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  • David Phillips
    Editor And Chief
    David Phillips is a long-time contributor to print and electronic publications in the U.S. and abroad, including Racer, Autosport, AutoWeek, Motor Sport and SPEEDtv.com, oversees the daily updating of news stories and assigns, edits and contributes feature material for inRacingNews.com.
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    29 years old, Dave Judson lives in Mentor, Ohio. Dave has grown up with racing, watching his father win races and championships at the local go-kart track as a youngster and continuing his love of racing while watching NASCAR, Indycar, Formula 1 and sports cars.
    Judson has enjoyed a successful sim-racing career of his own in the IZOD Indycar iRacing Open and Fixed Setup Series. He has race wins to his credits as well as the Division 1 Championship of the Open Series in Season 1 of 2013 and the Overall Championship of the Fixed Series in Season 3 of 2013.
    Dave has a Bachelor's Degree in Business Administration from Cleveland State University and is looking to expand his horizons by writing for inRacingNews.

  • Matt A Kingsbury
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    Kingsbury lives in Fairfield, Connecticut where he currently attends Sacred Heart University. He is a fan of any form of racing, from NASCAR to IndyCar, Formula 1, and especially endurance racing. The summer of 2013 saw Kingsbury attend IndyCar's return to Pocono Raceway as well as the ARCA race at Pocono which Corey Lajoie won and got some pictures (including the accompanying mug shot) in Victory Lane thanks to his aunt!

  • Raymond Kingsbury
    Contributor

    Ray Kingsbury is a motorsport enthusiast and full-time university student, born and raised in Connecticut. He started his own racing career in BMX, riding bicycles competitively on the state level. In eight years he claimed the state championship and was ranked nationally before moving away from the sport. This void of activities led him to rediscover sim-racing in the form of NASCAR Heat. After a championship in the game's most competitive league Kingsbury started focusing full-time on his involvement in Live for Speed. There he founded Last Lap Motorsports which today has more than 20 members worldwide.

    When a few Last Lap Motorsports members decided to give iRacing.com a chance to feed their desire for more oval racing, Ray teamed with his brother Matt, Nathan Lamothe and newcomer Jimmie Jones to enter the ETV! Live Team Series and claimed the title after a dominating performance at Watkins Glen. To this day the team continues in both Live for Speed and iRacing.com and Ray still takes much delight in his own sim-racing career. A reporter for his high school newspaper before moving to university, Kingsbury keeps-up his writing activities by contributing to iRacing News.

  • Jeff Jacobs
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    Jeff Jacobs started autocrossing with the SCCA in 1990 while a student at the University of Florida. He has competed in the SCCA's National Tour and ProSolo series since 1995, winning a ProSolo National Championship in H-Stock in 2011 driving a 2010 MINI Cooper. Jeff completed his SCCA Club Racing drivers' school in 2012 at Roebling Road in a Spec Miata. He currently writes a column for the SCCA's Northeast Division in SportsCar Magazine and is the Region Executive of the Philadelphia Region SCCA.

    Jeff joined iRacing in October 2012. After starting with the MX-5 and SRF cars, he has been concentrating on the Ford Mustang FR500S, competing in the iRacing.com Mustang Cup series and the Continental Endurance Sports Car Series.

  • Jordan Hightower
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    Jordan began sim-racing in 2005 with the NASCAR Racing 2003 Season sim and then joined the iRacing community in June of 2008. He hails from Fort Smith, Arkansas where he is currently enrolled at the University of Arkansas Fort Smith, after which he plans to attend the University of Arkansas to earn his MBA. Although he enjoys watching and playing basketball, most of Jordan's focus is on motorsports, particularly NASCAR: "Anything that burns gas and goes fast, I like."

  • Scott Kelly
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    Born and raised in the greater St. Louis, Missouri area, Scott Kelly has had a love for motorsports ever since his father did the right thing by introducing auto racing into his life. No longer able to quench his need for speed by spectating NASCAR races on TV and watching dirt track stars slide around local tracks, Kelly eventually picked-up sim racing in his teens, wheeling cars found in Ratbag Games' "Dirt Track Racing" and "World of Outlaws: Sprint Cars" while also becoming introduced into multiple Papyrus sim-racing series. Joining the iRacing ranks in late 2011, Kelly set his sights on the short track racing he was familiar with, focusing on the sprint car, while also driving the Legends and street stock in multiple iRacing.com leagues.

    Kelly brings not just his enthusiasm for racing to the highest-rated motorsports simulation, but also his B.A. degree in English; he covers the action seen in the iRacing.com Sprint Car Series, while also placing the spotlight on various leagues within the service. Enjoying his start to a career in motorsports journalism, Kelly also doesn't mind visiting victory lane from time-to-time.

  • George Wood
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    After beginning his racing career with go-karts at age seven, George then turned wrenches on street stocks until he could finally turn the wheel. Following the successes of his friends and family, George has since retired from real-world racing, where he is now a science and mathematics faculty member for several local community colleges. When George isn't grading laboratory reports or iRacing, he is performing at bluegrass festivals in the Northeast, making fishing lures, playing golf, and rooting for his beloved Baltimore Orioles.
  • Chris Hall
    iRacing.com Series Writer
    Chris Hall has been writing since the nineties and moved into motorsports reporting in 2005, covering series such as ALMS, British GT, FIA GT, Le Mans and 2CV racing for Full Throttle magazine, Motorsport.com, The-Paddock.net, GTGateway.com, L' Endurance and, of course, inRacingNews. During 2008 and 2009, he worked with the RSS Performance Porsche Carrera Cup Team (and former British GT(C) champions) as a data engineer for a variety of drivers and models of 997s.
  • Jason Lofing
    iRacing.com Series Writer
    Jason is 21 years old and was born and raised in Elk Grove. California. A big time NASCAR fan, he hasn’t missed a race on Sunday in years. Lofing is also a huge San Fransisco Giants fan and tries to take in at least a couple games a year. Other than sim racing, his biggest (and far more expensive!) hobby is photography. Although he is rather new to sim racing, Lofing has already accomplished some pretty impressive results, qualifying for the 2011 iRacing Oval Pro Series in Season 1, 2011, winning the inaugural Landon Cassill Qualifying Challenge and finishing runner-up in the second one.
  • Dylan Sharman
    Contributing Writer
    I was born in Adelaide and we moved-out for Angle Vale for a few years until I was about 7 years old, when we moved to the Barossa Valley where I live now. I'm 19 years old and currently traveling back and forth weekly as I'm studying for a Diploma of Furniture Design and Technology.

    I've always had a love for racing as my close family did some racing and we were always out at the local dirt track. I joined iRacing back in 2010 and slowly but surely got the hang of it as this is my first experience with sim racing and am loving it each time I race. I've won two SK Modified titles (almost had three in a row but finished P2 in 2011 S4), an iRacingNews Challenge championship (2012 S1 Mazda) and was also an AustralAsian Intel GT Series Finalist.
  • Katier Scott
    Contributing Writer
    I am a veteran sim racer who first started racing way back in 1993 on the SPRTSIMS section of Compuserve with a league who can trace themselves all the way to the present. Within that league I act as Chief Steward and try to bring the unique viewpoint that this experience gives me into my articles.
    I have a BA (Hons) in Journalism and Editorial design and have been writing for seven years and currently cover the Lotus 79 CTC and Radical series alongside my freelance work. Living in the UK, as well as motorsports I love Photography, Arts and Crafts and reading.
  • David Ifeguni
    Contributing Writer
    I was born in New Haven, Connecticut in 1988 and moved to Midland, Michigan when I was two years old. I stayed there until third grade when I moved to Farmington Hills, Michigan and now I currently live in Naperville, IL where I'm attending Metea Valley High School as a 9th grader. In the past, I have participated in soccer and this year I plan on joining swimming or water polo. My family includes my 15 year old sister, a 7 year old sister and my mom and dad. I have been writing since 6th grade and have participated in many writing contests in my school and have received several awards for writing.
    My fascination for motorsports began when I was nine. The first NASCAR race I watched on TV was the 2009 Toyota/Save Mart 350 at Infineon Raceway, won by Kasey Kahne. My favorite NASCAR drivers are Kyle Busch, Dale Earnhardt Jr, and Jimmie Johnson. I have watched all the races in the NASCAR Sprint Cup, Nationwide and Camping World Truck Series since 2010. I currently have three wins on iRacing, two of them in the Nationwide car at Daytona and one in the Street stocks at Charlotte. My favorite car and type of track on iRacing is the Nationwide Series (B Class) car and superspeedways.

iRacing’s Corvette: Good Enough is Not Good Enough

by Ian Berwick, Vehicle Dynamic Engineer, iRacing.com on January 8th, 2010

We’ve gotten approval to build the Pratt & Miller Corvette C6.R GT1 car!  SWEEEEET!  OK, what’s first?  Hmmmm. Dyno sheets.  That’s the most important thing, right?  That beautiful sounding motor, deep and rumbling, with earth-moving torque and acceleration.  Now that sounds like fun!

iRacing.com Corvette C6.R: Sound like -- and is -- fun.

iRacing.com's Corvette C6.R: Sounds like (and is) fun.

Getting the power to the ground is next, so what gearbox does it use?  What are the various gear ratios?  How many options of gear ratio, and what’s the layout and the inertia of all the components?  Xtrac builds the box, and my friends at Xtrac USA have been exceptionally helpful with data for component inertias in the past, maybe they’ll provide me with additional values…

And it’s got wings, well, one, and it’s HUGE.  That must make a TON of downforce.  But then there’s none on the front, and they’re not allowed to use an enormous splitter or multiple diveplanes, so how much of that rear wing can they actually use?  I guess get the front end to work, and balance it with whatever wing position works, then.

I’ve also heard this car generates a ton of downforce.  I just read an article in Racecar Engineering that said it made as much as 1800lbs of it, so 0.9 tons actually!  I’d say that’s BARELY an exaggeration, then.

Oh, but it’s supposed to handle amazingly well too, so I guess we need all the suspension motion data.  Camber gain, spring rates, wheel rates . . . all that stuff.  I guess damping rates are needed as well, since we have springs that need to be controlled.

From ? to virtual C6.R, a cmobination of ?, ? and ?

From WinGeo3 to virtual C6.R, a combination of precise data, painstaking calculations and educated assumptions.

But what are the sprung and unsprung masses?  What are these items you ask?  Sprung mass is anything that the springs hold off the ground.  Unsprung is anything that follows the road surface, like the wheels (with tires) and the suspension (well half of it anyway, the ends that are attached to the wheel).  And now that we’re worrying about masses, that leads us to inertias.  How much inertia for the sprung mass vs the inertia for the whole vehicle?  Does that data exist?  How was it determined?  If it doesn’t exist, I get to break the car down into smaller individual components and take my best shot at calculating it all.  Fortunately, most of the bigger teams/manufacturers have a good handle on the inertias so this time it’s pretty easy.  No more than a few hours to get the numbers laid out with a variable fuel load.

What about the masses and inertias in the engine and driveline?  Thanks to Xtrac USA, the gearbox is easy.  The engine?  Not quite so simple.  General Motors  is not going to give me those numbers.  Not a chance.  So now I get to calculate all the inertias for all the moving parts within the engine.

Exhibit A: C6.R by Pratt & Miller or iRacing.com? (See below)

Exhibit A: C6.R by Pratt & Miller or iRacing.com? (See below)

So how much does a 7.0 liter engine crankshaft weigh?  Thanks to Google (a wonderful source of arcane information), it appears that a Chevy 427 crankshaft weighs approximately 53-57 lbs.  How much lighter than that is the factory race version?   I figure it doesn’t rev very high, and with all that torque it needs to be tractable, so super light isn’t really necessary, so let’s go on the high side of the range at 56 lbs.  And that crankshaft is tough to calculate.  Draw a crankshaft, break it down into all the individual sections that are symmetrical and try to get a rough estimate to work using the material density and mass, and you’ve got a decent approximation.  But that’s still just a guess.  An educated one, but still a guess… Con (connecting) rods are fairly well documented (online) at approximately 480 grams.  Pistons?  540 grams there…

What about chassis and suspension component inertias?  Yup, I get to calculate those too, but this time Pratt & Miller have provided the masses of the individual components and a total inertia for several assemblies, as well as the whole vehicle from their own shaker rig testing and CAD data.  That makes it much easier to be within the 2-3% error I’ll accept.  (Much more than that, and I have to dig deeper to try to locate any assumptions that may not be correct or outright miscalculations.  It’s happened before, and it’ll happen again, but that’s the challenge!)

Exhibit B: C6.R by Pratt & Miller or iRacing.com? (See below)

Exhibit B: C6.R by Pratt & Miller or iRacing.com?

What about aerodynamics and downforce now? What’s the “perfect” ride height and rake to maximize downforce and minimize drag?  How about lift to drag ratio?  Is that what we want to optimize?  Or is this thing stout enough that it’ll overcome most any bit of drag with all its torque and just go regardless?  If that’s the case, balancing the downforce front-to-rear is really the key.  With the rear wing trimmed out to the available minimum, there’s less than a 10% drop in drag, so clearly most of the drag is in the body, and the body lines are quite clean, with a very smooth underbody helping to keep it nice and slick.  That means a relatively small difference in top speed from min to max rear wing with this car.  But min rear wing also means the aero balance shifts forwards making the car quite loose.  Sounds exciting in a video game…not a good scenario at 190 mph in real life!  As long as that front-rear aero imbalance gets adjusted, then it’s fine and it’ll gain you about 5mph at top speed.  Like I said, it’s small at roughly a 2.6% increase in top speed, but you trade-out 6% of your downforce.  Is that a worthwhile trade?  How long is the straight at this track you’re racing on?  Are you going to get anywhere near absolute top speed?

(Seeing as I have the benefit of seeing the aero equations, and a few setups straight from the manufacturer, I can clue you in to the rough setups.  2.5 to 3 inch front ride height, and 0.5 to 0.75 inch rake with fairly stiff springs to control ride height and pitch are what seem to work well.)

Exhibit C: C6.R by Pratt & Miller or iRacing.com? (See below)

Exhibit C: C6.R by Pratt & Miller or iRacing.com?

This is all well and good, but what is the MOST important element of any car?  The tires!  Let me just pick up my phone and call Michelin.  They don’t recognize my name?  And they won’t give me all their tire data?  Why not!?!  It’s only years of data they’ve developed and paid for with their research budgets.  Now what?  All that’s left is trial and error testing of the tires that no one has much information on.  Sure, I might be able to get some vertical spring rates, and maybe some cornering stiffness numbers, but longitudinal and lateral stiffness are critical to the way a tire responds, let alone absolute grip.  And is it a Pacejka-based tire model, or a Magic Formula Tyre model, or one of the many other derivations out there?  There are so many nuances that those models don’t effectively quantify, but they at least offer a starting point.  Ultimately it comes down to getting as much feedback as possible from real-world racers, and applying what we know about tires to what knowledge they can share with us.

So how long does this process take?  How much do I get to start with?  The more data I get, the faster some stuff gets done, but that can also delay the process.  If the wind tunnel data has one data point that’s not coincident with the equation, if the car has rubber bushings in the suspension, if the track performance isn’t in line with what the data is saying . . .  Or say there’s NO DATA.  Where do you start then?  Contract to have CFD data done?  Maybe you can find some dyno numbers and an established top speed, so you can get a drag number figured out.

Exhibit D: C6.R by Pratt & Miller or iRacing.com?  (See below)

Exhibit D: C6.R by Pratt & Miller or iRacing.com?

How long?  For a car like the Solstice, the Spec Racer Ford or the Legends car — you know something with limited aero –  it’s a fast three weeks or maybe a little more to establish performance limits before a public rollout.  For a car with limited aero, likely five-six weeks, just to make sure the downforce numbers are reasonable outside the “normal” ranges.  Aero dependent cars like the Dallara?  Eight-twelve weeks might be necessary, just to verify that all the individual pieces are working as intended, and the handling is correct.

The big thing is, no matter how good the product is, it can always be made better.  So keep your ears open, listen to what everyone says, and never settle for “good enough.”

*                                                           *                                                             *

A & C – Pratt & Miller (images by Wikipedia and Corvette Racing); B & D – iRacing.com (screenshots by Matt Orr and Bryan Heitkotter)

23 Comments or Trackbacks

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  1. Name Email

  1. Sean Siff
    January 8th, 2010 at 6:39 pm

    Awesome article Ian! I learned a lot from reading about the process! Keep up the good work.

  2. Sam Hazim
    January 8th, 2010 at 9:06 pm

    Fantastic insight, thanks Ian – this wasn’t prepared in 30 seconds and I appreciate that.

    I think this is just the sort of insight we all could hope for when the notion of a development blog was banded about a while back.

  3. Aaron Devaney
    January 8th, 2010 at 10:50 pm

    Great insight into the making of the cars. Thanks for taking the time to write an article. it makes you really appreciate the attention to detail.

  4. Daniel Buck
    January 9th, 2010 at 12:41 am

    AWESOME ONE, MAN! especially for the pictures!! great stuff right here everyone!!

  5. Marcus Caton
    January 9th, 2010 at 5:05 am

    wow…..
    Great read

    BTW keep up the good work and feel free to post more Optimum info
    maybe the COT next *prepares notpad*

  6. MM
    January 9th, 2010 at 8:08 am

    Thanks Ian, very cool to know a little more how things work to build a car in iRacing! :)

  7. Ray Bryden
    January 9th, 2010 at 3:00 pm

    Wonderful glimpse into the process – Great job, Ian!

  8. George Kuyumji
    January 9th, 2010 at 11:51 pm

    Great article. More of this stuff please

  9. Byron Forbes
    January 10th, 2010 at 2:55 am

    Fantastic – good to see you guys earning your money! :D

  10. Iain Mabbott
    January 10th, 2010 at 8:01 am

    Very interesting article Ian, thanks for sharing that with us.

  11. eddiespag
    January 11th, 2010 at 3:47 am

    Say… in that one screenshot where the Vettes are shown from the back, is that the new future build with all the redone track surface and environmental lighting?

  12. Lincoln Miner
    January 11th, 2010 at 5:17 am

    Thanks Ian! Great article!

  13. Don
    January 11th, 2010 at 8:41 am

    So basically lots of guessing are still involved! Anyway thanks for sharing!

  14. John Prather
    January 11th, 2010 at 12:18 pm

    Fantastic Article.

  15. James Andrew
    January 11th, 2010 at 12:33 pm

    Fascinating read!

  16. Ian Berwick
    January 11th, 2010 at 6:44 pm

    Thanks guys! I’m more accustomed to technical reports than news articles, so it was a little tough to make it not quite so impersonal and… boring.

    Don — I prefer to think they are EDUCATED guesses…

  17. m
    January 11th, 2010 at 11:22 pm

    You cheated with B – it has DOF (depth of field) – iRacing doesn’t (yet). Photoshopping is cheating! ;)

  18. Matt Orr
    January 12th, 2010 at 4:43 am

    Hey hey hey………

    I put in a lot more than just some DOF when I was editing that Screenie. I’m fairly sure that D also has some treatment done to it also. Heck, I could care less what the article said, I’m just amazed that I actually have a little tiny image that I did on this page.

    But I did read the article, and wow…. Out on track you don’t really think about the small little things, but man, the detail they do is outstanding.

  19. Matt Orr
    January 12th, 2010 at 5:35 am

    Sorry, forgot to answer a question directly.

    Eddiespag – Nope, that was taken week one @ VIR in a practice session. Just photoshopped heavily as are most of my other screenies. Think I used a orange-ish Lighting Effect, shifted the Hue and Saturation to give it a more “Fall” look if your interested in knowing. Except for DOF, I could legitimately see iRacing looking like that if that is your thing.

    I don’t think iRacing will let me touch the secretive stuff. lol

  20. Ben Styles
    January 22nd, 2010 at 1:05 am

    Fantastic.

    I love and appreciate your work.

    Please keep a developer blog for the Williams F1 car…would be SO INTERESTING!

  21. Bob
    February 9th, 2010 at 11:50 am

    This isn’t the same Corvette we already have? Same pic at the top of the pages…

    http://members.iracing.com/membersite/member/CarDetail.do?carid=26

  22. Merrill Geant
    November 8th, 2010 at 7:18 pm

    I’d be inclined to clinch the deal with you on this. Which is not something I typically do! I really like reading a post that will make people think. Also, thanks for allowing me to speak my mind!

  23. bidou.ca
    November 11th, 2010 at 5:16 am

    Hi there,

    I have a inquiry for the webmaster/admin here at http://www.inracingnews.com.

    May I use some of the information from this blog post above if I give a link back to your website?

    Thanks,
    Mark