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| Accuracy of Sync Gauge and Tacho's https://www.smwebhead.com/phpBB3/viewtopic.php?f=6&t=14734 |
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| Author: | GI Auz [ Sun Mar 27, 2016 3:48 pm ] |
| Post subject: | Accuracy of Sync Gauge and Tacho's |
In order to get the syncro gauge to zero (vertical) I have 3725 (left tacho) and 3600 rpm (right tacho) However I have the best aural balance (no harmomic) with 3675/3600 set. This has syncro a few notches off centre. Something doesn't quite seem right..... I believe the tacho's take their feed from alternator RPM? Sync gauge is probably just reading phase difference between L & R? I fly light twin aircraft and used to tuning with a sync gauge, so something just doesn't seem right here. Opinions and ideas most welcome. |
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| Author: | Surface Interval [ Sun Mar 27, 2016 6:15 pm ] |
| Post subject: | Re: Accuracy of Sync Gauge and Tacho's |
I believe the sync signal is taken from the ignition system of each gas engine. It's either that or an engine rpm sensor commonly used in the modern computer controlled engines. There is the possibility of alternator belt slip, and the alternator does not have a pickup or terminal for the alternating current before going thru the rectifier and being converted to direct current. If possible, check the electrical connections and also verify tachometer and sync gauge accuracy. You might check with the sync gauge manufacturer or a manual to see if the gauge can be adjusted. The tachometers, like many other gauges, can be off by more than many people would believe. In my days of working on aircraft I've seen tachs off by 100-200 rpm. We'd like to think they are a precision gauge, but they are not always. |
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| Author: | Surface Interval [ Sun Mar 27, 2016 6:23 pm ] |
| Post subject: | Re: Accuracy of Sync Gauge and Tacho's |
I found this in the Faria sync gauge manual: 10. Calibration: This gauge has been calibrated at the factory, and should never need adjustment. An exception to this is a diesel engine application where the alternator is the tach signal source. Due to variations in belt tension, and/or belt dimensions, engine alternators may actually spin at different speeds with the engines running at the same RPM’s. If you are experiencing problems with this type of application, the synchro can be adjusted to work with these differences by slightly rotating the adjustment potentiometer with a 5/64” Allen wrench. This adjustment can also be used to fine tune a synchro in any application. web site with link to manual: http://faria-instruments.com/manuals.php |
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| Author: | GI Auz [ Mon Mar 28, 2016 3:16 am ] |
| Post subject: | Re: Accuracy of Sync Gauge and Tacho's |
Great work - thank you!! I will calibrate that sync gauge. And I agree, the tacho's may be out by a bit as well. |
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| Author: | 298VISTA2000 [ Mon Mar 28, 2016 8:15 am ] |
| Post subject: | Re: Accuracy of Sync Gauge and Tacho's |
My engines are in sync at low rpms and then go their own way at higher rpms so how can you adjust that? I find most gauges on boats not to be very accurate and really only pay attention to the oil temp and gas gauges. I use my ear gauge for syncing the engines and eye gauge for trimming the outdrives. |
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| Author: | weather [ Mon Mar 28, 2016 11:34 am ] |
| Post subject: | Re: Accuracy of Sync Gauge and Tacho's |
According to my ears, my sync gauge is accurate, but my tach's read ~150 RPM different. I figure the tach calibration is off in my case. |
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| Author: | babbot1 [ Mon Mar 28, 2016 3:51 pm ] |
| Post subject: | Re: Accuracy of Sync Gauge and Tacho's |
You can buy a cheap laser tachometer. I think I paid like $15 or $20 or so. You stick a piece if reflective tape on the crank and point the laser at it. Pretty much can be used on anything because has nothing to do with the engine electronics. I use it more for small engines without tachs. Do a search on amazon for "laser tach" you'll see tons... |
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| Author: | signalstan [ Mon Mar 28, 2016 6:44 pm ] |
| Post subject: | Re: Accuracy of Sync Gauge and Tacho's |
when I first got my boat the tachs would seam to work fine then one or the other would just start going crazy I removed the dash panel and found all the wires on the back of the tachs where loose I would check , clean, and tighten all the conections before doing anything |
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