I am trying to set up my gear ratio for my 13b in VW bug, If you know what your RPM is at 70 MPH, that will help me to decide what gear ratio to use. Please post what year and what engine (Turbo/ N/A) and Manual or auto...Thank you...

 

In what gear?

Top Speed Calculator

You'll find transmission and differential gear ratios, along with tire sizes, in the standard spec sticky: https://www.rx7club.com/new-member-r...atures-963417/

 

I was looking for the 70MPH RPM in fifth gear. Thats the only one that matters to me. What I'm trying to find out is what the best RPM at 70 MPH for my rotary powered VW bug should be. I figured that since the RX7 is around 2900, that I could go to a lower RPM with my much lighter VW , but aerodynamics matter too...

 

Nobody????

 

I have a first gen with a 12a carb'd. I'll let you know in about an hour

 

I'm a hair above 3k. S4 Turbo trans with 4.1 rear end. On a side note though, our tachometer and spedometers are not known for their accuracy. Fiddling with the top speed calculator, 55mph was only 2500 rpm at top gear.

 

The two links I gave you will allow you to calculate RPM in 5th gear for a 2nd gen of any year/model.

Plug in 5th gear ratio, rear end ratio, tire size and adjust RPM until it says "70 mph" in the 5th gear box.

 

My appologies RotaryRocker88,

I did go through all the #'s with different tire size options. I really appreciate the info you sent as it was very helpful and contained other cool facts that I didn't know about...

i just wanted to see what other people were getting for their stock and other modified setups...

 

Dang forgot about this post!
With my stock 12a with stock trans and rear gears im about at 3400 rpms around 70mph

 

WOW!,

That's crazy high RPM. I wonder if that ratio was meant for optimum MPG for 55MPH??? With my current ratio I'll be at about 3700 at 70 MPH

 

0.806 5th gear (jspec transmission), 4.1 rear end and 225/45/17 tires puts my car at 3150 RPM @ 70 mph & 3600 RPM @ 80 mph.

An S5 us-spec TII transmission with 0.719 5th would be nicer at 2800 RPM @ 70 mph, 3200 RPM @ 80 mph. But I do find it very nice to have plenty of passing power in 5th.

 

I'm not sure on my gearing. (Ill check when I get home). My 86 rx7 FC is at 2600 in 5th at 70mph.

 

I'm already seeing alot of differnt #'s.

This is very interesting to me. Please if you can, specify as many details as you can. Such as: Turbo/non-turbo
Maunual/automatic
modified/stock
tire size
gear ratios if known
Miles per gallon Average

 

Gearing information for rx7's. I dunno about auto trans gearing, but it was 4-speed, thus the taller final drive:
Transmission
Differential Interchanges

Are you doing this for fuel efficiency? I'd shoot for 3000 rpm and choose whatever gear gets you near there. Best case scenario, you're going to pull low (mayyybe mid) 20's constantly driving at 70 mph.

 

YES,

Fuel efficiency was the main goal in tuning the RPM to the 1800Lb. VW beetle. I feel (just a gut feeling no real data) that I can max out my MPG at around 2600 RPM. Because it will be carbureted at first my MPG might not be as good as it will be once I tune it with mega squirt. Plus there wont be any emissions to lower the MPG. I was just wondering what other configurations were out there in the RX-7 community. I am some what limited on my gear configurations (that is with out spending big $$$). My 4 final gear configurations put my RPM at either 3700, 3400, 3000, 2700. Then I might be changing to larger tires later.

 

87 n/a racing beat cat back, 17inch tires, 2800 at 70 in 5th

 

1987 N/A 13B EFI, stock ECU and everything else except exhaust and emissions delete, swapped into 2300lb. 1979 SA22, .711 OD (FC 5spd NA trans), 3.90 rear gear, 23.4 inch tall rear tire. RB header, dual 2.5" exhaust, 2800 rpm @ 70mph. 26mpg highway in need of a tune (which I'll get to one of these days )

 

My AT 86 runs about 2400 rpm at 70 MPH.

 

On my 95 miata (2100lb) I was running 3.23 rear gear stock 95 rx7 tranny. I was cruising at About 2200rpms at 65mph 2800-3000 @ 72-75 mph in fifth gear... you can go lwer rpm but that changes how hard your 3 and 4th gears are gonna pull. With this gear ratio on stock tranny I would hit 58 in first gear and 93 in second with a stock redline (8100) and it would pull hard. But my 3rd and 4th gear wouldnt pull hard nor even compare to how hard it pulls with the 4.10s I have now in 3 and 4th.

 

My bone stock 83 gsl revs around 4 grand doing 130 km/h ( about 80 mph) in fith. I can't remember what it does around 70, it's been wintering in storage for the last 5 months. Not sure it this helps.