 | Home > Technical > Tacho install - how to set VDO gauge switches vs 'pulses'? |
 
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| donmacn Member Since: 06 Nov 2017 Location: Nth Scotland Posts: 1845  
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Hi,
I've just got a new VDO analogue rev counter to fit to my 300Tdi. It has three micro-switches to set for 4 cyl engines, and RPM range, but the instructions are on about various 'pulses'. I tried to search for this, and didn't get anything relevant. Can anyone help? Where do I find that info, or what setting do I use? Thanks Donald 1994 Defender 300Tdi 110 SW - owned since 2002 - 230k miles and going strong (The 'rolling restoration' or tinkering thread: http://www.defender2.net/forum/topic58538.html ) 2000 Range Rover P38 4.0L V8 in the past.. RR classic - fitted with 200Tdi 1984 RR classic - V8 with ZF auto box 1993 Discovery 300Tdi not to mention the minis and the Type 2 VW camper... Last edited by donmacn on 19th Jun 2019 9:55pm. Edited 1 time in total |
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19th Jun 2019 6:27pm |
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| dorsetsmith Member Since: 30 Oct 2011 Location: South West Posts: 4554 |
https://forums.lr4x4.com/topic/99198-that-...tdi-query/
switch 1 to off switch 2 to off switch 3 to on |
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19th Jun 2019 7:52pm |
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| donmacn Member Since: 06 Nov 2017 Location: Nth Scotland Posts: 1845
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thanks for that - I was just on there looking at tacho threads but hadn't found that one.
The switch locations are what I was after though, so that's me sorted. cheers. There's also a handheld, laser tacho linked from that thread for less than a tenner, which seems like a good idea for fine tuning. Ta Donald 1994 Defender 300Tdi 110 SW - owned since 2002 - 230k miles and going strong (The 'rolling restoration' or tinkering thread: http://www.defender2.net/forum/topic58538.html ) 2000 Range Rover P38 4.0L V8 in the past.. RR classic - fitted with 200Tdi 1984 RR classic - V8 with ZF auto box 1993 Discovery 300Tdi not to mention the minis and the Type 2 VW camper... |
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19th Jun 2019 8:08pm |
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| donmacn Member Since: 06 Nov 2017 Location: Nth Scotland Posts: 1845
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Just been thinking about this some more - I'll try asking this simple question here first rather than starting a new thread.
Having ordered a handheld laser tacho as above (£8.50 including postage - rude not to) where do I measure the revs to fine tune or confirm the VDO gauge reading? If I measure the crankshaft pulley is that one revolution or four? Would one revolution of the crankshaft equate to one revolution of the alternator pulley, or is there some sort of reducing (or magnifying) effect via the serpentine belt and different diameter pulleys? Donald 1994 Defender 300Tdi 110 SW - owned since 2002 - 230k miles and going strong (The 'rolling restoration' or tinkering thread: http://www.defender2.net/forum/topic58538.html ) 2000 Range Rover P38 4.0L V8 in the past.. RR classic - fitted with 200Tdi 1984 RR classic - V8 with ZF auto box 1993 Discovery 300Tdi not to mention the minis and the Type 2 VW camper... |
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19th Jun 2019 10:00pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6608  
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Alternator pulley is much smaller than the crank pulley so it spins at a multiple of the crank speed.
300 Tdi ratio is roughly 2.5 or roughly 3 depending on which alternator pulley is fitted.  1988 90 Td5 NAS soft top
2015 D90 XS SW |
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20th Jun 2019 11:20am |
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| donmacn Member Since: 06 Nov 2017 Location: Nth Scotland Posts: 1845
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Thanks Martin, I'll see if I can find a spec for my alternator pulley at some stage.
Am I right though that one rotation of the crankshaft = one engine revolution? That sounds right intuitively - I can't see how it could be anything else - but best be sure! Donald 1994 Defender 300Tdi 110 SW - owned since 2002 - 230k miles and going strong (The 'rolling restoration' or tinkering thread: http://www.defender2.net/forum/topic58538.html ) 2000 Range Rover P38 4.0L V8 in the past.. RR classic - fitted with 200Tdi 1984 RR classic - V8 with ZF auto box 1993 Discovery 300Tdi not to mention the minis and the Type 2 VW camper... |
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20th Jun 2019 5:39pm |
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