kdochert

Hi Y'all,

After completing my second track event in my 2016 Z06 / Z07 A8 I have questions, so here's some background first to put things into context regarding the overheating issue I encountered at the first event.

Track weekend 1 with the original cooling system

• Ambient temp 90 - 100 Deg F
• 4 x 20 minute sessions per day for 2 days
• My first time on the track (Houston MSR CCW)
• Frequently going into power reduction mode
• Overheated (full limp mode) in 4 - 5 laps (~10mins)
• Max coolant temp 270 Deg F
• Max engine oil temp 300 DegF
• Max trans temp 200 DegF

I know an LG Motorsport or G Speed solution is needed to completely cure cooling, but if I can get a point where I can run push laps for 20 minutes at around 80 - 85 Deg F I'd be very happy. After this first weekend session, to improve cooling I bought this Dewitts radiator which I installed myself (including lots of burping above thermostat opening temp to get air out). I also reduced coolant concentration to around 30% (coolant + redline water wetter) : 70% distilled water, installed a 174 DegF thermostat to help at least reduce my starting temps, and vacuum bled my Intercooler system.

Track weekend 2 with the above upgrades

• Ambient temp 65 - 70 DegF
• 4 x 20 minute sessions per day for 2 days
• Second time on the same track (Houston MSR CW)
• Went into power reduction mode two or three times in last afternoon, but only very briefly
• No overheating (no limp mode)
• Max coolant temp 245 Deg F
• Max oil temp 282 DegF
• Max trans temp 203 DegF
• Temps cooled down quicker on cooldown laps than first track event

Clearly not a like for like comparison between weekends as ambient temps were significantly different, but even in much cooler ambient my temps are still quite high, particularly oil. On the plus side though, even though it was cooler I was certainly pushing the drivetrain more given it was my second track event. I'm going to install some heat shrouding to shield the oil cooler and oil lines from the Cat's, and I also have another half day event in April where I'd expect the ambient temp's to be in the ~80's DegF, so that will be another key data point, but the above data leads to my first questions on getting oil temps down:

Q1) If I went down the path of installing an air to oil cooler, which cooler would you recommend? Is there anything better than this LG unit? It appears Dewitts has stopped selling theirs?
Q2) This should also put slightly less load on the engine cooling system right to help keep engine coolant temps down right?
Q3) Going to ping LG for installation instructions, but if anybody has done this or looked into this, what's the installation difficulty of this? I don't mind paying $1,500 for this kit, it's the installation I'm concerned about. Replacing the radiator was about the limit of my capabilities :-), is this similar or worse? Anybody seen any video's on this?
Q4) Anybody happen to know what the max trans temp is?

Edit: Dewitts have just re-instated their oil cooler.

Brakes

I have the Z07 package, thus carbon ceramic brakes. Regular trackers switch to steel rotors to reduce consumables costs, makes sense, which leads to me next question:

Q5) As I'm planning on only doing 2 - 3 track weekends per year, (each weekend consists of 8 x 20 minute sessions), do I still need to be concerned about wearing down the ceramic rotors as I was hoping to never have to replace them?
Q6) How many sets of pads (which are also expensive) do you go through before ceramic rotors need replacing? I heard they wear at similar rates?

Driving Modes / PTM

On day 2 I thought I selected PTM "dry" mode (double press of center button then select dry), but now I researched more I realize I wasn't actually in that mode as the "TC off" and "Stability off" icons weren't illuminated on dash, I was actually just in regular track mode where I was able to switch TC off though. I've realized this is because my Drive Mode Dial center button is sticking.

Q7) Any advice on lubricating the Drive Mode center button without disassembling the module? WD40 or is there something better (and less smelly for in the cockpit)?

Lastly just a comment that the max intake boost pressure in the PDR data appears to be an absolute pressure number (max 31.18 psi) vs the actual boost pressure (a delta pressure) shown on the dash gauge which only goes to 15 psi?

Thanks for any help on the above.

Kevin

Bill Dearborn

Kevin,
I have a 2015 M7 Z06/Z07 with the GMPP Secondary Radiator added. I haven't had any overheating with my car. With the stock thermostat, my coolant runs in the 219 to 223 range and the oil runs in the 265 to 270 range depending on ambient temps.

I don't think wrapping the stock oil cooler will provide much benefit. The majority of heat transfer from the exhaust to the cooler is through infrared radiation and the oil cooler design minimizes its absorption of IR energy. The air can conduct some heat when the car is sitting still but on track air movement at speed will minimize that type of transfer.

As for your ceramic brakes, it sort of depends on how hard the track is on brakes. Some tracks affect the brakes more than others. With my Ceramic Brake Rotors I got 13 days of track use on the front rotors and about 20 days on the rear rotors. By that time they were heavily pock marked and were eating brake pads. I could only get one or two track days out of a set of pads. While, I had gotten six days wear on the first set of front pads that reduced with the second set of pads finally dropping down to two days with the third set of pads. That is when I replaced the brakes with an AP kit. The rears went longer but the last set of rear pads only lasted one day before they were worn below minimum thickness. Both the front and rear rotors are well above minimum weight but the sharp edges on the pock marks just shave the pads down. You may get twice the usage out of your brake system but you will have to change rotors if you don't change cars first.

Sometimes I have to work with the center button on the drive mode control. I will hit it twice and nothing changes but if I repeat the sequence a few times I will see WET show up on the DIC and that is how I know I can select Wet, Dry, Sport 1, Sport 2 and Race. The C7 Corvette New Owner School at Spring Mountain recommends Sport 1 as the preferred track mode. It shuts down traction control and has a less intrusive stability control, it also dampens throttle response so the throttle which slows throttle opening but still lets it open all the way. PTM is still active and will control engine torque delivered to the rear wheels based on which rear wheel has traction. This is described somewhat in the OM. I have found that Dry mode is very intrusive. Sport 2 keeps throttle dampening and PTM while Race only keeps PTM. Sport 1 seems to be the sweet spot. To use PTM the OM says as you reach the part of the turn where you start adding throttle to open the throttle all the way (WOT) and let PTM control the power to the rear wheels as you are powering out of the turn. I have found that works in some turns and is somewhat limited in its ability in other turns. There is no way I can go wide open exiting turn 1 at VIR, I can hear PTM actively working to control torque to the rear wheels but the back end kicks out long before the throttle is open all the way. However, on some subsequent turns, I can go wide open and the back end stays planted, the car just shoots out of the turn, It takes getting used to and you have to pay attention or you could be in a wall.

Bill

kdochert

Hi Bill, always appreciate your input!

We all know the M7's are significantly better as that aux radiator is significant in size, but I'm scratching my head when I talk to some other A8 owners in my local Corvette club who don't seem to suffer the same overheating as I do when tracking, even in the Texas summer? It would be nice if the reason was I was so much faster , but sadly this ain't the case as I'm a track novice. I'm tracking on what I believe is a relatively low speed twisty track (Houston MSR) with four short straights where average speed on a push lap is ~80mph and top speed is 135mph. I don't know how this compares to other tracks in terms of pressure on the cooling system.

Insulating the cat from the oil cooler is just about reducing heat soak when stationary given how hot those Cat's get, my expectations on seeing different numbers is very low, but it's cheap and simple and I'm chasing every incremental gain I can right now, even if it's just the feel good factor that I'm doing everything I can.

Those brake wear numbers are very scary, can I ask how many hrs of running one typical track day is for you so I can at least correlate track hrs per day between you and me? This is all leading me to keep my track running down to once or twice per year in cool ambient temps, otherwise I'd have to go all in with more cooling upgrades and moving to steel rotors.

Thanks for the tips on PTM settings, I'll try Sport 1 next time out. So if I go to track mode without entering into PTM settings am I right in assuming both stability control and traction control are more invasive than the PTM dry modes upwards, but less invasive than sport mode? Traction control was super invasive so I switched it off.

2001PewterWS6

I got a 2019 radiator from Rockauto, Katech thermostat and a Cordes Heat Exchanger to keep my temps in check.

BrunoTheMellow

To be able to drive an A8 on track without overheating for 20 minutes you will have to install the lg or gspeed kit + their oil coolers. Don’t even waste your time and money on other ideas. Don’t get oil coolers without going to the cheek heat exchangers as that will make your radiator get even less cool air. Nothing else will work othe than the full kits. They won’t work. Just won’t.

The car just doesn’t have enough grill area for all those coolers. Once you get the engine coolant and oil temps in check, you will need the secondary trans oil cooler the newer cars got as your auto will overheat very shortly. 250 is max I believe.

I would give the car to a shop to install all this, cutting the bumper is annoying and it’s a long process to do the full kits and easy to make mistakes unless you’re technical.

just buy the full kits + trans cooler, give it to a shop and never worry about temps again. Here’s my car when it had the lg kit as comes from them (I’ve since had the bumper cutouts molded in to look more oem)

kdochert

Hi Bruno, read so many of your posts in all the cooling development threads (Dewitts, LG, & G Speed) that I feel your a legend in this regard, so thanks for being direct, I probable needed to hear that. I was always aware that the LG or G Speed were the true solutions, but I was hoping this was more for longer sessions and more back to back sessions, but it doesn't sound like this is the case, so I've backed away from the oil cooler option having looked at the install and unknown incremental gains tbh.

I have a half day event mid April where temps are normally 80 - 90 DegF so let's see how bad that goes as another data point that will set the boundaries for tracking with the car as it is. Not sure if I'd be willing to go all in for LG or G Speed, but if I did, knowing what you know now, would you still go LG or would you go G Speed and why? The Dewitts 70mm radiator I installed now enables me to run 20 mins @ 70 DegF ambient, so maybe I'll just track between fall and spring?

BrunoTheMellow

one of my good buddies had a 2017 A8 z06: he was a decent driver running inter to advanced pace on slicks but still a few seconds behind me in pace. Mods: 2019 thicker oem radiator, replaced aux trans cooler with Dewitt’s half trans half coolant radiator. Still could only run 3 hot laps before overheating in anything above 70 degree ambient even if short shifting at 5500 rpm in manual mod.

the problem is, you can add these incremental mods and then be back at the same place a few track days later because you will be getting faster and being on throttle more. I can decrease my coolant temps 10 degrees by slowing down 2-4 seconds a lap but who wants to do that! That’s why it’s important to know laptimes when discussing cooling.

and please don’t call me a legend. I just spent a lot of time reading this stuff and trying things myself.

regarding if I would do LG again or Gspeed? the LG kit is visually better but i don’t think it is not enough for automatic cars. For manual I would do LG kit with a bigger horizontal oil cooler instead of a secondary radiator. The gspeed stacked oil coolers is needed for A8 cars in my opinion. The Lg oil cooler is slightly too small. It works but i still hit 280 oil temp. Note I do still have the oem radiator so I could improve there too but I don’t need any more cooling for coolant.

heres my current setup in the middle with the oem supercharger hex as a secondary radiator for coolant instead of the little oem secondary aux radiator that’s 1/3 the size.



the LG looks phenomenal and fairly oem when you add better grills further back (originally they say to mount the mesh close to the front of the cutouts rather than rear) and have a body shop mold in the surrounds.

Bill Dearborn

Wet mode is super intrusive but if you try a few laps on a dry track it teaches you how the systems work together, you feel the stability control locking and unlocking various brakes as you go around the track, you feel traction control working and you hear and feel PTM working as you come out of a turn and it modulates the engine torque to keep the tires from spinning without causing the car to bog. Dry mode is less intrusive but is still too intrusive for me if I am running on a dry track and may still be similar to full-on stability and traction control. However, PTM is active and it works much better than traction control. In Sport 1 you have stability control that is similar to Competition mode in cars that don't have PTM. Sport 2 and Race have no stability control.

I use the following modes on the street: Weather (if required) and Tour. Sport is sort of worthless in my opinion. I tried it the first few days I owned the car and haven't used it again in 8 years. On the track, I use Wet (as required, although Pirelli Slicks don't work well on a wet track), Sport 1 most of the time but do use Sport 2 and Race at times. You sort of have to experiment with them for a while to see how the car works in each mode and how it responds to various track situations.

Bill

kdochert

It sure is tempting to create a track monster, but this is $10k + installation for cooling, then if I add swapping out my ceramic rotors for steel were are totaling > $15k and I just can't justify that additional expense on a car right now. Maybe one day tho!

kdochert

Are your road tires run flats? Since moving away from run flats I actually enjoy Sport mode now for driving on the road, it just tightens everything up nicely but still ok comfort, but yeah Touring for when I'm just bimbling along.

Thomasmoto

Yes, this is true. It's just what it takes to have a stress-free time on track. You might want to consider drag racing. That's about all I do with my Z06 anymore and in that environment, these are not issues that you have to worry about.

BrunoTheMellow

umm not quite. It’s $5k + labor for cooling last I checked. Maybe $7k Iron rotor swap tends to be no $ loss after you sell the ceramic rotors and pads.

kdochert

Here's the G Speed kit, they're only listing Stage 0 (no front facia cut) & Stage II which is $11k. I already have the Dewitts radiator so we can say $10k + install.

Was there a Stage I kit that was closer to the $5k you're quoting?

BrunoTheMellow

oh. LG kit is much cheaper it seems

GSpeed

For those of you on the cusp of cooling, Id recommend our oil cooler kit, and a 2019 radiator. Itll take 35* off the coolant temp, and 40* off the oil temp. it doesnt touch the blower circuit, so youll need to keep on that system being bled right and full at all times, but its a fraction of the cost for a massive gain in thermal capacity.

The oil cooler kit is not on our website, but Ill be sure to get it online soon. You may call and talk to Chris W, Kris K, Casey K, or Paul C. I will be sure they are in the loop.

BrunoTheMellow

what all entails this kit? Are these oil coolers under the headlights with fans? Or a horizontal oil cooler in place of the 2nd radiator ?

GSpeed

Removing the current engine oil cooler which is in the coolant circuit
2 additional cheek oil coolers, much like our C6 oil cooler kits, but with a slightly larger oil cooler and fan packs.
Cheek ducts are optional, but they are worth 20*+ with the fresh air.
our total surface area for the coolers is around 200 sq inch, which is pretty massive given the frontal area of the car.

coolers are worth 25-30*, and the 19 radiator is worth 5-10*

Should be a good combo for less money, and not a lot of hassle for those that just need a little extra.

kdochert

I’ll for sure take a look once you’ve posted to your website.

kdochert

Hi Bill,

I'm doing some number crunching on brake costs, and as you're somebody that has tracked with both ceramics and iron rotors, I'm curious how many track days you're getting from your iron rotor setup so I can compare with the above data?

Disk / pad replacement costs are approx. 4 - 4.5 times more expensive for carbon ceramic vs iron rotor setups, and although I don't expect the carbon ceramics to last 4 - 4.5 times longer, I do expect them to last longer, so I'm curious how much of a gap there really is on costs?

Cheers,

Kevin

kdochert

Hey chief, I still don't see this kit on your website, kind reminder, thanks!