John:

If I am not mistaken you were running pump gas in the cool morning and race gas in the hot afternoon. That might explain why your times didn't change. The DA was worse in the afternoon and the extra power generated by the race gas may have compensated for it. In either case your car was running like a champ that day. Still can't believe you had a 60 foot time in the 1.4's on one run. Just fantastic.

 

What Scott said, but to add to that the car needs time to adjust to the map/octane as well.

 

So then a back to back comparison between different tunes isn't really going to answer any questions, correct? Seems like a few members have attempted this with no luck. This may explain why

 

To be fair to both sides, that is my opinion, correct. The only way I could see is maybe doing a track rental, running say 10 or more runs with each, cool down period, load new tune, run 10 or more times. Grab as much data as possible and draw your own conclusion. Who really is going to go through the trouble? (I actually have done this with my watercraft business and it was a pain in the ***! You have to think of every variable down to adding gas, going both directions or lanes, etc. I'm a sucker for data so every variable counts. Even then people will argue though. Lose/lose)
I don't think there is a right or wrong answer and it ultimately is any consumers call on what they feel is the best value for their money and the best product for their use.
We all want to see our tuners/vendors do well for obvious reasons. If my tuner(s) do well, the amazing support I get will continue. My car will win. They will also not abandon my platform anytime soon. Plus, a few of the guys are great dudes on a personal level so it makes you want to see them succeed as well.
My $0.02

 

Well hopefully you had fun! 190.7 is a great time none the less.

I agree it is not apples to apples for sure, glad you were able to pick up some speed though.

Thanks Shifter,

Mitch

 

Vbox data is in! and it's very interesting to say the least.

I graphed the GIAC Stage 2+ pump tune run (red) against the Cobb Stage 3 100 octane tune (blue).

in the end, the Cobb tune won the mile by 85 feet or almost 6 car lengths.

you can clearly see the wheel slippage I got when it dropped into second gear on the GIAC run, which cost speed/time. my best estimate looking at the graph is that cost about 35 feet or 2.5 car lengths.

however, before that, you can see Cobb got off the line quicker as it was already pulling away before that.

however, the most interesting part I see is that you after recovering from the wheel spin, you can see GIAC closing the gap against the Cobb line the entire rest of the way.

what does this mean? it's clear the increased Cobb torque launches quicker, but perhaps this is showing the GIAC tune is stronger on the higher end?

unfortunately, it's only one run on each and I'm really bummed I wasn't running the GIAC race tune, so it doesn't mean a ton, but it was interesting to me nonetheless.

GIAC Stage 2+ Pump vs Cobb Stage 3 100 oct
¼ mi – 12.19@129.44 vs 11.41@132.36
½ mi – 18.39@159.89 vs 17.47@162.25
1mi – 28.62@188.8 vs 27.57@191.08

the second graph is the Cobb Stage 3 tune against the custom tune Mitch sent over.

you can clearly see the custom tune made a significant difference in time, but not really in speed. that seems weird to me since if I get there quicker, you think it should be faster also. perhaps the slight decrease in tail wind on the second run is what really hampered the speed.

¼ mi – 11.4@132.35 vs 11.25@132.69
½ mi – 17.47@162.25 vs 17.32@161.95
1 mi – 27.57@191.08 vs 27.44@190.43

 

Looks like you put a lot of work into it. Sorry the conditions and logistics got so difficult. The car looks strong though

 

No, it's the acceleration that matters. The car quits accelerating at some point but if it accelerates to the max speed sooner, it will get to the end quicker, that is why torque is important but you need lot's of HP to maintain the speed once there is zero acceleration or close to it as terminal speed is approached. Plots of speed vs time are acceleration, that is dv/dt. The blue curve is always at a higher speed and it gets to the the higher speed sooner which means it's covering more distance than the red curve sooner. That means the blue curve will cover the same distance in less time even though the terminal speeds may be equal. The Cobb tune is accelerating more than the GIAC tune and so it's going to be quicker.

 

so I've had the Cobb Stage 3 tune on my car for the last month.

I got several different tweaks from Mitch, who is always really responsive.

that said, I feel like the GIAC 2+ tune was much more drivable on a day to day basis. it felt like stock, just faster.

the Cobb tune jumps the boost really rapidly from about 6PSI to 14PSI which causes you to launch when you just press the accelerator down a little more. so then you let off the accelerator a little and it drops back down and you lose acceleration really fast and it just feels really jerky. Mitch was able to dial that down some, but it's still jumpy, which doesn't make for smooth daily driving, which is what I use the car for 99% of the time.

I'm going to get the new GIAC 2+ tune put back on my car soon and drive with it for a while to see if I'm imagining things, but I don't remember it doing anything like that.

I also want to compare the SOP benchmarks on launch and overall acceleration. at this point I've been driving the Cobb so long, I can't really remember the GIAC enough to compare other than the boost issue.

 

Very interesting. I noticed a similar drivability issue on my Cobb Stage 2 tune as well. When I'm cruising on the highway in 7th gear at 85mph, the throttle is very difficult to modulate and the boost would oscillate back and forth between 6psi to 12psi sometimes. Put simply, if I'm feathering the throttle to get some mild acceleration, the power comes on too strong and I need to back off the throttle, but the power goes down too much if I back off 100%. We need a new update please!

 

I noticed the turbo boost on/off switch like effect in my friend's 991 TTS when it had the off the shelf Cobb stage 2 tune. But when he was reflashed with the custom stage 2 file on John Morgan's car the jumpiness got much better he said. John Morgan's 991 TT with the Cobb stage 2 custom file did not seem very jumpy and it was much faster than the OTS Cobb stage 2.

 

So I take it you guys are driving the car in normal mode using automatic shifting? I never go to 7th gear, even on the highway, it doesn't save any gas. I always keep the revs above 2500 by driving in manual mode with sport and so I never experience the things described here. I guess if you want to drive the car like a regular DD then you should probably go with Stage 1? I think Americanmade says his drives great at Stage 1. The beauty of the AP is how easy it is to change the map.

Just a thought.

 

Nope, I always drive my car in manual in Sport Mode. I don't think I have ever driven my car in Normal mode automatic.

 

You will see a big jump in power with the new public release version of the GIAC Stage 2+ tune from the early version of the GIAC Stage 2+ that was on you car. It is still OEM smooth. But for all out speed I think the Cobb Stage 3 is a bit faster from what we have seen so far.

 

Oh yes, I see you are driving on the highway in 7th gear which I don't do. I have found 7th gear to be unresponsive no matter what tune or not I have on the car. It was unresponsive when I bought the car on the way back from Dallas before I ever got a tune so I just stayed away from it. I don't think that has to do with the tune, I think it has to do with that being nothing more than a cruising gear.