[Rushingman]

What are your guys' RPMs like in the highway?

I feel like mine are unusually high at 3-3.5k at about 80 mph, never had a car that keeps them that high.

 

[stine 304]

Yep- sucks. That and only having a 5 speed auto kills my mileage. My last car was bigger and heavier and did much better on mileage.

 

[CtheW0rld]

What are your guys' RPMs like in the highway?

I feel like mine are unusually high at 3-3.5k at about 80 mph, never had a car that keeps them that high.

4 cylinder?

going 70 - 75, on flat ground, mine are around 1500 with the 'eco' light on.

 

[Rushingman]

4 cylinder?

going 70 - 75, on flat ground, mine are around 1500 with the 'eco' light on.

Mines a v6

 

[accord_J]

What are your guys' RPMs like in the highway?

I feel like mine are unusually high at 3-3.5k at about 80 mph, never had a car that keeps them that high.

3.5 isnt high :lmao: my integra with b16 trans does like 4-5k from 70-80mph

 

[infinite012]

What size tires are on your wheels?

 

[RickBlaine]

Ha ha ha- this is like 20 questions. OP gives no info.

 

[Rushingman]

Ha ha ha- this is like 20 questions. OP gives no info.

My bad on no info. Haha

But it's a 2008 accord sedan ex-L
Automatic transmission 3.5L
Stock 17 in rims.
Nothing done to it, completely stock.

I think that's all that should be necessary for this question.

I may be wrong though

 

[stine 304]

I remember reading that Honda made the car with lower gearing so that there would be adequate power when the cylinder deactivation kicked in. But since the car doesn't stay in eco mode it burns more gas. Pretty piss poor engineering on that setup. I don't know how it got through.

 

[fastball]

I'm at 2400 in 6th gear at 70 mph, and when I take it to 80 it does hit 3k.

Honda engines are typically higher reving than other cars, especially if you're used to American cars. A Camaro SS 6 speed stick with the 368 will turn a sleepy 1800 rpm at 70 MPH in 6th.

Honda engines have never been big on bottom end torque, even the J series V6. So to keep the engine in the strongest power band they keep the gearing shorter. Even in "overdrive", Honda keeps the gearing shorter.

My 2000 Prelude 5 speed was at 3500 RPM at 70. As a gear head I love the sound of a well engineered motor at high RPM.

 

[jeb]

As a gear head I love the sound of a well engineered motor at high RPM.

Ohh I so agree. Music to my ears.

 

[BadBlackEXLV6]

4 cylinder?

going 70 - 75, on flat ground, mine are around 1500 with the 'eco' light on.

There is no way you are at 1500 at 70-75. More like 2500 but definitely not 1500.

 

[CtheW0rld]

There is no way you are at 1500 at 70-75. More like 2500 but definitely not 1500.

unless you are in the car with me - S..k it. you're in the sedan, coupe is different. different tires, different aerodynamics.

 

[illest_jay]

Mine is 2300-2500 going 70-80mph on flat ground. 2012 coupe i4 auto. :dunno:

unless you are in the car with me - S..k it. you're in the sedan, coupe is different. different tires, different aerodynamics.

lol you think aero has an effect on rpms at a specific speed.

That's not how it works at all.

 

[Tom 6-6]

My old 2002 4 cylinder did around 2500 rpms at about 65 to 70 mph. I can't see 1500 rpms at 65 - 70 ?

 

[CtheW0rld]

lol you think aero has an effect on rpms at a specific speed.

That's not how it works at all.

how does it work, genius?

like i said, since you're not in the car with me, S..k it.

My old 2002 4 cylinder did around 2500 rpms at about 65 to 70 mph. I can't see 1500 rpms at 65 - 70 ?

OLD being the operative word here....

 

[infinite012]

how does it work, guinness?

like i said, since you're not in the car with me, S..k it.

Guinness makes a delicious stout. Not that you'd know, since you're obviously a child.

Now as far as how MPH and RPM relate to each other (and why aerodynamics do NOT play a role in this relationship), you'll have to take a look at a few mathematical equations. Hang on to your diapers, kid. It's going to get messy.

Let's start with the circumference of your tire. You'll need tread width (W_t), aspect ratio (A), and wheel diameter (D_w) to calculate your tire circumference. You'll need to get the height of your sidewall by multiplying W_t and A by 2 (this accounts for both sidewall sections that make up the whole diameter), then convert that number into inches. Add this number to your wheel diameter to get the total wheel & tire diameter. Multiply that number by pi to get your circumference.

Let's make it easy, though, and say we have a 225/50/17 (W_t = 225 mm, A = .50, D_w = 17 in) tire which has a tire diameter (D_t) of 25.9 inches. Your circumference would then be tire diameter * pi = 81.2 inches.

Now we have the circumference of the tire (which is essentially a gear or a multiplier). To get from this number to MPH, we'll need the engine rpm you're running around at (let's say 1500 rpm, since that's what you're claiming you're at when driving at 70 mph), the final drive ratio (I think this number is 4.31 for the V6 coupe with 5 speed automatic transmission), running gear ratio (for 5th gear it's 0.612), and a way to convert inches per minute to miles per hour. Gear ratio numbers were grabbed from this brochure (http://automobiles.honda.com/images/2008/accord-coupe/downloads/2008-accord-coupe-brochure.pdf) and the conversion number is 1 mile per hour/1056 inch per minute (verify that on google if you want).

So, here we go:

(1500 rpm * 81.2 inches) / (4.31 * 0.612 * 1056) = Your speed in MPH.

What is that speed, though? Have you done the math?

The answer is 43.75 MPH. Not nearly 70 MPH. What rpm do you need to be at to get to 70 MPH?

2401 rpm.

 

[CtheW0rld]

Guinness makes a delicious stout. Not that you'd know, since you're obviously a child.

Now as far as how MPH and RPM relate to each other (and why aerodynamics do NOT play a role in this relationship), you'll have to take a look at a few mathematical equations. Hang on to your diapers, kid. It's going to get messy.

Let's start with the circumference of your tire. You'll need tread width (W_t), aspect ratio (A), and wheel diameter (D_w) to calculate your tire circumference. You'll need to get the height of your sidewall by multiplying W_t and A by 2 (this accounts for both sidewall sections that make up the whole diameter), then convert that number into inches. Add this number to your wheel diameter to get the total wheel & tire diameter. Multiply that number by pi to get your circumference.

Let's make it easy, though, and say we have a 225/50/17 (W_t = 225 mm, A = .50, D_w = 17 in) tire which has a tire diameter (D_t) of 25.9 inches. Your circumference would then be tire diameter * pi = 81.2 inches.

Now we have the circumference of the tire (which is essentially a gear or a multiplier). To get from this number to MPH, we'll need the engine rpm you're running around at (let's say 1500 rpm, since that's what you're claiming you're at when driving at 70 mph), the final drive ratio (I think this number is 4.31 for the V6 coupe with 5 speed automatic transmission), running gear ratio (for 5th gear it's 0.612), and a way to convert inches per minute to miles per hour. Gear ratio numbers were grabbed from this brochure (http://automobiles.honda.com/images/2008/accord-coupe/downloads/2008-accord-coupe-brochure.pdf) and the conversion number is 1 mile per hour/1056 inch per minute (verify that on google if you want).

So, here we go:

(1500 rpm * 81.2 inches) / (4.31 * 0.612 * 1056) = Your speed in MPH.

What is that speed, though? Have you done the math?

The answer is 43.75 MPH. Not nearly 70 MPH. What rpm do you need to be at to get to 70 MPH?

2401 rpm.

fail. noting in there about terrain, weight of the car, passengers, tire inflation and YES aerodynamics. i i suppose you think the auto industry is wasting their money studying and testing aerodymanics. wind-tunnels aren't just for the fun of watching smoke go over the car. you have my tire size wrong, too.

 

[infinite012]

Ok, show me your math. Prove to me that aerodynamics plays a role in engine rpm and mph.

You can't.

What's your tire size? 235/45/18?

Redo the math, you get to 70 mph at 2358 rpm.

What you're saying is physically illogical. Aerodynamics plays a role in handling and efficiency. Your drag coefficient is based on the total surface area subjected to the wind.

------------

To the OP:

You posted a picture of your speedo/tach at 65 mph and between 2000-2500 rpm. This is correct based on the values I've found for tires (225/50/17) and gear ratios (4.31 FD, 0.612 5th) for an automatic V6 Accord sedan.

65 mph = 2229 rpm
70 mph = 2400 rpm
80 mph = 2743 rpm

 

[CtheW0rld]

Ok, show me your math. Prove to me that aerodynamics plays a role in engine rpm and mph.

You can't.

What's your tire size? 235/45/18?

Redo the math, you get to 70 mph at 2358 rpm.

What you're saying is physically illogical. Aerodynamics plays a role in handling and efficiency. Your drag coefficient is based on the total surface area subjected to the wind.

please see my previous responses....