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We purchased a BGB diff cooler as well as the thread I read made it sound like the diff/gear oil was heating up the PDK oil. It made sense to me as the fluid volume in the PDK trans is so minimal, and the PDK has a cooler from factory. We'll know one way or the other soon since we have temps on both!
I think we may need the deep sump as well; we'll see as everything progresses and bugs begin to be worked out.
We are getting PDK temps from the Cobb AP we have. For gear/diff oil, we purchased a 2 wire temp sensor that is connected to our AIM unit. It isn't ideal, as one system doesn't read both; but it works.
The LN Deep sump drops engine oil temps noticeably -- roughly 10 degrees in my case. I have a Cobb AP as well -- I did not know the Cobb can track PDK temp. I'd note that I've documented fairly large discrepancy is data between the Cobb and my AIM Solo (wire to the CAN bus); I wonder if the PDK temps will be likewise as inaccurate. I contacted Cobb and have not been too impressed with their response; they indicated they'd do some testing and determine the source of the discrepancy, but I've not heard anything in 3 months.
The LN Deep sump drops engine oil temps noticeably -- roughly 10 degrees in my case. I have a Cobb AP as well -- I did not know the Cobb can track PDK temp. I'd note that I've documented fairly large discrepancy is data between the Cobb and my AIM Solo (wire to the CAN bus); I wonder if the PDK temps will be likewise as inaccurate. I contacted Cobb and have not been too impressed with their response; they indicated they'd do some testing and determine the source of the discrepancy, but I've not heard anything in 3 months.
Cheers,
DJM
DJM,
Noted on the deep sump and temp data. I appreciate the information. That is not ideal. Ultimately though, we want to see what temps do without a cooler and then what temps do with a cooler. It's not necessarily the accuracy of the temps, but the change in cooling of the temps. Obviously, it would be much more ideal if the temps were accurate; but temp deltas might be what we can do for now.
To add to our repetiteur of sensors on the car; we got some laser ride height sensors!
Izze Laser Ride Height Sensors
Utilizing (3) ride height sensors; we are essentially able to create a plane (3 points make a plane) on the underbody of the Porsche. With a bit of math wizardry, we are able to discern body roll, ride height changes, and overall the vehicle's demeanor on track. Some people like shock pots, we opted for laser ride heights for a few reasons. At the end of the day, it will help us set up the vehicle in terms of aero balance, calculate aero load (further validation), suspension adjustments, etc. We are really excited about the addition of these sensors on car!
Below are the locations we are installing them. One is installed on our flat underbody panel, around the center of the vehicle; and two are placed in front of each wheel around the radiator exit ducting which points straight down.
I apologize in advance, this post will be a bit longer as we have not updated in a while.
We were able to get out to the track again a weekend ago and were able to gather both temperature and ride height data. As far as track times we are running at the local track, we are currently ~3-4 seconds off 991.2 GT3 (slicks, manual) times and ~5-6 seconds off 991.2 GT3RS (Michelin Cups, PDK) times. This is with an engineer driving (me), not a professional race car driver; the others in the 991s are again, not race car drivers but frequent the track on an almost weekly basis.
Let's start with the temperature data.
We were able to get in a clean 12-13 laps before the ECU shut us out from transmission temps. The PDK was registering 235 degrees F on the Cobb AP; though we do not know how accurate this is at this point. The gear oil was 180 degrees on track; as we brought the car into the garages, this temperate went up to 210 degrees F. We believe that due to the location of the sensor, we are likely not getting accurate gear oil readings. With the engine off, the oil begins to mix more with the hotter transmission fluid above it. Once we get the pump and cooler on the car though, the sensor will be getting fluid flowing past it at a continual rate.
So currently we know where we stand with the transmission and it seems to be a common thing with these first-gen PDKs in the Cayman so we'll work towards a for sure fix for our car. We'll start with the gear oil cooler which adds some volume and a small cooler, and test again.
Ride Height Data:
Laser Ride Heights on Best Lap
The above photo is a lap around Putnam park showing the (4) corners in terms of ride height. As you can see, we have a large variation in pitch and roll for the car throughout the track. Ultimately the suspension is far too soft, which we knew but we wanted to capture with data for fun. In some of the corners, we are seeing 70-100mm differences in ride heights from inside to outside. That's 3-4"!
Anyway, we have some custom made coilovers going on the car shortly which should dramatically help us here and hopefully net us some more time on track by allowing the aerodynamics to perform better. The front splitter relies on being close to the ground to generate the downforce we need to work well with the rear wing. With the car moving around this much and changing ride heights from ~50mm to 170mm, we are seeing a large change in front downforce throughout the track.
The BGB Gear-Oil Cooler Kit in its entirety: BGB Gear Oil Kit
While looking through the install manual, they place the cooler in front of the center radiator. While this position is great for airflow, I wanted to do something a bit different to ensure the radiators get the best airflow possible as I know people state the radiator temps are hard to control on these cars as well. Placing a cooler in front of the radiator reduces the radiators' ability to cool. When stripping down our 987.1 chassis, I spotted the side inlet duct which only has a fan for cooling the engine compartment (see picture below). It seemed like a perfect spot to place a small cooler that needs just a hint of airflow to cool the gear oil a bit.
OEM Passenger Side Inlet Duct
We decided to CAD up a design and fabricate our own mounting and fan system using a SPAL 7.5" fan.
CAD, Picture 1
CAD, Pictures 2
We'll be 3D printing and test fitting these pieces this week. Once fitment is confirmed, we'll order sheet metal and fabricate this to see how it does on the track.
We have also changed out our factory dampers w/ H&R springs and Elephant camber plates (FOR SALE, ready to go on a car if anyone is interested) for some custom-built coilovers to handle the downforce. I'll be finishing up the string alignment this week. I am hoping to be back on track towards the end of this month, early next month for a shakedown on the coils and to see what the transmission will do with the added cooler.
Thanks as always for the data and detailed explanation. I'm interested in your height measurements. Can you elaborate on the sensors/setup?
Of course! We got Paul to explain how laser ride heights work in a short video. If you have any questions after watching the video, please don't hesitate to let us know and we'll answer those at that point. I think overall, the video answers most of your questions though.
I like the idea of the cooler placement. Looking forward to finished results!
Thanks! I am excited as well! Probably more than I should be but I really get excited about this kind of stuff. The only caveat, so far, install is a slight pain due to location. Once the coolant expansion tank is loose though it seems like it can be installed without anything removed.
Here are some images of the 3D prints test fit. I did have it in the car, but of course, forgot to take a picture.
Adapter "sheet-metal" Piece
The sheet metal pieces have been ordered from waterjet, we'll then bend them up, weld, and test fit again. Then onto testing!
I want to point out something. Sorry if it has been already discussed. Do you have the 3rd/middle radiator in your car? My 987.2 Cayman didn't have one. I live in Canada and Porsche didn't spec one for colder climates. I had one added last year and it made a difference in cooling on track.
These car have the same cooling system shared between engine and transmission, so it will lower PDK temps along with engine temps. Also for the 3rd radiator to function, there must be holes made in the bottom of the bumper, to allow air to flow through it. I don't see any holes in your slitter under-body. Another option is to add a GT3 smile vent with corresponding duct work to channel the air upwards.
Awesome work!!! Love the effort you guys are putting into the 987.2. Waiting impatiently for results!!
Which results? The gear oil or the aero kit? We have some back to back data from last year on the aero kit's performance on a manual 987.2 in NJ ran by GearOnePerformance. We plan to do some back to back testing later this year with our car which is PDK.
Originally Posted by olegd
Very interesting write-up, keep it up guys!
I want to point out something. Sorry if it has been already discussed. Do you have the 3rd/middle radiator in your car? My 987.2 Cayman didn't have one. I live in Canada and Porsche didn't spec one for colder climates. I had one added last year and it made a difference in cooling on track.
These car have the same cooling system shared between engine and transmission, so it will lower PDK temps along with engine temps. Also for the 3rd radiator to function, there must be holes made in the bottom of the bumper, to allow air to flow through it. I don't see any holes in your slitter under-body. Another option is to add a GT3 smile vent with corresponding duct work to channel the air upwards.
Yes, we are aware. We currently have not had issues with coolant temps though they do get up to about 210 F after ~15-20 minutes on track. That being said, we are keeping a close eye on coolant temps and if we need to vent the center radiator (which we have), we will be adding the smile vent from a GT3 first. Venting hot air from the radiators below the car hurts aero performance and we would like to avoid doing this. We may add the smile vent regardless as these cars do run hot. One way or another; we'll get the car to cool well enough to last on track for 30-minute stints. That's our goal. Both Paul and I come from a cooling system background and are not overly concerned with cooling, we just need to find the weak points, document it (which seems to be missing in the community), and fix it. There is a lot of "the car overheats on track" but with little actual information regarding what people have done to fix it; though there are a few good threads on it here and there.
Either way, we're having a good time learning the chassis, reducing lap times, and gathering data to help us further our aero knowledge/validation/suspension knowledge/etc!
I am curious what are the symptoms of overheated PDK or gear oils? I have not experienced any unusual behavior from PDK on the track during 20-25 minute sessions in hot summer weather. I use Sport Plus mode on track if that matters.
I am curious what are the symptoms of overheated PDK or gear oils? I have not experienced any unusual behavior from PDK on the track during 20-25 minute sessions in hot summer weather. I use Sport Plus mode on track if that matters.
We ran into it once we started to get lap times down as we are on the gas a lot of the track. The PDK will no longer shift from whichever gear you are in and the info says something along the lines of "Gearbox failure". I found a few threads, primarily headed by BGB that night, that has some info on it. This is the main reason I purchased their kit, they actually documented the issue and came up with a kit to fix the issue which made sense to me personally.
07-15-2019, 01:00 PM
