GT Mk1 aerodynamics

[James]

The Mk1 can achieve well over 160mph without any aero aids. We've seen this here in the U.K, almost on a weekly basis, during the summer months at the GTD hill climbs and sprints.

These cars have been honed to near perfection, using a methodical approach to suspension setup. If your 40 feels like it will fly at 150mph then something is wrong somewhere. Twin nostrils can cause nose lift, even modified twin nostrils cause extra un-wanted lift. A close look at the Gulf 40's gives an idea of what worked on the front. i.e single nostril. Interstingly Roy Smart's 40 has twin notrils, I'm sure it would go even better with a single nostril!

That said I'm sure a small chin splitter would help the feel of the car on fast & long corners(120 mph). I'm thinking of Goodwood! /ubbthreads/images/graemlins/grin.gif

Mark, you're onto a winner if you can get a splitter that works well.

I noticed that Brian Redman used some fitted some canard fins, over night!, to 1021 at the Road America event to reduce front end lift. They looked ridiculous! But they obviously worked because he got fasted laptime and won the event.

I hope to use a combination of a very subtle chin splitter, small canard fins (perfectly formed with mini air dams) and an adjustable spoiler on the rear - as per MKII's. Now the only un-original aid would be the splitter, and since you won't really be able to see it I don't see it as a "sin". Will they work! Time will tell.

Regards,

J.P

 

[Malcolm]

Had an intersting afternoon out with Julian (you know the guy with the red one!) when we went to GTO Engineering. Kevin prepped the first over the line GT40 from this years Goodwood revival meeting and we got to discussing lap times and tyres etc. So he has Jackie driving for him in an original car and I have me in my GTD copy. No wonder that we are so far adrift in lap times! But the interesting thing is that when we were chatting about the same tyres ie Dunlops, Jackie managed a 4 sec time difference between the narrow ones needed to be run at the Revival meeting and the fatter ones I use. Jackie had done 1 min 19 secs on the 12 inch rears and 1 min 23 secs on the 10 inch rears. 2 inches make for 4 secs? Wow! Top speeds mentioned were below 160 mph on the rear staright (Lavant) at Goodwood so it is all about going fast around corners. Part of the appeal to the Revival meeting is that you see these ace drivers floating the cars around the corners. That is so cool to me. If and when I can do that I will call myself a driver!

Paul and Roy are the closest I know to 160 at Lavant with over 155 mph recorded. I am sure Paul will correct me if I am wrong. Roys is a very special car. I usually get to about 135 mph. These MDAs must be wonderful JP! /ubbthreads/images/graemlins/grin.gif

Anyway back to the point of my post. Depressingly Kevin concluded that our cars cannot be set up properly to be so far adrift from the original cars, notwithstanding driver differences. He has an old JAG E Type that consistantly laps at 1 min 29 secs! He expects us to be better than that.

Of course Julian and I now know what to do to correct this situation but to share that on a public forum with all our competitor friends looking in... Nah, you gotta be kidding! /ubbthreads/images/graemlins/grin.gif

Malcolm

PS. Splitters, dams etc on the front of a 40 don't look good in my opinion. Canard wings are ok if done well.

 

[James]

[ QUOTE ]

Of course Julian and I now know what to do to correct this situation but to share that on a public forum with all our competitor friends looking in... Nah, you gotta be kidding! /ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]

Scum Bag! /ubbthreads/images/graemlins/grin.gif

J.P

 

[Jools]

Malc and i like to call it TEAMWORK! I distract them, while malc takes a "Sneaky Pete" look through the tech/set-up files!!Your garage is on our list J.P /ubbthreads/images/graemlins/wink.gif

 

I should know by Nov 1 when the pieces will be ready for sale. Initially we'll be making the front splitter, the side sill extensions and the rear diffuser. I guess it makes sense to offer these in both fiberglass and carbon fiber.

We'll start taking deposits once we can determine a solid date for first shipment.

 

[James]

[ QUOTE ]
Malc and i like to call it TEAMWORK! I distract them, while malc takes a "Sneaky Pete" look through the tech/set-up files!!Your garage is on our list J.P /ubbthreads/images/graemlins/wink.gif

[/ QUOTE ]

You'll be in for a big scare if you get into my garage. That's where I keep the GIMP!! /ubbthreads/images/graemlins/grin.gif

J.P.

P.S Mark, when ready I'll have the lot. Splitter, side skirts & r.diffuser. Any idea on how they'll look? I don't want to offend to many of the originalists!! /ubbthreads/images/graemlins/grin.gif

 

[Ian K]

Well, I'll wait for final word from Rick Merz, but in the
old Kit Car article regarding his car, he drove an indicated
180 mph (maybe 190). Of course, I think he's changed the set
up since then.

Rick - care to comment? How did it feel?

Ian

 

I will endeavor to make these items as unobtrusive as possible. Asthetics are utmost.

Does anyone know of a GTD GT40 in the Northern Va area? I can get access to RFs and CAVs but I'd like to compare dims on the GTD also.

Thanks,

Mark

 

[Gary Gibbs]

Rick Merz (GTD)is down in Va. Beach. I would expect that the GTD is similar to the CAV.

 

[Rick Merz]

Ian, That is correct, after I had my car running for about 2 years and had it sorted out pretty well I thought that I would see how fast it would go. I made a run down I64 where there weren't any on ramps for several miles and no traffic; my GT40 reached 195 mph before I started slowing down. I would have went faster but I started loosing wheel weights /ubbthreads/images/graemlins/shocked.gif (I was using clip on not tape on weights at the time), I use an electronic speedo that was calibrated at 120mph to indicate 120mph so the speedo was only off by 5 mph max at 195mph (manf claim). My car was sitting very low (3" at the rear 2" the front), at the time and I have a LeMans full flow nostril opening. My engine at the time I made this run was a 351W producing 450 hp with solid roller cam, lifters and rockers with stud girdles, Eagle rods, forged pistons and a Nascar crank (smaller main bearing dia. requires spacer bearings to run this crank), with a main girdle. This engine would spin 8,000 with out any problem of course it may only last 5,000 miles but who cares. With the gearing of my transaxle and tire size my car had the potential of going 216 at 7,500 rpm. Over the years I have had three different engines in my GT40, with the one that I have now my GT40 could only reach about 180 mph because of lower engine red line. But Gary knows that it pulls pretty good right on up through the gears. Gary, I think we were going a little fast for traffic that day! /ubbthreads/images/graemlins/shocked.gif With this engine I ran a 12.2, 12.0 and 11.9 in the 1/4 mile at Run and Gun but with a few more runs I might have seen 11.7. My car has seen 11.7 @ 123 mph with a different motor. Mark, I will email you with my contact info.

Over the years I have had many fast cars and I can tell you just how fast every one of them was except 1…

My GT40 /ubbthreads/images/graemlins/grin.gif

 

[Gary Gibbs]

Yes that motor pulls VERY strong in every gear. Reminds me of one of the super bikes (accel to redline in 1 - 2 seconds in ever gear). As a friend of mine says "VERY NICE" (need accent to appreciate). Concerning the traffic....What traffic? After breaking for a bit I looked at the speedo as we were going down through 125.

 

[Knighton]

[ QUOTE ]
Yes that motor pulls VERY strong in every gear. Reminds me of one of the super bikes (accel to redline in 1 - 2 seconds in ever gear). As a friend of mine says "VERY NICE" (need accent to appreciate). Concerning the traffic....What traffic? After breaking for a bit I looked at the speedo as we were going down through 125.





[/ QUOTE ]

Gary,

You were in the car? What are your impressions at those speeds?

How will your 427 stroker stack up seeing as you have an extra 150hp?

 

[Gary Gibbs]

[ QUOTE ]

Gary,

You were in the car? What are your impressions at those speeds?

How will your 427 stroker stack up seeing as you have an extra 150hp?

[/ QUOTE ]

Well my thoughts were "those cars next to us are going by very fast" and "this thing pulls very hard in every gear"

I think that Ricks car has 450 RWHP. Where mine is flywheel HP, thus I do not expect a huge difference. I expect it will be similar and maybe pull a bit harder. You are traction limited in the first two gears anyway, but third on up is unreal.

 

Sounds like the full open nostril rather than the split version is almost a requirement for high speed stability. Maybe I need to order one...Then again, maybe this is someone trying to tell me I don't need to go that fast...

 

And you know it don't come easy. (coolhand)

I have some good news and some bad news.

The good news is the splitter I'm making will go from the drawing board to model (positive plug) this coming week. I'm reluctant to say when a copy will be ready since I'm striving for a level of quality and not a time deadline.

The bad news is there are significant dimensional differences between the ERA, the RF and the CAVs. The ERA has a two inch longer nose than the RF and an inch longer than the CAV. Worse is the cross sectional area at the front wheel wells right at a line level with the bottom of the grill opening. Five inches difference.

Basically one size will not fit all. Ironically the piece I thought had to be model specific (the diffuser) may be the only piece where one size does fit all.

My plan is to make an ERA splitter, sill extensions and diffuser. The sill extensions and diffuser MAY fit other cars. I will put pics up on my website for all to see. If enough folks with RFs, CAVs, and GTDs request it I will make a model for a splitter for those manufacturers also.

 

[Howard Jones]

My understanding of the twin nose to single nose developement is the single nose was developed for slower road courses where a high downforce , within context of the then known information, setup was required. Lemans on the other hand required a mininum drag aero package. Thus the lower drag twin exaust nose. Most of the current road courses, in the US at least, are of this type. I just think the MK1's look better with the old twin setup. I have been looking at the front of my car and I believe that a very simple spliter could be attached to the under side of the flat portion of the nose. It could be as simple as a horzontial flat plate extending out to the leading edge of the nose. This could be removed for street driving and installed for the track or "late night flight's"

 

I was thinking along the same lines. Maybe it's a lot more complex than what the picture of the new GT shows in the picture, but it looks like a simple L-bend in a piece of aluminum wrapped to fit the nose would work. It would be cheap and at least worth a try.

 

[James]

Mark,

Sounds positive to me. When will you have some pictures ready, or dimensions. I would really ike to know how big the splitter is. Height in inches etc. Is the diffuser a single flat, or does it comprise of tunnels like the GT?

Anymore details?

Regards,

J.P

 

[Gary Gibbs]

[ QUOTE ]
My understanding of the twin nose to single nose developement is the single nose was developed for slower road courses where a high downforce , within context of the then known information, setup was required. Lemans on the other hand required a mininum drag aero package. Thus the lower drag twin exaust nose. Most of the current road courses, in the US at least, are of this type. I just think the MK1's look better with the old twin setup. I have been looking at the front of my car and I believe that a very simple spliter could be attached to the under side of the flat portion of the nose. It could be as simple as a horzontial flat plate extending out to the leading edge of the nose. This could be removed for street driving and installed for the track or "late night flight's"

[/ QUOTE ]

I assume you are speaking of the original gt40's. I am not sure that this is correct. My understanding is that the original car came with twin nostrils that were enlarged and eventually turned into the single. All of the lemans winning cars (high speed circuit) had the single nostril as this was supposed to have cured the front end lift/stability problem. I agree that the twin is a better looking setup. My 0.02.

 

[Knighton]

I noticed you have the single nostril on your 40...???