hkr4627@acf4.UUCP (Hedley K. J. Rainnie) (04/19/85)
Reply to Chris Kay's question: "Why is the new Corvette so fast and how fast were the older Vettes?" There are major three things to consider when one talks top speed. Horsepower, aerodynamics and gearing. The new Corvette excells in the latter two. Weight is more important for accelleration and handling than top speed, assuming all other things equal. In any case, the new Corvette standard (read loaded) weighs about the same as a standard late 60's Vette. You need a tall top gear so as to be able to cruise at a high speed without exceeding the redline of the motor. A five speed gearbox is nice with a high final drive in that you are still permitted to have a relatively low first gear to facilitate acceleration. The new Corvette has both the high final drive (3.07) and the 7 speed transmission (however you like to count gears). At the top speed, the amount of horsepower you need is determined by the quality of your aero specs. Since drag runs something like the cube of your speed, good aero specs can count for a lot of horsepower. The Corvette has an exceedingly low coefficient of drag. Now, onto the qeustion of yesteryear's Corvettes. First of all, aero-wise, they weren't so bad. In fact, I read that the aero figures for a 82 Corvette (which is the same body as the late 60's Vettes with some aero-mods stuck on) has about the same coefficient of drag as a 928! Boat racer Gale Banks and friends took a stock bodied 69 Vette a few years back, stuffed it with a twin turboed big-block and broke 220 mph at Daytona. So the aero figures aren't that bad at all. In fact, the 1963 Stingray is, to the best of my knowledge, one of the first if not the first American car to be designed with the aid of a wind tunnel. Using a 3/8 miniature of the experimental Stingray, GM rented wind tunnel time and a couple of fellows from M.I.T. to study the behavior of the body at wind velocities up to 160 mph. Gearing is a problem. Back then, almost all Corvettes were tested with final drive ratios like 3.70 or 4.11, making for truly hairy acceleration but redline-limiting their top speeds. We're looking at 120-130 mph here. On the other hand, the engines back then wound up a bit higher than engine nowadays: we're talking 6400 rpm for the 427 and 6500 rpm for the 327, as compared with around 6000 rpm for today's 350. Look at the rpm's for the top speed of the new Vette: 4100 rpm at 149 mph. The engine is not powerful enough to redline with that steep top gear. (If it could, you'd find yourself going 218 mph). Between the gearing and the engines, I've ever seen a test of an older Vette where it was unable to redline in all gears. Also, back then, there was a choice of two gearboxes, a close-ratio with a first gear of 2.20 and a wide ratio with a ratio of 2.52. Neither of these is close to today's 2.88 gearbox. The closer-ratio boxes of back then allowed you to keep the engine running at peak rpm's and made shifting nicer. Today, the point is to keep rpm's as low as possible for good milage in normal driving, but also holding a low first gear for quick acceleration. Thus the ultra wide ratio box. This allows a high (numerically low)* final drive ratio without killing accelleration--and thus a higher top speed. NOW, to the question of top speeds of older Vettes. With the right gearing (say 3.08) an older Vette could easily hit 150 or so well under 6000 rpm and probably faster. Without some sort of aero aid, it might well start flying at this speed, however, and the tires back then would probably give up. So as far as the standard, everyday Vettes go, top speeds haven't changed that much, for the reasons we've outlined. BUT back then, you didn't have to remain content with an everyday Vette. You could factory-order engine options to make for a super Vette for $1000-$3000 over the standard high performance option. The fastest Vette from Chevy has to be the ZL-1 aluminum Can-Am engine Corvette of 1969. Rated way under peak at a low 430 hp, they were very rare. Zora Arkus-Duntov, considered the 'father' of the Corvette, had one around the GM test track at 185 mph. The somewhat more common L-88's would make about 180 mph with the right gearing. Both of these are with open exhausts-- the factory exhaust was designed for you to throw it away--but otherwise stock cars. We've been talking a lot about top speed, and I've kept saying that the cars of that time were meant for acceleration. What kind of acceleration you wonder? Well, the pedestrian 435-hp big blocks were good for 0-60 in 5-1/2 seconds but the L-88 with the proper gearing was a real screamer: 0-60 in 4.2 sec, 0-100 in 8 sec. 0-140 in 17 sec., 1/4 mile in 11 @ 120mph. sources: Road & Track various issues from Oct 62- Sept 70 Road & Track 1985 Buyer's Guide Corvette: America's Star-Spangled Sportscar by Karl Ludvigsen Vette magazine: Nov 84, Mar 85 (signed) Speed Racer * 'low' gearing implies a high numerical ratio (engine to wheel): low gear or first has the highest ratio, over 2:1, while high gear has the lowest ratio (1:1).
man@bocar.UUCP (M Nevar) (04/22/85)
< 0-60 in 4.2 sec, 0-100 in 8 sec. 0-140 in 17 sec., 1/4 mile in 11 120 mph This is very impressive, but lets not forget the fastest production car ever built: The 1967 427 Cobra that went 0-100-0 in 12 seconds. That's truly amazing. It's top speed was around 190. Note that this was a 'production' car with sales over 100 per year. The ZL-1 was never a 'production' car. Shelby also had a limited run Cobra. He only built two. One for himself and one for Bill Cosby. It was a 427 Cobra Semi/Competition roadster with an out-of-the-box NASCAR engine (which all S/C roadsters got, but not all 427 Cobras) with TWO (count 'em) Paxton superchargers, and a 40 gallon fuel tank. This car was actually gotten up to 210 by a test driver (pilot ?). On one of Bill Cosby's comedy albums, he relates a great story on recieving delivery of his baby. Mark
hkr4627@acf4.UUCP (Hedley K. J. Rainnie) (04/24/85)
I have to disagree about the ZL-1 not being production. The engine was offered as a $3000 option in 1969. It is probably true, however, that they didn't sell enough for homologation. The version of the oft-told 0-100-0 of the Cobra I've always heard was 14 secs. But in any case, this is truly amazing performance. Not too many cars today can begin to even make 100 in 14 seconds. I read an interview with Shelby where he talked about a double supercharged Corbra "That thing would run right along up to 189 mph." He claimed that the Cobra was so solid that they never had to change a thing with the sus- pension. He did complain, however, that the bodies were really rotten: "build by a bunch of winos under a bridge in England" or something to that effect. In any case, the Cobra always had a slight edge over the Corvette because of weight. But I think that the superior engines of the Vette closed that gap a lot towards the end. And the Vette could be lightened a lot: the GS racers of 63-65 weighed something like 1990 lbs with 500 hp engines. I bet a lot of people out there are surprised that there were 180-190 mph cars made on THIS side of the Atlantic! (signed) Speed Racer p.s. Summer's coming! Let's get those car covers off, blow the dust out of the pipes and hit the road!
rdz@ccice5.UUCP (Robert D. Zarcone) (04/25/85)
> > Gearing is a problem. Back then, almost all Corvettes were tested with > final drive ratios like 3.70 or 4.11, making for truly hairy acceleration > but redline-limiting their top speeds. We're looking at 120-130 mph here. On > the other hand, the engines back then wound up a bit higher than engine > nowadays: we're talking 6400 rpm for the 427 and 6500 rpm for the 327, as > compared with around 6000 rpm for today's 350. Look at the rpm's for the > top speed of the new Vette: 4100 rpm at 149 mph. The engine is not powerful > enough to redline with that steep top gear. (If it could, you'd find yourself > going 218 mph). Between the gearing and the engines, I've ever seen a test > of an older Vette where it was unable to redline in all gears. > > (signed) > Speed Racer > I'm obviously missing something here. My problem is with the last sentence. I can see how a car would be unable to redline in top gear. But how could any car be unable to redline in all gears? If seems like one could easily hit 6400 rpm in first before they ever approached 130 mph. Someone please point out the fault in my logic
hkr4627@acf4.UUCP (Hedley K. J. Rainnie) (04/27/85)
Response 3 reads:
" I'm obviously missing something here. My problem is with the last sentence.
I can see how a car would be unable to redline in top gear. But how could
any car be unable to redline in all gears? If seems like one could easily
hit 6400 rpm in first before they ever approached 130 mph. Someone please
point out the fault in my logic"
From: rdz@ccice5.UUCP (Robert D. Zarcone)
I'll try.
Where: rx - able to redline in xth gear,
You're thinking:
~r1 * ~r2 * ~r3 * ~r4 (1)
= ~(r1 + r2 + r3 +r4) (2)
where I was thinking:
~(r1 * r2 * r3 *r4) (3)
where: + logical or
* logical and
~ negation
Now, I would consider your thoughts to be closer to
"unable to redline in ANY gear." One might make the case that
the word ANY implies OR, and the word all implies AND. For example,
"ALL the Cleavers" would become "Ward AND June AND Theodore AND Wally"
whereas "ANY of the Cleavers" would be "Ward OR Jun OR Theodore OR Wally"
So, we expand "unable to redline in all gears" to
"unable to redline in 1st and 2nd and 3rd and 4th"
Let's distribute redline:
"unable to redline in 1st and redline in 2nd and redline in 3rd and
redline in 4th"
Now YOU distributed UNABLE, and by doing so:
"unable to redline in 1st and unable to redline in 2nd and
unable to redline in 3rd and unable to redline in 4th."
which is equivalent to (1).
You assumed that "UNABLE" binds more closely than "ALL". I disagree.
If we apply DeMorgan's to (1), we get (2) which reads:
"Unable to redline in first or second or third or fourth." Replacing
the ORs with the ANY structure, you get:
"Unable to redline in any gear." Which is what you meant.
But!
If you bind the "ALL" first, that is, the gears, you get the unable
stuck outside and something resembling (3). This can be expressed
"unable to redline in 1st and redline in 2nd and redline in 3d and
redline in 4th." I.e., there exists a gear such that one cannot
redline the motor while in it."
(3) is the meaning
I intended to convey. I think that ALL and ANY always bind first
since they are abbreviations for AND and OR, respectively.
Since the sentence IS confusing AND there's no reason to bring in the
three lower gears since if the car will redline in top, it will in lower
gears, AND since there is a typo in the original, let's change the sentence
to read:
"In every review I've ever seen, the older Vettes had no trouble redlining
in top gear."
(signed)
speed racerrdz@ccice5.UUCP (Robert D. Zarcone) (04/30/85)
> > I'm obviously missing something here. My problem is with the last sentence. > I can see how a car would be unable to redline in top gear. But how could > any car be unable to redline in all gears? If seems like one could easily > hit 6400 rpm in first before they ever approached 130 mph. Someone please > point out the fault in my logic > My fault has been pointed out. All != any. Thank you. *** REPLACE THIS LINE WITH YOUR MESSAGE ***
rdz@ccice5.UUCP (Robert D. Zarcone) (05/03/85)
Whew! Thank you? [:-)]