Power to Weight Ratio (traction or lack of)

[Cobrat24]

So I personally am finishing up a project with my builder on my FF. What I would love to hear from you all is your HP issues with traction and what gear it starts in..

For example my old motor setup had 241hp when I bought the roadster (I don't want to talk about it, total ego killer ). But on that motor plant, it would break the tires loose on hard accel in 1st but hooked up going into second.

I should tell you I took it to the local weight scales to see what she weighed and the number was 2178.

Now with the new motor plant, this was the text I received from my motor builder..

My fellow cobra friends, let me hear your power to weight issues..

[1795]

Most of these cars will have traction issues if you hit the throttle hard in a low gear. You pretty much have to start at about quarter-half throttle and then once going you can add more throttle.

To give you an idea of the degree of power-weight ratio many of these cars have. My cobra has approximately 500 hp and it is an FE, so torque is high on the low-end. When I first started driving the car, there were a few times as I was getting used to the shift pattern that I started in 3rd gear and the car did not chug at all and I did not feather the gas. The only way that I knew that I was in 3rd gear was that the rpms were running too low for 1st and I wondered why? With a 3.54 rear-end ratio the car gets up and moves without flooring it.

a lot also depends on the rubber that you are using. A softer compound will grip more and break loose less than a hard compound.

[Tommy]

Every car has a weakest link in the drivetrain. It might be the engine, transmission, driveshaft, u-joint, differential, tires or driver. On most family sedans on dry roads, the weakest link is the engine. They can't produce enough power to cause loss of traction. If you have a car with big power and great traction, you'll likely be replacing and upgrading things like u-joints, transmission and diff. So, unless you like fixing things, its not a bad idea for the weakest link in your car to be the tires (traction). Of course that means you have to either be a prudent driver who controls the throttle to prevent loss of traction, or a skilled driver who can handle a car that is on the verge of going out of control. I strongly suggest you be a prudent driver on public roads and take your car to the track to learn to be a skilled driver who can handle all that extra power you now have available.

My car has a 410 ci small block producing about 400 lb-ft of torque through most of the power curve. I'm running a Richmond 5-speed and 315-35/17 tires on the back. On most roads the tires will break loose at any speed in 1st, 2nd or 3rd gear just by pushing the throttle to the floor. Full throttle in 4th gear means I'm immediately above all the local speed limits, so I seldom see full throttle unless I'm at the track. You may want to do the same thing.

[patrickt]

Cobrat24 -- if you are used to 240HP, and now you double it, and you punch WOT on the street, and you're not pointed exactly right, you will end up being towed home. Or worse. Take your car to somewhere where there is absolutely nothing to hit, and learn what happens when you are overly rough with the throttle -- both laying it on too hard and lifting it off too quick.

[Cobrat24]

I totally get it, I also understand short wheel base means the ass ends comes out quicker than can be controlled with an inexperienced driver. With that being said I am not a newbie to track racing and horse power. I am a newbie to the Shelby and for that my respect for this chassis is much greater than any other vehicle I've played with on the street or track. I've never owned a vehicle this light. So I will drive with caution. But my reason for the post was to hear the stories of others and there love for the power to weight ratio.

[twin turbo]

Gearing, tires, suspension optimization, air temps, road conditions, and rolling into the throttle vs punching it will determine where your traction (or lack of it) occurs. With my previous engine and transmission, I consistently fully hooked in 1st gear (Gforce 5 speed with 3.08 rearend gears, Nitto 555R 315/17 tires), as long as I rolled into full throttle with 420 rwhp (Mustang dyno). It felt good in 1st, but 2nd gear onwards was lacking for me. I just don't drive around much in 1st gear.

Nowadays, I typically drive with 550-600 rwhp and "usually" hook up from 2nd gear onward when the temps are 70 degrees and above, but have changed my set up to a full manual auto trans, 2.73 rear gears, and stickier Nitto NTO5R tires. Cold air temps, I can't hook up 2nd at all, even at 500 rwhp.

[patrickt]

Originally Posted by Cobrat24

I totally get it, I also understand short wheel base means the ass ends comes out quicker than can be controlled with an inexperienced driver. With that being said I am not a newbie to track racing ...

The problem is, even experienced Cobra drivers can be fooled. And fooled in an instant. Undy's almost killing himself five years ago comes quickly to mind. He had the balls though to own up to it all here on this thread, so others might learn: Speaking of morons doing spin-outs with excessive power...

[ct clint]

Just putting a johnex slab side back together. And it's only car that has me wondering how to keep it on the road. Large stroker sb alum headed vortech v4 charger with meth and nos. It's been back halfed with a trianglelated 4 link. So far it only weights 1700 lb. I one hand I can't wait to try it other hand pretty fond of living lol

[Cobrat24]

Out of curiosity what's the lightest anyone has seen for these cars? Not that it needs to be any lighter but I am curious.

[ct clint]

I think mine will be 2200lb done but that is just a guess little things add up quick.

[undy]

Originally Posted by patrickt

The problem is, even experienced Cobra drivers can be fooled. And fooled in an instant. Undy's almost killing himself five years ago comes quickly to mind. He had the balls though to own up to it all here on this thread, so others might learn: Speaking of morons doing spin-outs with excessive power...

Damn Pat, once again you make me regret ever posting that...

I've learned now to do a bit of a drag radial preheat before getting too froggy.

BTW, not all of us drive around like old ladies with our twin roll bar garage stuffers.

[patrickt]

Originally Posted by undy

BTW, not all of us drive around like old ladies with our twin roll bar garage stuffers.

Well, it was either your post or the pics of the guy out in CA that let his girlfriend take the wheel for the first time... and she killed them both.

[undy]

Originally Posted by patrickt

Well, it was either your post or the pics of the guy out in CA that let his girlfriend take the wheel for the first time... and she killed them both.

Wasn't my post or pics... I don't need mama tearing my crap up as I can do a fine job of it myself.

[mdross1]

Agree Undy not all of us drive with the fear of getting hurt. After my car was at a point where I knew it was ready for road courses had to get a good feel for it's limits. Chose to creep up on it cornering hard till the rear end was coming around.
These cars scaled with a good bias front to back you learn real quick racing seats are a must, without one cornering hard will wear you out in a hurry. Drag racing is an absolute ball once you get a handle on launching the car and keeping the wheel spin down to a minimum. My 295x50 do a pretty good job a pair of slicks really gets the job done.
It really all boils down to what you want to do with the car.