VX RPMs on highway

[James]

Just wondering what RPM your vx runs on the highway, and whether they put different ratios in different model years. Mine hits 2,000 RPM at 57-58 MPH. I have one size wider tires than stock, 175/70/13s.

[Matt Timion]

not that I can add anything, but 2000rpm at approx 60mph is awesome. I think the Fit has around ~3300RPM at the same speed.

[jadziasman]

It's about 67 mph with my VX at 2000 rpm. The speedo is off a couple mph now with the larger 175 70 R13 tires I have on mine now - the 165 70 R13 were stock. At 50 mph, it's 1500 rpm. Don't know how accurate my tach is though.

[cems70]

My '95 DX hatchback w/ the VX/CX tranny turns about 2050 - 2090 RPMs at 60 mph, and my speedo is precise according to my GPS.

Originally Posted by jadziasman

It's about 67 mph with my VX at 2000 rpm. The speedo is off a couple mph now with the larger 175 70 R13 tires I have on mine now - the 165 70 R13 were stock. At 50 mph, it's 1500 rpm. Don't know how accurate my tach is though.

jadziasman: If I'm not mistaken, the tire size affects the odometer accuracy, not the speedometer accuracy. That said, 67 mph at 2000 RPMs sounds way off. As I recall from my former VX, it was closer to 60 mph at 2000 RPMs, and my DX is showing about the same. If I can find a cheap VX gauge clusterone of these days, I'll replace my DX cluster so I can have a tach again...I really miss the tach from 12 years of VX ownership.

[James]

Ok good to hear. I was pretty sure it was the stock tranny.

I am tempted to draft trucks but they go a little too fast. They usually are going 67-75, which is at/above the 2,500RPM threshold between 2 valves and 4 for the vtec-e. I think the 2 valve mode is more efficient for lean burn because it creates a swirl in the combustion chamber. I almost wish there was a taller gear for aero mods (basjoos style), or drafting trucks on the hwy.

[cems70]

Originally Posted by theclencher

You're mistaken.

Please explain why I'm mistaken.

[bobski]

Every car I've taken the time to look at runs both the speedometer and odometer on the same cable or signal pulse.
The odometer records total shaft rotations, the speedometer records shaft rotations per period of time (commonly measured as RPM). The fact that the observed shaft is attached to a wheel which is in contact with the road surface allows the rotations to be correlated to distance traveled or vehicle speed.
It goes something like this: wheel rolling diameter * shaft rotations = distance traveled, wheel rolling diameter * shaft rotations/min = distance traveled/min. Distance/min can be changed to a more common form such as miles/hour or kilometers/hour by simple unit conversion.
When you change tire size, it affects the rolling diameter of the wheel, and thus the number of shaft revolutions required to travel a set distance, or the distance travelled by a set number of shaft rotations. Since the odometer is recording shaft rotations, not actual distance travelled, that will pretty obviously affect odometer accuracy.
The speedometer reading is no different than the odometer, except it includes time in the equation. Time is not affected by the rolling diameter of the wheel, so with the other variables (shaft rotation/min) being the same, changing the rolling diameter of the wheel will affect the speedometer's accuracy just as the odometer was affected.

[Ryland]

you are mistaken because the speedometer and the tac are running off the same device, the tranny, if you jacked the car up, took the front wheels off, and ran reved it up, in 5th gear the speedometer would still give you a reading, the same reading.
was the VX made in a high altitude modle? I know the CRX HF was, with slightly lower gearing for going up steep grade.
in my vx, I'm going about 78mph befor I hit 2,500 rpm and the v-tec kicks in.

[jadziasman]

Seeing is believing.

Go to the garage and click on the photo in the gallery.

[Bill in Houston]

Wow. I would love to have gearing like that...

[James]

Hmmm. Looks like I have a different ratio. I wonder if they made different ratios for different years. mine is a 94. I think i should look for a 92 vx tranny! The gearing on mine seems like it has a fairly tall 2nd and 3rd, but i am wishing for a taller 5th.