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Old 09-02-2010, 07:09 PM   #1
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Default cranking rpm

What's normal cranking rpm?
I'm consistently seeing 175-185 rpm in my logs which seems a bit slow although my battery is supposed to deliver 680A for 5 secs (I have a tiny 17Ah PC680).

Last edited by WestfieldMX5; 09-03-2010 at 10:34 AM.
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Old 09-03-2010, 11:18 AM   #2
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That is a little bit on the low side, but should be ok. It's a matter of compression and voltage. You're spinning a 9.5:1 motor with a tiny battery, so it's going to crank slow. As an experiment, you could temporarily hook up a full size battery (even with jumper cables) and see if it spins faster. My car cranks about 100 rpm faster than yours with a "full size" miata battery.
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Old 09-03-2010, 12:25 PM   #3
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Might also explain why it takes a bit longish to catch. Will try with jumper cables.
So with a healty battery I should see 250+ rpms?
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Old 09-03-2010, 01:46 PM   #4
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Yes, with more battery you should see more rpm while cranking.

The opposite extreme is a "tight" engine will still turn slowly, but I think you would probably notice a spun bearing...
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