Kevin

I should get a GT2RS intercooler group buy going.. Jean you are correct about the price increase. Once the sales volume numbers go up Porsche raises the price!

Jean

Good idea if you can negotiate good price and enough stock from the suppliers. Tuners will buy stocks and prices will be pushed up, I saw this with my 997GT2RS, when I needed replacement ICs, price had doubled.

No I am using larger aftermarket ICs and meth, IIATs are good, but I will go back to stock coolers and meth next week, they work better for the track/circuit.

Kevin

What Meth kit are you using? Aquamist, Snow or Aim?

Jean

Its Snow Performance if I am not mistaken.

Pdtp#16

pepinozaur

Originally Posted by Kevin
I should get a GT2RS intercooler group buy going.. Jean you are correct about the price increase. Once the sales volume numbers go up Porsche raises the price!
Good idea if you can negotiate good price and enough stock from the suppliers. Tuners will buy stocks and prices will be pushed up, I saw this with my 997GT2RS, when I needed replacement ICs, price had doubled.

No I am using larger aftermarket ICs and meth, IIATs are good, but I will go back to stock coolers and meth next week, they work better for the track/circuit.

I have 3 comments here:

1. My 991.2TTS had way bigger top speed at the end of straight lines after upgrading to big ICs (same tune, quite same conditions) - maybe from 152mph to 157mph on average, I have no logging device, but from vbox and even harry laptimer I can clearly see that.
2. Speaking of regular oem Gt2RS coolers, the 991 Clubsport GT2RS is using even bigger ICs from the factory, so my guess is OEM coolers arent going to perform better than aftermarket.
3. If we do meth, should work even on stock coolers, as meth is so efficient, maybe you can keep the big IC and just add meth, just my opinion..

Jean

Bruce H.

I'd like to add some other considerations I need to learn more about on the TT platform before mapping out my own upgrades for road course tracking.

IATs can be lowered by doing modifications that improve the engine's volumetric efficiency, which in turn allows the turbos to run at higher efficiency, which means they provide their boost while generating less heat. Intercoolers designed with less resistance through their cores (less pressure drop) achieve that, as does improved flowing intercooler piping, throttle bodies, as well as the turbine sections of the turbo chargers. The design goals of the 991 Turbo were more for street use where shedding constant high IAT causing boost wasn't the important factor that it is for the 991 GT2 RS. So where the Turbo's IC's surely do a decent job for their intended use I would trust the factory's RS intercoolers to offer the best results under road course conditions over aftermarket offerings that provide dyno test data that is meaningless under road course use.

I already know that water/methanol injection directly into the intake ahead of the throttle body is by far the most effective way to lower IAT's, and likely so much so that the particular intercooler, intake pipes, TB and turbines used become less critical. But what I don't know is how restrictive some of those other components are at stock boost levels, and if replacing them provides enough benefit to warrant the effort and cost if using methanol injection. I suspect the use of methanol injection would not even require a change in tune, making it not only the most effective way to reduce IATs, but also among the simplest.

Bruce

Pdtp#16

Jean

Definitely, but improving VE of an engine like a Porsche turbo where it is a top management tradition that each new model achieves a minimum of 5% improvement in BMEP/VE is not easy, when measured in terms of Max. torque per absolute Bar of pressure. without going into internals, cams or intake. The GT2RS has a plastic intake tested previously on the previous 997 version, improved greatly for strength that optimizes flow quite dramatically, and has shorter and narrower runners and increased port diameter, to improve air acceleration and efficiency, also the exhaust side features a short catalytic tank for better exhaust flow.

One finding while using meth/water injection is that the intake charge stabilizes at some point during a run (slows down the temperature increase pace) however on a circuit, it does not prevent temps from keep going higher. I have been against the use of Methanol with every turbo iteration I have had, but new management systems and the evolution in technology has made it so safe and efficient, and I am currently very happy with its use. I have yet to prove any lap time improvement with it, if not marginal though. First straight line run when methanol is injected into the port at a certain preset boost level, you will clearly see your IAT stabilizing if not dropping a bit, but after a few turns and ongoing load, the effect is not at all that clear.

The GT2RS spray system is however not only boost dependent, like a meth system or other aftermarket IC water spray, but RPM , engine load and IAT together.

TPC have road race experience with turbos through Levitas racing his own 991 turbo, I am sure they must have some good learnings.

The chart below from my own data shows almost 2 laps on a rather small track, see how clearly the IAT keep increasing in straight line, this includes methanol and a large IC tank.. The time it takes to cool down the larger heat sink is fundamental in road/circuit racing to keep the power in the next straight, you can see temps barely decreasing in the braking zones down from 160mph.. expect 70-80HP drop between first and second lap alone, and much more subsequently on a modified turbo. The thermodynamics at play are on another level from any 0-200mph single run. And by the way, timing being pulled is minimal if any, across the runs.

Bruce H.

Well Jean, that's good information but rather sobering data. In post 17 you said that IATs were good with your larger ICs and meth injection but a loss of 70-80 hp seems huge (and caused by lower air density if timing wasn't being pulled). I know you've carefully optimized your whole setup to manage IATs. Btw, what would the boost levels have been in the upper range on these runs?

Mike is a talented engineer and experienced builder but he's fighting physics with very few options it would seem. Combining an IC spray with methanol injection would be one obvious option but not sure what else would be practical.

Thank you for sharing your track knowledge and experience in these various threads! And let me know if I should cancel my TS build for track use...or keep it as a stylish winter beater and keep tracking the Viper TA, lol.

Bruce

Jean

Bruce H.

Hopefully this discussion will be informative for some of those who might be considering the RS spray system to address IATs.

Your first plots in post 25 show how temps increase steadily under continuous and prolonged full throttle loads from low to high speeds, with very little recovery time in-between which is the most demanding scenario possible. That won't be the case for many road course configurations, and thankfully not my home track, Mosport, or Mont Tremblant where some of the fastest local Porsches come to play. Vipers do lose power as rising IATs cause timing to be pulled, but even still logging pretty consistently shows my best times closer to the 8th lap, more a function of my lapping day driving style than anything else.

Your plots in post 27 look more encouraging with IATs recovering well during periods of partial load which will be more typical on local tracks. I hope to be satisfied at stock boost and power levels and will look to IAT management, tires and suspension for improved performance. And speaking of which, I had a chance to compare Mike's TA to my own, and a pro driven ACR-E, at a track in New Orleans where Mike had his DSC/Tractive dampers installed with Hoosiers and those transformed the car more than I would have thought possible. It'll be interesting to see what he comes up with for IATs on his TT build!

Bruce

pepinozaur

First I will start to say that I respect you Jean a lot and your knowledge, I was reading your posts here and on 6speed (I am Fadi on 6speed), but for this time only I have some concerns regarding what was posted above.

Running 25-30psi on tiny vtgs means a lot of heat buildup, for sure 991gt2rs turbos will help A LOT as they have huuge hot side. If I remember right even 991.2 tts has bigger conpressor wheels but so bigger turbine wheels. Even for the bigger turbine wheels I would say 1.8-2bar is way tok much... thats gt30 turbine suze boost to deliver excellent results. My guess is 1.45-1.5bar and overboost of 1.6bar should be the sweet spot for regular 991 turbos using meth.

So running 1.8-2bar on vtgs is for sure out of their efficiency and will delicer HOT air, even on slighlty bigger upgraded ones, and upgrading just the conpressor wheels will not help. Do you have any dynos or 100-200 at 1.6bar compared to 2bar for example? My guess is the car will do only more torque but no more hp.

Another thing to consider is how the measurements were done..
- I know you race in very hot weather, I see even from the initial IAT at idle, so temps recovery will be quite different in respect to outside temperatures. Please take into consideration that OEM gt2rs clubsport is using bigger ICs very similar to aftermarket ones. Why?! And that is Porsche OEM.
-it depends how much meth you are injecting and injection strategy. I use 2x1.2mm (900cc each) aquamist injectors on my 996tt and I dont see heatsoak, without meth and using big 4.5 cores, will get pretty soon to heatsoaking. Also we can simulate gt2rs injection conditions, IAT included as aquamist has possibility to be triggered by external sensors, adding temperature sensor shouldnt be too hard. Engine load can be simulatef by injector duty cycle, rpms by boost etc...So which injectors are you using on your car? Do you know how your meth kit is set up?

And in regards to straight line guys, in my opinion the stress/engine load on the engine for some (mexican) guys running 4-5 races in a row from 50-200+ mph is higher than what we do at the track. So I wouldnt exclude all the info coming from the "dark" side

Jean I am in Dubai now LOL, going to the Autodrome on 2nd of January, I have rented a 458ch this time.. tried mclaren sprint and lotus racecar last year. Looking forward to having some fun as at home is snowing.

Happy New Year everybody!!!

Jean

Hi Fadi, I think the logs are pretty conclusive regarding the difference between a straight line run to 200mph and a time attack environment. Even if back to back, straight line events always provide large amount of fresh airflow into the intake and cooling of all hardware components, and an idle time between runs that you don't have on the track.... So the ultimate test for an IC in terms of cooling and recovery time remains the harshest environment the car can be subjected to, which is how Porsche build their engines, keeping safety levels in check.. For the past 10 years I have seen many logs of high speed runs, nothing really compares to circuit racing or time attack or hillclimb at 10,000 feet where air density is such a challenge.

You and Bruce are right, turbos are running out of their efficiency levels, methanol is "supposed" to move the needle back 10-15% on the efficiency map which still keeps you at 68-70% efficiency on the turbos, my checks and balances are timing and AFRs.. timing being pulled is barely existent at these levels and AFRs excellent, we had to pull back the tune several times compared to what my tuner does for his half mile cars, from his own words based on comparable maps and logs, he has never seen a car driven so hard, because 99% of his customers race in straight line or just do track days, not racing. it has taken a lot of back and forth and testing and log scrutiny with the tuner and COBB to get what I needed, I have 68mm compressors btw. Of course also tested different meth setups over the past year.

I doubt the clubsport has larger coolers than the GT2RS street version, it has the exact same engine, if there is any evidence of that, it would be great if you could share. As for the turbos on the GT2RS , all I know is that the compressor (only) has been increased by 10mm vs the 991.2 Turbo, which is the same size turbo as the 991.1, so your data seems a little off. I can bet on this anytime, a stock IC will do better than a 4.5" aftermarket on track, at 24 or 28PSI.

There are many posts on this as you know, I would go Marston (or looks like DO88 are quite similar to stock density) as only options to stock for the track.

I am in Bahrain on the 11-13th if you feel like flying over for a track day!
Happy New Year to all!!