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NYTerminat(at)aol.com
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 Posted: Sat Dec 31, 2005 4:41 pm Post subject: Tach RPM error |
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I am aware that the Rotax fires on each stroke. The Straomaster E-1 is set up
to look at that signal on every revolution. It seems to be reading way low
in low and high RPM. I can set the Stratomaster to a .7 or .8 setting which
will fake it into getting a closer RPM range( .7 is high by approx 400 and the .8
setting is low by about 400 RPM). I can't set it inbetween (ie .75) to make
up the difference. This is the 2nd Stratomaster and it reads the same as the
1st one. The Tiny tach which picks up inductance off the plug wire is low by
well over 1000 RPM in the upper RPM range. How accurate are everyone elses tach?
I reset the prop to 13 degrees and get a optical tach reading of 5395 at max
RPM, which is real close to the 6% less than max RPM at static test that
Woodcomp reccomends. I pulled the plugs and checked the ratio between the prop and
piston TDC and it looks like the 2.43 to 1 is correct. Do I have to live with
this inaccuracy?
Bob Spudis
N701ZX CH-701/912S
do not archive
In a message dated 12/31/2005 6:42:39 PM Eastern Standard Time,
daberti(at)sbcglobal.net writes:
This is a standard practice on most new electronic ignition systems. They
see the trigger on every revolution of the crankshaft and fire on every
trigger.
Dave 601-HD 912ULS
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craig(at)craigandjean.com
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| Posted: Sat Dec 31, 2005 5:12 pm Post subject: Tach RPM error |
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A number of people have complained about the accuracy of a variety of tachs
that try to pick-up signals from the ignition system. Mark Langford for one
over on the Corvair list. What appears to be the most reliable is a
gear-tooth sensor. Mark is changing over his GRT engine monitor to use that
with an additional black box from GRT. William Wynne of Corvair fame is
using a gear tooth sensor on his 601xl/Corvair.
When I ordered my Stratormaster Ultra Deluxe Whoopie Wizbang glass panel I
also ordered their sensor:
"GT-1 Geartooth sensor for Rotor RPM, $85"
http://www.sportflyingshop.com/Instr/Stratomaster/Ultra/ultra.html
While this is intended for rotor speed Rainier at MGL says it should work
fine for engine rpm. Here is another sensor to consider: a tach signal
"Giant Magnetoresistive" pickup:
http://www.msdignition.com/2006/06-22.htm
-- Craig
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cgalley(at)qcbc.org
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| Posted: Sat Dec 31, 2005 6:34 pm Post subject: Tach RPM error |
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Harley used that method for years. My V-6 Buick uses only 3 coils and uses
the same lost spark scheme. Nothing wrong with it.
Cy Galley - Webmaster
www.edgewoodaggregates.com
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NYTerminat(at)aol.com
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| Posted: Sat Dec 31, 2005 11:04 pm Post subject: Tach RPM error |
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Craig,
The signal for the tach on the 912 is a seperate pickup coil seperate from
the ignition system. The gear tooth sensor may have some issuse at the high RPM
of the Rotax. The MSD sensor may be something that may work. I will see what
MSL has to say on monday.
Happy New Year to all.
Bob Spudis
do not archive
In a message dated 12/31/2005 8:15:10 PM Eastern Standard Time,
craig(at)craigandjean.com writes:
A number of people have complained about the accuracy of a variety of tachs
that try to pick-up signals from the ignition system. Mark Langford for one
over on the Corvair list. What appears to be the most reliable is a
gear-tooth sensor. Mark is changing over his GRT engine monitor to use that
with an additional black box from GRT. William Wynne of Corvair fame is
using a gear tooth sensor on his 601xl/Corvair.
When I ordered my Stratormaster Ultra Deluxe Whoopie Wizbang glass panel I
also ordered their sensor:
"GT-1 Geartooth sensor for Rotor RPM, $85"
http://www.sportflyingshop.com/Instr/Stratomaster/Ultra/ultra.html
While this is intended for rotor speed Rainier at MGL says it should work
fine for engine rpm. Here is another sensor to consider: a tach signal
"Giant Magnetoresistive" pickup:
http://www.msdignition.com/2006/06-22.htm
-- Craig
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craig(at)craigandjean.com
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| Posted: Sun Jan 01, 2006 12:00 am Post subject: Tach RPM error |
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Interesting, where does the built-in coil pick up its signal from? Is it
conditioned at all? If it is more of a sine wave than a square wave the slow
rise and fall times may trigger false signals in E-1's input circuit. But it
is true that all the MGL manuals I have looked at show the RPM pickup going
directly to the engine.
The link below points to a spec sheet for the GT-1 (look at page 57). It
says the GT1 has "Fast operating speed - over 100 kHz".
http://stevenengineering.com/Tech Support/PDFs/31SSS.PDF
Good luck and Happy New Year.
-- Craig
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thilo.kind(at)gmx.net
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| Posted: Thu Jan 05, 2006 3:00 pm Post subject: Tach RPM error |
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Hi there,
I have a Rotax 912. I'm using the Grand Rapid Engine Information System as
well as a MicroTach 100 from Aircraft Spruce. Both use the signal wire from
the Rotax 912. Initally I had trouble with the MicroTach (neddle went all
the way to the left when RPM exceeded 3,500. Got that fixed by installing a
resistor. Now. both tachs show the same numbers.
Good luck
Thilo Kind
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Larry Martin
Joined: 10 Jan 2006
Posts: 31
Location: Cabot, Arkansas
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| Posted: Tue Jan 10, 2006 7:26 am Post subject: Re: Tach RPM error |
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I had a problem with my tack on my Harley engine. It read only half. I had to get a signal converter from www.datokadigital.com. A little expensive, $78, but it fixed the problem. Might be worth looking at.
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701 with a Harley, www.skyhawg.com |
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