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Best cruise RPM

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Old 06-04-06, 02:39 PM
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Question Best cruise RPM

I'm thinking of putting a 13B rotary into a 1974 VW Beetle but what worries me a bit are the gear ratios. I've read that rotaries are rev happy but from what I've seen they normally only run at about 2500 RPM at 100km/h or 3000 RPM at 120km/h in the RX-7's.

Using a stock bug tranny would mean the engine would run at 3000 RPM @ 100km/h (62.5 MPH) and 3500 RPM @ 120km/h (75MPH) or ~500 RPM higher than normal.
What would long periods of 3500 RPM do to the longevity of the engine?

Thanks
Paul
Old 06-04-06, 05:35 PM
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talk to this guy
https://www.rx7club.com/showthread.p...&highlight=bug
Old 06-04-06, 08:40 PM
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Originally Posted by Surge
I'm thinking of putting a 13B rotary into a 1974 VW Beetle but what worries me a bit are the gear ratios. I've read that rotaries are rev happy but from what I've seen they normally only run at about 2500 RPM at 100km/h or 3000 RPM at 120km/h in the RX-7's.

Using a stock bug tranny would mean the engine would run at 3000 RPM @ 100km/h (62.5 MPH) and 3500 RPM @ 120km/h (75MPH) or ~500 RPM higher than normal.
What would long periods of 3500 RPM do to the longevity of the engine?

Thanks
Paul
You'll be fine. My 1990 n/a convertible turns 3500 rpms at 80 mph on the highway with no problems.
Old 06-06-06, 06:28 PM
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My 1st-gen turned about 3600ish in 5th at 60mph, before I ran out of 1st-gen gearboxes and had to put in an FC unit. (Nonstock rearend, 4.78 vs. stock 3.91)

Now it's only turning maybe 3100ish at 60mph, the '86-up trannies have way-tall 5th gear. It's not as happy on the highway, and the 5-4 shift (which is now more necessary) has a huge drop.

Anyway I'd drive all day long at 4500ish RPM and still knock back 27ish MPG give or take a couple.
Old 06-06-06, 07:08 PM
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Great! I'm worrying about nothing again.

Paul
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