Mullet
FORD GT OWNER
I think Performance Power runs their GT without the splitter and says it is stable.
I think Performance Power runs their GT without the splitter and says it is stable.
Indy GT
Yea, I got one...too
Ok Mark, I am here for you and Shawn. Let me see if I can shed a little light on the subject. But let me first address the lead post-
HH, as has been posted over the years, the FGT design engineers not only did a stellar job of giving us owner’s one hell-of-an engineered halo vehicle, but they described and documented (as best they could without giving the competition all their secrets) their engineering design efforts on this Detroit supercar offering. There are Society of Automotive Engineers (SAE) papers (11 papers on our current model FGT and 7 historical papers on the “old” Ford GT) bound and offered as a “book” publication “The Ford GT – New Vehicle Engineering and Technical History of the GT-40” SAE paper number PT-113. IMO, this is really must reading for anyone having technical interest and appreciation in the design intricacies of our FGT.
Ford engineers Kent Harrison, Michael Landry and Tom Reichenbach wrote SAE paper No 2004-01-1254,”2005 Ford GT – Vehicle Aerodynamics – Updating a Legend”. I have read (and reread) their paper and defer all technical facts to the published report. It is apparent the Ford design team (including powerplant, heat exchanger, aerodynamics, suspension and wheels/tires) had a design objective of the FGT achieving a Vmax (maximum road speed) of a little over 200 mph (reference SAE paper 2004-01-1257). To sell a car of this speed capability to the general public it is reasonable to expect the team to assess aerodynamic attributes (stability) of the car slightly beyond the design Vmax goal, knowing some buyer can or will add speed options to drive the car faster than it’s (Ford) governed speed of 205 mph. (Little did we know Ray’s impressive need for speed….)
So Dave’s comment from Tom, that the team investigated speeds up to 265 mph is certainly reasonable and knowing the source, likely accurate. The powerplant OE supplied in our car can “only” push our car to a maximum speed of approximately 212 mph (Nardo, 211.89 mph) and since drag force increases at a square function rate, the amount of power a modifier would have to add to the base engine power to push the car to the 265 mph region would be huge (and probably not possible). Thus aerodynamic investigation to 265 mph seems pretty reasonable. Report 2004-01-1254 does not state the maximum speed for which data was recorded.
When one asks about the “limit for these cars’ front end design” it is a bit unclear. There may or may not be any “limit”. The aero design might continue to generate downforce until such time that the produced aero loads exceeded the nose structural ability to channel the downforce to the suspension. The Ford engineers electronically limited the car to a 205 mph Vmax, certified the maximum speed of the saleable vehicle at 212 mph and windtunnel tested the design with favorable results to 265 mph, they are covered technically. The nose may structurally fail at 266 mph (we know it will not) or it may continue to work to 318 mph (complete conjecture), we just do not know what the “limit” is as it does not appear to have been encountered in covering the OE design up to 265 mph. Anyone pushing their FGT beyond the 265 mph wind tunnel reviewed speed then becomes the fleet “test pilot”.
As a pilot (both of his aerobatic airplane and his TT FGT) Chip’s aerodynamic comments are also accurate. The FGT design team benchmarked wind tunnel testing with an original 1968 GT40 (chassis #1030 Le Mans winner) to document the aerodynamic characteristics of the original form. The GT40 was found to have an average front coefficient of lift equal to POSITIVE 1.2 (varied from 0.0 to +2.45), meaning the front of the car was being lifted off the roadway when in fact you want just the opposite. The report states the obvious conclusion, “As can be seen from the data, it was clear why GT40 drivers complained of front-end lift on the Mulsanne straight!” From this testing the team generated “normalized” (a way of publishing relative values without having to release the actual values selected or recorded) coefficients of lift of less than -1.0 for the front end lift (again negative here meaning we definitely want DOWN force not lifting) and less than -1.0 for the rear end lift. Overall shape drag coefficient and Lift-over-Drag (L/D) were also booked and goaled but you can read those challenges in the report for yourselves.
A 0.45-scale aero “buck” model of Camilo’s early design studio styled shape was wind tunnel tested in California and both the front and rear aero design coefficient targets were still nowhere near the team targets. “There were four phases of development with the 0.45 scale aero buck on a moving road surface wind tunnel. Each phase produced an enhanced aero package.” The final aero development phase (T4) “produced an aerodynamic package that minimized the vehicle drag (better than target), produced balanced (40/60) front rear downforce (both better than target), and a lift over drag (L/D) ratio better than target.” Recognizing all collected data contains variability, report Table 4 gives the final coefficient values of 0.88-0.97 overall drag (target less than 1.0), -1.2-0.0 front lift coefficient (target less than -1.0), -1.95-0.0 rear lift coefficient (target less than -1.0) and 0.0-1.98 L/D coefficient (target greater than 1.0).
Specifically referring to the resulting production front aero package, the report states, “The front spoiler affects downforce in a variety of ways. By reducing the gap between the vehicle and the road, the front air dam reduces the flow area and increases the speed of flow under the vehicle. This produces a high-speed, low-pressure region of flow that pulls downward on the nose of the vehicle. The front airdam also creates a high-pressure stagnation zone at the front of the vehicle, which pushes down on the horizontal splitter adding additional downforce. The mini underbody diffusers in front of the front tires accelerate airflow into the wheel wells improving the front spoiler efficiency.” The report further discusses in similar engineering language (only appreciated by few) the intricacies of the aft aerodynamic treatments, side air dams, underbody diffusers, converging/diverging air diffuser, NACA mini diffusers and rear spoiler.
Hopefully through what I have related above (or better, reading the SAE report yourself) you come to appreciate the amount of attention, detail and work which Ford designed into our car 200+ mph aerodynamics and that the package is a completely INTEGRATED SYSTEM. The front and back aerodynamics are harmonized to work together providing a system aerodynamic package. Longer chin spoilers, side air splitters or rear diffuser geometries may look aesthetically more pleasing to some, but what do they do to the integrated aerodynamic package designed, TESTED and certified by Ford? They may be fine, they may have some shortcomings. You be your test pilot.
After the aero package was finalized on the 0.45 scale aero buck, further sensitivity testing was performed by workhorse #2 (WH2) on the 11,800 foot airport runway in Oscoda, Michigan. The “CP” configuration vehicle “was equipped with linear potentiometers to measure shock travel, and wheel force sensors, which were developed in the Ford Racing Technology group and currently used for vehicle testing in various racing series.” Three phases of on-the-road testing were conducted; two in Oscoda and the final phase in the Speed Bowl at Nardo Italy. Measured parameters included vehicle speed, lateral and longitudinal accelerations, yaw rate, airspeed, wheel forces in the z-direction, wheel moments about the y-axis and shock travel at all corners. Phase I consisted of 36-runs to assess aero package sensitivities with regard to 1) Front Axle Lift, 2) Rear Axle Lift, and 3) Coastdown/Drag. An experienced Ford test driver also completed a subjective vehicle performance evaluation. Phase 2 was for signoff of the design intent aero parts for high speed performance. And the final phase in Nardo was high speed validation testing at sustained speeds in excess of 150 mph.
From the report Table 6 with regard to the topic of this thread, Front Axle Lift is “highly sensitive” to 1) Front Under Tray, 2) Front Splitter Width and 3) Vehicle Rake. (See Chip’s correct assessment based on conversations with Mark McGowan). Front Axle Life is “mildly sensitive” to 1) Side Splitter Position, 2) Front Splitter Height and 3) rear NACA Ducts. Front Axle Lift is “negligibly sensitive” to the Rear Spoiler Extension.
Mark, I hope this helps you and others. The report(s) are a very interesting read and identify the enormous amount of detailed engineering and associated manpower/equipment costs which Ford expended while developing our vehicle. We can be proud of their efforts to give us such a spectacular vehicle in the compressed delivery time frame they were allocated.
Bill,
IMO, that was one of the best posts that has ever been put up on this Forum, perhaps the best. I have read the book (of SAE papers) you referenced but I think I got more out of your brief distillation of that material than I did from the book itself. Thanks for the time & effort you put into that writeup. It was outstanding.
A side note as we approach GT Speed Day on April 21 with an extended run of 1.7 miles, an understanding and appreciation of the information in Bill's post is important. Especially the part about being your own test pilot. Just because our cars, especially the TT's, can effortlessly achieve velocities that were unfathomable in a street legal auto just a few years ago doesn't lessen the physics (read that-violent destructive forces) if something comes apart causing a loss of control. During my years on the airshow circuit over 40 of my friends died in their airplanes. The annual mortality rate in that profession is 2%. About 1/3 of those who died were killed by mechanical or structural failures. Time and again, one of my buddies would describe to me the "new innovation" that he had incorporated into his aerobatic plane and the cool things it was going to do for performance. But nature sides with the hidden flaw and every flight with that new improvement was indeed a "test flight". Way too often that improvement failed in a completely unexpected way, often causing the loss of the plane and the death of the pilot.
I could relate stories of 6 pilots who were killed when aerodynamic mods caused a structural failure and most of these occurred at lower speeds than our GT's are running at these mile events. Let that sink in.
At 200+ MPH you and your GT are a ballistic missile with a tremendous amount of energy. A structural failure, blown tire, or loss of control at these speeds would probably not be survivable in a car without a roll cage and serious safety equipment.
In aviation it is well known that there is no safety in theory, hypothesis, or conjecture, no matter how well thought out they are. There is only safety in history. Don't tell me what you "think" is going to happen based upon theory because unforeseen variables often come into play with unforeseen results. What "did happen" in actual testing is all that really matters. Actual test results (history) is where safety resides. Mark H and Ray have taken Hoosier R-6 tires to 255+ MPH. The stock aero has been taken to 269.9 MPH. I'd be a lot more nervous if I was the first guy going there.
Chip
IMO, that was one of the best posts that has ever been put up on this Forum, perhaps the best. I have read the book (of SAE papers) you referenced but I think I got more out of your brief distillation of that material than I did from the book itself. Thanks for the time & effort you put into that writeup. It was outstanding.
A side note as we approach GT Speed Day on April 21 with an extended run of 1.7 miles, an understanding and appreciation of the information in Bill's post is important. Especially the part about being your own test pilot. Just because our cars, especially the TT's, can effortlessly achieve velocities that were unfathomable in a street legal auto just a few years ago doesn't lessen the physics (read that-violent destructive forces) if something comes apart causing a loss of control. During my years on the airshow circuit over 40 of my friends died in their airplanes. The annual mortality rate in that profession is 2%. About 1/3 of those who died were killed by mechanical or structural failures. Time and again, one of my buddies would describe to me the "new innovation" that he had incorporated into his aerobatic plane and the cool things it was going to do for performance. But nature sides with the hidden flaw and every flight with that new improvement was indeed a "test flight". Way too often that improvement failed in a completely unexpected way, often causing the loss of the plane and the death of the pilot.
I could relate stories of 6 pilots who were killed when aerodynamic mods caused a structural failure and most of these occurred at lower speeds than our GT's are running at these mile events. Let that sink in.
At 200+ MPH you and your GT are a ballistic missile with a tremendous amount of energy. A structural failure, blown tire, or loss of control at these speeds would probably not be survivable in a car without a roll cage and serious safety equipment.
In aviation it is well known that there is no safety in theory, hypothesis, or conjecture, no matter how well thought out they are. There is only safety in history. Don't tell me what you "think" is going to happen based upon theory because unforeseen variables often come into play with unforeseen results. What "did happen" in actual testing is all that really matters. Actual test results (history) is where safety resides. Mark H and Ray have taken Hoosier R-6 tires to 255+ MPH. The stock aero has been taken to 269.9 MPH. I'd be a lot more nervous if I was the first guy going there.
Chip
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GT38
GT Owner
Great post, Bill. :thumbsup For those who don't already know, Bill was associated with the SR-71 engine program and is no stranger to speed related engineering issues.
(Maybe someday you'll be discussing Mcr for the GT...!)
(Maybe someday you'll be discussing Mcr for the GT...!)
Indy GT
Yea, I got one...too
Thanks very much Specracer, Chip and Dick.
I try to put forth words (as best I can) to educate our owners, as many of these engineering related topics are complex, convoluted and interrelated. Chip you are absolutely correct, at 200+ mph things happen very quickly and tire/rim/suspension/aero package failures can be catastrophic. I am glad you reinforced the image of you being your own test pilot when you get beyond the test/prior experience range. Because you are....
And I really would not heap the accolades I do on the FGT team if I did not feel in my heart; these guys DID sweat the details! The GT product Ford delivered in the time allotted for the price they charged is IMO pretty spectacular. Having the privilege of talking to a number of the GT "team members" Dave has encouraged to attend our FGT rally’s has given me (as well as others) behind the scenes insight as to the blood-sweat-and tears these members went through to deliver our vehicle. I am proud to own one.
And although I certainly appreciate your nomination for the best Forum post ever, I must say your (Chip’s) dissertation on boutique blended gasoline has to be my favorite of all time. As we have had a number of new Forum members join us here, those who have not read this amazingly educational post should use the search function to find and read "My" all time favorite post.
Ok now Marky Mark, where are you???
I try to put forth words (as best I can) to educate our owners, as many of these engineering related topics are complex, convoluted and interrelated. Chip you are absolutely correct, at 200+ mph things happen very quickly and tire/rim/suspension/aero package failures can be catastrophic. I am glad you reinforced the image of you being your own test pilot when you get beyond the test/prior experience range. Because you are....
And I really would not heap the accolades I do on the FGT team if I did not feel in my heart; these guys DID sweat the details! The GT product Ford delivered in the time allotted for the price they charged is IMO pretty spectacular. Having the privilege of talking to a number of the GT "team members" Dave has encouraged to attend our FGT rally’s has given me (as well as others) behind the scenes insight as to the blood-sweat-and tears these members went through to deliver our vehicle. I am proud to own one.
And although I certainly appreciate your nomination for the best Forum post ever, I must say your (Chip’s) dissertation on boutique blended gasoline has to be my favorite of all time. As we have had a number of new Forum members join us here, those who have not read this amazingly educational post should use the search function to find and read "My" all time favorite post.
Ok now Marky Mark, where are you???
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Mullet
FORD GT OWNER
Indy
I'm debating something on another forum and think this is Right up your alley.
At a standing Mile I have said and FIRMLY believe every foot counts in relation to trap speed at the Mile. The main argument is my belief that if you do not hit it like a 1/4 pass all the way down you will not get as high of a speed if you were to rollout first gear at a medium pace.
Any wasted foot/feet means a lower trap speed.
I'm debating something on another forum and think this is Right up your alley.
At a standing Mile I have said and FIRMLY believe every foot counts in relation to trap speed at the Mile. The main argument is my belief that if you do not hit it like a 1/4 pass all the way down you will not get as high of a speed if you were to rollout first gear at a medium pace.
Any wasted foot/feet means a lower trap speed.
fjpikul
GT Owner
Mullet
FORD GT OWNER
Based on all the drag racing I used to do, I would think the effect of launching a car over the course of a mile would have a negligible effect. MPH is a function of horsepower, not 60 ft. If I ran my Z06 at the track and pulled a 1.68 60 ft, I'd run 11.3@~125. If I ran my Z06 at the track and pulled a 2.0 Z06 ft I'd run an 11.9@~125. Dead hooking or bogging both always hurt the mph. If I spun hard out of the hole, I'd often end up with the highest mph I'd see that day.
I remember that time the orange gallardo that flipped ran something like 248 or 249. He rolled out, bogged, and basically botched the first 150 feet of the run. I thought "no way will this be a good number." It ended up being the fastest the car had ever gone to that point. If there is science to hitting it hard out of the hole, I'd still argue it's not worth it in mile racing due to breakage.
The Weekly Standard, April 2, 2012
Bill,
It appears that my "Boutique Gasoline" post is still circulating around. It was cut and pasted on many websites and a copy made it's way to both Chevron and Exxon-Mobil top management who distributed it to their executives coast to coast. I have read segments of it almost word for word (most often without credit) in several petroleum related articles. Rush Limbaugh quoted a section of it on his show some time back. But the topper came just this week. I opened my April 2, 2012 copy of "The Weekly Standard" (which I subscribe to) and on page 10 was a feature article by Steven F. Hayward titled "Bureaucratic Gas, To lower prices at the pump, abolish the boutique fuel regime". Mr. Hayward followed the structure of my writeup very closely and in sections nearly quoted me word for word. To illustrate:
__________________________________________________________
My words:
Ahhh, I'm sure there's a big environmental payoff for all of the economic pain that these blend requirements have imposed upon us right?? We now have the answer to that question. President Bush understood that problem because after hurricane Katrina he immediately issued an executive order suspending all fuel blend requirements nationwide. He knew that without taking this decisive action there is no way that America's remaining undamaged fuel refineries could keep up with demand. For about two months after Katrina all gasoline sold in the United States was essentially the same blend. There was no detectable difference in air quality during this time.
From Steven Hayward's article:
But hey, it's all worth it if our children can breath cleaner air right?...Indeed, the boutique gasoline requirements were waived in the aftermath of hurricanes Katrina and Rita in 2005, when half of the gulf coast refineries were knocked out of commission for several weeks. During the waiver...there was no noticeable uptick in ozone levels in EPA data.
__________________________________________________
Steven Hayward is a fellow at the American Enterprise Institute and has published several books. I'm glad he liked my GT Forum post!
Chip
Bill,
It appears that my "Boutique Gasoline" post is still circulating around. It was cut and pasted on many websites and a copy made it's way to both Chevron and Exxon-Mobil top management who distributed it to their executives coast to coast. I have read segments of it almost word for word (most often without credit) in several petroleum related articles. Rush Limbaugh quoted a section of it on his show some time back. But the topper came just this week. I opened my April 2, 2012 copy of "The Weekly Standard" (which I subscribe to) and on page 10 was a feature article by Steven F. Hayward titled "Bureaucratic Gas, To lower prices at the pump, abolish the boutique fuel regime". Mr. Hayward followed the structure of my writeup very closely and in sections nearly quoted me word for word. To illustrate:
__________________________________________________________
My words:
Ahhh, I'm sure there's a big environmental payoff for all of the economic pain that these blend requirements have imposed upon us right?? We now have the answer to that question. President Bush understood that problem because after hurricane Katrina he immediately issued an executive order suspending all fuel blend requirements nationwide. He knew that without taking this decisive action there is no way that America's remaining undamaged fuel refineries could keep up with demand. For about two months after Katrina all gasoline sold in the United States was essentially the same blend. There was no detectable difference in air quality during this time.
From Steven Hayward's article:
But hey, it's all worth it if our children can breath cleaner air right?...Indeed, the boutique gasoline requirements were waived in the aftermath of hurricanes Katrina and Rita in 2005, when half of the gulf coast refineries were knocked out of commission for several weeks. During the waiver...there was no noticeable uptick in ozone levels in EPA data.
__________________________________________________
Steven Hayward is a fellow at the American Enterprise Institute and has published several books. I'm glad he liked my GT Forum post!
Chip
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2112
Blue/white 06'
You are referring to this post I believe (for those who have not read it yet);
http://www.fordgtforum.com/forums/s...such-a-rip-off&p=280646&viewfull=1#post280646
http://www.fordgtforum.com/forums/s...such-a-rip-off&p=280646&viewfull=1#post280646
Matech GT1
GT Owner
Our ex-race engineer at Matech is a highly experienced aero chap, and I'm sure would be able to contribute to this debate on improving front end downforce and controlling unwanted rake above 200 mph, potentially at the reduction of comfort below those speeds.
There were lots of trials, adjustments and tweaks made both during the development and during the season of the GT1 car to improve aero performance for both handling and speeds - though clearly in the same speed bands that you are discussing here.
Steve.
There were lots of trials, adjustments and tweaks made both during the development and during the season of the GT1 car to improve aero performance for both handling and speeds - though clearly in the same speed bands that you are discussing here.
Steve.
PeakCompletions
Boost is an addiction...
Some great posts and information in here for sure!
When we analyzed many different options and configurations for the GT and what we could do to get "cheap" or "free" HP by reducing drag and trying to increase MPH this was something we spent a lot of time on. In fact we even had MATECH design and send a lower downforce front end for the yellow car.
At the end of the day, all of the efforts and reviews that we put in pale in comparison to the engineering that was put into the car in the first place and we decided to leave the AERO alone for now. This was evident from the testing we did in Miami with the car before the Exotics Rally race and how stable the car felt at speed with a BONE STOCK OEM AERO configuration. (minus mirrors and wipers actually)
AMAZING JOB FORD IN DESIGNING WHAT I THINK IS THE BEST AERO PACKAGE OF ANY STREET CAR BAR NONE!!
We will be experimenting with some of the things we have in place for the next level and still need to get my schedule sorted to take the yellow car back out again to show what we have done in the last year and a half even with stock aero :biggrin
we are still debating the use of the custom aero we had designed but again, at 270+ things happen fast so once we have pushed the stock aero and our current design platform as far as we can then we will start easing into the testing of the new aero... a true test pilot scenario which has been detailed in the previous posts and not always with the best results LOL
One of my biggest worries is the tires and as such have 2 full sets of rims and heat cycled brand new hoosiers. No one can tell us what they are good for. We know at these speeds they are fine for at least 6 runs (8 miles per set?? HAHA)... we just switch them out for new ones to eliminate any risk of breakdown in the tires or risk of blowout...
Good news is there is a lot more MPH available in the stock aero so we don't really have to worry about that just yet :cheers
When we analyzed many different options and configurations for the GT and what we could do to get "cheap" or "free" HP by reducing drag and trying to increase MPH this was something we spent a lot of time on. In fact we even had MATECH design and send a lower downforce front end for the yellow car.
At the end of the day, all of the efforts and reviews that we put in pale in comparison to the engineering that was put into the car in the first place and we decided to leave the AERO alone for now. This was evident from the testing we did in Miami with the car before the Exotics Rally race and how stable the car felt at speed with a BONE STOCK OEM AERO configuration. (minus mirrors and wipers actually)
AMAZING JOB FORD IN DESIGNING WHAT I THINK IS THE BEST AERO PACKAGE OF ANY STREET CAR BAR NONE!!
We will be experimenting with some of the things we have in place for the next level and still need to get my schedule sorted to take the yellow car back out again to show what we have done in the last year and a half even with stock aero :biggrin
we are still debating the use of the custom aero we had designed but again, at 270+ things happen fast so once we have pushed the stock aero and our current design platform as far as we can then we will start easing into the testing of the new aero... a true test pilot scenario which has been detailed in the previous posts and not always with the best results LOL
One of my biggest worries is the tires and as such have 2 full sets of rims and heat cycled brand new hoosiers. No one can tell us what they are good for. We know at these speeds they are fine for at least 6 runs (8 miles per set?? HAHA)... we just switch them out for new ones to eliminate any risk of breakdown in the tires or risk of blowout...
Good news is there is a lot more MPH available in the stock aero so we don't really have to worry about that just yet :cheers
STORMCAT
GT
Hey Ray,
Ford really needed the front Splitter for the Ford mandated stock ride height. Once you rake the car that requirement goes away. The wind tunnel reading we got with a raked car and stock splitter was 4 to 1 front to back. You know our old Friend JB with the white car has run over 250mph with no front splitter at all just a raked set up.. That front splitter is probally costing you some serious top speed.. I am sure there is some concern in your mind but it's been done. Take it off and do a run to 240 and I am sure she will feel fine.. removing the front splitter would reduce the front down force and give you some more rear down force and improve traction..