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Old 10-29-2017, 11:43 AM   #1
Jim M
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Default Rpm????

Been reading a number of posts that include questions and answers involving RPM's. Does that mean that many (most?) owners have installed tachometers on their A's? If not how would you know you are cruising at 2200 RPM'S. I do not have a tack but wold love to know what the RPM's are at a certain speed. Thanks, Jim
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Old 10-29-2017, 11:53 AM   #2
Merc Cruzer
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Default Re: Rpm????

You can always download the RPM app on your phone. I have found it to be close, give or take. If it doesn't work for you, it can just be deleted.

Last edited by Merc Cruzer; 10-29-2017 at 07:58 PM.
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Old 10-29-2017, 11:56 AM   #3
1955cj5
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Default Re: Rpm????

You can use online calculators like this one....just picked it with google, there are lots of others...

http://www.advanced-ev.com/Calculators/TireSize/


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Old 10-29-2017, 12:00 PM   #4
old31
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Default Re: Rpm????

I temporarily hooked up my dwell meter to get a reading.

Jim M, you brought up something interesting. How does that app actually work?

How many of you guys are using the RPM phone app?
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Old 10-29-2017, 12:07 PM   #5
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Default Re: Rpm????

Jim-
I have a tach on one of my cars. It was installed in the car before I bought it, so I left it. On the other car, I temporarily hooked up my "tune up" dwell/tach to the coil and went for a drive. If you note the RPM on the tach in each gear at some specific speed (bring a passenger to do this and write it down) you can easily use the speedometer in the future as a tach.

You don't need a tach installed all the time. The tire size and gear ratios do not change.

The RPM in 2nd gear at 20 MPH will always be that, and you can scale up and down from that to any speed/RPM (the RPM at 10 MPH in 2nd will be half of that, at 30 MPH will be 1.5 times that, etc.).

The RPM in 3rd gear at 30 MPH lets you scale up and down from that to any other speed/RPM in that gear.

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Old 10-29-2017, 12:21 PM   #6
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I have a '28 with 21 inch wheels and a 3.78 rear. I have a tach. and I am going 22.79 MPH per 1000 RPM. in high gear. I also have a Mitchell overdrive 2.80 ratio and with that in OD I am going 30.77 MPH per 1000 RPM.
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