Originally Posted by sdg1871

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.

Originally Posted by sdg1871

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.

Originally Posted by stef@europipe

What's the name of that company and do they have experience with our 991 Turbo S sport exhaust?There is no such thing as cat protection mode. Cats can handle temperatures of over 980°C no problem.

Originally Posted by sdg1871

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.

Originally Posted by sdg1871

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

Originally Posted by wrs

I don't think so. Something isn't right about your combination of things. Mine doesn't do that. My drag slips don't show any effect of heat soak until after three runs or so. At SA Raceway I had three 135mph runs that were 20 minutes apart. The slowest was the fifth and last at 132.8 but I beat the CTSV and the car still ET'd at 10.86, the fastest ET was 10.65. At Ennis the results were similar. My Vbox data from the track day at COTA doesn't show heat soak loss but those runs were about 45 minutes apart although they were 20-25 minutes long each.

Here are the times, ET and trap for SA

7:19 10.65@1354.4
7:39 10.80@135.2
7:57 10.71@135.1
8:21 10.87@134.4
9:00 10.81@132.8

The last two might show some heat soak but mostly I think it is because the humidity was increasing.Yes but it shouldn't happen so quickly. I don't think spending money on intercoolers should be your solution because others are not having the same issue and we have the same intercooler. My tune isn't as aggressive but it's producing good results in the quarter mile and on the track. Maybe you should drop back to the Stage 1 tune and see what happens. Another thought is to do headers, they would increase the flow to the exhaust. Maybe it's the stock headers that are the bottleneck and not the exhaust.

Originally Posted by sdg1871

Well those times and traps are very consistent so your car really isn't having much in the way of heat soak issues.

I do think my tune is more aggressive than yours and I think as GIAC has said that, as a result, they have built-in safeguards for the engine to keep the intake air temperature is within normal limits which may very well be the reason why the subsequent runs are much slower than the first. I really would prefer not to lose the power of the tune so I do think intercooling combined with the revised GIAC tune is my next mod.

I have heard mixed things about headers. Some people say they're good. One of the big US tuners who I trust told me that for nonturbo upgrade cars they delay the spooling of the turbos

Originally Posted by sdg1871

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.

Originally Posted by wrs

I think they allow the turbos to spool faster because of decreased back pressure. The ones I bought were $1850 plus install. I think you could try that now and it's cheaper than intercoolers. You could also dial your tune back and still get good results but without the heat soak. However, others with the stage 2 GIAC are not reporting this heat soak so there does seem to be something else about your configuration that is a contributing factor. It's frustrating to see you not getting good consistent performance gains after spending so much money and effort. Tuning is a tricky business though, it's not the same for every car, I know this from my work with BMWs. This is the third car I have tuned an it's the best and most consistent in terms of performance.

Originally Posted by Nfall

Well said. I have a 991tt stage 2. Although I do not have any numbers to prove it. Rolling with my friends after a couple hard pulls, I can notice a slight decrease in power. I honestly do no think it's significant, maybe a couple tenths in the quarter.

Originally Posted by sdg1871

The person who told me that is one of the top roll racers in the U.S. and holds records. He doesn't sell anything. But he has modded many cars and won races and awards over and over again. His experience was from the 997.2. He switched from EP to Tubi catless and said he got large performance gains in his drag and roll races.

I actually love my Europipe (great sound and build quality) so my first change will be to get the Champion intercoolers when they come out with the revised GIAC tune. If that eliminates the heat soak power loss issue then I am good to go. The last thing I really want to do is go catless due to the hassle and expense in New York of having to take out the countless exhaust and put in a stock or catted exhaust before every yearly emissions inspection

With respect to cat protection mode I was told this by Powerhaus Performance after they dynoed the car and took data. I can post the dyno run if you would like. I know EP puts in super high quality 100 cell cats and protects them well against thermal shocks. What we saw on dyno run three was a wheel horsepower loss of 50 from the first run and the car puffing out black smoke at a point which the tuner said was from dumped fuel.

Originally Posted by Porsche Boy

In my opinion, 100 cell cats are nearly as good as it gets. Going between cat-less and 100 cell should not make that much of a difference. If you are facing heat soak on this magnitude it is probably something to do with the tune taking into safe parameters.

Before jumping to anything why don't you try data logging for a bit? Do you have any faults? I highly recommend going for a good inter-cooler set up but before you do, try to pin point the exact cause. The heat soak you are facing does not sound normal, in fact I do not see any members facing heat soak to this degree.

Originally Posted by stef@europipe

My experience with a tuned catless 997.2 TTS is different. A stock TTS has 530 hp and with an ECU upgrade youÂ’re at 560 hp. Adding our 100 cell sport exhaust bumps it to 580 hp. Going catless added an extra 5 hp at 585 hp.

The maximum backpressure of the stock 991 Turbo S exhaust is 0.35 Bar measured at full boost near redline in at least 4th gear. With our 100 cell sport exhaust the backpressure is down to 0.14 Bar. Going catless at 0.10 - 0.12 Bar wonÂ’t result in a night and day performance difference really.

The GIAC Stage 2 is meant for cars with a better flowing sport exhaust. I see no mention of 200 cell - 100 cell or catless though.

Originally Posted by Porsche Boy

In my opinion, 100 cell cats are nearly as good as it gets. Going between cat-less and 100 cell should not make that much of a difference. If you are facing heat soak on this magnitude it is probably something to do with the tune taking into safe parameters.

Before jumping to anything why don't you try data logging for a bit? Do you have any faults? I highly recommend going for a good inter-cooler set up but before you do, try to pin point the exact cause. The heat soak you are facing does not sound normal, in fact I do not see any members facing heat soak to this degree.

Originally Posted by sdg1871

I would be happy to add a data logger to see what is going on. Austin from GIAC FYI.

But regardless I will be getting the Champion intercoolers and the revised GIAC tune. There will be a large power bump and there should be a nice fall in ETs as the tune will not need to be as protective with respect to intake air temps.

Originally Posted by Porsche Boy

You are on the right track. Hope you will be satisfied with the results.
All the best