Okay, I'm back with an update on my Diablo inTune i2 for my 2014 CTS4 3.6!
It's been a while, but that's because I was waiting for Diablo to setup my transmission tune. The engine tune worked right away, but it kept saying "Unknown TCM" so I had to keep sending files to a person at Diablo while he tried to add support for my specific transmission module. Finally a few days ago, he fixed me up and the tune went through.
First thing I did, months ago now, was to install the 91 octane tune with no additional settings changes. I was running 89 octane gas during this period, because in Michigan we have 87, 89, and 93 octane available at most places. It was definitely a noticeable boost over the stock engine tuning. I heard no knocks or anything bad, so I went ahead with the next one, the 93 tune, and started running 93 gas. I am still running this tune and 93 gas. It gives another noticeable boost! It is always pretty good off the start, but you notice it when the RPMs get above 3000 and the horses really kick in. I am pushed farther into the back of my seat until the next shift comes. And the extra power is even better when I switch to manual shifting. It feels like there is less delay from hitting the pedal to moving when it is in manual mode.
Also, I put the car into Sport mode when I feel like accelerating fast. It makes a big difference. In tour mode, it still drives just like stock, there are no downsides, if you know what I am saying. The engine tune is just great. I'm sure it is making a dent in my fuel economy, but I have not really measured it or done a before and after of my economy.
So I finally got the transmission tune, and I chose the Firm tune, as opposed to the Hard tune. I haven't had that much time with it yet, and I've been stuck on <45 MPH roads, but here's what I noticed so far. It seems to put the transmission in a better place to have quicker starts. Like maybe the default tune is set to apply some torque to the wheels when you just start, but with the tune it really opens up the gear right away. That's what it feels like, anyway. Also, I swear the car cruises easier. My old '92 Seville would do this: once you get up to 45 or above, you can let off the gas and the car keep rolling smoothly. Well most modern cars that I've driven seem to keep the gear active a bit, but it slows you down. It feels like that, where when I let off the gas the car will roll for longer than before. That is a really nice feeling. Other than that, I haven't tested the transmission tune enough to say any more.
I'm very happy with the tunes! The Diablo unit itself could be a bit faster though; it takes a long time to boot up. But since you will only do it a few times, it's not a deal-breaker. I recommend this to anyone looking for more power and an overall sportier feel to their CTS or ATS!
-Matt