Pdtp#16

I'm interested to know what has been folks experience with heat soak under track conditions. I recently received my car back from TPC (which by the way did a fantastic job, she is a beast) and have been able to do 3 days at the track. One at PBIR and two at Sebring. The thing that has surprised me the most, is the difference in power between morning runs and by the end of the afternoon. The power loss is significant, even with water misters. For example, today during my morning run which included a driver's checkup (first time running with Chin and they wanted a checkup for red group) i ran a 2:16.55. by the afternoon i was lucky to get into the 2:19's and was lossing at least 15 mph on the straights.
I have ran now several files on track which I'm working with Mike with the hopes of making changes after analyzing the data. Ultimately we both agree that running bigger turbos with less boost will help a lot but i'm wondering if anyone else has done anything else. In terms of upgrades i'm running TPC's intercoolers including their Y-Pipe, exhaust, cobb etc.

Steve Cole

Once you heat sink bigger intercoolers, they take longer to cool (they've got more mass) or at the very least, just as long. The key is to figure out how to cool them - water misting definitely works to a degree but as you said, when you are talking about road course performance, there is a reason why the winning teams always have the best tech. It's so much easier to drag race cars in many ways. That's where most tuners have the most experience.

KONG991TT

Subscribed: I literally was having the same discussion with Mike when I swung up there to pick up my DSC Sport. He echoed Steve's sentiment that these gigantic intercoolers were only good for short bursts (i.e. drag racing) as the moment they used for track duty, they hold a lot of heat. IAT's jump and power gets pulled. 15mph is a lot! I'd be interested in everyone's thoughts here. I hear that Meth injection is the best way to keep temps low.

Did you pick up the GT2RS misters or go with a different aftermarket option?

onfireTTS

How much boost ?

Bruce H.

What kind of ambient temps morning vs later?

Jean

Mike has experience running these setups in racing environments and should be able to tell through your OBD datalogs what’s going on. I am sure the program he is using is not running insane boost.

It’s very unlikely that you could lose 15mph at the end of the straight because of heat soak, unless something is wrong, I have seen that happening only when the car goes to protection mode and boost gets cut back to 1 Bar and this happened only under full attack mode after several racing laps in 100F temps.

Your tires could have been gone by the afternoon run, I would check exit speed at the corner before the straight between the 2 runs and if it is the same, yet you reach 15mph less at the end of the straight, then you need to look closely at the engine datalogs to understand what is happening. Especially if you are misting the ICs, that sounds unreasonable.

If you are ok to use meth on your car, I would install meth with stock turbos first, IAT difference is substantial.

Dr Chill

Do you have any lap times at Sebring stock before mods? Also curious on stock top speeds on front and back straights.

flsupraguy

Does the 991.2 turbo s experience heat soak like the .1's do?

Pdtp#16

Mike sent me a file last night. Car ran better today. Yesterday the data showed that AIT's at 157 F and with quite a bit of timing correction (this was done in the afternoon but at the beginning of a sessions). After updating the new file car ran better with AIT's of 145 on my last run at the end of a hard driven session. So all in all better. I was able to get 5 strong laps before starting to notice any significant power loss. Will continue working on it.

Jean do you run meth on track? i pretty much use this car solely for track. Not interested in drag strip. Have you done any other mods to help with this issue?

Dr. Chil i do not have times with the car 100% stock. Ran Sebring (after 10 years) with suspensions changes only and was running 2:25's (car could have gone faster for sure). Right now i'm running (third time with the car at the track so still being cautions and getting to know it) consistently around 2:19 with traffic and have been as low as 2:16.55 in the morning run with no traffic but with passenger. Today's top speed on the back was 158MPH. I still feel if i had better exit on 16's and broke a bit later could definitely dip into 160 +. Biggest difference i have noticed since i got the car from Mike was breaking and high speed turns. I can break so much later specially after the long straight aways. Right now i can take bishops bend pretty much flat out which i never thought i could before. With that said, my speed on the straight away at PBIR were higher before all of the aero work.

I'll try posting some pics from the weekend


So for now i want to work on my driving, getting to know the car and FIXING the heat soak issue. Makes it really hard to adjust during a session, Breaking points and speed differential is drastic. I also need someone in FL that can help setup my VBOX. Is driving me crazy. Not working right and not data logging.

Pdtp#16

pic from today

Jean

I run a stage 4 from ByDesign, with modified VTGs and methanol, IPD, Kline exhaust and larger intercoolers. I only run my car on circuit and hillclimb, I do not do drag. I have seen 160F+ IATs, however starting with idle @140F in the pits, on the long straight, going from ~60mph to 177mph the temps fall off reasonably quickly, the tough part on the temps are the slower turns at full throttle in 4th gear, 120-130mph where load is at max. yet not enough cooling airflow

In crazy mode I ran a custom map with 1.9 -2.0 Bar of boost for one lap, this is not advisable but it served the purpose for the lap record in Time Attack. Sam has designed a series of maps depending on my usage, on the more conservative racing maps @1.6 Bar temps reach ~140-145F with Meth.

For fun track days, I do 20 minute sessions without issues at 80% pace, enough to match well driven 650S laptimes. Stock turbos and intercooler deal better with heat if they're run at 1.4-1.5 Bar Max and would do great with meth. Your car will be super competitive. I am exploring misting the coolers, and might be getting a Marston IC from Sam soon.

Jean

Stunning!

kouzman

Excellent info guys!

One of the most I formative threads in weeks!

Steve Cole

Something to consider: the linear-turbo setups ByDesign (and at least one other) are using now for "beyond stage 4" should be a big help in keeping temps down at really high power levels. If you wanted 800hp or thereabouts and you could give a crap about how quickly boost comes in off a stop sign (amirite?!) then those setups should be much better for what you're trying to achieve. The VTG setups definitely work and may be more street-friendly (though Emre claims it's a wash) than standard-frame turbos but for your track application, I don't think there is any advantage at all for VTG - they're also marginally heavier.

A/S

We see temperatures rise 25 degrees and more at Sebring. The track becomes 2+ secs slower in afternoon sessions in the 90s compared to a morning session in the mid 70s.

Congratulations on the build. TPC (Mike and team) built a fantastic 991.1 Turbo S for the Optima Series, and yours seems to be a similar build.

You need to look at data, separate segments, then look at exit speeds from the beginning of the segment to top speed in the segment. Normally, I take exit of 5, exit of 7 and exit of 16 to check for power loses, I use the outside end of the rumble strips on my video, then look at speed at that point in the data (RaceStudio).

So, if the track grip has degraded, or a combination of that with your tires aging (no idea what tires you ran), your speed by the exit point should be lower and you can't expect to reach the same top speeds as exiting T5, T7 or T16 with more grip.

For example, in my 991 TTS, I reach a top speed of 156mph, and after 5 laps, the speeds are down to 152mph between T16 and T17. In my old 991.1 GT3RS I would reach 150-151mph lap after lap after lap (my RS was one second faster per lap compared to my current TTS). I haven't done Sebring with the .2 GT3RS yet.

Be aware that the speedometer in all the 991s report fake speeds. Mine (I have 2 991s and had 2 more before) are consistently 3% over rated, so my GPS speed of 150mph reads 155mph on the dash.

You're just experiencing a combination of heat soak and the track getting slower.

The best time to run Sebring is January up to the middle of February, this is when the best lap times are posted.

If you're on the East side of Florida: Orbit Racing. If you're on the Left side: Autoquest. Both places are the most prestigious, knowledgeable and experienced Porsche shops I know off in this State. Down here in South Florida, I use Tuners Motorsports, but there are plenty other good shops. Orbit and Autoquest can setup the Racelogic for you.

By the way, a 15mph speed difference is something going really wrong with the car. My TTS would top at 141mph if it loses 15mph before T17, that's what my Cayman S with 300hp reached at that point on that track, and even with Zero turbo boost, the 3.8 should be producing at least 350hp.

Try removing the Cobb tune (using the Accessport) if you continue to see such a power drop, then run a session and check if the speeds are dropping by that much. The Cobb tune cannot override the ECU safey controls, so if the ECU is detecting a heads temperature out of range and pulls timing, it could explain the problem. My now gone C7-Z06 would drop from 153mph to 130mph at the back straight in PBIR due to heat soak, it would completely release any boost from the SC.