Guest Thurem Posted December 27, 2001 Share Posted December 27, 2001 Was just playing around with the Transmission Calculator and I got topspeeds in the neighborhood of 199Mph with a reasonable 6300 redline. HEHEHE... This was with a 0.68 5'th in my T5 (.68 is the correct ratio, right??). So am I way off? will a 400 hp motor pull anywhere near those speeds, or maybe 180 or so. Does anybody know how much horsepower it takes to go 150 or 180 or 200 mph?? (Thats horsepower, not brains.. I think brains are inversely proportional with topspeed. ie. less brain more speed.) Thure Quote Link to comment Share on other sites More sharing options...
DavyZ Posted December 27, 2001 Share Posted December 27, 2001 Thure, That may not be the final drive ratio. It may be a .73 (or something very close like that..foggy memory). The T5's have at least two different 5th gears that were available--check your calculations with the .73 and see what the top speed is. I don't think you'll go anywhere near that fast due to severe wind resistance from the brick-like aerodynamics of the Z. Plus, you may actually get airborne before you ever find out how fast you can go, and if you live to tell about it (fat chance) make sure you post it. Thanks, Bud lol Davy Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted December 27, 2001 Share Posted December 27, 2001 Seems like I read somewhere that it take 4 times as much HP to get to 200 mph as is does to get to 100mph. This was the main reason Shelby made the special version of the Cobra for Le Mans. He needed much greater top speed than the open design could take him. Quote Link to comment Share on other sites More sharing options...
Guest Fast Frog Posted December 27, 2001 Share Posted December 27, 2001 The WC T-5 Camaro tranny has a .63 stock 5th gear ratio. A few yrs ago I talked to a GM customer service rep who said GM came out with a close ratio WC T-5 with a 2.75 1st gear and a .74 5th gear. But I've never seen one or know of anyone who has. Any good tranny performance shop can machine or have machined a diff ratio 5th gear. I had my T-5 5th gear redone to a .72. This ratio makes for better performance without taking away too much economy while cruising in 5th. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted December 28, 2001 Share Posted December 28, 2001 Look through some of th eFord T5 sites - there are shops that can give you most any ratio you want. As for attaining that speed - no way. That 5th gear will blow LONG before you get there. 5th is weak in the T5 and WOT shouldn't be used in 5th nor should you powershift 5th. Ford guys found this out long ago (sigh). Quote Link to comment Share on other sites More sharing options...
Guest Thurem Posted December 28, 2001 Share Posted December 28, 2001 quoteThat 5th gear will blow LONG before you get there. 5th is weak in the T5 and WOT shouldn't be used in 5th nor should you powershift 5th. Sniffle, But I did put in a fifth gear stabilizer/bearingretainer out of billet steel, instead of the cheesy stamped potmetal one. Actually my real concern was wether I could make it redline in fifth with about 400 hp or would my bricklike aerodynamics make that impossible. Obviously this is only of acedemic concern, I lack the cojones to actually go this fast (ie. 150+ mph). Thure Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted December 29, 2001 Share Posted December 29, 2001 The stabilizer might help but the 5th gear is still way out on the back of the trans and weaker than the rest. And yeah, I'd NEVER make it to 150 in the Z myself. 100+ I've hit once on a dark road but it was an accident I swear. 150 would be scary for sure. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 29, 2001 Share Posted December 29, 2001 200MPH!!! HI Carumba and hang on. Actually there is alot more to going that speed than you might think.What is your rear-end ratio,there is a .68 T-5 fifth gear, but is a lot more to consider. Tire height will mean a bit and over-all weight to HP will all influence top speed. If you have the areo package to keep it on the road and the tires to take the heat at that speed, a steady hand, balls of steel and a straight road I want to hear about it If not, just dream on,PLEASE Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted January 9, 2002 Share Posted January 9, 2002 You'll hit the aerodynamic wall I'd wager at near 150-160 maybe less with that sort of HP. The Z is a brick flying through the air and it would take major HP to overcome its drag co-effecient. My T56 would gear out to like over 200, but ain't gonna happen without massive HP and even then you will probably become a pilot at much over 160 without some serious wind tunnel time. Make sure you have on clean undies because you'll go to the hospital for sure when your flight ends even with a 100 point roll cage. Regards, Lone Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 10, 2002 Share Posted January 10, 2002 After looking over many past posts on this board something struck me as odd! there are (3) basic ways to make your car faster (1)add more EFFECTIVELY USEABLE HP (2)reduce the cars total weight moved by that hp (3)reduce aerodynamic drag now a reduction in weight of about 100lbs is equal to about 13 hp gained in engine output in a car thats in the 3200lb-3500lb range and sometimes its cheaper and easier to lose 100 lbs than get more hp(especially the first 200lbs or so) and I see very few posts on good ways to reduce weight (yes I know the driver could stand to lose 50lbs in my case) but Im working on it honest, now a reduction of 200lbs =about 26hp or a reduction in your ET of about 2 tenths(in the 12-14 second range) and an increase in mph of about 1.7 mph.TRY IT OUT HERE: http://www.prestage.com/carmath/calc_HP_fromETandWeight.asp so lets hear some good ideas guys! btw a reduction in the drag coefficient will have little effect untill about 80 mph but the numbers mean a great deal more as your speed exceeds 120mph and greater and by 175 mph those number easily can provide a winning edge to a car and is one of the reasons some of the late model cars can run as fast as they do!look here, Aerodynamic drag force may be defined as follows: Fd = (1/2) Cd r A V^2 (1) where Fd = aerodynamic drag force Cd = coefficient of drag r = density of air A = frontal area of vehicle, into the direction of motion V = velocity of vehicle, into the direction of motion This equation may be found in any fluid mechanics text. In fact, the equation is quickly recognizable as the first integral of a basic momentum equation, which makes sense, since the aerodynamic force is created by the momentum change of the air as the vehicle moves it out of the way. This equation shows that aerodynamic drag force increases with the square of the vehicle velocity. One way to state this is to say that a doubling of the vehicle velocity increases the drag force four times. Or, a 41.4% increase in vehicle speed doubles the drag force. Of course, astute mathematicians will immediately note that this makes sense, as the square root of two is 1.414. Horsepower Aerodynamic drag force is one thing; the power required to overcome it is something entirely different. If drag force goes up quickly as vehicle velocity builds, then the power to overcome it grows even more ferociously. Specifically, it increases with the cube of the vehicle’s velocity. Power is widely defined as follows: P = F x V (2) where P = power, F = force and V = velocity The force in question here is aerodynamic drag force, of Fd. Substituting Fd into (2) yields: P = Fd x V (3) where P = power, Fd = aerodynamic drag force, V = velocity Substituting (1) into (3) yields: P = ((1/2) Cd r A V^2 ) * V or (1/2) Cd r A V^3 (4) This shows, mathematically, that the power required to overcome aerodynamic drag force really does increase with the cube of the vehicle’s velocity. Every doubling of the vehicle velocity requires an eightfold increase in horsepower. Or, a doubling of horsepower only results in a velocity increase of 26%. As before, an astute mathematician will recognize that 1.259 is the cubic root of two. your cars Top Speed So how does this affect your top speed? Or more importantly, what are the real world guidelines which result from the math shown above? A Corvette is a slippery and powerful vehicle. It has a small frontal area, a low coefficient of drag, and a throbbing engine eager to dump power to the pavement. It can hurtle forward at high speeds, but some wish to go faster still. They make power mods to their car, maybe getting another 100 HP or more, and then are terribly disappointed when they see a single digit gain in top speed. Is this realistic? Is the problem with their modification, or with their expectation? It is the latter. Here are some sample numbers. They are not pertinent to your car necessarily, but they are typical. In general, 60 MPH requires about 15 HP. Table 1 shows the power rise that must accompany an increase in speed. Speed (MPH) Change (%) Horsepower Change 60.00 -- 15 -- 75.60 25.99% 30 100% 95.24 25.99% 60 100% 120.00 25.99% 120 100% 151.19 25.99% 240 100% 190.49 25.99% 480 100% Table 1 - Speed/Horsepower Correlation for a Typical Passenger Car SO IF THE QUESTION IS CAN YOU DRIVE 199MPH,?? MAYBE IF YOU HAVE ENOUGH HP AND A LOW ENOUGH DRAG AND FRONTAL AREA, your car can remain stable at those speeds and you can drive but you will be as crazy as I am to try it without a great roll cage, tires ratted for over 200mph and 13" disk brakes minimum on all four wheels and carbon brake pads Quote Link to comment Share on other sites More sharing options...
Guest Thurem Posted January 10, 2002 Share Posted January 10, 2002 Grumpyvette You hit my question square on, with the aerodynamic properties and the mechanical losses, how far will 400 hp take a Z? I am propably not going to actually test the limits, BUT it would be nice to know your theoretical boundaries. Anybody got actual experience in this area, how fast have you been in your Z ? Thure Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted January 10, 2002 Share Posted January 10, 2002 just for fun I ran your 400 hp z-car through the computer and the computer thinks 163mph is where a 400hp z-car will top out! now granted its only a computer but that sounds like a reasonable guess to me also Quote Link to comment Share on other sites More sharing options...
Guest Tim78zt Posted January 10, 2002 Share Posted January 10, 2002 check out the latest Road&Track with the new Mini on the cover or just go to roadandtrack.com. Inside is a read on the Ruf Rturbo. Over 200 mph with over 500 twin-turbo HP!!! WaaaaHoooooo!!! Yes, it takes over $200,000 to go that fast according to Ruf! Tim78zt Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted January 10, 2002 Share Posted January 10, 2002 Hey Mikelly, how fast did you have yours going? Wasn't it right around 160? Regards, Lone Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted January 10, 2002 Share Posted January 10, 2002 I have played with the Z car aerodynamic numbers a little bit, and would be interested in other peoples numbers. To begin with, I wanted to get values for the product of drag coefficient and frontal area, and a number for the static rolling resistance. I use the following equation for total drag force(Fd): Fd = 1/2 * rho * V^2 * Cd * A + Csr * V also Fd = M dV/dt where M is the mass of the car. Using this equation and a plot of the 240Z coast down data(1970 Road and Track), I solved for the unknowns Cd*A , and Csr. This is what I got: Cd*A = 5.2 ft^2 Csr = 1.92 Lbf/mph Using the above numbers, and the formula P=F*V, I get 336 RWHP to go 160 mph, and 390 RWHP to go 170 mph. Quote Link to comment Share on other sites More sharing options...
pparaska Posted January 10, 2002 Share Posted January 10, 2002 Cool thread! Grumpy, you first state that making the car fast we can do 3 things: lower it's mass, lower it's drag, and raise it's horsepower. For "fast" (speed) only drag and power matter. For "quick" (ET) all three matter. In fact, all the equations you list have NO mention of mass of the car there. The way I see it, the only thing removing mass from the car will do is to lower the rolling resistance a tiny bit (but you'd over come that effect to add downforce to keep it planted) and the amount of time to get to terminal velocity. Were you just testing us? Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted January 10, 2002 Share Posted January 10, 2002 Pete, Here is where mass comes in. Ftot = m * a = M* dV/dt Ftot = Fr - (1/2* rho * V^2 * Cd * A + Csr * V) = M * a where Fr is the reaction force of the road on the tires Therefore, M * dV/dt = Fr - (1/2* rho * V^2 * Cd * A + Csr * V) or dV/dt = Fr/M -(1/2* rho * V^2 * Cd * A + Csr * V)/M which in the limit that dV/dt = 0 (top speed) reduces to Fr = 1/2* rho * V^2 * Cd * A + Csr * V but Fr = (Teng * GR_t * GR_diff)/tire_dia Your torque to mass ratio determines your acceleration, but doesn't affect the top speed. The only factors that affect top speed are Cd*A, Csr, and HP. These are the relationships I use in the excel application that I sent you. Any chance of posting it. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted January 10, 2002 Share Posted January 10, 2002 hey guys where can i find the frontal area and drag coefficient specs for a 79 ZX on the web? Quote Link to comment Share on other sites More sharing options...
John Scott Posted January 11, 2002 Share Posted January 11, 2002 Hmmmm....I don't condone high speed runs, but in my ignorant earlier Z days I hit 5600 rpm in 4th a .7 overdrive, locked up, on a 700R4 w/3.54 rear, 24.75 diam tires. It was still pulling hard! I was seeing if the Vette 700R4 really stayed in 4th at WOT and got carried away. It was too damn fast and didn't take very long. My car has a slight nose down rake, with no aerodynamic mods. Its cool to know your car is really fast, but I really have no desire to do top end runs again. I'm afraid one of these days we're going to hear of someone doing this and having a catastrophic wreck. Not a smart experiment. JS Quote Link to comment Share on other sites More sharing options...
Guest Thurem Posted January 11, 2002 Share Posted January 11, 2002 Thanks Guys, I have only ever been about 150 Mph, on the speedo (+-10%) on my bike. Not too dramatic, except my helmet squishing my face. Thure Quote Link to comment Share on other sites More sharing options...
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