What is the RPM at 60 mph on a 5 spd?

[fujioko]

Hi 'ya folks,

I'm running a B3 powered Mazda Miata. I was wondering what is the RPM of a 5 spd Festiva at 60 mph.

I could do the math, but I though I would ask first.

Thanks

Jim

[KingFish]

22k, 23k. I never run at 60 long enuf to look, but runs a steady 2500 For 65mph.

[sketchman]

22k, 23k. I never run at 60 long enuf to look, but runs a steady 2500 For 65mph.

With stock size tires?

[Bert]

With stock 5-speed transmission and B3 but with Aspire-derived wheels (175/70-13) I'm running just around 2600rpm at 100 km/p/h (62 mph).

[KingFish]

I'm running 155/65r13

[freshtiva]

[fujioko]

3500 rpm @ 80 MPH? I'm impressed!

The Miata tachometer is a little flaky so I'm going to measure the RPM with a frequency counter tomorrow.

Hopefully my setup comes close to a stock Festiva in 5th gear.

[Skrapbob]

Ugh! I want to swap my auto for a 5spd so bad.

[freshtiva]

3500 rpm @ 80 MPH? I'm impressed!

It doesnt even turn 3500 @ 85 MPH. Its a huge difference from a four speed or automatic.

[sketchman]

Makes me wanna swap out my 323 GT's trans for a spare Festiva one. Maybe cryo it to be safer. Thing is geared to keep it in boost, which sucks on the highway. Gotta work hard to keep it efficient on our roads.

Sub 3500 @ 85 would be sweeeet.

[fujioko]

Hi ya folks,

Thanks for posting the RPM vs speed numbers.

I was able to get some measurements today.

My B3 powered Miata with a modified RX7 5th gear is running at exactly 3000 RPM at 65 MPH. Measurements taken with a frequency counter and a GPS.

Looks like the engine is spinning 500 RPM faster than a Festiva.

The car has plenty of torque and pulls well in all gears. I might be able to go with a slightly lower axle ratio to get the RPM in line with a Festiva.

Thanks again for the help!

Jim

[Bert]

Playing with gear ratios is a curious thing. I put a 3.0 ratio rear axle and a 5 speed into my 86 F150 last summer (as opposed to the original 3.55 axle and 4 speed) which resulted in the speedo reading almost 20% low (that's since been fixed with a fewer teeth sending gear refit). However wind resistance etc being a factor, and optimum engine rpm also involved, I have yet to notice a significant increase in fuel economy.