Horsepower To Weight

[john chesnut]

Very interesting thread. Weight is obviously a huge determining factor in final performance. Of equal importance is the suspension design, gearing, open or locking diff, tires, driver, and how much you are willing to abuse the car to achieve the ultimate time. As speed increases the horsepower required to over come aerodynamic drag goes up exponetially. If your car tops out at 150 you need to approximately double the horsepower to make 200.
I never considered the Cobra to be about drag racing. I want a great handling, accelerating, steering, and braking car. The lighter the weight the better the potential to excel in these areas you have. To reach that potential you need to have a torsionally stiff chassis, the proper suspension geometry and other parts. You can have all of the horsepower in the world and still have a car that is fairly slow and drives like crap.
I run fairly low horsepower in my cars, about 400hp at the crank and can beat most high horsepower cars in the drags but where they excel is on the road courses. To me, that is where the fun is! John

[LRcobradreamer]

BIG VARIBLE----how many of them HORSES are PONIES?????

Yes, but some horses are minature horses, which is smaller than a pony.

Lee

[SP01715]

Originally Posted by greg schroeder

Here's my opinion.

A 400 wheel HP FE should pull ahead of a new stock ACR Viper from a low speed roll. Most the 550 engine HP FEs aren't making over 400 at the wheels though. Both the cars are probably good for mid to high 11s in the 1/4 on an average day with out having drag radials.

The 475 wheel HP Superformance with a small block that I recently sold would beat the ACR Viper 1st gear to half way through 4th gear(125 mph) without question.

They were doing dyno runs at Hillbank on Saturday, and a SPF with a 550 hp Roush 427R windsor pulled 473hp at the rear wheels. This was on a hot day as well. Either the 427R is putting out more than 550hp at the crank, or the drive train is not taking as much hp as people think. I was suprised at the #. I wish I had taken my car.

[sparks]

did it have the stock headers and exhaust??

[SP01715]

Originally Posted by sparks

did it have the stock headers and exhaust??

As far as I know it did. It looked like the standard SPF exhaust.

[RodKnock]

The CC moderators must look at this thread and go

In that order. Thank you very much.

[RICK LAKE]

eschaider I love a crazy data printout. Jag rearends don't have a 3.46 rearend ratio to start. 2.88/3.07/3.31/3.54/3.77/4.09/4.54 and up. I have seen very few cobras in the 10's with even a warm 427 motor through street side pipes. Low 11's yes. This car you came up with I would like to see myself. Keith Craft showed up with a goodyear tired Kirkham and a 527 monster motor and ran about a 10.38. The weather was not perfect but the times show that his car was running well. This story book cobra is not running a 10.27 period. You give the cobra a higher gear for the rearend and also a higher trans ratio for 1st and 2nd gear. It's also got a 900+ lb advantage in weight to boot. Viper 3.07 gear and a 2.66 first gear in the trans is no race at all. The torque of a V10 makes this race close. Run the test with the same rearend gear, you will not like the out come. There was a race done years ago with an L88 vette and a 427 cobra. Vette gave 500 pounds and both had the same gearing. It was a split on 2 races. The cobra hurt the clutch and the vette blew a half shaft. Both car where in the 11's. My car runs low 12's with 335/35 17" tires and a 3.31 gear. 482 cubes and a race trans. 500+ HP and Torque through street side pipes. It will not hook up well on any track with a ton of glue on the surface. I know from smoking 2 clutches. A cobra will beat the Viper 6 out of 10 times. It's also hard for a cobra to do a 1.59 60' time. More like high 1.7- 1.8. Your time is .59 seconds from prostock numbers. I will look up the articles for the ACR viper and get the times and speeds from them. Round 2 coming up. Rick

[TerrysSPF]

I just looked at the specs of the ACR Viper and, in a nutshell, here it is:
3408 lbs (or 40lbs less if you do the radio-delete option)
600HP @ 6100rpm and 560lbs tq @ 5000rpm
Gear ratio is 3.07 (and 1st gear is 2.66)
1/4 mile time of 11.8 @ 125mph
0-60 time of 3.7 seconds.

-Heck.........even you guys with small blocks in your Cobras should be able to handle that!

[sparks]

W/ The Chip And Factory Headers They Claim 675hp...not Bad 4 A $110k.

[sparks]

All Black W/a Carbon Wing And Black Wheels It Is A Bad Azz Lookin Car.

[TerrysSPF]

No, not bad at all..........................but he's still about 900lbs heavier!

I can't wait to see the battles that will no doubt come up in all the car mags between the new Viper and the new ZR1 Corvette. -Should be a terrific match up.

I agree with Rick though. It's very difficult to get these Cobra's into the 10's. Too many variables come into play (especially tires, suspension, and gearing in many cases). I had a friend that also had one of KC's monster 527 alum engines, only it was in a SPF. -Over 740HP!
He could only muster low 10's (I know......"only") but his trap speeds were near 140mph, which says he should have been in the 9's (his trap speeds also got him kicked off the track!). He was running on Yokohama street tires (15's), and had a lot of traction issues. I always wanted to know what he would do with some BFG Drag radials on the back...............but unfortunately he sold the car before I could find out.

[eschaider]

Originally Posted by RICK LAKE

eschaider I love a crazy data printout. Jag rearends don't have a 3.46 rearend ratio to start. 2.88/3.07/3.31/3.54/3.77/4.09/4.54 and up. I have seen very few cobras in the 10's with even a warm 427 motor through street side pipes. Low 11's yes. This car you came up with I would like to see myself. Keith Craft showed up with a goodyear tired Kirkham and a 527 monster motor and ran about a 10.38. The weather was not perfect but the times show that his car was running well. This story book cobra is not running a 10.27 period. You give the cobra a higher gear for the rearend and also a higher trans ratio for 1st and 2nd gear. It's also got a 900+ lb advantage in weight to boot. Viper 3.07 gear and a 2.66 first gear in the trans is no race at all. The torque of a V10 makes this race close. Run the test with the same rearend gear, you will not like the out come. There was a race done years ago with an L88 vette and a 427 cobra. Vette gave 500 pounds and both had the same gearing. It was a split on 2 races. The cobra hurt the clutch and the vette blew a half shaft. Both car where in the 11's. My car runs low 12's with 335/35 17" tires and a 3.31 gear. 482 cubes and a race trans. 500+ HP and Torque through street side pipes. It will not hook up well on any track with a ton of glue on the surface. I know from smoking 2 clutches. A cobra will beat the Viper 6 out of 10 times. It's also hard for a cobra to do a 1.59 60' time. More like high 1.7- 1.8. Your time is .59 seconds from prostock numbers. I will look up the articles for the ACR viper and get the times and speeds from them. Round 2 coming up. Rick

Rick,

You're nitpicking. The basic Cobra I used was an SPF and they all come with 3.46 rear gears since about mid to late 2005. Your comments about the Viper are surprising. Thats just the way Dodge made them. I didn't add anything or subtract anything those are their specs not mine including the 900# of additional weight.

With respect to the performance you're entitled to challenge it. I think the challenge has little credibility, especially in light of the post immediately preceding mine. If you read the post immediately before mine you will see a 10.70 Cobra (and can watch the actual run) go 130 MPH with a (by his own admission) soft launch and what is clearly granny shifting the car through the gears. Drive it hard and you will very closely approximate the simulation.

Fiddling with the gears on either car will only at best fine tune the performance of either. It will not make quantum leaps in performance.

The bottom line here is HP/#. The more you got the quicker you go. It's that simple! If the driver is a clutz, scared of the car, born under a full moon on Feb 30 - it don't matter! If you want to know how quick the car goes get a driver that can actually drive the car without going into catatonic shock.

The only thing that matters is HP/#. If you put chicken fat on the tires of one of the cars you are adulterating the test. Make the HP, hook them up, launch both cars, drive them like race cars (assumes the driver can) and the car with more HP/# wins every time.

Road racing is different. What the poster asked about was a good old fashioned drag race - street style. The Cobra is the unquestionable winner.

By the way I respect your right to a different opinion - I just think you're wrong, on this one anyhow.

Ed

[CHRIS DAMSCH]

I don't agree with Cobras not being able to pull 1.5 60' times. I have multiple handfulls of timeslips with my SPF with 60' times anywhere from 1.50 to 1.57. This was on drag radials and full street exhaust and 3.73 rear gears.

I also have about 5 or 6 timeslips with 1.6-1.7 60' times on BFG Radial T/A's (295/50/15).



I've seen a bunch of Vipers at the strip, just not an ACR. I know the ACR is set up better than a stock Viper. But none of the Stock Vipers I've seen have run deep into the 11's. Most are running 12's and 13's. Most likely driver error...............

[greg schroeder]

That calculator is about right for a sea level pass for the car I had. If the car was at a DA of sea level I'd run about a 10.3 @ 132 mph with a 1.5 60ft. The video in my signature is a 750FT DA with a 1.7 60 ft starting from 1000 rpm. My shifts are pretty good though. They're about .25 seconds according to computer data acquisition
.

Here's the 750ft DA pass time slip


The car has the Roush 427R. As it was with Superformance exhaust and the way the dealer set it up it made a little over 400 corrected HP at the wheels. That's why you see similar Superformace prep cars in the mid 120s mph for trap speed all the time. I changed the exhaust, fuel line, carb and intake and it made quite a bit more power with the changes to be 475 at the wheels. It was a 561 crank HP engine corrected. With that it could break over 130 mph trap speed.

FE Cobras are slower heavier and generally don't make the same power as Windsors once they're in the car.

The basic routine I've seen for stock supercars is they're not even close to magazine specs once you see them at the drag strip on an average day. I really think the new ACR Viper would be a mid 11s car in the low 120s. Stock C6 Z06s the day I ran that 10.7 were in the low 12s @ 118 or so.

[Sharroll Celby]

About that .730 Reaction time.......You know you CAN go when the light turns green!!! lol !!!

[ROUSHAC]

Looks like a .130 to me, not a .730.

[eschaider]

Thanks Greg,

When I modeled the car I used sea level as opposed to the 750 DA which makes your pass all the more impressive. You babied the car down the track and it still gave you an excellent 10.7 at 130. Very impressive!

Your observations about the FE engines coincides with my own observations. I am not entirely sure why the power drop off in an FE car is as great as it frequently appears to be. That type of behavior usually causes me to suspect the fuel system as not being able to keep up with engine demand.

Other than a correction for ambient air temperature in car power levels (after factoring about 15% for drivetrain losses) usually agree fairly well with engine dyno numbers unless there is some other issue. Usually that other issue is fuel delivery.

Good looking car, impressive pass!

Ed

<Begin Edit> p.s. My shifting comments were not to diminish your shifting speed. From the audio it sounded like you were trying not to abuse the trans. Computers are always better than ears and quarter second shifts are fast gear changes.<End Edit>