How Accurate is it?.......(Regards to Dwell & Tach meter

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How Accurate is it?.......(Regards to Dwell & Tach meter

Postby chuckwood » Sat Jul 11, 2009 7:10 pm

Thinking about getting a automotive digital mutilmeter which has a function that shows you the RPM of the car (I'm not interested in buying a rpm gauge at this stage but I would like to know what rpm is when its idling).

Just wondering how accurate are they? is it worth it and if you got one, would you recommended?

There is one for sell at Supercheap for $65-75 and a few on trademe for about the same price.

eg.
http://www.trademe.co.nz/Trade-Me-Motor ... 368673.htm
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Postby slammed_integral » Sat Jul 11, 2009 8:59 pm

buy apexi rsm
http://www.cardomain.com/id/slick_ep

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Postby MAGN1T » Sat Jul 11, 2009 10:01 pm

Most "good" digital multimeters have a Hz measurement which can easily be converted to RPM. If you're a car enthusast then a multimeter is a necccesity.

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Postby chuckwood » Sat Jul 11, 2009 10:15 pm

How would you convert Hz into RPM? and where would you connect the terminal ends? red +ve probe to the -ve terminal of the coil? and black -ve probe to ground?!?!
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Postby nz_climber » Sat Jul 11, 2009 10:31 pm

Jaycar do a range of multimeters that are all pretty cheap, I got an auto ranging one that does frequency etc for $30! ones that do dwell and rpm are a bit more expensive, but check out their website
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Postby Akane » Sun Jul 12, 2009 6:01 am

slammed_integral wrote:buy apexi rsm


I don't even know if they're that accurate, i was bouncing off the rev limiter @ 9k RPM on the dash but my S-AFC 2 only shows 7.7k as peak. Who do I trust?
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Postby chuckwood » Sun Jul 12, 2009 10:02 am

I found a multimeter in the garage that does freq, so how do I hook it up? Been looking at a few website and found : freq x 60 to get rpm.
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Postby xsspeed » Sun Jul 12, 2009 10:21 am

yep, hertz is revs per second so x 60 is rpm
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Postby Lloyd » Sun Jul 12, 2009 11:47 am

Or x30 if you're going off a pulse for a single coil setup on a 4 cylinder
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Postby fivebob » Sun Jul 12, 2009 12:54 pm

xsspeed wrote:yep, hertz is revs per second so x 60 is rpm

only on a single cylinder two stroke ;)

For a multi cylinder four stroke with a single coil, it's 60*2/Number of cylinders*Frequency. So a four cylinder is 30*Frequency and a six cylinder is 20*Frequency
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Postby xsspeed » Sun Jul 12, 2009 1:29 pm

fivebob wrote:
xsspeed wrote:yep, hertz is revs per second so x 60 is rpm

only on a single cylinder two stroke ;)

For a multi cylinder four stroke with a single coil, it's 60*2/Number of cylinders*Frequency. So a four cylinder is 30*Frequency and a six cylinder is 20*Frequency


haha yes you are right, while I was out before after I wrote that I was thinking about what I said and thought 'oh shit that wasnt right'
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Postby chuckwood » Sun Jul 12, 2009 1:54 pm

so.....do I just hook it up like a rpm gauge? one end to the coil and the other end to the ground?!?
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Postby Lloyd » Sun Jul 12, 2009 2:13 pm

Why do you want to check that stuff exactly? Just buy an automotive multimeter and it should tell you what you want
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Postby chuckwood » Sun Jul 12, 2009 2:34 pm

To adjust my carby -need to find out my idling rpm in order to do that.

Why spending $70 for a tach meter? if I got a multimeter that can measures freq (convert to rpm). Also I'm poor so I would like to spend as less as possible to get the job done! :D
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Postby Dragger_Dan » Wed Jul 15, 2009 11:36 pm

fivebob wrote:
xsspeed wrote:yep, hertz is revs per second so x 60 is rpm

only on a single cylinder two stroke ;)

For a multi cylinder four stroke with a single coil, it's 60*2/Number of cylinders*Frequency. So a four cylinder is 30*Frequency and a six cylinder is 20*Frequency


Dammit, I thought my 20v was pulling 16,000rpm :lol:
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Postby xsspeed » Thu Jul 16, 2009 12:26 am

you must have the hydraulic lifters model :D
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