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This why RL is the preeminent Porsche racing site.
Even on the 987 chassis the base issue exist, it is midenegine and the gearbox fluid wants to abandon the ring and pinion. The early Napleton Interseries cars ran as high as 300 F at the differential. These are generally 6 Spd cars.
The oil wants to evacuate the bell housing. On the PDK that space gets sliced in half to send fluid to the wet clutches.
I'm glad Tecce and Spencer are commenting. They've both met my 3yo first born. I would trust either one to look after her and they will both have a role in rebuilding my recently purchased 'SuperCup. Not many out there who know more about Caymans or water pumpers than these two guys.
Would the 991 gt3 PDK-s go thru the same issues with temps? Mike
It will suffer from fewer issues because of the rear engine. The oil wants to pool at the differential because of momentum. The
Cays layout is superior but presents engineering issues with the layout.
Any idea how the gt3 smile vent may improve things? Jake Raby stated that they saw significant improvements when cooling when they went to gt3 front end on their 4.2L cayman x project. I've never seen any other mention or data on this option.
What is the temp on the stock thermostat? Maybe a lower temp one will help but it does appear the system is over-whelmed pretty quickly...or Porsche wants temps that high.
What is the temp on the stock thermostat? Maybe a lower temp one will help but it does appear the system is over-whelmed pretty quickly...or Porsche wants temps that high.
I've been talking to the guys at LNEngineering/BRS about mods to cool the Cayman. They do suggest a 160 degree thermostat for track cars, but they said this could be a problem with street driven cars as, in some cases, the engine my not reach proper operating temp and will throw a CEL.
For emissions purposes, the cars do in-fact run 'hot'. In fact, oil temps are hotter when cruising on the highway when in normal mode vs Sport or Sport+. The idea being that when in Sport/Sport+ you are likely on a 'spirited' drive and the engine should optimize for cooling, while in normal mode, you are just cruising and the engine should optimize for emissions/MPG.
Any idea how the gt3 smile vent may improve things? Jake Raby stated that they saw significant improvements when cooling when they went to gt3 front end on their 4.2L cayman x project. I've never seen any other mention or data on this option.
Because the air can be removed from the area more effectively, allowing more air to pass through the cooler or radiator. I gathered the data first hand while developing my 4.2L engine and I have seen it over and over again.
Jake, was that with an actual gt3 bumper cover or just the vent? I'm not clear if there's any differences between a stock bumper with the vent added and the OEM gt3 part. Thanks!
Because the air can be removed from the area more effectively, allowing more air to pass through the cooler or radiator. I gathered the data first hand while developing my 4.2L engine and I have seen it over and over again.
Jake,
Are you talking engine temps or gearbox temps? We've seen differential temps in excess of 300 degrees F when hit with a gun usually used for measuring brake temps. That's about 70-80 degrees too hot for what we want to see at the diff...
As cooling is a major issue I am going big on the cooling side. I have a concern pushing engine oil to the front of the car so I am installing coolers for the trans and engine in the rear quarters and venting them through the rear bumpers. Will use a 190 degree thermostat on the engine oil cooler and 195 degree temp switch to control the trans cooler pump.
Their is no practical way to install protection. As with the front radiators they are exposed. I will carry a spare to the track. From a practical point if i get hit i am out of the race anyway.
Would the 991 gt3 PDK-s go thru the same issues with temps? Mike
Missed this the first time around. I think we will see the GT3 with fewer issues than the Caymans. This is midengine versus rear engine. Even the 6spd cayman diffs run really hot because all the oil wants to pool out in the gear stack.
On the rear engine cars the oil pools around the differential. The old 911 problem was 5th and 6th getting hot. That's why the rerun for the factory cooler on 996&997 GT3s dumps right into the tailcone.
Well designed Cayman gearbox coolers out the oil return to the differential.
Alright...to give an update, we have brought the car home having run the factory front plastic grills with mesh screens up front and the factory radiators with our gearbox/LSD cooler and power steering cooler added. (photo below).
Yes, Caymans have their OE power steering hydraulics already run through the factory oil cooler but we found that to have a track life of less than 2 hours. And yes, we are robbing frontal area from the center radiator but in creating more air flow for the radiators to exhaust air, we can still keep temps down while robbing from the center radiator. I do not like to use heat exchangers on Caymans or run coolers in the back because the poor car struggles for engine bay heat dissipation. Between the headers, the exhaust and the motor, it's a mess!
In the rear, we wrap the headers and we leave the PDK cooler alone. I have always been afraid to touch the wet clutch fluid or run engine oil to the front of the car because these cars are crashed, driven off-ro ad, etc. and if that happens, then the limp home on a 2.5 + mile road course could prove deadly for a car with oil leaving the system. This IS NOT to say that running a front mounted oil cooler would not solve all hot oil problems. I think it would actually but the goal is to work with the factory components as much as possible since we were required to by rules.
What I can confirm is that the: the "PDK cooler" we make which is really a gearbox/diff cooler for the other side of the bell housing, stops any sort of Limp Mode from happening, most likely from the fact that we are cooling the fluid in the gear stack and the LSD and therefore reducing radiant bell housing heat to the PDK side of the trans. Yes the bell housing is finned and designed to cool but there's hardly any air flow going on in that engine bay since it's a mid-engine car. The cutting out of a rectangular shape where the license plate goes on the rear bumper cover helps this some but it's not making a dent in the engine bay heat soak problems.
I started this thread before we built our first PDK car ever and I can't believe that it was 2011 that I wrote this original thread. It's been 3 years and we are still trying to refine the approach but we started with the 1st phase of adding coolers to the PDK and power steering to see if we could keep them cool for extended periods on track.
Phase II will be conducted at the PCA event at Daytona next weekend when we add the PWR radiators and remove all plastic grills from the front intake openings for the radiators in the front bumper cover. We're going with the classic 360 Ferrari Challenge look in an attempt to see how much air we can have flowing through the Cayman bumper cover without having to switch to 911 which has been proven to be very efficient. You will see in this photo that we are running all factory black plastic bumper trim but the experiment for Daytona will be what removing that and adding larger, more efficient motorsport radiators nets us.
Hergesheimer Motorsports out of Orange County, CA used CSF side radiators on a boxster 986 in 2012 in 110 ambient temperatures for a global time attack event. Was the only car left on the track, and was able to complete the full 30 minute session.
Renn-Sport 1 (RS-10 out of Florida uses our 3 piece 987 sets for all of his cars, and says temperatures are very much in check - even with larger engines installed.
Great way to increase durbailty of the cooling system with the aluminum versus plastic OEM tanks, as we as 2 rows of cooling versus the OEM 1 row.
Venting is also very crucial for proper cooling as it allows the hot air to escape, and air to flow through easier.
The 3 most important factors of cooling:
- airflow (entry and exit) - this is where different fasica designs will help with airflow
- surface area of coolers - especially how much of the cooler is getting direct airflow
- capacity - especially when in enviroments where drafting is occuring.
10-11-2014, 03:41 PM
