tim hunt Posted July 26, 2018 Report Share Posted July 26, 2018 I know my tachometer to be reading high and would like to know the error. I cannot get any sensible results from the inductive pick up that came with my Maplin multi-meter, possibly due to high performance plug leads? I have a digital photo-tachometer. Any ideas where best to take reading? I tried a search but could not find this topic addressed. Tim Quote Link to post Share on other sites
Waldi Posted July 27, 2018 Report Share Posted July 27, 2018 (edited) Hi Tim, I would install the reflective tape (or a big white piece of tape) on the disk at the front of the engine where your timing marks are and the V-belt is running on. Here is a video with some background of how it works: (I hope the link shows above if not, then google it on You-tube.com) Enjoy. Waldi Edited July 27, 2018 by Waldi Quote Link to post Share on other sites
Lebro Posted July 27, 2018 Report Share Posted July 27, 2018 It didn't Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 27, 2018 Report Share Posted July 27, 2018 (edited) I bought a digital photo tacho for precisely this check on my TR. (bought from Maplins) On a 4 cyl there is limited places or space for the reflective strip to attach and remain attached whilst revving and reviewing. You need 2 people also to do the check. The Maplin digital photo tacho works fine compared to my hand held Smiths chronometric tacho - I compared readings of lathe chuck speed (nice flat area on chuck to attach the tape to and single central point for probe of Smiths unit) and they were as good as the same reading. Smiths Item:- https://1.bp.blogspot.com/-FDHkkfMWkzA/VFtiuTbnLrI/AAAAAAAAJW0/mPDqRJVOz_Q/s1600/Smiths%2BAT%2Bhand%2Bheld%2Btachometer%2Bset.1%2B004.jpg Peter W PS All this said and done, this job is easier done on the bench rather than on your lap in a TR - recalibrating your standard rev counter will involve removing the needle and refitting it in the correct place to suit your requirements. In my youth I worked in an instrument repair shop and my memory says that the standard TR rev counter and speedo, if the needle is set correctly, are not too far wrong. You need to decide the important speed readings and set the needle at those. ie with a known 3000 rpm input to the instrument, fit needle pointing at 3000. Then check at say 5000 and be aware of any discrepancies. Edited July 27, 2018 by BlueTR3A-5EKT Quote Link to post Share on other sites
Waldi Posted July 27, 2018 Report Share Posted July 27, 2018 It didn't Funny, the link is shown in my screen, tried several times, different ways, I give up. Quote Link to post Share on other sites
boxofbits Posted July 27, 2018 Report Share Posted July 27, 2018 If you know someone with a Snap on timing light you could check it that way. They are top quality and accurate. Kevin Quote Link to post Share on other sites
boxofbits Posted July 27, 2018 Report Share Posted July 27, 2018 (edited) If you know someone with a Snap on timing light you could check it that way. They are top quality and accurate. Btw is your tacho the standard TR4a cable driven unit, and does it waiver or is the needle steady? Kevin Edited July 27, 2018 by boxofbits Quote Link to post Share on other sites
mike3md Posted July 27, 2018 Report Share Posted July 27, 2018 Tim, If you have a satnav (gps), it will give you accurate road speeds, and from that you should be able to calculate engine rpm, knowing the diff ratio and tyre sizes. It used be a look up on the mintylamb site, but that has dissappeared. I did keep a hard copy of the results based on 3.7 diff and 185x70 tyres, which gives 3000rpm in direct 4th as 60.8mph. Otherwise this may help: https://wahiduddin.net/calc/calc_speed_rpm.htm Mike Quote Link to post Share on other sites
RobH Posted July 27, 2018 Report Share Posted July 27, 2018 Funny, the link is shown in my screen, tried several times, different ways, I give up. I think there is a problem now with embedding you-tube videos in posts. You were linking to this: youtube.com/embed/QVSQLfnKytk?htm15=1&fs=1 If you paste that into a browser with the usual prefix it does seem to work. Quote Link to post Share on other sites
john.r.davies Posted July 27, 2018 Report Share Posted July 27, 2018 (edited) If adhesive tape will not stick, how about SnoPaque? Its a densely white paint, used to correct typed errors on paper but stick well and dries fast. probably unobtanium in this digital age, but any white paint might do. John Edited July 27, 2018 by john.r.davies Quote Link to post Share on other sites
RogerH Posted July 27, 2018 Report Share Posted July 27, 2018 If you right lick on the Utube screen and then select copy URL. Then paste on the screen https://youtu.be/QVSQLfnKytk Roger Quote Link to post Share on other sites
stillp Posted July 27, 2018 Report Share Posted July 27, 2018 If you right lick on the Utube screen and then select copy URL. Then paste on the screen Then use a mouthwash, and dry your screen. Pete Quote Link to post Share on other sites
RogerH Posted July 27, 2018 Report Share Posted July 27, 2018 Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 27, 2018 Report Share Posted July 27, 2018 here is a TR based XL spreadsheet. Oh no it isn't, you cannot upload XL files to this forum. You can get it here http://www.buckeyetriumphs.org/technical/Calculator/road_speed_vs_engine_speed_calcu.htm Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.