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991 Turbo track car

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Old 01-09-2018, 02:23 PM
  #31
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Absolutely Adam. They can even go below ambient and we discussed it. But we wanted to try and do the best we could without methanol first. Running around on racetrack with cars all around and take turns adds to the conditions. Interestingly. We were able to notice that in the first lap or twi the mass of the larger coolers did quite well but once they get hot thereĺs little air running through them and whatever is is pretty damn hot ha ha. Another thing about running the Hillclimb, methanol was not permitted in our class so we sprayed water on the coolers and radiators. This helped helped tramendously as seen on the new RS. I think one of those options are in our future for this application we just want to find the best set up without it first.
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Old 01-09-2018, 04:12 PM
  #32
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I would like to avoid an in-depth discussion about intercoolers and temps etc.. on this thread to try to keep it on topic. I have massive amounts of data on the subject from the early air cooled days and of the 997GT2RS and the 991TT though. Where I disagree with Adam is concerning an airfield run vs. track. No airfield is long enough to trigger loads and temps like circuit racing. The only venue I can think of would be the German Autobahn where you can run at full boost for minutes at once. Over the years I have not seen data posted on this forum related to a turbocharged engine in circuit racing conditions, only road or straight line racing conditions, by far not enough to really test these engines.

Methanol will definitely cool things down, and Sam proposed it, as well as water spraying the coolers when I explained the conditions of my usage and even before he sent me the kit but I wanted to keep it simple.

Through many racing years and experience with 911 turbocharged engines by top professional racing teams in 24H races, only water-cooled intercoolers have proven to work in professional racing. Beats the old day Secan on 993GT2s. The 997GT2RS runs cooler than the modified 991TT on circuit, largely due to the better sized compressor/turbine ratio of the RS as Sam well pointed out. After a couple of laps, the GT2RS will be faster than a full blown 991TT like mine on the straight, I have the data.

To answer MaxLTV, no I am not saying Sam's intercoolers perform worse than stock, but under the conditions I drive my car, heat, 91 octane (or race fuel) and circuit racing, the larger intercoolers heat soak, and it takes them longer to dissipate heat, be it By Design or any other out there of that size. These conditions will not be experienced by hardly anyone here.. For street performance and high speed runs up to 200+mph, these coolers perform great, they will not get nearly as much heat as a couple of circuit laps at full boost and high loads in slow turns and fast conditions where airflow is much more restricted. IATs in lap one are great, top speed is great too, comes lap 2-3.. things go south.

With further custom programming and fine tuning, we will be able to improve things, the latest files Sam sent me improved performance noticeably, more to come!! This is what's great about having great support, by far more important than the components, which are all almost the same between all the different shops.
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Old 01-09-2018, 05:18 PM
  #33
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This mimics the issues with the 993TT, which Jean is familiar with. I have recently received quotes from Marsten Motorsports division (racing intercooler cores). The pricing was more favorable than previous years. I also feel that compressor technology (wheel choice) >less sometimes being more efficient. Building aerospace quality (very efficient) intercoolers with low mass thin gauge aluminum endtanks with the latest turbocharger compressor wheel designs (based on target boost pressure levels) 1.6bars, 1.8bars or 2.0 bars (select from three different compressor wheels) might be the preferred racing/motorsports decision. You can get the 991GT2RS compressor wheels and the sister research and development wheels. I have used the previous generation for the 996TT for years.. In the end, water injection that mimic the 991GT2RS might offer a quick inexpensive solution! Cheers
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Old 01-09-2018, 08:43 PM
  #34
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Originally Posted by Jean
Where I disagree with Adam is concerning an airfield run vs. track. No airfield is long enough to trigger loads and temps like a circuit.
I didn't make a comment in that regard so if you want to know, my data shows airstrip start IATs 40-70c (because the intercoolers are hot from motor idling no wind flow @stationary waiting to race) dropping to close to ambient by the finish line on an airstrip run.

On a circuit 30c/90F degree day i have to find the logs but from what i remember I was seeing IAT's below ambient. Using dual 630cc CM7 nozzles good for around 1,000 crank HP (it's a lot of meth). Now granted on stock PZero's N0 so I couldn't push the car as hard as you but my lap times were around the same as an instructor in his 991 GT3RS. So pretty much just cruising lol. Maybe pushing much harder IATs rise significantly. And yeah I might not have done more than 5 laps as my tires were getting greasy awfully fast.

Perhaps meth in conjunction with an intercooler sprayer would be fantastic. I've used both separately but never together.
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Old 01-09-2018, 09:04 PM
  #35
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Originally Posted by Jean View Post
To answer MaxLTV, no I am not saying Sam's intercoolers perform worse than stock, but under the conditions I drive my car, heat, 91 octane (or race fuel) and circuit racing, the larger intercoolers heat soak, and it takes them longer to dissipate heat, be it By Design or any other out there of that size. These conditions will not be experienced by hardly anyone here.. For street performance and high speed runs up to 200+mph, these coolers perform great, they will not get nearly as much heat as a couple of circuit laps at full boost and high loads in slow turns and fast conditions where airflow is much more restricted. IATs in lap one are great, top speed is great too, comes lap 2-3.. things go south.
I see. What I'm trying to understand is at steady state lapping (so laps 5-10), would these big intercoolers produce lower or higher IATs compared to stock? The mass of the intercooler stops playing a role at that point and all that matters is how much heat can the intercooler dump into the ambient air, which is proportional to surface area multiplied by airflow. Surface area increases with the size of the intercooler, but airflow may go down if the bigger intercooler is more restrictive for ambient air passing through it.
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Old 01-10-2018, 03:54 AM
  #36
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Once 991GT2RS parts become available I am sure I will look into some upgrades.. I have been waiting for some real life data about Marston on a 997 or 991 but nothing came out on the forum. Fueling upgrades on the 991.1 would also go a long way I believe.

Longboarder, I have no user knowledge about methanol at all but temps below ambient can probably only be achieved at idle?

MaxLTV, steady state lapping, even fast pace, can be sustained pretty easily and with good temps, this setup is very strong and reliable for track days. My datalog observations are at time attack pace 10/10ths, same times as Viper ACR extreme, 4 seconds faster than stock 991 turbo with tune and exhaust and a couple of seconds on well driven 991 GT3RS on a 1m:20s track.
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Old 01-10-2018, 09:32 PM
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Originally Posted by Jean
Longboarder, I have no user knowledge about methanol at all but temps below ambient can probably only be achieved at idle?
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Hi Jean, methanol is activated typically on a boost or injector duty cycle reference. You don't want it to flow until you are in boost.

I don't know the chemistry behind methanol but all I know is that i use my hands sometimes in a pinch to check the meth level in my fuel cell and it is extremely cold to the touch. A few seconds and it would start freezing my fingers. Injecting that post intercooler directly into your Y pipe and it is going to drop intake temps dramatically and sometimes below ambient. Doesn't happen all the time, but sometimes in my logs I've seen IAT drop below ambient on sustained WOT pulls.
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Old Yesterday, 01:56 AM
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Originally Posted by longboarder View Post
sometimes in my logs I've seen IAT drop below ambient on sustained WOT pulls.
One thing that can foul things up - I've used meth on a few non-Porsche cars and found that if any meth gets on the IAT sensor itself, the evaporative cooling cooled the sensor way too far, way more than the ambient air. The cooling effect of meth is definitely no joke, though. Be careful with those big nozzles, meth being flammable is scary stuff if it pools. (the 991 intake manifold doesn't really have a spot where it can pool...)

Anyway, it's good to measure as far from the meth nozzle as possible.

With regards to intercoolers not cooling at circuit speeds, it really depends on airflow and the efficiency of the intercooler. Again, no data on the Porsche turbo cars, but my time with forced induction S2000s and Evos showed that an ideal sized intercooler would never heat soak, with the right ducting and airflow. If you are seeing heat soak, ever, that means that you your intercooler either doesn't flow that well or your ducts don't work that well. The larger mass of an intercooler is not that large and with sufficient airflow will not heatsoak, even in endurance racing. Again, no experience with the particular brands and setups being discussed in the thread, but have spend a lot of time nerding out over thermocouple plots.
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