RPM's

[blanchardkeith]

On a stock 1800 what RPM's are most of you at in 5th doing 80 mph? MIne seems high at 4200+? Let me know if this is normal. Maybe I am just so used to my jetta at 2200
Thanks
Keith

[mbouse]

that reading will depend on what rear end you have.

example....the '78 with a stock rear end will run higher rpm per mph than the '76. sorry, not a gear ratio expert, but i've been down this discussion path before.

my wife's '78 runs prox. 3500 rpm at 60 mph, which compares to my buddy's '76 with 3000 rpm at 60 mph. my '80 with stock rear end and a 2 litre, runs nearly identical to my buddy's '76.

I have no idea how either of these compare to a volkswagon.

[engineerted]

That sounds about right. The 1600, 1800 cars have a 4.3 to 1 ratio diff thus the high (normal) rpm at cruising speed.


Ted

[Mark_vaughn]

These cars were built in an era of 55 mph speed limits. Thus you have higher rpms at 80 mph

[mdrburchette]

They're also happy in the higher rpm range. Before my rebuild, I'd feel a little extra pull around 4k on my 72. After the rebuild, I'm not afraid to go up to 8k, but the cams don't come "in" until past 3500.

[So Cal Mark]

the most efficient operating range on a motor is usually about where the peak torque is, so the rear gear should be chose accordingly

[fiater]

I've never had my '76 up to 80mph, but at 75mph it turns 4,200rpm +. I was surprised at those rpm's but it gave more insight into the design of the engine.

[ventura ace]

Keep in mind that the speedometers and tachometers are not always the most accurate, especially if you have had parts replaced with different than stock (for example, running 14" wheels rather than the stock 13" wheels). Use http://www.f-body.org/gears/ to calculate speed vs rpm at different transmission and rear end ratios and tire sizes. As stock, your car likely had 4.3 rear end, .881 gear ratio in 5th gear, and 13" wheels (165/80). This calculator suggests you would have 4350 rpm at 80 mph (or 77 mph at 4200 rpm).

Alvon