IMSA - Behind the Pit Wall

[Kevin]

Hello Everyone,

I do not post much on here, nor do I attend many WSCC events so I feel I should take a second to introduce myself.

I am currently in my final year of Mechanical Engineering at the University of Manitoba and have been involved with the Formula SAE team at the University since I started my degree back in 2013.  I do not attend any WSCC events with vehicles of my own, but I have done a few Autocross events with the FSAE car.

As with most (if not all) of you, cars have been a passion of mine for as long as I can remember. I set a goal for myself to try and find a job in motorsports where I could combine my engineering background and love of racing. This past year I was able to secure a few positions working as a DAG/Data Engineer for a few different teams and this year I have secured a position with Pfaff Motorsports who is competing in the GTD class in IMSA for the full season.

I am in Daytona until Sunday for the series-mandated test session for competitors in the Daytona 24-hour race at the end of the month. If any of you are interested in knowing what goes on behind the scenes at sportscar races such as these let me know. Obviously I am not able to disclose all details for privacy reasons, but I will do my best to answer any questions that you have.

[Jim Eh.]

Interesting. Thank you.

[Kevin]

Just some pictures from preparing for the Roar at the start of the month. The car has been under development for a while in Europe, but the North American tracks are presenting a new challenge for Porsche so we are all learning together at this point. It has been a big help having Lars Kern as one of our drivers since he has done a lot of the development for the new car in Europe. All pictures were taken by Jordan Lenssen (https://www.instagram.com/lenssenphoto/)

Edited January 21, 2019 by Kevin

[Kevin]

Thankfully when we were at the Roar we were able to use one of the garage spaces and qualified high enough to secure one for the race this week as well. It's nice having a garage to work in since it eliminates the time required to setup and take down the trailer awning, the only downside is that you have less room to work on the car.

This past week we finished up all the final prep for the car, including almost an entire day of fuel drop tests to match our required BoP for the weekend for in-car tank volume and flow rate. I always had heard teams complaining about how long it takes to get their setups perfect and now I finally understand why. So many factors are at play to ensure results are repeatable: fuel level in fuel rig, length of hose, height of re-fueler, distance of car from fuel rig and of course restrictor size.

Today we officially released our livery for the Rolex 24 Hours of Daytona, a very Canadian buffalo plaid. At first it started off as a joke between our team manager (Steve Bortolotti) and the Pfaff creative director (Laurance Yap) but our sponsors got on board with it and we may even be securing a sponsorship from Smoke's Poutinerie because of it.

[Kevin]

Some big news today for us Canucks north of the border; all IMSA Weathertech Sportscar Challenge races will be broadcast live on the Discovery Velocity channel as well as TSN will be airing tape-delayed "cutdown" recaps from events. Of course that is on top of the live streaming that has always been available at https://imsatv.imsa.com/.

[mcorrie]

Great stuff, thanks for posting!

[chkdsk]

On 1/22/2019 at 8:12 PM, Kevin said:

Some big news today for us Canucks north of the border; all IMSA Weathertech Sportscar Challenge races will be broadcast live on the Discovery Velocity channel as well as TSN will be airing tape-delayed "cutdown" recaps from events. Of course that is on top of the live streaming that has always been available at https://imsatv.imsa.com/.

Another reason to keep my Disc Velocity subscription going. I checked the link you posted and I can't see when it will be on Velocity and I could be blind. If you know, can you post it please? 
Thanks 

[Kevin]

23 hours ago, chkdsk said:

Another reason to keep my Disc Velocity subscription going. I checked the link you posted and I can't see when it will be on Velocity and I could be blind. If you know, can you post it please? 
Thanks 

To my best knowledge they are covering all 24 hours live (see linked article: https://sportscar365.com/imsa/iwsc/200-countries-set-for-weathertech-championship-tv-coverage/). I have also heard that because the deal with Velocity was finalized so recently, it was too late to update the TV listings for this week.

Hope this helps!!

[Kevin]

Just a heads up that the hour long race re-cap will be airing tonight at 5pm on TSN2 if anyone wanted to catch the highlights of the race.

[Kevin]

The days leading up to the race were pretty hectic and we didn't have much of a chance to relax before the green flag dropped. Porsche had a 35+ page manual of updates that had to be completed on the car in addition to the typical race weekend prep and setup optimization. On top of all that, we had a coolant leak from the gearbox heat exchanger during the last practice session that required dropping the gearbox to fix.

The middle picture is my view during all on-track sessions. I use my laptop screen to run a software connected to the live timing feed and also have a direct connection to messaging with race control and timing and scoring. The screen right in front of me is an extension from my laptop and displays the telemetry feed from the car. Our telemetry uses connection to a 4G cell network to broadcast its information so typically at the start of the race when everyone is posting on social media our connection does not work. The screen to the left of me is the live TV feed of the race and the screen to the right of me is an array of all the cameras around the track in live time. We access these TV feeds from coax bulkheads installed in pit lane which also includes channels displaying weather information, radar and timing.

[Miguel]

Very cool

[Kevin]

For those  of you who did not know, our race was cut short due to an accident during the re-start after the first red flag period. A car had spun out in front of us at the start/finish line and our driver had nowhere to go, thankfully he was able to brake and slow significantly before impact. Footage of the impact can be seen at 4:17 in the video below:

 

[Kevin]

The crash ended up damaging the firewall and sheared lower a-arm mounting points. It was decided to write-off the tub because it would be easier to get a new tub than try and repair the damage and end up with a chassis that isn't square anymore. The tear-down and total re-build took almost 2 weeks altogether but the team got it back together in time for use to head down to Sebring this week for a test.

An interesting point to note is that the tub is a production street-car chassis that has had its fenders cut out and a roll cage installed. The triangulated node in the front wheel well area is the upper mounting point for the front damper assemblies. I do not know the selection process for how chassis get selected to become racecars but I am fairly certain that it is not like the Ferrari FXX's which are chosen because of defects that make them unsafe for street use.

During tear-down we were able to get a good look at the pedal box and the brake pedal/master cylinder assembly. It is becoming more common now for the driver seat to be in a fixed position and the driver controls adjustable. The reasoning behind this is to prevent longitudinal weight distribution being thrown off by different drivers. It also makes it easier to design the safety cell around the driver if every one will be in the exact same position relative to padding and the roll cage. Of course Porsche has to be different from everyone else and uses brake master cylinders that pressurize under extension and not compression. 

[edmond]

Mister Kevin, i would like to get in touch with you if you don't mind. I am also from Manitoba and been doing some racing in and out of Canada.

[Kevin]

I know I have been pretty quiet on here, it has been a hectic summer with not much time off. Hopefully once the season winds down I can find time to provide some insight on how these teams function and what racing at this level is really like. My last race of the official 2019 season is this weekend at Road Atlanta and we are lucky enough to have our trailer parked beside Corvette's, who has the new C8R at the track this weekend for display and demo laps. The only technical details released so far is that it has a 5.5l flat-plane crank engine. It looks pretty tame from the outside, but if it is anything like the current C7.5R, it is an absolute spaceship beneath the skin.

[chkdsk]

17 minutes ago, Kevin said:

I know I have been pretty quiet on here, it has been a hectic summer with not much time off. Hopefully once the season winds down I can find time to provide some insight on how these teams function and what racing at this level is really like. My last race of the official 2019 season is this weekend at Road Atlanta and we are lucky enough to have our trailer parked beside Corvette's, who has the new C8R at the track this weekend for display and demo laps. The only technical details released so far is that it has a 5.5l flat-plane crank engine. It looks pretty tame from the outside, but if it is anything like the current C7.5R, it is an absolute spaceship beneath the skin.

 

 

Hello @Kevin , you and I need to swap jobs. Thank you.  

[Jim Eh.]

There seems to be a line forming ....

[beppca]

Very Cool! Thanks

[Kevin]

As the Rolex 24hr is coming up this weekend, I figured I would re-visit this topic and provide addition insight into what really happens during the Rolex 24 race weekend.

A common misconception about any 24hr race, is that the crew needs to be alert and awake for 24hrs straight. Certain crew members such as mechanics are only required during pit stops so they will often sleep between stops. The time between stops varies for each class in IMSA since each class burns a full tank of fuel at different rates to ensure that under green flag running, there are not multiple classes pitting at the same time. In the GTD class, time between stops from a full to near-empty tank can be anywhere from 50-65 minutes. IMSA positions teams from different classes beside each other on pit lane in an effort to maximize the chance of having clear pit box entry and exit for drivers. If there is a full-course yellow (FCY) and the safety car is dispatched, pit lane will only be open to specific classes following the order of DPi/LMP2 then GTLM/GTD. The opening and closing of pit lane to specific classes under FCY safety car is controlled by the race director over the race control radio channel.

For other crew members such as the engineers and crew chief, the Rolex 24 is closer to 36hrs than 24. Teams arrive at the track around 6am on race day to complete final vehicle checks, spares preparation and pit equipment servicing. The race starts at 1:40pm and provided your vehicle makes it the entire 24hrs to Sunday afternoon, you need to tear down and pack up your pit lane and garage setups and vacate the track by 5:30pm on Sunday. The fact that a 24hr race is significantly more than just 24hrs was the biggest eye-opener to me last year and made me gain even more respect for teams who make it look so easy.

A lot can happen in a 24hr period regarding position changes on track and teams who have been more than a lap down at some point in the race have come back to win. As important as outright pace is to maintaining or gaining track position, I learned early in the season last year that the easiest and most effective way of passing a car ahead of you is by fuel saving. Through saving fuel, if you pit on the same lap as the car ahead of you, there is a significant chance that you burned less fuel than them. While filling the tank back to full, you require less fuel and thus less time in your pitbox. Often the ability to fuel save while setting competitive lap times is what differentiates the best drivers from the mediocre ones. The most common strategy for fuel saving is lifting off of the throttle early and coasting into braking zones after high speed sections of track. Drag force is equivalent to the square of air speed so the faster the car is going, the greater the "braking" effect caused by aerodynamic drag will be.

Remarkably, a good portion of IMSA documents are accessible by the general public. For timing reports, weather reports, official schedules, team briefing slides and other race event-specific documents see the following: http://results.imsa.com/notice-board.html. For technical bulletins regarding regulations and BoP tables see the following: https://competitors.imsa.com/102019/2020-technical-bulletins.

[Kevin]

A few more tidbits of information to share while watching the on-board live streams tonight:

The additional lights that you see mounted on the GT cars for night races are actually referred to as "apex lights" and are angled outwards so while braking in a straight line, the apex of the corner is illuminated. While not highly effective at Daytona, they are incredibly useful for the after-dark portions of the Sebring 12hr and Road Atlanta 10hr races.

The GTD cars actually have driver air conditioning systems installed that either blow air at the driver, into their helmet, at their back or all of the mentioned. In the Porsche, the system had varying intensities from completely off to being on all the time. The most commonly run position during hot weather was the "performance" setting which would engage the A/C compressor clutch only when under the throttle pedal position was below a certain threshold. Similar engine performance favouring logic is used for battery charging as well. If the battery state of charge (SOC) is below a certain amount, then the alternator would always be engaged. If the SOC is at 100% or close to it, the alternator would not engage at all and if the SOC is just below full-capacity, the alternator would only engage under braking.

Electrical failures do happen and sometimes the crew will loose radio communication with the driver. At tracks were crew members can access the front straight wall from across pit lane, IMSA allows the usage of signs to communicate with the driver. Our protocol was that as long as the car was functioning mechanically sound, the driver was to stay out until the low fuel alarm came on.

The fuel system in the car is designed such that you can only see the exact level of the last 6L of fuel in the central collector. The cell has 4 pumps (one in each corner) that feed a central collector at the top of the tank. It is in this collector that the level sensor is located and from here that two high-pressure fuel pumps (one primary and one spare) feed the engine. In the Porsche 911 GT3R, the 6L capacity was enough for at least 2 full green-flag laps at every track we competed at. The car also has selective engine maps that vary how rich/lean the engine runs. Under FCY behind the safety car, the driver would use map 0 which is the most lean and under normal running would use map 3. Map 4 is the richest and is only used when an opportunity to pass is present. The last 6L in the fuel cell are all that really matter when it comes to knowing exact fuel level. The car does have a fuel-flow meter installed so we were able to keep track of how much fuel had been burned since the last fueling. The ECU also outputs fuel usage data based upon injector duty cycle for where the engine is operating within the loaded engine calibration and fuel maps. It is nearly impossible to mount a level sensor in the fuel cell to measure the entire level because of capacity blocks that have to be added to ensure cell capacity matches the specified amount as outlined by the BoP tables. The fuel cell has a full capacity of 120L but the car typically has to run in the 94L capacity range. The fuel rig in pit lane has load cells attached to it so we know exactly how much fuel was put in the car at each pit stop. Even when the car is filled in the paddock for practice sessions, it is common practice to measure fuel capacity by weight and not outright volume.

This leads to my next point, one of the most over-looked positions on an endurance racing team is that of the fueler. The IMSA BoP mandates that GTD cars cannot fill an empty car to full during a pit stop quicker than 40s. A typical 4-tire change takes no longer than 20s so the remainder of the pit stop is dependent on the fuel going in the car. If the fueler does not plug the head in perfectly straight or bobbles it slightly, the flow will be disrupted significantly and slow the rate of fuel passage to the car.

Another massively over-looked position is that of the tire guy. Though he may not be any of the mechanics going over the wall to actually put the tires on the car, the tire guy is responsible for ensuring their preparation. Each set that comes off the car needs to have their balancing weights removed, cleaned and inspected for any cracks or damage. They then are taken to a designated area where Michelin technicians are set up to dismount the used tires, mount new ones then balance them. Tire pressures are highly critical to vehicle performance and tire longevity, especially on the Daytona banking. Pure nitrogen is used in the tires to ensure repeatable pressure ramp-up and maintenance since target hot pressures need to be accurate within 0.15 psi. The mounted tires from Michelin are purged of whatever pressurized gas is put in them then the tire guy fills them with nitrogen from one of our own tanks. The pressures are always set higher than required, then bumped down a lap or two prior to the car coming in to pit. This is because the engineer may call for a change in cold pressures based upon driver feedback or change in ambient weather conditions.