Larger side vent opening

[mikeinatlanta]

Originally Posted by ERA2076

Are you F3g Serious?



Do you have a side view of the rear diffuser. It appears it is in the same plane as the bottom - surely not?

and stop crying and flip the rad -

x-chr

I like the diffuser how it is, but thanks for the advice.

[ERA2076]

Originally Posted by mikeinatlanta

I like the diffuser how it is, but thanks for the advice.

chr

[john chesnut]

I built my own Cobra tribute. The radiator is small and mounted vertically. The air flows through the radiator and is diverted out the side of the car behind the front wheels. I am not running front inner fenders. The body is sealed in front and along the sides of the engine compartment. I added a second set of side vents. I'm not an engineer and I haven't tested air flow.

I wasn't building a race car. I have been on a road course and have driven it a lot on the street with out overheating issues. The Engine is an LS6 hooked to a Tremec 6 speed. I use C5 Corvette suspension. It only has a Cobra body shell I know. But, I like it.

[ERA2076]

Cool - thanks for posting. Not sure what I am seeing. The exhaust side of rad vents to this duct and the on to diffuser behind front wheels?



Is the front of the rad ducted?



Comfortable top speed?

Serious side vents

x-chr

[john chesnut]

I haven't tried any high end speed runs. The only time I was on a track was Run n Gun 2008 at Gateway. I had just painted the car a few days before the event. I loaded the car on the trailer and took it to the race track. There wasn't any dash in the car and I hadn't wired it, plumbed the brakes or fuel lines, or aligned it.

The first 2 days of the event were spent taking care of those things. I did a string alignment, hooked up a water temp gauge and started it up for the first time at the track. I went out on the road course and set fast time for Cobra's running street tires. Then I put it on the trailer and took it home. Since then I've only driven on the street.

I can tell you the car is very well planted and the C5 suspension is terrific. I don't have PS but with zero scrub I can turn the wheel with 1 finger even at a stop.

My frame comes to a V behind the radiator. The frame/footboxes are 16 inches tall. They are skinned with .40 T6061 aluminum. In the picture you can see the aluminum V diverter that I made to ease the transition of air to the sides of the footboxes and out the side vents. The front of the radiator is ducted as well. I was going to install the Cobra style louvers but I like seeing my headers which flow over the top of the footboxes and down to the side pipes.

[ERA2076]

Originally Posted by john chesnut

I haven't tried any high end speed runs. The only time I was on a track was Run n Gun 2008 at Gateway. I had just painted the car a few days before the event. I loaded the car on the trailer and took it to the race track. There wasn't any dash in the car and I hadn't wired it, plumbed the brakes or fuel lines, or aligned it.

The first 2 days of the event were spent taking care of those things. I did a string alignment, hooked up a water temp gauge and started it up for the first time at the track. I went out on the road course and set fast time for Cobra's running street tires. Then I put it on the trailer and took it home. Since then I've only driven on the street.

Wow -

Scratch build?

You really have it sealed up. The T56 is a monster, how mush does the car weigh? How much HP does the LS make? Is the bottom sheeted?

You should take it and run it once. I would have to know.

x-chr

[cycleguy55]

I'm thinking 0.40 aluminum is a typo and should read 0.040" unless, of course, that's supposed to be 0.40mm.

[john chesnut]

It was a typo. Old and need glasses.

The LS6 is stock. It' rated at 405hp.

The bottom of the car is completely flat. The oil pan doesn't stick below the frame rails. A full belly pan is possible. But, I haven't done it as I built it to cruise the street. I do have a custom fuel tank and I molded in the bottom of the body at the rear so that its smooth and the tank is not exposed.

The C5 3:42 diff has been converted to take a driveshaft. It bolts into the back of the backbone trans tunnel.

The car has 52% rear weight and is heavy at 2550lbs. I have another car that I built using C5 parts and drivetrain that is under 2000lbs. I built that one with weight reduction in mind. Knowing the Cobra was for the street I didn't worry about the weight too much.

My Cobra tribute is plenty fast for me. And, its a great driver. I have the reliability and repairability of a C5 Vette. With the double overdrive it gets great fuel mileage as well. I know that's not a consideration for most Cobra owners. To me, its an added bonus.

[Thor maine]

Wow looks great! Those GM components truly make a better COBRA. As AC cars Heritage found , and use GM engines in genuine AC Cobra's . Long live the Bow Tie COBRA

[ERA2076]

Nice chassis - fully boxed with door bars and a backbone too. Did you happen to weigh it? FFR says their Type 65 chassis is 300 lb.

I would have guessed a little heavier than 2500. Did you dry sump to get the flat bottom? Are all of the components structural to bending moments in the chassis or are some of them to facilitate mounting aluminum panels?

I'll bet that thing is rigid as hell

Side note => I think Shelby listed the 427 @ 2500.

[ERA2076]

forgot to ask - is the track and wheel base stock Cobra?

x-chr

[mikeinatlanta]

John, I like how you are thinking outside the box.

Careful on sharing too much build info, it's just troll food. First you answer a couple of questions and before you know it, someone will be "concerned" about the how high your air intake is over the tarmac because they read something about it in a book once.

[ERA2076]

It has much to do with authors that have tested their stuff and taken the effort to document it. PM me your address and I will send you a couple of good ones. You could check out corner-carvers.com - a great place for you to start and it is free. You do read?

Wiki - Carroll moved to Europe where he befriended John Cooper. Driving a Formula Junior Cooper, he won his first race. After waning success in the Cooper cars, followed by a characteristically clear-eyed personal assessment that he lacked the ability to drive race cars at the highest levels, he returned to the United States and began working with Carroll Shelby and the Ford Motor Company on the GT40 Le Mans program. Smith oversaw the preparation on the cars that won the 1966 and 1967 24 Hours of Le Mans.

Carroll Smith Books . The Official Carroll Smith Site

Next time you are at the track, take your infra-red and measure the tarmac temp.

"I'm going to build a ram air system for my Cobra, but since I can't figure out any other way, I'll just pull in the hottest external air I can find and call it a day."

I had an idea for you - what about putting an air to water heat exchanger in your lower air intake tract and cooling the charge much the way Ford cools their inter-coolers.

Please share what "out of the box" thinking you see in Johns car?

x-chr

[J.Jensen]

Thanks for posting more images

How much speed do you need to overcome the engines air consumption and start building pressure?

[mikeinatlanta]

Originally Posted by J.Jensen

Thanks for posting more images

How much speed do you need to overcome the engines air consumption and start building pressure?

You are welcome, but be warned that the answer will start another debate.

Pressure is all relative. When you use pressure readings taken at the airbox as reference, you will begin building pressure at pretty much anything above idle, even without forward motion. The reason for this is the nature of a divergent system. At the risk of oversimplification, the divergence will cause the higher velocity air at the inlet to begin "packing" the air as it slows. Also think Bernoulli's principal, as the air velocity decreases, it's pressure will increase. On a proper divergent ram air system, the combination of these two forces will result in a "less vacuum" reading as compared to no system at all, which can be counted as a pressure increase.

Without counting the effectiveness of the divergent system, pure ram air will net ABOUT 1.2psi at 200mph.

[mikeinatlanta]

ERA,
You want the full excel spread sheet or just the meat? C'mon, take it like a man.

[cycleguy55]

"There's none so blind as those who will not see."

Like many, I've spent a good portion of my life dealing with people who are so sure they're correct they find it impossible to consider other possibilities. More often than not it's because they heard it from someone they know and trusted, so it must be true, right? The Internet has only compounded the problem, allowing near-universal access to a great wealth of incorrect opinions and misinformation - especially if they 'Google' it using terminology that's stuck in their tiny little brains.

Notwithstanding the foregoing, it is entirely possible to use the Internet to find correct and accurate information, but it takes more than technology and an Internet connection, it also requires an open mind. If only there were more of them.

[mikeinatlanta]

Originally Posted by cycleguy55

"There's none so blind as those who will not see."

Like many, I've spent a good portion of my life dealing with people who are so sure they're correct they find it impossible to consider other possibilities. More often than not it's because they heard it from someone they know and trusted, so it must be true, right? The Internet has only compounded the problem, allowing near-universal access to a great wealth of incorrect opinions and misinformation - especially if they 'Google' it using terminology that's stuck in their tiny little brains.

Notwithstanding the foregoing, it is entirely possible to use the Internet to find correct and accurate information, but it takes more than technology and an Internet connection, it also requires an open mind. If only there were more of them.

I have to admit that when I decided to do this testing that I would be focusing my energy on mitigating factors such as the effects of traffic, crosswinds, and recovery times. I was blown away to find essentially no temp rise over tarmac at all. I was expecting somewhere in the area of 20% of tarmac differential temp, not 0%.

My favorite quote in the world is: "The larger the circle of light becomes,the greater the perimeter of darkness around it." Albert Einstein.

[ERA2076]

Wow - 30 degrees in 1.25" and no significant change after - that is amazing. Regardless of belief, I would not have expected it. 75 is a fairly cool condition. Did you ever run it in hotter conditions? Not debating, just surprised and wondering the affect of radiant off the surface at higher temps i.e. as temp rises the differential zone rises too and is it linear? It has been my experience on a hot day (90+) I can instantly feel the difference in temp when walking from the grass onto the track. It would be interesting to test at Phoenix or Riverside in August.

Appreciate your work -

At the risk of oversimplification, the divergence will cause the higher velocity air at the inlet to begin "packing" the air as it slows. Also think Bernoulli's principal, as the air velocity decreases, it's pressure will increase.

Without counting the effectiveness of the divergent system, pure ram air will net ABOUT 1.2psi at 200mph.

How much pressure do you expect @ 100mph with divergent?

I don't think you ever told us the intended use of your car? I assume by the aero, road race.

Will you run a splitter?

x-chr

[mikeinatlanta]

Originally Posted by ERA2076

Wow - 30 degrees in 1.25" and no significant change after - that is amazing. Regardless of belief, I would not have expected it. 75 is a fairly cool condition. Did you ever run it in hotter conditions? Not debating, just surprised and wondering the affect of radiant off the surface at higher temps i.e. as temp rises the differential zone rises too and is it linear? It has been my experience on a hot day (90+) I can instantly feel the difference in temp when walking from the grass onto the track. It would be interesting to test at Phoenix or Riverside in August.

Appreciate your work -
Thanks, while I share your curiosity with testing a more diverse range of conditions, the testing I did makes it very clear that the radiant heat from the tarmac is not absorbed by the air, and any that is absorbed is quickly mixed with surrounding to form the wider ambient. In hindsight it should come as no surprise as ambient air absorbs very little heat on the first pass, which allows the tarmac heating in the first place. I also feel the obvious heat when venturing onto the tarmac, but the data is clear, it is radiant heat, not actual air temps. I believe the biggest flaw in my testing is the reference sample. I believe the reference was artificially high due to radiant heat from the shaded ground. While irrelevant to the on track temperature/elevation gradient, I believe it was giving an artificially high ambient of about 1 degree at 75.





How much pressure do you expect @ 100mph with divergent? While I have the technology to design an appropriate divergent, that calculation is beyond my abilities. We well have to find out with data acquisition.

I don't think you ever told us the intended use of your car? I assume by the aero, road race.Trailer queen, show car, waxer fodder, just another fpsb. .

Will you run a splitter? A splitter is included in the high downforce configuration. I will be using wind tunnel data to decide if the low downforce configuration requires a mini splitter. If so, it's a three hour add on and will not be used for the street.

x-chr

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