Newbie questions on optimal RPM for cruising
11-07-2013, 05:52 PM
#1
Racer
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Newbie questions on optimal RPM for cruising
Does anyone know what will be the most economical optimal RPM (in the tallest gear) when cruising on your C7 in the V4 or V8 modes?
Will it be 1500 RPMs for both? or maybe a different RPMs for both? or maybe a different RPM for each mode?
Thank you
Will it be 1500 RPMs for both? or maybe a different RPMs for both? or maybe a different RPM for each mode?
Thank you
11-07-2013, 07:01 PM
#2
Team Owner
In My C6 Z06 I don't like to drop below 1100 RPM. Anytime I'm cruising I drive so that I see at least 1,100 RPM. On the highway I drive in the tallest gear that keeps me above 1,100 RPM. I downshift if I fall below 1,100 RPM or when I need to pass a slow moving car. The gear I downshift to, depends on what the conditions are at that time.
11-07-2013, 07:16 PM
#4
Team Owner
The rest of the drivers on the highway will be most happy if you drive a speed that does not hold up traffic or makes you speed, causing you to weave in and out of traffic to keep your MPG up.
Ignore the MPG and drive the speed at what the prevailing traffic allows, in the tallest gear that keeps your RPM above 1,100.
If you adjust your speed to maximize MPG, and start pissing the other drivers around you off,.......you're asking for a lot of trouble.
Ignore the MPG and drive the speed at what the prevailing traffic allows, in the tallest gear that keeps your RPM above 1,100.
If you adjust your speed to maximize MPG, and start pissing the other drivers around you off,.......you're asking for a lot of trouble.
11-07-2013, 07:26 PM
#5
Racer
1300 RPMs in 7th gear is the most economical cruising speed for my C7. If you bump it up to 1500 you are running 80 mph and the mpg goes down. The car also stays in the V4 mode more consistently at the lower rpm. At 1500 it shifts to V8 mode more frequently and stays there longer.
11-08-2013, 03:30 PM
#7
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In V8 mode, I've noticed 1300 to be optimal.
In V4 mode, I've noticed 1500 to be optimal.
Both of these scenarios, the engine never lugs. But dropping down to 1200 in V4, occasionally, the engine lugs and I down shift. So I stick to my general rule of thumb.
For fuel economy, V4 mode is better in 6th gear unless going over 80 MPH. Above 80, 7th gear in V4 mode will give you better results.
BTW, I have a 7-speed Z51. So the non-Z51 will probably want higher speeds for better fuel economy.
In V4 mode, I've noticed 1500 to be optimal.
Both of these scenarios, the engine never lugs. But dropping down to 1200 in V4, occasionally, the engine lugs and I down shift. So I stick to my general rule of thumb.
For fuel economy, V4 mode is better in 6th gear unless going over 80 MPH. Above 80, 7th gear in V4 mode will give you better results.
BTW, I have a 7-speed Z51. So the non-Z51 will probably want higher speeds for better fuel economy.
11-08-2013, 04:22 PM
#8
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I remember a similar thread about 10 years ago, the Vette was less expensive back then but the thought of spending $60,000 to $70,000 on a car and worrying about saving a few pennies.
Let's assume you find a speed that will have your car get one or even two miles per gallon, but that slowed speed adds a few hours to your trip. Whatever you save in gas will be wasted in paying for a motel that you probably could have made the trip without a overnight sleepover and you will probably need to make extra stops at a diner or restaurant.
Let's assume you find a speed that will have your car get one or even two miles per gallon, but that slowed speed adds a few hours to your trip. Whatever you save in gas will be wasted in paying for a motel that you probably could have made the trip without a overnight sleepover and you will probably need to make extra stops at a diner or restaurant.
11-08-2013, 05:38 PM
#9
I remember a similar thread about 10 years ago, the Vette was less expensive back then but the thought of spending $60,000 to $70,000 on a car and worrying about saving a few pennies.
Let's assume you find a speed that will have your car get one or even two miles per gallon, but that slowed speed adds a few hours to your trip. Whatever you save in gas will be wasted in paying for a motel that you probably could have made the trip without a overnight sleepover and you will probably need to make extra stops at a diner or restaurant.
Let's assume you find a speed that will have your car get one or even two miles per gallon, but that slowed speed adds a few hours to your trip. Whatever you save in gas will be wasted in paying for a motel that you probably could have made the trip without a overnight sleepover and you will probably need to make extra stops at a diner or restaurant.
11-08-2013, 05:45 PM
#10
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But that doesn't mean when I'm not stepping on the gas I want to use more gas forcing me to stop at a gas station more often. It's NOT about the money. It's about having to stop at a gas station for me. I hate gas stations. They're dirty and stink.
11-08-2013, 05:47 PM
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11-08-2013, 06:41 PM
#12
Team Owner
In V8 mode, I've noticed 1300 to be optimal.
In V4 mode, I've noticed 1500 to be optimal.
Both of these scenarios, the engine never lugs. But dropping down to 1200 in V4, occasionally, the engine lugs and I down shift. So I stick to my general rule of thumb.
For fuel economy, V4 mode is better in 6th gear unless going over 80 MPH. Above 80, 7th gear in V4 mode will give you better results.
BTW, I have a 7-speed Z51. So the non-Z51 will probably want higher speeds for better fuel economy.
In V4 mode, I've noticed 1500 to be optimal.
Both of these scenarios, the engine never lugs. But dropping down to 1200 in V4, occasionally, the engine lugs and I down shift. So I stick to my general rule of thumb.
For fuel economy, V4 mode is better in 6th gear unless going over 80 MPH. Above 80, 7th gear in V4 mode will give you better results.
BTW, I have a 7-speed Z51. So the non-Z51 will probably want higher speeds for better fuel economy.
Your C7 Z51 in 7th gear(.48) is just a tiny tad bit higher geared than my Z06 in 6th gear(.50).
A non Z51 is geared at .42 in 7th gear so it might have more of a tendency to lug at lower speeds than your Z51.
11-08-2013, 06:49 PM
#13
Racer
11-08-2013, 06:49 PM
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I have found with my Z06, that I get slightly better fuel mileage in 6th gear when I'm running 70 than when I'm running 65. I'm not exactly lugging the engine at 65, but 70 seems to be my car's sweet spot.
You C7 Z51 in 7th gear(.48) is just a tiny tad bit higher geared than my Z06 in 6th gear(.50).
A non Z51 is geared at .42 in 7th gear so it might have more of a tendency to lug at lower speeds than your Z51.
You C7 Z51 in 7th gear(.48) is just a tiny tad bit higher geared than my Z06 in 6th gear(.50).
A non Z51 is geared at .42 in 7th gear so it might have more of a tendency to lug at lower speeds than your Z51.
What I noticed here is that in 7th gear below 80 MPH, the AFM kicks off a LOT. Maybe on long flat road it would stay in AFM mode, but here in LA with lots of ups and downs, 7th gear with AFM on is short lived. In 6th gear, there's enough gearing that the car stays in V4 mode much longer and doesn't remotely ever lug. I tested this by driving from my parent's house to mine in near identical traffic and temps...
First time was in 7th gear in Eco mode with cruise control set to 72 MPH. I averaged 27 MPG.
Second time was 6th gear in Eco mode with cruise control set to 72 MPH. I averaged 31 MPG.
The distance is 8.4 miles. All freeway with lots of turns and ups and downs.
I haven't tested what the economy is like in both situations without Eco mode. (Nor do I plan to do check. When I'm not in Eco mode, I'm driving my car like its ment to be driven.)
11-08-2013, 06:52 PM
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11-08-2013, 07:56 PM
#17
Racer
In V8 mode, I've noticed 1300 to be optimal.
In V4 mode, I've noticed 1500 to be optimal.
Both of these scenarios, the engine never lugs. But dropping down to 1200 in V4, occasionally, the engine lugs and I down shift. So I stick to my general rule of thumb.
For fuel economy, V4 mode is better in 6th gear unless going over 80 MPH. Above 80, 7th gear in V4 mode will give you better results.
BTW, I have a 7-speed Z51. So the non-Z51 will probably want higher speeds for better fuel economy.
In V4 mode, I've noticed 1500 to be optimal.
Both of these scenarios, the engine never lugs. But dropping down to 1200 in V4, occasionally, the engine lugs and I down shift. So I stick to my general rule of thumb.
For fuel economy, V4 mode is better in 6th gear unless going over 80 MPH. Above 80, 7th gear in V4 mode will give you better results.
BTW, I have a 7-speed Z51. So the non-Z51 will probably want higher speeds for better fuel economy.
It sounds like you are able to set and keep your C7 in V4 or V8 mode? Is that true? My car shifts back and forth from V4 to V8 on it's own. At 1500 RPMs my car is running over 80 in 7th. It shifts more frequently out of V4 mode at this speed. In fact, it will only be in V4 when going down hill! At 1300 RPMs (75 MPH) it stays in V4 mode longer.
As I'm sure you know, it takes more HP to keep a car moving at 80 than at 75 and thus the car uses more fuel. Since most Interstate speed limits are in the 70 to 75 MPH range across the nation, I'm sure that Chevy and most auto makers install final gear ratios that get the best fuel mileage at these speeds.
Above 80 MPH my car is seldom in V4 mode. It just takes more than the 150 or so HP the engine produces in V4, to keep the car at this speed. Conversely, when cruising around town in Eco Mode, my car will stay in V4 most of the time in almost every gear.
11-08-2013, 08:06 PM
#18
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It sounds like you are able to set and keep your C7 in V4 or V8 mode? Is that true? My car shifts back and forth from V4 to V8 on it's own. At 1500 RPMs my car is running over 80 in 7th. It shifts more frequently out of V4 mode at this speed. In fact, it will only be in V4 when going down hill! At 1300 RPMs (75 MPH) it stays in V4 mode longer.
As I'm sure you know, it takes more HP to keep a car moving at 80 than at 75 and thus the car uses more fuel. Since most Interstate speed limits are in the 70 to 75 MPH range across the nation, I'm sure that Chevy and most auto makers install final gear ratios that get the best fuel mileage at these speeds.
Above 80 MPH my car is seldom in V4 mode. It just takes more than the 150 or so HP the engine produces in V4, to keep the car at this speed. Conversely, when cruising around town in Eco Mode, my car will stay in V4 most of the time in almost every gear.
No, I don't have a way to keep it in V4 mode. It's automatic. But it STAYS in V4 mode unless I give it a bit more gas. However, it only does this in 4th, 5th and 6th. In 7th it will not stay in V4 mode and I wouldn't expect it to.
I've learned how to get the car in and out of the different modes by manipulating the gas pedal. However, in 7th gear, it does not like to be in V4 mode unless I'm going at least 75-80. Anything less and it won't stay in V4 mode.
While you're right that it takes more power to go faster, the engine generates more power as its higher in the RPMs. Meaning, that the car could produce MORE than enough power to push you to 90 MPH in V4 mode as long as you're in 6th gear due to its higher gearing. But do it in 7th and you technically need more power at a lower RPM to do the same thing. That's why V8 mode is more necessary.
According to Tadje, the Corvette only need 14HP to keep it rolling at 60 MPH on a flat road. In V4 mode at 1500 RPM, you're making a lot more power than that. Maybe 60+ HP.
11-08-2013, 08:23 PM
#19
Melting Slicks
A C7 Corvette only requires about 40-45 hp to run at 80 mph. It runs as a V8 above 80 mph because it is no less efficient to do so and easier on the engine (because of balance issues) with all 8 cylinders producing power.