Which car has lowest rpms at 75mph.
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Base model C6 Corvette is 1600 rpm at 75 mph.
Originally Posted By: Gator
I was wanting to no which auto has the lowest rpms at 75 mph on interstate. Honda's rev a little too high, which translates into lower fuel economy.
Not necessarily. A smaller, higher revving engine will often produce better MPG than a larger, slower revving engine.
If it was just that simple, cars would have super tall gearing.
I was wanting to no which auto has the lowest rpms at 75 mph on interstate. Honda's rev a little too high, which translates into lower fuel economy.
Not necessarily. A smaller, higher revving engine will often produce better MPG than a larger, slower revving engine.
If it was just that simple, cars would have super tall gearing.
I think the Viper or a Vette might have the lowest rpms in top gear... The Vette gets great mileage for a high performace car but a buzzy civic will still beat it, for mileage.
My parents 08 CRV with the 5 spd auto might be at 2400rpm at 75. At 55mph its always downshifting on the highway to go up hills though...
My parents 08 CRV with the 5 spd auto might be at 2400rpm at 75. At 55mph its always downshifting on the highway to go up hills though...
My 06 M45 cruises at 3100rpm at about 75mph with a 5 speed auto. It's not great on gas either.
A smart man once told me " Revs are Free " the higher the revs the less force it takes to push the car. Therefore one is lighter on the pedal. The ONLY variable in milage is conditions and your right foot.
The last thing you want is a vehicle to struggle to maintain speed or get to speed because of poor gearing. 4 cylinder engines are meant to rev, let them do it.
The last thing you want is a vehicle to struggle to maintain speed or get to speed because of poor gearing. 4 cylinder engines are meant to rev, let them do it.
Originally Posted By: Gator
I was wanting to no which auto has the lowest rpms at 75 mph on interstate. Honda's rev a little too high, which translates into lower fuel economy.
In all the new cars I've had as rentals- I travel a lot- it seems to me that the slowest turning on the highway are the Ford Modulars. Doesn't seem to matter if its a 4.6 in a Crown Vic or a 5.4 in an Expedition, they turn significantly less than 2000 RPM on the highway. Its been a while since I had one, but I seem to remember 1500 RPM or just a little more at 70 with the torque convertor locked and cruising.
My daughter's Jeep Cherokee 4.0 / 5-speed combo is right at 2000 RPM at 70. Wife's PT Cruiser, on the other hand, is up close to 2800 at 70, and is one of the highest revving modern cars at cruise that I've seen recently. Of course my 60's vintage 3-speed v8 cars cruise at over 3k. No overdrive.
I was wanting to no which auto has the lowest rpms at 75 mph on interstate. Honda's rev a little too high, which translates into lower fuel economy.
In all the new cars I've had as rentals- I travel a lot- it seems to me that the slowest turning on the highway are the Ford Modulars. Doesn't seem to matter if its a 4.6 in a Crown Vic or a 5.4 in an Expedition, they turn significantly less than 2000 RPM on the highway. Its been a while since I had one, but I seem to remember 1500 RPM or just a little more at 70 with the torque convertor locked and cruising.
My daughter's Jeep Cherokee 4.0 / 5-speed combo is right at 2000 RPM at 70. Wife's PT Cruiser, on the other hand, is up close to 2800 at 70, and is one of the highest revving modern cars at cruise that I've seen recently. Of course my 60's vintage 3-speed v8 cars cruise at over 3k. No overdrive.
You may want to rephrase your question. The vehicles with the largest displacement generally have the lowest rpm on the highway. If you are looking specificly at 4 cylinders you have to compare auto and stick in the same model. My rpm is much lower with the automatic compared to someone that purchased the manual version of the same car.
Originally Posted By: nfs480
The rpms should not be a factor for determining gas mileage
That's just not true, otherwise we wouldn't have overdrive transmissions. Its also easy to disprove- burn a tank of gas in your Accord while running it in its highest gear (overdrive) on the highway. Then repeat the experiment limiting yourself to one gear lower (direct gear). You'll see that you burn significantly more fuel in direct than in overdrive.
Its true that for certain engine/car combos you can hurt the mileage by "lugging" the engine too low. A lot depends on where the cam grind installed in the engine is most efficient at scavenging without wasting fuel out the exhaust, and of course combustion chamber shape and its effect on flame propagation is very important.
But in general, its more efficient to turn the engine slower, run LESS spark advance, and operate at higher intake manifold pressure to fill the cylinders and minimize scavenging to fill. Less spark advance means less time that the flame front spends working against the piston. Higher intake manifold pressure serves to raise the cylinder starting pressure so that the flame front can complete the burn before the exhaust valve opens even with less spark advance, and it also fills the cylinder effectively. Reducing reliance on scavenging helps prevent blowing unburned air/fuel mix out the exhaust valve during overlap.
Friction in the engine is largely independent of RPM, so it takes the same torque to spin the engine against its internal friction at high RPM as low. But power is proportional to torque times RPM, so the power wasted to engine friction does go up linearly with RPM. Another reason to turn the engine slower.
The rpms should not be a factor for determining gas mileage
That's just not true, otherwise we wouldn't have overdrive transmissions. Its also easy to disprove- burn a tank of gas in your Accord while running it in its highest gear (overdrive) on the highway. Then repeat the experiment limiting yourself to one gear lower (direct gear). You'll see that you burn significantly more fuel in direct than in overdrive.
Its true that for certain engine/car combos you can hurt the mileage by "lugging" the engine too low. A lot depends on where the cam grind installed in the engine is most efficient at scavenging without wasting fuel out the exhaust, and of course combustion chamber shape and its effect on flame propagation is very important.
But in general, its more efficient to turn the engine slower, run LESS spark advance, and operate at higher intake manifold pressure to fill the cylinders and minimize scavenging to fill. Less spark advance means less time that the flame front spends working against the piston. Higher intake manifold pressure serves to raise the cylinder starting pressure so that the flame front can complete the burn before the exhaust valve opens even with less spark advance, and it also fills the cylinder effectively. Reducing reliance on scavenging helps prevent blowing unburned air/fuel mix out the exhaust valve during overlap.
Friction in the engine is largely independent of RPM, so it takes the same torque to spin the engine against its internal friction at high RPM as low. But power is proportional to torque times RPM, so the power wasted to engine friction does go up linearly with RPM. Another reason to turn the engine slower.
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i'm talking by model, comparing models by how much they rev on average shouldn't determine whether one gets better gas mileage than the other. If you rev the car higher, you'll get less gas mileage than the same car with lower revs for sure.
440 was responding to what you said, not what you were thinking.
Originally Posted By: TaterandNoodles
You may want to rephrase your question. The vehicles with the largest displacement generally have the lowest rpm on the highway. If you are looking specificly at 4 cylinders you have to compare auto and stick in the same model. My rpm is much lower with the automatic compared to someone that purchased the manual version of the same car.
That's not true for all vehicles. Take Jeep Cherokees for example. The automatic versions have a 0.75 overdrive in the transmission and are normally equipped with 3.55 ratio axles, for a final drive ratio of 2.66:1
On the other hand, the 5-speed stick versions have a 0.79 overdrive and are equipped with a 3.23 axle unless optioned otherwise, for a final drive ratio of 2.55:1. Very close to the same, but the automatic actually turns a few more RPM at cruise than the stick.
You may want to rephrase your question. The vehicles with the largest displacement generally have the lowest rpm on the highway. If you are looking specificly at 4 cylinders you have to compare auto and stick in the same model. My rpm is much lower with the automatic compared to someone that purchased the manual version of the same car.
That's not true for all vehicles. Take Jeep Cherokees for example. The automatic versions have a 0.75 overdrive in the transmission and are normally equipped with 3.55 ratio axles, for a final drive ratio of 2.66:1
On the other hand, the 5-speed stick versions have a 0.79 overdrive and are equipped with a 3.23 axle unless optioned otherwise, for a final drive ratio of 2.55:1. Very close to the same, but the automatic actually turns a few more RPM at cruise than the stick.
Originally Posted By: nfs480
i'm talking by model, comparing models by how much they rev on average shouldn't determine whether one gets better gas mileage than the other. If you rev the car higher, you'll get less gas mileage than the same car with lower revs for sure.
Absolutely right- my wife's PT gets better mileage on the highway than my daughter's Cherokee, despite the fact that it revs a good 800 RPM higher.
I was stating that IN GENERAL, low RPM helps efficiency.
i'm talking by model, comparing models by how much they rev on average shouldn't determine whether one gets better gas mileage than the other. If you rev the car higher, you'll get less gas mileage than the same car with lower revs for sure.
Absolutely right- my wife's PT gets better mileage on the highway than my daughter's Cherokee, despite the fact that it revs a good 800 RPM higher.
I was stating that IN GENERAL, low RPM helps efficiency.
Originally Posted By: 440Magnum
Wife's PT Cruiser, on the other hand, is up close to 2800 at 70, and is one of the highest revving modern cars at cruise that I've seen recently.
My previous A4 1.8T would cruise at 3100 rpm @ 70 mph, 3300 @ 75, but it didn't sound stressed at all. This engine loved to rev. And at 70-75 mph, it would still deliver about 31 MPG, despite being permanent all-wheel-drive.
Wife's PT Cruiser, on the other hand, is up close to 2800 at 70, and is one of the highest revving modern cars at cruise that I've seen recently.
My previous A4 1.8T would cruise at 3100 rpm @ 70 mph, 3300 @ 75, but it didn't sound stressed at all. This engine loved to rev. And at 70-75 mph, it would still deliver about 31 MPG, despite being permanent all-wheel-drive.
I only get about 30mpg in my cav 2.2, because the 3 speed auto keeps it at 3600RPM at 75 MPH.
I put a "wrong" 5-speed in my SOHC saturn, making it spin 2800 RPM at 65 instead of 2300 at its published torque peak. Still got 42 MPG which beat the EPA estimate by 3 MPG.
It was annoying though from a motor noise perspective. There is something nice about a V6 or V8 just loping along.
It was annoying though from a motor noise perspective. There is something nice about a V6 or V8 just loping along.
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