I finally decide to run the turbo in the quarter mile. I just want to do this at least once to get an idea if my car is making the rated horsepower. I recalled motortrend had a fantastic run but their car is definitly making more power based on their trap speed but mine is close. Probably 10-15 less hp.

http://www.motortrend.com/roadtests/...ecs_price.html

The tires cannot grip and I recall other 6 speed members also ran a 2 sec 60ft as well. I realize this car likes to wheel hop so I rather start soft. For some reason i'm getting an error uploading the time slip.

Here goes:
60FT 2.0201
330FT 5.4362
1/8 ET 8.1368
1/8 MPH 95.81
1000' 10.4271
1000' MPH 107.11
1/4 ET 12.3220
1/4 MPH 118.77

 

Your car is making it's rated power. That's a great run. A few mph either way can be affected by shift speed, environmental conditions, track conditions, etc..

Your car is running strong. Good job.

P.S. - Email your slip to Divexxtreme@hotmail.com

 

Lower the pressure in ur tires to 22 psi and launch at 2800 rpms...
good luck,
markksi

 

I never thought about that . I don't plan to running my car again unless i get a chip or something.

I had made other runs at 12.40@118.77 exact same speed and a 12.6@118.36. The speed doesn't change much but the time depend on my 60 foot. Pretty interesting how it works that way.

 

Here's why:

Originally Posted by Carver, on 25 Oct 06

First off, I'm Andrew, the guy who was working with Scott on the formulas.
My education and background is in mechanical engineering, working in the past for Borg-Warner as an ME and currently write financial market algorithms for index mapping software on the side in addition to my day job.
Scott and I were talking about why so many of the calculators out there are wrong. After looking at the data and the formulas, I came to the conclusion that it was an issue of the formulas being written too closely to theory and without adjusting the assumptions by taking enough real world data into account. A simple way to see this is through a graphical analysis of data points.
If you look at the Hale formulas along with the graphical points shown below, you can see that a) the formula is close, but needs slope and curvature adjustments to be more accurate, and b) there aren't enough points from a variety of vehicles to represent the outcome within a reasonable statistical confidence window for most cars.
What I did was include many more data points from multiple vehicles and graph the results next to the Hale equation lines. I then rewrote the algorithms to more closely represent the real world graphical results. These formulas now work well for street vehicles in the 50-1000bhp range. Adjustments to the algorithms would have to be made for pro drag vehicles that can transfer launch energy at a statistically abnormal rate.

Regarding the trap speed vs. e.t. discussion, there are multiple ways to visualize what is happening to make it more clear. And to be fair, both sides are correct for their given questions. The problem is that the specific question in each case is not clearly defined.
Think of the difference as transferred energy to the ground in time (e.t.) and transferred energy over distance (trap speed), which are two very different ideas, as we’ll see. If it weren’t for launch energy transfer and tire capabilities ie. all of the power/energy could be transferred on the launch immediately with consistent accuracy, we wouldn’t be having this discussion as e.t. would be as representative as trap speed. But that’s not the real world.

The force available to accelerate a vehicle from a stop to the first 30-60ft. is mostly based on traction or g-force capability. That’s why a mid-hp car can have similar 60ft. times to a very high-hp car. It’s not a good indicator of hp since the max g loading of street tires is around .5-.6g no matter what you do. In first gear along with a revved engine (significant stored flywheel/crank/piston/rod/pressure plate energy) most cars have the ability to generate .5-.6+ g or break the tires loose for some distance. That’s why as one car may hook better than another, they’re still limited to approx. .5-.6g on the launch….this enables a car that has spun its tires or bogged off the line to essentially re-match the other car’s acceleration and speed, at a given distance within the .5-.6g exceedance zone, very quickly since in the lower gears it’s a traction issue and not a power issue. Notice I said speed at a distance and not speed at a time. The time already left the station, so to speak, the distance didn’t.

And here is where people get the disagreement. The time measurement is a constantly moving reference which is unaffected by the car’s performance. But distance is not ie. as you are slower than another car, you have more relative distance left but not more time left. So if you make a mistake on the launch ie. excessive spin or bog, that time measurement will be permanently changed because time marched on unaffected by your mistake. But your rate of distance coverage was changed and reduced giving you some distance to make up the mistake. And in addition, the distance where the loss took place is approx. 3% of the distance of the race, and a distance where max power could not be transferred due to the .5-.6g tire limit….as a result, speed at a snapshot time ie. 2 sec., with time continuing at the same rate, was affected but speed at a distance past the spin/slip zone, with distance traveled reduced, along with the ability to rematch .6g quickly, had little to no change. If the tire spinning/bog continued much beyond the zone where the car could no longer exceed .5-.6g acceleration, then you would start to see the reduction in trap speed in addition to the increase in e.t. as overall avg. power over distance would start being affected. But since it takes place in this “.5-.6g max zone”, the speed at time is changed but not the speed at distance. This is why e.t. is significantly affected by launch and trap speed isn’t.

Now here is where it all comes together. Both cars weight the same. Car A runs a 1.7 60ft. and turns a 12.2 @ 120mph. Car B runs a 2.0 60ft. and 12.6 @ 120mph…..what happened? Car A got a better launch enabling a .3sec better 60ft., but car B had an extra .3sec at .6g to accelerate up to car A’s speed at the 60 ft. They were both going approx. the same speed after the 60ft., although car A reached that speed in less time, but the same distance, and have the same whp because they accelerated together after that point. Car A was able to transfer more avg. power to the ground over time ie. in 12.2 sec it had traveled farther and reached 120mph quicker but at the same distance as car B (the difference in time being in the launch energy transfer) although car B was still able to reach 120mph in the ¼ mi. distance ie. the same total power transfer with respect to distance showing whp and not transferred whp over time.
So as has been stated before, if you take the .5-.6g launch window out of the equation, and compare cars from say a 3rd. gear roll, you might as well throw away the e.t. too and go by trap speed because the e.t.'s variables are no longer in play.

1-1.2g (.5-.6/tire) and in this case a total of 1.5g of thrust....and the car is still losing traction in second gear. This is what causes e.t. to be launch dependent, or responsible for a time loss, and not responsible for a trap speed loss. Consider for a second the main point that I alluded to but didn't explain well enough in my previous post. Speed curves over distance look like 1/2 parabolic curves ie. they start off steeply vertical and than begin to shallow and converge at an asymptote as distance passes, with speed on the Y axis and distance on the X axis. One more way of saying this is that the whp of a vehicle is most influential to a car's acceleration as speed increases ie. as a greater percentage of the distance of the 1/4mi. elapses, the launch becomes a smaller percentage of the performance, and drag, and as a result whp, becomes the most significant factor. This favors a confluence or matching of trap speed, or speed at a given distance, for a given wt/whp and a lessening of the effect of the launch. This effect continues to build, throughout the run, obviously, since on a percentage basis the launch distance/total distance traveled, is decreasing at an increasing rate as speed increases while time of launch/time of run is decreasing at a fixed rate as time elapse rate is constant. This causes the et differences at the launch to be maintained while the trap differences at a given point or speed at distance tend to merge. That is your key.

 

Is your car stock?

 

Yeah, but it has the X50 factory option. This time is actually not that great compared to Motortrends. Any other X50 people ran their cars? I'm curious where mine stands.

 

No one has touched Motortrend's time. Not even another magazine.

 

WOW! Motortrend ran an 11.86, that's pretty insane!

 

Maybe, but I feel Motortrend's time is definitly one of the best. I feel their time is due able under the "perfect conditions". I guess it may be possible that they had a press "ringer" high boost special car supplied by porsche or they converted their acutal times for the ideal condition? I also remember when they tested the 1/4 mile for the Corvette on MTTV back in the days they had like 10 cars and they ran them all and published the fastest ones, go figure.

I had a mild launch and did not powershift any gear because the track was traction limited and i never drag any car this powerfull. I was concerned about wear and tear for that reason. The 911 shifter is also very sloppy compared to the Hurst shifters.

I really miss my hurst spring loaded shifter from my mustang days . I had executed every gear fast and perfect with hurst. I wish all sports car had them.

 

i'd be very happy w/ your run in a stock car. 118mph trap speed is nothing to sneeze at - it will beat 90% of the fast cars out there on the street.

you don't have any context for the MT run - temps, altitude, track, etc...

- chuck

 

very nice run. with a 1.8 60' time, you would be at 11.9 and would prob gain that extra trap of 1-2 mph you missed compared to the MT time. 119 mph trap is still very very strong.

 

What is with motortrend anyways, didnt they test the 997 turbo at 11.2 as well which no one has even seen in the horizon????

 

Keep in mind that magazines use all sorts of temp/altitude/humidy corrections for their testing data. Motor Trend is know, among industry folks, to have the most optimistic correction formulas. This is why all the vehicles they test appear to run quicker in their hands than in the hands of any other magazine (even the same press cars).

-shiv

 

If your statement is fact, then my theory is true .