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The "issue" with the Cobb tune is that when you do a pull or are on track you don't really use the very large gains in torque low in the rev range. In most performance situations (and the gearing reflects this) its what is happening above ~ 4000RPM.
The huge amount of low - mid-range torque would be great in a rally car
So I'm not really surprised on a road pull its even stephens.
Either way its good to see good gains and the engines appear to be holding up well too = good
The gts is a beast even stock. I wanna see how my car pulls against steve’s powerkit as our dyno plots are basically overlays.
Interestingly, I was doing some street pulls with the Cobb T and my giac tuned T today (great drive btw) and its basically dead even, despite cobb slaying everyone in the dyno. Its puzzling. Gears 2-3 are too close to tell. Whoever got the jump was gone. We didnt try 4th gear because its too fast for the street but Im surprised how well the giac tune performs with such low relative boost. We are both running kick *** tires now so traction was a non issue. .
You make less torque down low, but with your headers and high flow cats, you're spooling up quicker. This is from the MotoIQ test of the Vektor headers. With headers and high flow cats, the reduction in spool-up time should be even greater.
The second to third (the go to gear) change (~7500rpm in second goes to ~5250rpm in third) is at about 5,250RPM and if you look at the graphs above...........there is very little meaningful difference between the GIAC and Cobb tune
You make less torque down low, but with your headers and high flow cats, you're spooling up quicker. This is from the MotoIQ test of the Vektor headers. With headers and high flow cats, the reduction in spool-up time should be even greater.
Originally Posted by groundhog
The second to third (the go to gear) change (~7500rpm in second goes to ~5250rpm in third) is at about 5,250RPM and if you look at the graphs above...........there is very little meaningful difference between the GIAC and Cobb tune
Thanks guys this could explain alot. So looks like the headers/cats actually make a real difference on the street. Several times the cobb guy felt like my car “jumped” as soon as we hit the gas. I will say the throttle response with my current setup is ludicrous with the small turbos. You can also see an early dip in power in the S with powerkit and cat delete. Steve, you need headers man. Lol
The car already feels like a beast but you can feel the tabletop tq curve in 4th gear and it doesnt really “set itself on fire” until high revs. Especially since 4th gear isnt typically engaged at very high rpm due to the tall gearing. This plateau is less noticeable in 3rd gear, and boost is achieved like a dagger in 2nd. Hoping a revised giac stage 2 map will take advantage of my current setup without a huge gain in tq. Im convinced just letting the turbos run free to 19 psi by removing the mid range boost limit will make a noticeable difference and carry alot of momentum in a large part of the power band. Waiting for giac to weigh in on this. Maybe they already tried it and the car wasnt happy. Who knows? It would really elevate the performance by allowing the car to pull harder at high speeds (which is where supercars tend to excel).
Here is a dyno graph the shop gave me of the Carrera T's with COBB and GIAC tunes, and ny C2S with X51 PowerKit and cat delete that is called a "Base".
My curves are the Red and Blue 'solid' lines.
The Cobb tune on the T, with the 'longer dashed' lines, is impressive.
I in fact both tuned T's are impressive. Makes me want a COBB, with its additional AccessPort functions...
So drove my 991.2 c4s with just the stage 1 tune and the Fabspeed sport cats again today and just wow. Also, PDK feels even better now, which is funny as I don't think that's being adjusted...maybe it just feels sharper with the power. The car runs like nothing else honestly...its a 991.2 turbo S with sound and more spritely handling now, and I just came from one!
Does the Cobb AccessPort system allow the owner to modify the tune in any way? The big jump in torque at low rpm, compared with the GIAC suggests a big boost increase at those engine speeds. In fact, since the torque is even greater than the X51 curve at those rpms, it suggests to me it might be risky for the engine.
I would be more comfortable with the tune, if I could limit the boost to the 18.25 psi that the X51 engine uses. Since the base engine is the same across all of these 991.2 Carreras, that would seem to be a safe and conservative option, while still offering a substantial power and torque increase in a base car.
Does the Cobb AccessPort system allow the owner to modify the tune in any way? The big jump in torque at low rpm, compared with the GIAC suggests a big boost increase at those engine speeds. In fact, since the torque is even greater than the X51 curve at those rpms, it suggests to me it might be risky for the engine.
I would be more comfortable with the tune, if I could limit the boost to the 18.25 psi that the X51 engine uses. Since the base engine is the same across all of these 991.2 Carreras, that would seem to be a safe and conservative option, while still offering a substantial power and torque increase in a base car.
Giac stage 1 is basically same as the gts map on my car, based on my logs. But I also have headers and sport cats and might be hitting tq limits with less boost. It appears safer nonetheless. I believe giac max target is 20 psi, whereas I have seen cobb logs with boost as high as 24 psi prior to cutting power completely near redline.
As far as I know you cannot self tune with the accessport, just switch maps and log. Both of these features are really nice
05-27-2019, 11:33 PM
