After running my GIAC Stage 2/Europipe/IPD Plenum 991 TTS in several events (a 1600 ft roll race event by Slipstream Racing, a drag race during Goldrush Rally 7 and a runway quarter mile race held by Driving Force Club and by dynoing the car), I have confirmed that it suffers from significant heat soak power loss.

The dyno run, done by Powerhaus Performance on an AWD Mustang Dyno, showed a loss of 50 wheel horsepower from the first to the third pull despite cooling fans in all the right places.

At the Albuquerque Dragway, my E.T. increased by .5 seconds after the first run.

At the Slipstream roll races my trap speed fell, after the first run from almost 147 mph to 141-143. In the first run, my Porsche destroyed my Renntech tuned E63 S but, due to the effects of heat soak power loss, my E63 S BEAT my Porsche on the next two runs. It was like driving a different car after the first run.

At the DFC event (which was not timed), the indicated speed on my spedometer by the quarter mile flag fell by 5-6 mph.

I believe their are or may be several culprits behind it.

One, I believe the stock intercoolers are a cause. I intend to solve with Champion upgraded intercoolers when they come out. I understand that the revised GIAC tune will not cut boost/timing as much I understand the current one does at high RPMs/speed (to protect the IATs from getting too hot).

Two, I have been told by people in the racing community that my catted Europipe exhaust is a cause and that I should go with the Tubi catless race exhaust in order to lose the cats. The dyno run showed the car going into Cat protection mode on the third run and dumping fuel. We witnessed this by the black smoke that came out of the exhaust when this happened.

Third, I suspect that my metal IPD plenum might be a cause given that the stock one is plastic.

Any idea or solutions?

What are people's experience with the Tubi catless race exhaust? I love my EP (great sound and so well made) but if it is limiting my speed at events I may go catless.

I can post the dyno run, time slips and videos if people want to see the proof of the heat soak in action.

 

Here are my time slips from my three roll races of the 991 TTS vs. my E63 S.

The E 63 was car number 37.

The 991 TTS was car number 38.

Pretty embarrassing for a $200k modded 991 TTS to be beaten two of three times by a giant tune only and free flow muffler sedan.

To be clear, the trap speeds on the Porsche in the second and third runs are wrong but the ETs are not. Slipstream had timing system problems all day.

 

See video at 3:23. My E63 S beats my 991 TTS in both's second or third run after lunch and a one hour cool down.

 

I think this is something that you are only experiencing. My car runs great. I've done multiple pulls back to back with the same outcome.

Watch the video and you can see the same outcome. The car is constant for sure in my case.


I've also done a lot of 60-130 and they are always the same. More than 5 times in a row. Different day different temp. Also where I live is very hot most of the year.

My car has Cargraphic full catless exhaust + IPD + BMC racing filter + GIAC stage 2.

I hope this helps you.

 

There is a one big difference between ours cars. Yours is catless. Mine is not.

 

The most likely reason are you intercoolers getting heat soaked. Porsche, as most manufacturers, design the intercoolers for efficiency given the OEM boost levels and airflow. When you push the turbos higher intercoolers on most platforms including the 991 become one of the first modifications necessary.

Our recommendation for starters would be 1) exhaust 2) intercoolers and a tune made to take advantage of these modifications accordingly before any other hardware modifications are considered.

Let me know if any other questions at all, I'd be happy to help.

Dzenno@PTF

 

I have high flow cats (100 cell cats with my Europipe). So you recommend going catless?

I do intend to get upgraded intercoolers. Champion will be coming out with them shortly for the 991 TT and TTS.

 

I have been waiting for champion intercoolers as well. I've got the same mods you have, but my exaust is a fab speed 200 cel cat, I just picked up there cat delete by pass tubes. I haven't installed them yet. FYI Emre at ESMotors has aftermarket intercoolers out already and Cobb has there access port out. I need to have my set up by September for the next roll races.

 

Thanks! Yes I will wait for Champion's intercoolers to come out as opposed to getting them from Turkey. It should be soon.

 

Quality 100 cell cats will flow very well. Decat is always better but it won't be night and day at all and the most of what you'll gain will be in the exhaust gas "smell" department, not much in performance that would be worth it.

Definitely get the intercoolers on the car asap. They are not a power adder type mod on the car unless the OEM intercoolers are highly restrictive to flow (this won't be the case here) but they do allow for run to run consistency as they prolong the time it takes to heat soak the car which means 1) multi-gear runs will feel stronger start to finish 2) back to back runs won't start feeling slower and slower as quickly as they do with the OEM intercoolers 3) You may be able to push a bit more boost with the tuning depending on your octane and other mods 4) given a quality set of aftermarket intercoolers you won't have as much of a pressure drop as with the OEM units which means your turbos will make the same boost easier (i.e. less stress on the turbos)

Dzenno@PTF

 

Thanks! Yes I expect the Champion intercoolers and the revised GIAC tune to do a lot of what you are saying can happen. I am expecting a good bump in bhp, much less heat soak due to lower IATs and less cutting back of boost and timing at sustained high RPMs. The same mods worked wonders for the 997.2s, allowing quarter mile times on bolt on mods alone with stock turbos to drop into the 9s.

 

With stock intercoolers on the car, we're pretty hard nosed about retaining power reduction at a specific Intake Air Temperature set point. If we allow power to remain consistent while allowing the IATs to reach an unsafe point, it will create excess heat in the combustion chamber (power reduction will occur at this point through loss of air density or through pre-detonation anyways). That will lead to high exhaust gas temperatures which can damage the turbochargers. We've managed to keep EGTs at or below factory levels despite running much higher boost, which aids in keeping the turbochargers safe and reliable (VTGs are extremely sensitive to heat).

It is a very fine line that we have to walk with these cars to get the power that our customers desire, with the reliability they demand. Luckily, we've got a ridiculous amount of testing on the platform and are very well educated as to where that line is. We've definitely got some more aggressive options on the horizon that will be paired with additional hardware. The power we are making is second to none.

 

So you have tested all available piggy back systems? Tell us more.

 

The last time we did that, it was removed and we were given an infraction on here.

 

Yes the protective measures that the GIAC tune has in place to keep the car safe are one of the reasons that I bought the GIAC tune and not someone else's or a custom tune which might be more aggressive. The tune does produce a ton of power when the engine is cold.

For the tune to reach its full potential and deliver consistent results over many roll races or drag races in a short period of time it really needs enhanced intercooling. Every day I wait for the champion intercoolers to come out which I know, with the revised GIAC tune, will take the car to an even higher performance level. I certainly never noticed the heat soak power loss on regular driving or highway driving (the GIAC Stage 2 makes the car feel a lot faster than stock and at Albuquerque Dragway mine destroyed a stock 991 TTS even when hot).

It's just something that happens in events with repeated hard runs like roll races or drag events or dyno pulls.