Tachometers in EVs

Technical discussion on converting internal combustion to electric
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Plugger
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Tachometers in EVs

Post by Plugger »

I'm wondering whether an existing tachometer can be retained to do the same job in a conversion. As I'm probably going to use a series DC motor the rpm range in the ICE pretty well matches that for the replacement electric version (0-9,000 rpm). Does the analogue display rely on the ICE computer? Also what sensor would be used to detect motor speed? The probable donor car would likely be in the 1995-2000 range.
antiscab
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Tachometers in EVs

Post by antiscab »

Hi Plugger,

what electric motor are you using that can go to 9k?
are you planning on retaining the gearbox?

whether the tacho will work post conversion will depend largely upon your choice of donor vehicle.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
Plugger
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Tachometers in EVs

Post by Plugger »

Hi Matt,
It was the tacho on the vehicle that went to 9,000. I'm only at the planning stage so far. I've read that the max rpm for the ADC 203-06-4001 is around 8,000 and the FB-4001A is 7,000. I'm probably looking at the latter (9",144V, 6,000rpm continuous). The vehicle was a 1997 Toyota Paseo. Again yes I'm thinking of keeping the existing gear box-it just seems simpler at the moment. But you've raised an issue that I was going to make the subject of a separate topic. Having read on a previous thread of the possible problems of converting a modern car due to so many systems being under the control of the on board computer, I thought I'd ask about the tacho. A related question is whether any of th other gauges like that for fuel can be re-jigged. Good instrumentation and data logging are further down the track, but sometimes these things have to be looked at up front. So we're proceeding slowly.
antiscab
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Tachometers in EVs

Post by antiscab »

Hi plugger,

very little power is developed by an adc 9" (FB4001) at 7k rpm.
ideally in 5th at 100kmh you would want a rotational speed of 3-4k rpm.
since you are keeping the gearbox, getting it perfectly ratioed isnt quite as important.

go for a bigger motor if it will fit.
the larger the motor the more efficient it is (out of the motors you are likely to fit in a paseo).
if you are going lithium you better start out with good instrumentation.
no point skimping $300 for good instrumentation when your spending $13k for a battery pack.

Matt
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
gttool
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Tachometers in EVs

Post by gttool »

Gday Plugger,
when making the coupling between the motor and box i have machined teeth into this for a proximity switch to read so you may need 4 teeth for a 4 cylinder etc check the crank trigger or dizzy for the pulses required??
sounds simple enough

Geoff
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Tachometers in EVs

Post by Goombi »



This is rev counter sensor removed from Suzuki barina distributor . Would i need 4 magnetic contact points or just one?

uploads/437/DSC02163_sensor.jpg

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Tachometers in EVs

Post by gttool »

Im Guessing you would require 4
you need to look in the distributer
This was a carby engine with electronic ignition ?
you would need to try and see if the output from the trigger would operate the tacho as it would most probably be connected to the neg on the coil

Geoff
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Tachometers in EVs

Post by Goombi »

Yes, that sounds very reasonable The wire from the rev counter is still there and the connection on the sensor from the distributor is also there--Problem: the system is 12 volt auxiliery the mnagnetic field will be infected with one high voltage through the armature or would it? since there is no direct contact? Still 96 volt in this
case..Interesting. What will blow fist the viring and fuses or the tacho. OR NOTHING. How close will the sensor have to be the the 4 poles (or teeth) in this case?
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Tachometers in EVs

Post by Goombi »

If the sensor didn't have to connect and be spaced eg. 1-2 m/m and connected to the 12 volt The senseor will recieve the wave and the 12 volt will only be the reciepient of the signal --Not the voltage I think that sounds a bit better.. Any ideas?
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Tachometers in EVs

Post by gttool »

dont think it would cause a problem dont try and run it on 96 v though
the sensor would mostprobably only want 1 or 2mm clearance unless you use an industrial type proximity switch
Have you thrown the dizzy out ? check it
Geoff
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Tachometers in EVs

Post by Plugger »

Um, here's where I have to confess complete ignorance . Does the tacho (or computer?)depend on receiving separate signals from a rev counter and timer which are combined to drive some sort of (stepper) motor that drives the tacho needle? Also, if one uses a double ended motor is there an off the shelf sensor that can be attached to on the non gear box side-simply?
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Johny
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Tachometers in EVs

Post by Johny »

A tacho in a car converts rate of pulses (frequency) to a linear voltage generally applied to a moving coil meter with a 270 degree range of movement. The needle movement part of your tacho is just a fancy volt meter.
The pulses are generally provided from the low tension side of the coil of some derivation of it. Some later models have a tacho take-off point on the engine computer and this signal may vary from manufacturer to manufacturer (any comments from anyone here).
For the older standard system, a 4 cyl, 4 stroke engines provide 2 pulses per revolution. The distributor runs at camshaft speed which is half engine speed but has 4 lobes (or equivalent). After market tachos expect these 2 pulses per engine rev (4 cyl).
Check the distributor on the donor car and figure that if it is running at half engine speed (i.e. from the cam) how many times per distributor rev would the sensor get a signal. Then halve that for signal per engine rev.
Last edited by Johny on Tue, 02 Sep 2008, 08:19, edited 1 time in total.
Plugger
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Tachometers in EVs

Post by Plugger »

Thanks Johny. I went back to have another look at a 97 Paseo on the weekend. When I arrived there was an auto electician in disconnecting the engine immobiliser. According to the car yard these commonly fail for a lot of vehicles at this vintage. Anyway he didn't think there was a distributor, but mentioned that he thought he could see a couple of coils. I shall pay more attention in the future.
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Tachometers in EVs

Post by Thalass »

I'm not keeping the gearbox, but I'm going to try and commandeer the tacho to display battery amps (in or out, depending on whether I'm stopping or going).

How your tacho works depends on the car. Older cars will have a mechanical shaft that spins in the back of the display, with a magnetic clutch to the needle. But newer cars use voltmeters, iirc. Either driven by the VSS or by the ECU. Depends on the car.
I'll drive an electric vehicle one day.
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