Technically speaking, redline does not mean the optimal shift point but a maximum safe RPM. The best shift point is the RPM where the torque curve in one gear crosses the torque curve in the next gear or redline, whichever comes first. I haven't plotted the curves to see where they cross but would not be surprised if in some gears they cross before redline and therefore the optimum shift point would be lower than redline.So, if the turbo can't keep up at high rpms, why is the redline/shift-point around 6.5k? Wouldn't the car be faster with a shift-point that's before the power dive (like 5.7k)?
Those are 2 separate items. One is an assumption and one is a question.So, if the turbo can't keep up at high rpms, why is the redline/shift-point around 6.5k? Wouldn't the car be faster with a shift-point that's before the power dive (like 5.7k)?
Are there dyno's of the 2.0T holding its hp from 5500 to 6800? I thought they all show it dropping (tuned or not tuned).Those are 2 separate items. One is an assumption and one is a question.
What is the basis for saying the turbo can't keep up? It can hold the its HP from 5500 to 6800 rpm, so it definitely can flow more more air above 6000 rpm. With a tune it can run more boost at 6800 rpm than the turbo achieves under the factory tune at any rpm. It's just that as rpm increases TQ is falling. GM could have put a turbo on the car with less low end response and the same top end, and it would feel like its keeping up. Don't get me wrong, I'd like a bigger turbo, or at least a different compressor map biased towards the higher rpm. It's just that the car is designed for a lot of midrange TQ and to spool quickly at low rpms to overcome the fact there's only 2l of displacement to respond to heavy power demands.
As to the shift points, GM has them set at 6600 rpm and this is below redline. As HD described, the the torque can drop a lot on the top end before the next gear results in more TQ to the wheels. This is because the gear ratio are spaced around a 30% drop off. You'll feel a drop off in torque of 20%, so your butt dyno is correct that acceleration is slowing on the top end; its just not slower than the next gear. Also gear changes are violent events at WOT, so they feel bigger than they really are. The car is accelerating; then for part of second, the car isn't accelerating (or is barely accelerating) and then boom the car is back at full TQ or even slightly above due to a TQ spike of boost.
You mean like this?Are there dyno's of the 2.0T holding its hp from 5500 to 6800? I thought they all show it dropping (tuned or not tuned).
We're actually doing some consistency testing as I type this....I bought a Diablo tune, and it did pull much stronger in the top end than stock. However, I ended up only running the tune for a total of 1,500 miles. This tune was very in consistent in my car. Sometimes it would pull strong, other times the acceleration was lumpy, and about 50% of the time, the power was very diminished, almost as if the car had no turbo at all. I tried multiple different brands of gas with the same result. Who knows. The stock tune is very smooth in my car, but I do miss the extra power (when it worked). At some point, I might do the Vermont tuning kit with upgraded turbo internals, catless dp, intake, and tune. We'll see...