|
Sponsored Links (Register now to hide all advertisements) |
|
|
Thread Tools | Display Modes |
06-16-2019, 11:41 AM | #1 |
Member
Join Date: Dec 2018
Location: Syracuse, NY
Posts: 51
|
Calculating engine RPM at idle
I was curious how to know my engine’s revs at idle. I tried a HF “photo” tach but was disappointed in ease of use and accuracy so I calculated my own numbers with simple math.
I measured the outside circumference of the crank pulley where the belt runs, the outside circumference of the fan belt and found the drive ratio. In my case the engine turned exactly 2.71 times for one full revolution of the belt. Then I painted a little white mark on the belt… Belt mark.jpg and I count how many revs it makes in one minute (or, for simplicity, count 30 seconds and double). It’s a lot easier to count the belt revs since it runs about 2 ¾ times slower than the crank. In my case here are the engine revs (rounded off), YMMV. Belt Engine 140 380 145 395 150 410 155 420
__________________
Cave Luther Syracuse, NY 1931 Deluxe Coupe (Rose) ______________________________________ "... I'm pullin' for ya, we're all in this together." Red Green |
06-16-2019, 04:07 PM | #2 |
BANNED
Join Date: Apr 2017
Location: Sacramento
Posts: 1,262
|
Re: Calculating engine RPM at idle
get a cheap tach /dwell meter..I find them at garage sales for a few bucks,it calculates rpm from the point operation..
|
Sponsored Links (Register now to hide all advertisements) |
|
06-16-2019, 06:50 PM | #3 |
Senior Member
Join Date: Jun 2013
Location: Marana Arizona
Posts: 1,776
|
Re: Calculating engine RPM at idle
Sponsored Links (Register now to hide all advertisements)
Only oops I found is that it is best to unplug the 9vt. battery between uses. Chap https://www.amazon.com/Digital-Photo...gateway&sr=8-3 |
|
|
Sponsored Links (Register now to hide all advertisements) |
|