Hi Speed Lift
- Thread starter Bill D
- Start date
Ron is referring to the Audi 016 gearbox[/i] that was fitted to the RF that Gordon was driving.
Lynn Larsen
Lynn Larsen
I am with Mark on the issue of splitters and diffusers or, at least, what he (and I) would call a diffuser. Sorry, Kevin, but almost every Grand Am car I have seen has both a chin splitter and the series of inverted Us shaped device at the lower rear that I would call a diffuser. If you have seen me, you know how laughable it would be to even wonder if I have ever gotten under one to see if there were tunnels also:-D
Lynn
Lynn
I think we have gotten into a matter of semantics. The little U-shaped things on the rear of the Ford GT will produce a small amount of downforce. A car with true diffuser tunnels can produce it’s own weight in downforce at 150 MPH. There are 2 street cars that I am aware of that use Diffuser tunnels, the Ferrari 360 and Enzo. (I think Porsche may be using them on their new mid engine car, but I haven’t seen one and can’t say for sure.)
One thing you will notice is that both the 360 and Enzo do not have air dams, and in fact have raised areas in the center of the nose designed to channel additional air under the car to feed the tunnels. If you ever get a chance to see the underside (Up on a lift, hopefully) you will see that they are beautifully smooth with no protrusions to affect the airflow to the tunnels.
On racecars, you have to find cars where the rules don’t prohibit diffuser tunnels. Most classes don’t allow them because they work so well. Real diffuser tunnels will start at about 60% of the wheelbase back and require a purpose designed and built chassis to make them work. (One reason why you usually only see them in prototype classes, they would be nearly impossible to fit to a production based car) You have to use inboard pushrod coilovers for example, because the tunnels take all of the space between the transaxle and the inner faces of the rear tires and you can’t have a lot of stuff in there messing up the airflow. In order to make the tunnels as wide as possible, you need to attach the rear suspension directly to the transaxle with no frame pieces taking up space. This means a transaxle, bellhousing and engine block designed to take torsional and suspension loads.
In any case, this is all somewhat moot when talking about GT40s as they would require almost a total redesign to allow you to fit tunnels. From the standpoint of a “Fun to Drive” car, you don’t want large amounts of downforce anyhow. The cornering forces become very unpleasant (Remember the old movies from the early 60s of astronauts being spun in giant centrifuges to see how many Gs a person could take before passing out?) Secondly, a car that creates a lot of downforce is very unforgiving to drive. If the car gets at all sideways, the flow through the tunnels (or over the wings) is disturbed which causes you to loose part of your downforce. At that point, your chances of saving the car are minimal.
The GT40 is a great car, partly because it’s performance envelope is somewhat accessible by reasonably good, but not professional drivers. I am all for small mods to improve the cars (I plan to make a few myself). My point in all of this was not to discourage anyone from trying to improve the aerodynamics of their cars. Only to caution that you have to look at the car as a whole and not do something that will increase downforce at the front unless you are also going to modify the rear to keep the car balanced. Some of the Gulf cars (1076 comes to mind) used a slotted, sliding rear spoiler extension similar to what was used on the Mk II cars. That would be a good combination with a front spoiler. Another issue is to put some sort of ductwork inside the nose to make sure that all the air entering the intake goes through the radiator and out the top. That alone would make a noticeable difference in front end lift.
Have Fun,
Kevin
One thing you will notice is that both the 360 and Enzo do not have air dams, and in fact have raised areas in the center of the nose designed to channel additional air under the car to feed the tunnels. If you ever get a chance to see the underside (Up on a lift, hopefully) you will see that they are beautifully smooth with no protrusions to affect the airflow to the tunnels.
On racecars, you have to find cars where the rules don’t prohibit diffuser tunnels. Most classes don’t allow them because they work so well. Real diffuser tunnels will start at about 60% of the wheelbase back and require a purpose designed and built chassis to make them work. (One reason why you usually only see them in prototype classes, they would be nearly impossible to fit to a production based car) You have to use inboard pushrod coilovers for example, because the tunnels take all of the space between the transaxle and the inner faces of the rear tires and you can’t have a lot of stuff in there messing up the airflow. In order to make the tunnels as wide as possible, you need to attach the rear suspension directly to the transaxle with no frame pieces taking up space. This means a transaxle, bellhousing and engine block designed to take torsional and suspension loads.
In any case, this is all somewhat moot when talking about GT40s as they would require almost a total redesign to allow you to fit tunnels. From the standpoint of a “Fun to Drive” car, you don’t want large amounts of downforce anyhow. The cornering forces become very unpleasant (Remember the old movies from the early 60s of astronauts being spun in giant centrifuges to see how many Gs a person could take before passing out?) Secondly, a car that creates a lot of downforce is very unforgiving to drive. If the car gets at all sideways, the flow through the tunnels (or over the wings) is disturbed which causes you to loose part of your downforce. At that point, your chances of saving the car are minimal.
The GT40 is a great car, partly because it’s performance envelope is somewhat accessible by reasonably good, but not professional drivers. I am all for small mods to improve the cars (I plan to make a few myself). My point in all of this was not to discourage anyone from trying to improve the aerodynamics of their cars. Only to caution that you have to look at the car as a whole and not do something that will increase downforce at the front unless you are also going to modify the rear to keep the car balanced. Some of the Gulf cars (1076 comes to mind) used a slotted, sliding rear spoiler extension similar to what was used on the Mk II cars. That would be a good combination with a front spoiler. Another issue is to put some sort of ductwork inside the nose to make sure that all the air entering the intake goes through the radiator and out the top. That alone would make a noticeable difference in front end lift.
Have Fun,
Kevin
One thing not differentiated is street driven vs track driven cars. Ground clearance on a street driven car is an issue.
Since my car is primarily a street driven car, I don't plan on ever going 200mph in it. Ground clearance is set about 5 inches, and I've already drug the front end twice in 3000 miles. As far as the nose sticks out from the CL of the front wheels, you need to be really careful of parking lot transitions, inclines, etc.
Anything that limited clearance further than it is, would require extreme care and judicial choices what you run the car over.
5" in my neck of the woods won't even clear a dead opossum or groundhog unless a truck hauling pulpwood has made them a little thinner. /ubbthreads/images/graemlins/shocked.gif
If I were on a track planning on going that fast, where minimum clearance is not an issue, I too would explore any aero aids available.
Since my car is primarily a street driven car, I don't plan on ever going 200mph in it. Ground clearance is set about 5 inches, and I've already drug the front end twice in 3000 miles. As far as the nose sticks out from the CL of the front wheels, you need to be really careful of parking lot transitions, inclines, etc.
Anything that limited clearance further than it is, would require extreme care and judicial choices what you run the car over.
5" in my neck of the woods won't even clear a dead opossum or groundhog unless a truck hauling pulpwood has made them a little thinner. /ubbthreads/images/graemlins/shocked.gif
If I were on a track planning on going that fast, where minimum clearance is not an issue, I too would explore any aero aids available.
I'm with you Dave. Unless you are planning to race semi-competitively, it's pointless to attempt the ultra high speeds on the street with aero devices, as obstacles and potholes can appear out of nowhere.
My ride height is set at 4.5"F & 5"R, and I am VERY careful
of any roadkill or trash. I learned the hard way, as I have "touched" a curb and a couple of parking lot barriers. I have a nice dent in my oilpan from hitting a dead cat at 80MPH (he sneaked up on me!). How it hit the pan, and not the front clip, I still haven't figured out. At very high speeds with a splitter making clearance even lower, that could have been disastrous, even fatal!
For the track, properly sorted aero devices are the $#iT, but for the street, they are just plain impractical.
My 0.02 worth.
My ride height is set at 4.5"F & 5"R, and I am VERY careful
of any roadkill or trash. I learned the hard way, as I have "touched" a curb and a couple of parking lot barriers. I have a nice dent in my oilpan from hitting a dead cat at 80MPH (he sneaked up on me!). How it hit the pan, and not the front clip, I still haven't figured out. At very high speeds with a splitter making clearance even lower, that could have been disastrous, even fatal!
For the track, properly sorted aero devices are the $#iT, but for the street, they are just plain impractical.
My 0.02 worth.
Ron Earp
Admin
I think Bill is on the money here. I haven't driven my 40, obviously, but other cars I've had that have low ride heights take a beating on the street. My Lotus is around 5 inches front and rear and it scrapes often. Other owners, particularily the ones with the late model styling, regularily replace front spoliers due to damage.
Since I don't plan on hitting much over 130 in brief spurts on the street (read desolate highway with no other cars) then it wouldn't matter. Appears to be a nice track addition but not so feasible for the street car. And, I intend to drive mine as much as I can. I do the same with the Lotus.
What gets me is I meet fellows with fun cars that don't drive them. Excuses range from not wanting to rack up miles to it isn't street friendly. The heck with all of that - I'm building this thing to drive and drive I will - to work, to the store, etc. I'm not "saving" any of my cars for anyone. My philospohy is that they've been put on the planet for me to use up, and use'em up I will! /ubbthreads/images/graemlins/laugh.gif
Since I don't plan on hitting much over 130 in brief spurts on the street (read desolate highway with no other cars) then it wouldn't matter. Appears to be a nice track addition but not so feasible for the street car. And, I intend to drive mine as much as I can. I do the same with the Lotus.
What gets me is I meet fellows with fun cars that don't drive them. Excuses range from not wanting to rack up miles to it isn't street friendly. The heck with all of that - I'm building this thing to drive and drive I will - to work, to the store, etc. I'm not "saving" any of my cars for anyone. My philospohy is that they've been put on the planet for me to use up, and use'em up I will! /ubbthreads/images/graemlins/laugh.gif
Good point Dave. There are other clearance issues too. On level ground with 6" ground clearance in back and 5.5" in front I can open the nose and the splitter clears. Anything less and it's the formula car quick jack just to open the nose. This is not an issue with me but it will be with others. I have always had to quick jack my Lotus so doing the GT40 is natural for me.
So on the street I plan running 6" & 5.5" clearance but I'm thinking I'll pick up some stiffer springs for the track and lower the car to 4" & 3.5". I'd swap out the 15" period correct tires and coil-overs for 17" "Y" rated rubber or DOT racing tires and stiffer/lighter coil-overs. Re-align the suspension and set the corner weights again.
There are a lot of people who do not have this flexibility. These folks need to consider if they can deal with the clearance issues. Well that ought to cut sales by 50% but I don't want anyone to be suprised. These are "maxed-out" cars and "maxing them out" more will cause compromises in other areas.
Dave, thanks for bringing up the subject.
Mark
So on the street I plan running 6" & 5.5" clearance but I'm thinking I'll pick up some stiffer springs for the track and lower the car to 4" & 3.5". I'd swap out the 15" period correct tires and coil-overs for 17" "Y" rated rubber or DOT racing tires and stiffer/lighter coil-overs. Re-align the suspension and set the corner weights again.
There are a lot of people who do not have this flexibility. These folks need to consider if they can deal with the clearance issues. Well that ought to cut sales by 50% but I don't want anyone to be suprised. These are "maxed-out" cars and "maxing them out" more will cause compromises in other areas.
Dave, thanks for bringing up the subject.
Mark
the idea of a "deep nostril" was brought up a few posts back here... In the GT40s I've seen, the single nostril doesn't go down all the way to the aluminum/steel paneling... there is a gap.
Why do it like this? Does anyone know how much this effects aerodynamics? Seems like it would allow air to get under the front bonnet... possibly creating some kind of lift and increasing drag... all the while allowing water to get in there potentially.
Anybody make one that extends all the way down?
John
Why do it like this? Does anyone know how much this effects aerodynamics? Seems like it would allow air to get under the front bonnet... possibly creating some kind of lift and increasing drag... all the while allowing water to get in there potentially.
Anybody make one that extends all the way down?
John
You are correct that the original MK I twin nostril does not go all the way down to the panelling and that was surely a design flaw allowing air underneath to cause lift, and also not maximising airflow through the radiator with the consequent cooling benefits.
However, Frank Catt at Wealden Engineering can supply deep nostrils for GTDs that retain the twin nostril appearance but have the aerodynamics of the single nostril. My car and a number of the guys that race in the UK use these modified nostrils. I have also seen original cars running with these modified nostrils at Goodwood Revival (whether legal or not!) Here is a picture of mine:
I can't speak for the other club racers and their GTDs but in competition use or on track days I have had no problems at all with front end lift. Having said that, on most UK circuits, you can only get up to around 160 MPH before you have to be on the brakes for the next corner.
I think Roy's GTD has been driven over 180 MPH at an airstrip circuit but I am not sure if they experienced any front end lift. Paul, maybe you can shed some light?
Martin
However, Frank Catt at Wealden Engineering can supply deep nostrils for GTDs that retain the twin nostril appearance but have the aerodynamics of the single nostril. My car and a number of the guys that race in the UK use these modified nostrils. I have also seen original cars running with these modified nostrils at Goodwood Revival (whether legal or not!) Here is a picture of mine:
I can't speak for the other club racers and their GTDs but in competition use or on track days I have had no problems at all with front end lift. Having said that, on most UK circuits, you can only get up to around 160 MPH before you have to be on the brakes for the next corner.
I think Roy's GTD has been driven over 180 MPH at an airstrip circuit but I am not sure if they experienced any front end lift. Paul, maybe you can shed some light?
Martin
Paul Thompson 'Hooligan'
Admin
Hi Martin -
Roys GTD logged 176 at Heyford Aerodrome - no major problems with lift. Steering remained light at speed but car was beginning to be affected by strong cross winds on the day.
Car has been much modded since in suspension settings and engine power so another high speed test would be interesting.
ps - on circuit, the max we've achieved is 155.4 at Goodwood on Lavant straight. Interestingly - we can do it in 4th on the road tyres, but require 5th on the slicks - although the slicks feel much much safer should you really need to stand on the brakes. /ubbthreads/images/graemlins/blush.gif
Roys GTD logged 176 at Heyford Aerodrome - no major problems with lift. Steering remained light at speed but car was beginning to be affected by strong cross winds on the day.
Car has been much modded since in suspension settings and engine power so another high speed test would be interesting.
ps - on circuit, the max we've achieved is 155.4 at Goodwood on Lavant straight. Interestingly - we can do it in 4th on the road tyres, but require 5th on the slicks - although the slicks feel much much safer should you really need to stand on the brakes. /ubbthreads/images/graemlins/blush.gif
I have 5.5 Front 6 in. rear ground clearance on my MK-IV and Lola. Works fine on the street. I would not go lower. P4 will hopefully be same. On the street I've had no problem with lift. MK-IV does have a small splitter. P4 has canards. Some Lola's were fitted with Canards as well. In Can Am form my Lola had chin spoiler which worked as well as anything did in 66...
[ QUOTE ]
The Mk 1 went through 3 or 4 completely disinct noses over a period of about two years before they settled on the final one. Some of the earlier ones had masive lift problems. That is why it would have helped if they had specified which version.
[/ QUOTE ]
Take a look at the blue GT40 behind the yellow GT. That was the Mk I they tested.
http://www.fordvehicles.com/fordgt/media_gallery.asp?gallery=CONCEPT_PHOTO&bhcp=1
The Mk 1 went through 3 or 4 completely disinct noses over a period of about two years before they settled on the final one. Some of the earlier ones had masive lift problems. That is why it would have helped if they had specified which version.
[/ QUOTE ]
Take a look at the blue GT40 behind the yellow GT. That was the Mk I they tested.
http://www.fordvehicles.com/fordgt/media_gallery.asp?gallery=CONCEPT_PHOTO&bhcp=1
Here is a question for all. I have read in the past that in one of the races back in the 1960s one of the GT-40s hit a top speed of 235 mph. Is this true and if it was which one was it and how much hp did it have. On the Hollman web site he has a video of one of his cars at a Savanha, Georgia track hitting 220mph. Joe /ubbthreads/images/graemlins/confused.gif
John,
"In the GT40s I've seen, the single nostril doesn't go down all the way to the aluminum/steel paneling... there is a gap."
"Why do it like this?"
The difference between a full depth nostril (one or two hole) and a nostril that doesn't go down all the way to the radiator is that the original piece (full depth) had a two part mold.
KVA made the first kits and I'm just guessing here but they compromised and made the spare cover (nostril) with a one piece mold in order to save time and money and make the car more affordable.
You can't really fault them for this as it made the kit and subsequent ones after that available to more people who couldn't afford something like an original or a MK V. It just one of many compromises that make the kits more affordable, you can always upgrade later if you're going to be going high speed.
"Does anyone know how much this effects aerodynamics?"
Probably quite a bit, above 100mph or so. Air comes in the big front rad opening but all of it doesn't get out the exit. Like a cup pointed into the wind, not aerodynamic at all.
"Seems like it would allow air to get under the front bonnet... possibly creating some kind of lift and increasing drag..."
there are horror stories about the nostrils coming off at speed, especially if you put the dzus clips on the wrong side of the body.
"all the while allowing water to get in there potentially."
I think water gets in on pretty much all the kits (I could be wrong), most of them are water tight further back at the front bulkhead.
"In the GT40s I've seen, the single nostril doesn't go down all the way to the aluminum/steel paneling... there is a gap."
"Why do it like this?"
The difference between a full depth nostril (one or two hole) and a nostril that doesn't go down all the way to the radiator is that the original piece (full depth) had a two part mold.
KVA made the first kits and I'm just guessing here but they compromised and made the spare cover (nostril) with a one piece mold in order to save time and money and make the car more affordable.
You can't really fault them for this as it made the kit and subsequent ones after that available to more people who couldn't afford something like an original or a MK V. It just one of many compromises that make the kits more affordable, you can always upgrade later if you're going to be going high speed.
"Does anyone know how much this effects aerodynamics?"
Probably quite a bit, above 100mph or so. Air comes in the big front rad opening but all of it doesn't get out the exit. Like a cup pointed into the wind, not aerodynamic at all.
"Seems like it would allow air to get under the front bonnet... possibly creating some kind of lift and increasing drag..."
there are horror stories about the nostrils coming off at speed, especially if you put the dzus clips on the wrong side of the body.
"all the while allowing water to get in there potentially."
I think water gets in on pretty much all the kits (I could be wrong), most of them are water tight further back at the front bulkhead.
