Preference: Replica GT40 or Ford GT?

[George]

jmvelez, for me its hard to see aero dynamic advantages of the GT because they pretty much got identcal exterior styling. The GT however being larger, allows for more wind resistance, so even if it was slightly better aero dynamicaly because maybe the corners somehow are a fraction different from the original, the sheer size to me would kinda level it out. Ofcourse I could be totaly wrong, but I dont see it physicaly being any different to the 40.

And as far as the cobras etc with 13" brakes and so forth... stick 18" wheels on a GT40 and stick 14" billet alloy brakes, your car will stop harder than you will tolerate.

Thing is, weight. An F1 car uses tiny wheels and small brakes, because theres no weight to stop, so no need 'adding' weight by going large brakes etc. The GT40 being half the weight of a GT, 12" brakes would be equivalent if not better than 14" brakes on other super cars, simply due to the weight factor. This means the car would stop better than other super cars. Also being so much less weight, theres less inertia wanting to pull the car off the track. You can also match the spring rates etc to allow for propper handling, dont overspring, dont underspring, udjust the camber etc to match the cars weight. Suspension is there to control the cars weight when turning side to side and accelerating/braking front to back weight distribution. Springs dont care what kind of body is ontop. Also being such a light car, there is less work for the springs to have to overcome, thus makes the task easier to control and thus can produce superior handling. So, I dunno, doesnt make sense to me.

 

[Mike]

Why not CF brake discs if you're going all out? I was not aware that brakes discs were made from billet? How do you figure a GT weighing double that of a GT40?

Regarding aeros... there are stock bodied GTs running 260mph+ in the mile. The fact that they stay stuck to the ground at that speed is impressive. Would anyone try that in a GT40?

 

[Ian K]

jmvelez, for me its hard to see aero dynamic advantages of the GT because they pretty much got identcal exterior styling. The GT however being larger, allows for more wind resistance, so even if it was slightly better aero dynamicaly because maybe the corners somehow are a fraction different from the original, the sheer size to me would kinda level it out. Ofcourse I could be totaly wrong, but I dont see it physicaly being any different to the 40.

You are wrong - the Ford GT has a real splitter at the nose, and a huge rear diffuser in the back. The GT40 has none. I am also willing to bet the the whole underside of the GT has been carefully designed to improve airflow. You could add those things to a GT40, but it would stop looking like a GT40, especially if not done well.

Ian

 

[David]

Once upon a time I looked as a theoretical exercise at the aero on the GT40.

A rear defuser is pretty easy, the tail is already shaped that way although I haven't looked at the angles to see if it actually works.

Sills you'd want to square off and run skirts, shorten the tanks and run a vent from the rear of the front wheelwell out the side along with a deflector ahead of the rear wheels

Front end is tricker, you want to vent above the front wheels, add a splitter with deflectors for the front wheels, ensure all air that passes through the front radiator entry goes through the rad and then out of the top vent(s). Make sure that there is no gap between the bodywork and the floor.

That's the simple version, the details are rather tricker. IMO it would look pretty similar but not like a 60's race car.

 

[George]

Why not CF brake discs if you're going all out? I was not aware that brakes discs were made from billet? How do you figure a GT weighing double that of a GT40?

Regarding aeros... there are stock bodied GTs running 260mph+ in the mile. The fact that they stay stuck to the ground at that speed is impressive. Would anyone try that in a GT40?

I thought about the Ceramic brakes. I think thats the best you can get for stopping power.

GT weighs in near 1600kg.

GT40 carbon fibred weighs in 760kg. Alloy version chasis, around 900. So half/close to half, thus less work for springs to do.

Sorry for my ignorance, but can someone show me what a 'rear' defuser is that the GT has and GT40 does not? Ive looked at the rear shot of both cars, looks the same to me... so what exactly is being spoken off?

I also doubt very much so that ANY car goes 260mph in any circuit racing environment, thus those figures are just good on paper. Like the veyron which is a gimmik car. 2 tonn super car? lol.

 

[Jac Mac]

Your good friend Mr Watkins was kind enough to post a photo of a GT rear end in a transporter that gave a clear view of the diffuser, If you can bring yourself to re-read some of his recent posts you might find it.

 

[George]

THanks

Will see if I can find it.

 

[Velez]

George: Somewhere in my house I have a SAE publication on the Aero study that Ford did on the GT. The study cost Ford over 1M. They pullout a GT40 from a Museum to make the test. An ERA customer sells a side and front changes to make the car more stable at speed. He did not play with the end of car. We all can see the difference a diffuser makes in F1 cars and the amount of money that is speed on it.

F1 wheels are 13". The caliper wraps the rotor completely. Rotors are carbon fiber to operate a very high temperature. Between AP and Brembo they spend a fortune in F1 brakes (AP is owned by Brembo).

 

[Mike]

Sorry for my ignorance, but can someone show me what a 'rear' defuser is

I also doubt very much so that ANY car goes 260mph in any circuit racing environment, thus those figures are just good on paper. Like the veyron which is a gimmik car. 2 tonn super car? lol.

George, it's hard to take you seriously when you speak of building some insane version of a GT40 yet demonstrate time after time a severe lack of knowledge in the area of high performance autos. You must understand how you reinforce the stereotype of some teenage kid sitting at his mums computer in the basement right?

I would hardly call the Veyron a gimmick car given it's second fastest spot on the Top gear track almost besting the featherweight Atom. As you can see it is faster than many "light weight" exotics. Maybe light weight is not the end all be all you have asserted?

BBC - Top Gear - Power Laps

Here's a Ford GT doing 266mph in a standing mile. It would annihilate the Veyron in that setting.

266 MPH: Hofman Motorsports & Heffner Performance Twin Turbo Ford GT - Exotics Rally 4-25-2010 - YouTube
Ray Hofman testing - YouTube

You really should spend more time vetting your theories before expounding upon them in a public setting unless you are prepared for the inevitable ridicule surely to be directed at you my friend.

 

[George]

The veyron isnt much faster than the Enzo around the track yet its 600hp more, showing the problem of all that weight. I mean real super cars are not 2000kg.

Koenigsegg
Pagani Zonda

Both are all way under power of the Veyron and are faster (the standard veyron). The Lamborghini Aventador is 3rd with 690hp. The super Sport Veyron is 1200HP, do u realise that any one of those cars with more HP would kill the SS? And I kinda understand your statement about teenage whatever, but I dont because I ask honest questions?

In my mind, I look at it like this JUST AS AN EXAMPLE

I go buy an Enzo Ferrari. Does that car handle/go fast etc etc etc? Yes.

Do I know what on earth they did to the car to make it achieve that? No.

So, looking at that basic concept. I buy a Gt40. I pay for it to do X-Y-Z, the people that KNOW (just like the enzo builders KNOW) build the GT40 to do x-y-z. Do I know what on earth is needed to make it do that? No, hence all the questions I posted to help me get some idea as to what would be needed to achieve that goal.

So in the end though, maybe I dont need to know. I just need to tell the Builder "I want the GT40 to corner just as hard as a Koenigsegg, I want the weight transfer to be perfectly balanced etc because I want this car to handle as good as a hyper car. 600 Hp will also do because its gonna be a 9-10 second quarter mile car given the power-weight ratio.

N then just sit back and get the builders (like the enzo builders) to put together the parts from experience/track testing that will achieve what I asked for (whether that is BB or SB, whether they add splitters or not, etc etc). That way given the basic concept above, I pay the Money, does the car handle like a hyper car? Yes, do I know what these GT40 builders did to get it there? No (just like I dont know what enzo did either)

And for the Record. Im 28 and married. Am I ignorant about technical things in cars? Yes, but Im sure you are ignorant in other areas that I do know, does that make u a teenager now sitting behind his mums computer? So ignorance in a topic does not indicate a teenager cause thats just stupid. Do I know what I want though? Yes. A car that handles seriously well (like in the above example). Now I just need someone that DOES know this field to put the car together to achieve what I want. I just woulda liked to have some sort of understanding to what is needed so that when it gets done I atleast know to some degree what was used rather than being totaly oblivious why the car handles like an Enzo, but it seems to want to know makes me a teenager behind his mums computer simply because I dont know automotive. Guess I can wipe my ass with Music that I played all my life and understand how music effects the mind, how we think etc (used to play rock, queen, beatles, so forth, however impacts the mind in a negative way, now I play the Trumpet in classical music, as this music heals, and people with emotional problems such as suppressed hormones, depression etc, research has found that classical music is linked to healing this disease as it effects the mind positively while rock music usualy gets u in that state) with understanding how to prevent diseases by looking after your health, good food, bad food, how different things stimulate the body in a negative way such as caffein and whatever else, with understanding different models of business as I was part of a few network markettig company ideas, one such one was endorsed by Donald J Trump, and ofcourse traditional business which is based in the corporate world where the boss gets rich of his workers, and the workers get nothing (putting it in simple terms). Guess all that means nothing cause Im here asking questions which shows my lack of technical understanding in automotive.

And I am meant to take you serious when thats how it looks to me?

Can you understand why from this side of the screen it looks like this forum is full of stupid kids or arrogant adults to me given the replies?

N btw - thanks for the links.

 

[Ian K]

An ERA customer sells a side and front changes to make the car more stable at speed. He did not play with the end of car.

Sadly, Mark LaVea passed away, and Xtreme Classics is no more. So, more more splitters and sills (which were made in carbon fiber, and he had ERA and CAV/GTD versions).

Ian

 

[David]

As an example of the differences in aero between the GT40 and a modern supercar, this is the underside of an Enzo.

And this is the underside of an (original) GT40, tragically I can't find a better one (ideally with bodywork on) at the moment.

Notice the ribs along the bottom of the GT40 that would ruin the airflow? Arguably the space frame based replicas are actually better in this regard as they have a flat bottom.

Also notice the big fat hole for the engine/gearbox in the GT40 and the way in comparison the Enzo has the gearbox end faired in?

A mildly interesting thread on the subject (if only for the links) is at The Great FD3S Under-body Aerodynamics Thread: Photos, Products, Ideas, Results - RX7Club.com

Also see Mulsanne's Corner, technical analysis of contemporary sports prototype racing cars

 

[George]

Very interesting David.

Thanks very much.

 

[Velez]

Sadly, Mark LaVea passed away, and Xtreme Classics is no more. So, more more splitters and sills (which were made in carbon fiber, and he had ERA and CAV/GTD versions).

Ian

Sorry to know that he passed away. I talk once him over the phone several years ago. He tested the parts in a airport runway.

 

[Velez]

"Also notice the big fat hole for the engine/gearbox in the GT40 and the way in comparison the Enzo has the gearbox end faired in?"

My first ERA GT I requested that the gearbox and engine bay to be fully covered. My concern was not aero but water in the road (rain) which would pull dirt inside the bay. I have not looked at the current car if they did it again.

 

[David]

You do need to be careful about fairing in the engine/gearbox on a replica as a number are designed to be (partly at least) air cooled. If your engine has fins on the sump for example it might be a good idea to add an oil cooler. Same goes for the gearbox, especially if you are running over the original power/torque of the donor car.

Of course that assumes you don't have the sump lower than the floor anyway! :laugh:

 

[Dalton Veitch]

One of the engineering factors for springs is not the weight of the body, as in larger weight making them work harder. The body is intended to move smoothly while the wheels and suspension move up and down. Hence one of the important factors is the ratio of unsprung weight (wheels, brakes, suspension, etc.) to sprung weight (the rest of the car). More tricky with a light car than a heavy car. So you start moving weight from un-sprung to sprung side of the ledger, as in moving the springs and dampers into the body, or inboard brakes. Just one small aspect of correctly engineering a performance car. However, guys on the forum here know lots about this, right through aerodynamics to practical, hands on experience, so a bit of respect is in order for these guys who are usually very willing to help.

 

[Velez]

You do need to be careful about fairing in the engine/gearbox on a replica as a number are designed to be (partly at least) air cooled. If your engine has fins on the sump for example it might be a good idea to add an oil cooler. Same goes for the gearbox, especially if you are running over the original power/torque of the donor car.

Of course that assumes you don't have the sump lower than the floor anyway! :laugh:

The car has Oil coolers with fans at the back of the car. Also the back clip the vents are the Gulf type (round holes instead of louvers.). The GT40 also vents thru the side scoops pushing air to the back. The car never had any issues with temperature. Even the newer version that the engine is bigger. ERA did a good job.