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Tacho...just how accurate??

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Tacho...just how accurate??

Postby Bri663 » Fri Mar 18, 2016 4:42 am

Tacho,
Not sure how accurate mine is ( well I know it's not) and wonder what other options there are out there. I have the inductive sensor with two tabs. I set the sensor at 0.0010 gap but that has left no thread on the body it is wound right in. Tabs seem equidistant from edge of flywheel. I found a graph in the paperwork ( I don't have it available to me just now but from memory) it shows that at

2400 ind rpm = true rpm 2700
2600 ind rpm = true rpm 2850
2700 ind rpm = true rpm 3000

something very similar too that not strictly linear but a curve as it gets higher. Flat out level I get about 3200 rpm indicated 110 kts so the lines seem to meet. (Didn't hold it for long CHT quickly approaching 350 F)

I was usually setting for cruise at 2250 rpm indicated with 280F CHT showing and IAS 85kts. Working off the graph it was around 2600 rpm true If I remember right. I don't have a digital tacho available to me and they seem to be very expensive anyway. Is there a better way to set-up to have a truer reading from the instrument, rather than referring to an old scrap of paper all the time, that was done back in 2013.

Any decent easy to fit kits out there?

cheers
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Re: Tacho...just how accurate??

Postby Steevo » Fri Mar 18, 2016 10:34 am

First off, do you have the standard VDO tachmometer?

There could be a couple of problem. The tach sender may be worn. If this is the case, it may be mis-reading pulses. The senders are only cheap (about £15) so replacing it is a good test for that. If it has always been like this, it could also be that someone has entered the wrong amount of pulses per revolution in to the tachometer itself. If you download the manual for your tach, there is a procedure for adjusting the pulses and sensitivity of the gauge itself.

There are also other options for the sender that are a lot more reliable. Dean may well post shortly and he has made an alternative one that is much better than the original Jab one.
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Re: Tacho...just how accurate??

Postby Bri663 » Fri Mar 18, 2016 11:59 pm

Good evening,

yes standard VDO tachometer, I had heard something about setting up the correct pulse count so I will look that one up. I wasn't aware of the price so on my return I may well order a new sensor and re-set it up takes one thing out the loop.

Thanks for the info.
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Re: Tacho...just how accurate??

Postby diablo » Sat Mar 19, 2016 8:50 am

Hello,

take a look at this mod. Well worth doing and far more accurate and tolerant than the standard Jabiru setup.

http://www.jabiruownersgroup.org/viewtopic.php?f=30&t=576

dean
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Re: Tacho...just how accurate??

Postby Bri663 » Sat Mar 19, 2016 8:34 pm

Ah brilliant solution! I will have a look at that once I get home, and I'll post the results on here let folks know how I get on.

cheers.
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