer said my speed was in 3rd gear at ~3100 rpm's and tried to anticipate the shift out of 2nd a bit before that speed. Based on the improved 1/8th mile speed compared to last weeks pulls, where I let the car shift, it seemed to be a fruitful insight.