VX, hf, dx gearing excel file

[steffen707]

This is what I came up with. The first gen insight and Civic VX have almost identical curves, the gearing is all different, but the final rpm and mph is almost identical. All curves are in 5th gear.

Its interesting that the CRX HF is 228 rpm less at 65mph than Civic VX and 1st Gen Insight.

Also interesting is how the CRX DX is 917 rpm more than the CRX HF at 65mph.

[steffen707]

Hello all, i'm making an excel spreadsheet of the vx, dx and hf gearing. I want to compare mph to rpm and I believe the formulas are

RPM=(MPH x Gear Ratio x Final Drive x 336) / Tire Diameter in Inches

MPH=(RPM x Tire Diameter in inches) / (Gear Ratio x Final Drive x 336)

From various sites I have:
CRX HF
first 3.25
second 1.65
third 1.033
fourth 0.823
fifth 0.694
final 2.95

92-95 CIVIC VX/CX
first 3.25
second 1.761
third 1.066
fourth 0.853
fifth 0.702
final 3.25

97 CIVIC DX
first 3.25
second 1.762
third 1.172
fourth 0.909
fifth 0.702
final 3.722

From my excel file if you have a 22.5" tire, with a civic vx at 70mph=2385rpm and 45mph=1533rpm.

Can anybody with a VX let me know if this is accurate, or can you post your tire dimensions and mph=rpm in 5th gear numbers so i can plug your tire diameter into my excel file to see if this is accurate?

[some_other_dave]

Your CRX Si figures are very close. I find that I'm pretty much dead-on 500 RPM per 10 MPH in my 1990 CRX Si.

Curiously, the Si has the same gearing as the "standard" 5-speed CRX (AKA the "DX") but a different ring/pinion ratio so the Si gearing is effectively much lower.

-soD

[steffen707]

Originally Posted by some_other_dave

Your CRX Si figures are very close. I find that I'm pretty much dead-on 500 RPM per 10 MPH in my 1990 CRX Si.

Curiously, the Si has the same gearing as the "standard" 5-speed CRX (AKA the "DX") but a different ring/pinion ratio so the Si gearing is effectively much lower.

-soD

2 problems with your statement.

1. the x axis intersects the y axis at 15mph
2. your idle should be like 700-900 i would imagine, so it would probably be inacurate if you were trying 5th gear at 500 rpm.

Any VX drivers out there know their tire diameter and can tell me if the graph for VX is correct?

[steffen707]

Well judging by this guys video.

http://www.youtube.com/watch?v=v5HzM-p-Dhs

My calculations are spot on. 2nd gear, 50mph=4200-4500, 60mph=5100rpm ish.

Granted this guy could be using non stock tires, speedo could be off, its hard to see where the rpm needle is actually pointed, ect. ect., but ballpark for what his gauges were showing and my excel file calculated, things look pretty good.

[hondaguy72]

My vx is just about the same as the vid. I run a slightly larger tire 175/70/13. Michelin destiny. 44psi max inflation was the deciding factor, and I only run Michelins if I can help it. When the weather turns nice I can verify speed with my gps.

[some_other_dave]

Originally Posted by steffen707

2 problems with your statement

What I meant is that for every 10 MPH of road speed, I turn 500 RPM. Not that I drive at 10 MPH at 500 RPM. I will drive it at ~1500 RPM at 30 MPH, 2000 RPM at 40 MPH, 2500 RPM at 50 MPH. (And not much faster than that.)

Granted this guy could be using non stock tires...

That, at least, is not a factor. The speedo reading is taken from the transmission, so it merely is a measure of how fast the drive axles are spinning. To get an actual MPH figure, the speedometer assumes a given tire size; if you change to larger-diameter tires then your speedometer will still read the same MPH for a given RPM in a given gear. Your actual speed will be different, though.

The other concerns you mention could be problems, but from hondaguy72's post it sounds like they aren't.

-soD