Inductive Tachometer

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Mark Nunn
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Inductive Tachometer

Post by Mark Nunn » Wed Aug 14, 2019 2:15 pm

I’m a new Model T owner and have not driven my car on the road. I need to get a feel for shift points and maximum safe engine RPM’s to prevent damage before heading beyond my driveway. I can’t tell what RPM my engine is running by sound. I had an inductive tachometer on my lawn tractor for years and it worked well. I want to get one for my Model T too.

Inductive tachometers work simply by wrapping the inductance wire around a sparkplug wire a few times. The sensor picks up the spark and displays RPM based on the number of firings per 2 revolutions. I don’t know if an inductive tach will work on a Model T.

Does the sparkplug normally fire once per ignition cycle or is there more than one spark? Since I don’t have a magneto, I can only run on 6V. Would an E-timer fire a single spark per ignition cycle?

I have not seen any mention of digital tachometers on the forum so I suspect they do not work.


Bill Crosby
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Re: Inductive Tachometer

Post by Bill Crosby » Wed Aug 14, 2019 6:19 pm

Mark, If you want a digital tack the pictures are of the components from a source on Ebay (they sell it in red or blue) and I show how I mounted the magnet ( I glued it to the crank starting pin) an mounted the pickup to the cam gear cover. You can see the magnet through the hole In the pulley. Total cost was $5.59 + .29 shipping from China. It works great.
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Scott_Conger
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Re: Inductive Tachometer

Post by Scott_Conger » Wed Aug 14, 2019 6:27 pm

Mark

if you're 1/2 way through the intersection, from a dead stop, and you're still in low gear, you've already waited too long to shift. Low gear will rapidly run out of torque, and once you're done accelerating with 1/2 - 2/3 throttle, you're done.

Pretty much everything other than starting out from a dead stop, and climbing steep hills, is done in high gear including going slowly around corners.

I would recommend that you do NOT get in the habbit of down-shifting to come to a stop, either. The throttle is used to slow down...the brake is used to stop. Low is for starting up, and hill climbing. Period.

Do not overthink this.
Scott Conger

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Ruxstel24
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Re: Inductive Tachometer

Post by Ruxstel24 » Wed Aug 14, 2019 7:29 pm

Mine has a way of telling me it's time to shift...
Kinda like a "death rattle" !! :o

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kelly mt
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Re: Inductive Tachometer

Post by kelly mt » Wed Aug 14, 2019 7:36 pm

I have one on my Tudor like you describe, but I have a distributor. I use it for top end driving. I run 48 to 50 pretty regular. I have an overdrive Warford and like to keep an eye on the RPM. Don't know that they will work with coils.
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JohnH
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Re: Inductive Tachometer

Post by JohnH » Wed Aug 14, 2019 7:37 pm

Mark Nunn wrote:
Wed Aug 14, 2019 2:15 pm
Would an E-timer fire a single spark per ignition cycle?
The E-Timer provides a continuous spark just like when a mechanical timer is used with original coils. In terms of knowing the 'safe' rev range of the engine, you'll find it's not something to worry about too much. In top gear, a standard car just can't drive fast enough to get into the danger zone (unless it's going down a steep hill perhaps). In low gear, it's unlikely you'll over rev it, but when I'm ascending a steep hill in low gear, I just keep an eye on the speedometer ( a bike speedo with magnet on one of the front wheels). I stay under about 25 km/h (16 mph).

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Jem
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Re: Inductive Tachometer

Post by Jem » Thu Aug 15, 2019 2:21 am

Ford put a built-in governor in all their sidevalve engines in the design of the inlet & exhaust. If you have a stock engine it will run out of breath before it can hurt itself, unless you let it get out of control down a hill, as has already been said.

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