Can a Cobra hang with Z06, GTR, GT3 on Track?

[Ant]

I dont know whether this argument is balanced, as it depends on how the Cobra or Corvette is prepared for track work, in my opinion the road going Corvette Z06 is one helluva car as far as top speed, fuel economy, handling etc, BUT they are heavy and on a tight track where top speed isnt so important it doesnt surprise me that Scott and Morris can beat them, and some of the Thundersports UK cobra cars would decimate a corvette unless it was a track prepared Le Mans ZO6 like the Aston DB9R it races against and no Cobra is going to even come close to either of those cars due to their aerodynamics speed etc, as displayed on Top Gear with the DB9R doing 1.08 lap compared to the best production supercar at around 1.18 second lap, and I think the 505BHP Corvette did something like 1.22 second lap so I guess if you develop them into a race car anything can happen!!!!!!

As far as road versions go I found this comparison between a 430BHP Cobra and the latest 630bhp Corvette.

http://www.youtube.com/watch?v=LDUTRTd7SMU

http://www.youtube.com/watch?v=YP3WLoZ4Wuo

[SimonSays]

Ant has a point there, it's apples and pears really... If you'd spend a few 100K building whatever race car, it might be quicker than anything else on the track, but to what expense, and furthermore, will it still be road legal?

If the topic opener wants to know if it's possible to build a road legal Cobra that will keep up with other cars like a Z06 or Exige, yes it's possible. Will there be faster cars around the track? More than likely...

I've done lots of trackdays in the past, and i'd suggest to get something with similar performance to your buddies, so you can keep up, have lots of fun, and learn. Because that's what a trackday is all about

[Jerry Clayton]

As to just how modified Scott's car is----It is an E-M 90wb car with C4 suspension--the car's main mods are the coil overs that he uses, brakes and of course tires--common disposable race stuff-- and then a front chin deflector and a upper mounted rear airfoil to hold down the rear for more braking---and this year a LS7 427 and a lighter hand laid body--he is probably 400 lbs lighter than he was as the earlier Run n Gun events

He also is a highly talented driver, running a dirt late model so he is used to max brakes and max acceleration(while turning), and he also feels the car!!!!

[1ntCobra]

Originally Posted by SimonSays

Here's my buddy Phil in his Cobra at Spa Francorchamps. Will beat Z06es with one hand

http://www.youtube.com/watch?v=kZrZw74rkC4
Near the end you can see him use a handle near the gearlever, that's a lockout to prevent shifting down into the wrong gear

And just to show the car is street legal:

http://www.youtube.com/watch?v=BPD1yCzO5lM





At Spa, they run an open exhaust... It's errrrr loud

If that seat was back any further, he'd be in the trunk (or boot for those on the other side of the pond).

[Ant]

This is an interesting topic as when I first built my FE390 cobra 20 years ago I thought I was going to beat almost everyone and what a pig this car was it didnt handle due to the flex in the ladder frame chassis, it cooked the brakes and I was p***ed off, so I went and purchased the car now owned by Bevan Wright (NZ) which is an Almac New Zealand produced car with hilborn injected LS7 454, Seanz race box, 9" IRS Locked which was not nice, this car was made of Kevlar and weighed 1100kg wet would keep up with most cars in a straight line, it was a brutal motor car but twisted axles really needed a good LSD instead of the spooled diff.

With the benefit of experience I have sort of done it again and built what I think is going to be a very quick track car, but I am under no illusion that this car will take sorting to make it quick and that involves hard work time and money.
If I was going to just do track driving and wanted a car that was great to drive and real quick Lotus have just built a car called the (eleven) with 250bhp apparently this car is fantastic to drive at around £40,000 this car would see off most road cars on some tracks and be a real joy to drive with race car handling already built in.

Also if I lunched the Yates engine I would seriously look at what Scott has done and fit a modern LS7 505BHP engine and have probably almost as good lap times with a possible 30mpg on the road.

[john chesnut]

I relayed my experience to illustrate the dynamics of the longer wheelbase, wider track, better balance, and lower center of gravity of my T bucket to the Cobra dimensions. Both cars have the exact same drivetrain and suspension. The year that I ran the T bucket at Run n Gun was the first time I drove the car. Those that know me know that I have a habit of showing up with cars that I haven't finished yet!
I was runniing rock hard run flat tires, the computer was set up wrong and was in full rich mode the entire time, on the big sweeping corner the engine quit running for a couple of seconds because of a fuel stavation problem, I ran the stock brakes, sway bars and bushings, ect. Based on weight and quarter mile calculations I think that the engine was putting out about 350hp. Even so I ran very fast times.
I believe that just switching to racing slicks and fixing the 2 issues that I had that I would have cut 5-6 seconds off of my time. This woulld put me in the 1 minute 5 second range. I think that the fastest time at the event that year was around 1 min 5 seconds. That time was posted by Aaron Quine in the full race prepared Mongoose GTP car. Aaron is a great driver and the GTP car is a great race machine Aaron in the GTP owns alot of track records around the country. A Noble with 750 hp, racing slicks and a great driver was a couple of ticks slower.
Again, I am not a driver. I built my car for about 30,000 dollars. I think that my car proves how great the Z06 engineering is. That if you combine the Z06 parts with Colin Chapmans approach to race cars (light as possible) it is possible to build a serious track car for not much money. I am hoping that I can be at Run n Gun this year with racing slicks and get Aaron to drive it! Ir would be fun!

[jdean]

A Cobra won the Optima Street Car Challenge. Ran against a Z06, GTR etc. Lots of mods, but still a Cobra. The Z06 below ran in it, had a lot of mods too.

[lovehamr]

Originally Posted by jdean

A Cobra won the Optima Street Car Challenge. Ran against a Z06, GTR etc. Lots of mods, but still a Cobra. The Z06 below ran in it, had a lot of mods too.

The link: http://www.saac.com/index.php?option...d=234&Itemid=2

[fuzzyface]

But, here's the best part: 140mph in an open roadster is a hoot. When you skim that inside wall at 100mph, it makes your heart go pitter-pat. Don't worry about beating the corvettes and GT-R's, just go and have a good time.
Amen to that!!!!!

[DMXF]

Originally Posted by john chesnut

I relayed my experience to illustrate the dynamics of the longer wheelbase, wider track, better balance, and lower center of gravity of my T bucket to the Cobra dimensions. Both cars have the exact same drivetrain and suspension.

John, no one will dispute that a wider track will enhance handling and longer wheelbase provide more stability, as stand-alone variables, ie; yes, all else unchanged (incl weight, roll centers, etc), by increasing track the lap times will definitely go down. But that is not really what we're dealing with here.

First of all, by moving the suspension out on your cars, you are no doubt altering relationships of roll center to cg, ackerman, etc, which are probably more optimal at the Corvette track width they were designed for.

More pertinent to a comparison of the Cobra to a Vette, however, is that the Vette appears to be a much bigger, taller and obviously heavier car.




The handling characteristics of a Vette should remain constant if you scaled the car down to 75% of full size, 50% or 5%. So from a parametric standpoint, it looks like a Cobra is probably close to being a scaled down version of a Corvette (track narrower, length proportionately shorter, weight less than proportionately lower, etc). With that scaled relationship of all parameters, you can't accurately say the narrower track, etc of a Cobra would alone make it handle inferior to a Vette. Note that a Cobra's track and wheelbase are almost the same as a Mazda Miata and a lightweight spec Cobra with aluminum FE engine, etc is essentially the same weight as the Miata (around 2200lb). I recall a Miata was recently tested against a number of modern supercars like the Corvette (ZR1?) on some race track and written up in one of the big car magazines... it's lap times were middle of the pack, with only around 1/2 the horsepower of the other cars along with narrower tires, and I believe the Mazda only has a rinky-dink McPherson strut suspension (correct me if wrong).

Note that I am not saying that going to a wider track on a Cobra wouldn't improve its handling, just that a narrower track on a lighter, smaller car like a Cobra doesn't mean it will have worse handling than the Vette. Yes, there are other attributes that could be hurting the Cobra, like if the cg to roll center relationship were worse, but that is a separate issue. I believe one of the things that messes up handling on alot of Cobras is running too small of a diameter and width front tire (ref Kirkham thread which linked to an article about Nissan GTR handling).

[john chesnut]

I agree that my observations are not that pertinent to this thread. My comparison of my Cobra is not really to the vette ect. It is more to what if the Vette was stripped down and was as light as the Cobra how would they compare. My T bucket has the exact wheelbase and track as the vette. My Cobra is a 90 inch wheelbase and has the stock Cobra track. I made changes to the steering mounts,had a custom steering rack made, changed the rear tie rod location, and aframe mounts to allow for the change in wheelbase and track to compensate for roll center, ackerman. My T bucket has 54% rear weight, my Cobra 53%. The cobra has 18 inch wheels all around, with 275 tires on the front. Don't get me wrong, I LOVE my Cobra.

[DMXF]

Originally Posted by john chesnut

I made changes to the steering mounts,had a custom steering rack made, changed the rear tie rod location, and aframe mounts to allow for the change in wheelbase and track to compensate for roll center, ackerman.

John, I think you may have to change a-arm lengths and perhaps other things in order to get the roll center proportionately in the same place when decreasing track.

Regardless of academic curiosities, you are obviously quite skilled to be able to create such machines, and get them to work as well as you have on track!