It can't possibly go 140 mph right?
September 14, 2008 7:39 PM Subscribe
What is the top speed of a Chevrolet Corsica? 1993-1996 would be appreciated.
This guy says the governor in his '95 Corsica limits it to 115, and this guy says the 1991 Corsica's governor kicks in around 110.
posted by box at 8:03 PM on September 14, 2008
posted by box at 8:03 PM on September 14, 2008
140 is impossible. I had one of these with turbo and managed to put the speedometer in Park on more than one occasion. That's about 110 miles an hour. I was sixteen years old; young, dumb, and -- well, dumb anyway.
posted by word_virus at 10:18 PM on September 14, 2008
posted by word_virus at 10:18 PM on September 14, 2008
Best answer: the transmission used in 95-96 corsicas has a 4th gear ratio of 0.68 and a final drive ratio of 3.63:1. that's a total engine to wheels gearing ratio of 2.46:1. the stock tire size is 185/75R14, which means the circumference of the tire is 78.3 inches.
140 mph * (63360 inches/mile) * (1 hr/60 min) * (1 wheel revolution / 78.3 inches) * (2.46 engine revolutions / wheel revolution) = 4644 rpm. in 3rd, 140 mph is 6853 rpm.
not sure where the rev limiter kicks in on this car but usually it's 6-7k - so, i call bollocks on the notion of the rev limiter being involved, unless whoever it was was in 3rd and going REALLY fast. (and i would expect a car like the corsica to start shedding parts at that speed.) but at least it appears the transmission is capable of taking it up that high unless i did my math wrong.
you can estimate the ungoverned top speed from the aerodynamics which will be the main power sink at those speeds. the drag coefficient and frontal area of the corsica (not sure what year this refers to, so take it with a grain of salt) are apparently 0.28 and 26 sqft = 2.42 m2 and the max engine power is, being generous and assuming that the max power rpm is close to the max speed rpm (plausible), 120 hp = 89 kW for the 4cyl and 160hp = 118 kW for the 6cyl. (again, using the 95-96 numbers here).
then at standard conditions the drag force at N meters/sec is F = 0.5 * 1.2 kg/m3 * N2 * 0.28 * 2.42 m2 = 0.406N2. power being force times distance over time, the drag power is then 0.406N3. set this equal to the engine power and solve for N to find the top speed is 60.29 m/s or 134.6 mph for the 4cyl and 148.2 mph for the 6cyl. so it sounds not totally unreasonable, even considering extra losses in the drivetrain and rolling resistance et cetera.
at least, it should be possible if not for the speed governor, but i have no idea what that's set at. the top speed governor is usually set to whatever the maximum speed rating is on the stock tires. if the corsica came with H-rated tires or better, or your buddy had disabled the governor, i think it's not so far outside of the realm of possibility that he be lying.
posted by sergeant sandwich at 12:28 AM on September 15, 2008 [1 favorite]
140 mph * (63360 inches/mile) * (1 hr/60 min) * (1 wheel revolution / 78.3 inches) * (2.46 engine revolutions / wheel revolution) = 4644 rpm. in 3rd, 140 mph is 6853 rpm.
not sure where the rev limiter kicks in on this car but usually it's 6-7k - so, i call bollocks on the notion of the rev limiter being involved, unless whoever it was was in 3rd and going REALLY fast. (and i would expect a car like the corsica to start shedding parts at that speed.) but at least it appears the transmission is capable of taking it up that high unless i did my math wrong.
you can estimate the ungoverned top speed from the aerodynamics which will be the main power sink at those speeds. the drag coefficient and frontal area of the corsica (not sure what year this refers to, so take it with a grain of salt) are apparently 0.28 and 26 sqft = 2.42 m2 and the max engine power is, being generous and assuming that the max power rpm is close to the max speed rpm (plausible), 120 hp = 89 kW for the 4cyl and 160hp = 118 kW for the 6cyl. (again, using the 95-96 numbers here).
then at standard conditions the drag force at N meters/sec is F = 0.5 * 1.2 kg/m3 * N2 * 0.28 * 2.42 m2 = 0.406N2. power being force times distance over time, the drag power is then 0.406N3. set this equal to the engine power and solve for N to find the top speed is 60.29 m/s or 134.6 mph for the 4cyl and 148.2 mph for the 6cyl. so it sounds not totally unreasonable, even considering extra losses in the drivetrain and rolling resistance et cetera.
at least, it should be possible if not for the speed governor, but i have no idea what that's set at. the top speed governor is usually set to whatever the maximum speed rating is on the stock tires. if the corsica came with H-rated tires or better, or your buddy had disabled the governor, i think it's not so far outside of the realm of possibility that he be lying.
posted by sergeant sandwich at 12:28 AM on September 15, 2008 [1 favorite]
Note: In 1993, you could only get 140hp in the V6; in 1994, it got bumped to 160hp.
posted by davejay at 1:27 AM on September 15, 2008
posted by davejay at 1:27 AM on September 15, 2008
Sergeant Sandwich: I think there may be an issue with your maths, there. I don't know of a car that isn't a Supercar that will do 140mph in 3rd... They just don't gear cars that low for low power engines - it'd never go anywhere once you changed out of second as the slightest gradient would cause it to run out of torque. There is also no earthly reason to justify gearing a car that long, especially with only 160hp - My old BMW 535i had 230hp and was only geared for 155 in 5th gear at red line. In 4th it would rev out at around 110-115mph.
I haven't got time to look into it now (I have to go to work) but maybe revisit it.
posted by Brockles at 5:14 AM on September 15, 2008
I haven't got time to look into it now (I have to go to work) but maybe revisit it.
posted by Brockles at 5:14 AM on September 15, 2008
Lots of ECMs in this time frame had a high vehicle speed fuel cut-off in the 105 - 115 MPH region based on the rating of the base tires.
posted by rfs at 1:42 PM on September 15, 2008
posted by rfs at 1:42 PM on September 15, 2008
Brockles writes "There is also no earthly reason to justify gearing a car that long, especially with only 160hp"
Fuel economy.... Few cars will hit their rev limiters in over drive (or now a days double over drive) as they are naturally limited by engine power. However at 65MPH-110Km/s a 20-30% overdrive will get a good 15%+ increase in fuel economy vs. the straight thru box.. The vast majority of cars are faster in top gear -1 than they are in top gear because the close ratio box that would give top speed in top gear would require more shifting and return lower mileage.
Tall gearing like that is one of the reasons I could easily get 25+ mpg with a huge Chrysler big block mounted in a 4500lb car. Even though it had a 1:1 3 speed auto the 2.70s in the rear coupled with tallish 15" tires gave good mileage (if you could avoid the temptation to play with all the available torque).
... And marketing. More is better. A 6 speed tranny _has_ to be better than a 5 speed right?
Brockles writes "I don't know of a car that isn't a Supercar that will do 140mph in 3rd... "
Maybe you'd consider it a super car; however, a properly equipped '69 Polara could see the North side of a 140 no problem. 150 wasn't unheard of. And that with a non over drive, non lockup 3 speed auto in 4DRSDN trim no less.
posted by Mitheral at 5:43 PM on September 15, 2008
Fuel economy.... Few cars will hit their rev limiters in over drive (or now a days double over drive) as they are naturally limited by engine power. However at 65MPH-110Km/s a 20-30% overdrive will get a good 15%+ increase in fuel economy vs. the straight thru box.. The vast majority of cars are faster in top gear -1 than they are in top gear because the close ratio box that would give top speed in top gear would require more shifting and return lower mileage.
Tall gearing like that is one of the reasons I could easily get 25+ mpg with a huge Chrysler big block mounted in a 4500lb car. Even though it had a 1:1 3 speed auto the 2.70s in the rear coupled with tallish 15" tires gave good mileage (if you could avoid the temptation to play with all the available torque).
... And marketing. More is better. A 6 speed tranny _has_ to be better than a 5 speed right?
Brockles writes "I don't know of a car that isn't a Supercar that will do 140mph in 3rd... "
Maybe you'd consider it a super car; however, a properly equipped '69 Polara could see the North side of a 140 no problem. 150 wasn't unheard of. And that with a non over drive, non lockup 3 speed auto in 4DRSDN trim no less.
posted by Mitheral at 5:43 PM on September 15, 2008
Fuel economy....
Not with 160bhp, I imagine. It'd have so little power that it'd struggle to pull it at all, never mind maintain speed with it.
The vast majority of cars are faster in top gear -1 than they are in top gear
Not in any European/Japanese car (and I'm talking possibly into the hundreds) I have driven that wasn't made in the 1980's or before. This may be the time warp that american cars have again that harks (even now) to that era, but I honestly can't think of any contemporary car that has such a massive overdrive any more. It implies such a large ratio gap that, even if you change gear right at the red line in (top -1) to top, the car can't pull the gear to go any faster. They simply don't make them like that any more (outside the US - I haven't v-max'ed too many over here, but WAY too many at home).
1970's cars had an odd idea of 'economy' - they had such massive engines that they could pull such crazy gearing, but emissions these days means you struggle to produce that much torque with any success.
posted by Brockles at 6:12 PM on September 15, 2008
Not with 160bhp, I imagine. It'd have so little power that it'd struggle to pull it at all, never mind maintain speed with it.
The vast majority of cars are faster in top gear -1 than they are in top gear
Not in any European/Japanese car (and I'm talking possibly into the hundreds) I have driven that wasn't made in the 1980's or before. This may be the time warp that american cars have again that harks (even now) to that era, but I honestly can't think of any contemporary car that has such a massive overdrive any more. It implies such a large ratio gap that, even if you change gear right at the red line in (top -1) to top, the car can't pull the gear to go any faster. They simply don't make them like that any more (outside the US - I haven't v-max'ed too many over here, but WAY too many at home).
1970's cars had an odd idea of 'economy' - they had such massive engines that they could pull such crazy gearing, but emissions these days means you struggle to produce that much torque with any success.
posted by Brockles at 6:12 PM on September 15, 2008
"I don't know of a car that isn't a Supercar that will do 140mph in 3rd... "
Admittedly, I hadn't thought of a 3 speed automatic. Again, they're from the 1970's, too. 5 speed gearboxes and up was my assumption.
posted by Brockles at 6:13 PM on September 15, 2008
Admittedly, I hadn't thought of a 3 speed automatic. Again, they're from the 1970's, too. 5 speed gearboxes and up was my assumption.
posted by Brockles at 6:13 PM on September 15, 2008
Yeah, my maths has 4th gear (from sergeant sandwich's base numbers of tyre size and gear/diff ratios) at 7000rpm equating to 130 mph, which sounds much more realistic to me. 2000 rpm rev drop between gears sounds horrific, too.
I think the car may have been geared (in fifth on the manual box) to 140, which is where the original confusion comes from, but it's top speed is massively limited by it's aerodynamics and lack of power. It was geared for a nominal 140 but just for economy once you get into top. It wasn't expected to get there by any means (this side of HOOOGE turbochargers and nitrous).
posted by Brockles at 6:42 PM on September 15, 2008
I think the car may have been geared (in fifth on the manual box) to 140, which is where the original confusion comes from, but it's top speed is massively limited by it's aerodynamics and lack of power. It was geared for a nominal 140 but just for economy once you get into top. It wasn't expected to get there by any means (this side of HOOOGE turbochargers and nitrous).
posted by Brockles at 6:42 PM on September 15, 2008
This thread is closed to new comments.
The 120 was downhill with a tailwind and the wings of an angel spurring it on.
posted by SpecialK at 7:47 PM on September 14, 2008