A418t81

I decided to throw my car on the dyno because A: I wanted to maximize my setup on the dyno and B: I was curious what my car was making in order to run a 5.9 60-130. I guessed around 630 whp based on what other 997TTs have made on this dyno and what their 60-130 times were showing. I also wanted to correct a few drivability issues I've had since swapping over to the ID1k injectors about a year ago. Dzenno and Mitch @ Cobb have been exemplary to work with, but a good buddy of mine Rob Harper of robtuned.com who happens to do all of the high end GTR tuning for Topspeed (a local tuning shop and GTR mecca), as well as multiple other well known GT-R shops, recently bought another good friend's 997 with Proto 63.5mm turbos and ID1300s. Rob is responsible for all the tuning on this car as well, and on E85 it makes 700 whp and 680 wtq (torque is intentionally limited, roughly 19 psi climbing to 24 by redline). He's spent over 20 hours in drivability calibration on this car since making it his, and I was hoping that his effort in this area would translate over to my car. In addition, I've driven this car and it is a damn BULLET (there is a 100 whp delta between my car and his at 6800 rpm!)...it makes my car feel slow.

Before starting the new tuning, I swapped in a new Bosch 3 bar MAP sensor, so I could actually see what peak boost was. We started street tuning with an E85 base map that had all of his drivability changes as well as appropriately scaled for the 3 bar map sensor. Immediately I noticed a huge improvement in the drivability. There was always a subtle hesitation when going from idle or decel fuel cut back into load. This is totally resolved. Lean backfires into the intake while warm was also history. Finally, it was faster and smoother. We made a couple more small revisions, and then decided to call it it a day and throw it on the dyno the next morning.

To get a baseline, and to see what it actually takes to push a 997 coupe to a 5.9, we loaded the old map in. As you can see, the car is well tuned and puts down great numbers with very smooth curves. This map is not pushing the car at all on E85. Timing and boost are very conservative and torque is well within the limitations of the rods. The power plateau is very, very broad as well with excellent area under the curve and confirms my butt dyno that power did not fall off any significant amount as redline approached.



Next we loaded up Rob's new street tuned map, and made a few more pulls making small changes to both timing and boost. Fueling was cleaned up a touch as well. As you can see, the car was picking up great power while keeping things safe (peak of 23 psi or so). I wanted to limit torque to around 680 wtq or so, but even with another 3-4 deg pulled out in peak torque regions versus the map I was running earlier, the car continued to make nearly 700 wtq...oh well Final numbers as you can see are 656 whp / 693 wtq! It actually made over 660 whp, but the additional boost pressure wasn't worth the power, so we backed it back down.



One more small change was made, and then this happened. The car became very laggy, and power fell off hard there-after. This was literally one pull after everything looked so beautiful. Other than the power, the car ran and idled completely normal. No noises or smoke. We tried flashing back to older maps and a lot of other tricks....nothing changed



The car felt gutless until it finally spooled up, then it hit hard and fell right back down again. WTH. We thought about boost leaks, smoke tested fine. Thought about cat failure at these flow rates, pulled the exhaust and it was fine. The whole time in the back of my mind I was wondering if the dreaded Variocam collar slip had reared it's ugly head. The car had no CEL and idled fine, zero misfires either. We didn't think to log cam deviation during the pulls, but decided to hook up the durametric for potential codes anyway. There it was, bank 2 intake cam deviation, but no CEL yet.
This is looking like it is going to be roughly a $5k fix. You no longer have to buy new intake cams (at $2k a pop!) as Topspeed (and I'm sure others) have a machine shop that can correct and pin your spun cam shafts, which brings the price from $8-10k down to about half.

The warning is that this appears to be an up and coming "common failure" as the 07s (most prone to this) continue to end up in the mileage range where this occurs most commonly (35-50k). Cars making a lot of torque are also prone to it. TopSpeed as well as multiple other regional shops have seen a large uptick in the number of stock and modified cars coming in with this issue.

Anyway, you pay to play, and that's fine. I'm looking forward to getting the car back soon and setting some new 60-130 records

Oh, and one final pic of the 997 with my new toy and my brother's TA viper

changster123

Do you know if this variocam probem will happen on the 997.2's as well?

Great looking graph. Rob is the man. I'm having him tune my 997.2 as well. Rob tunes many of my friend's high power GTR's and if it can be worked out could tune my high power GTR as well.

A418t81

It does not happen on the 9A1. Completely different motor and architecture. Mezgers may have more character, but they also have a lot more endemic issues which are annoying to fix. The DFI motors appear to not really have any kind of common issue across the board like the GT1 based motors do. Once I fix the cams, I will have about $13k in maintenance and basic/preventative repairs over the 2 years I've owned this car (and the cam is the only failure the car has had, all the rest has been preventative).

Rob did do a really great job, and I'm sure you will enjoy your new-found power as well

Ibanezgod

looks awesome, just bought that same bird house for my sister

CincyScott

I've had lots of PM's and other experience with the cam issues, and you're certainly not alone. It's definitely not mileage related, and it can happen to any of the 997.1's, not just the 2007's. It also doesn't seem to be rev related. Mine happened when loafing in stop and go traffic, and others have happened when not going ***** out either. Just one of those things of "when it's your time, it's your time."

I'm glad to hear you're pinning them, that's the only long term fix. Others have had good luck with it going away on its own, and many may never have the problem at all. The garbage propagated by some dealers that the new cams they are installing are different somehow is just not true. We had brand new cams next to my old ones and they are most certainly the same design.

Good luck,

CincyScott

dup

A418t81

Yea, pinning them is the only solution that I am happy with. I want it to be over and done with. I'm also taking this opportunity to swap in a BBi slave and rid the car of another common failure point. Finally, throwing in some torque solutions engine mounts to help keep everything in place when making 700 wtq. I've noticed a positive improvement in another car making even more power over my factory mounts, and there was no extra vibration.