Tach signal -- pulses per second? Voltage?

[fmaxwell]

I've been considering an aftermarket tach for my smart car and was wondering if anyone knew anything about the tach signal supplied by smart. Specifically, is it one pulse per revolution? Three pulses per two revolution? Is it 12V pulses? 5V pulses? (I could put an o-scope on the connector after taking the dash apart, but I'd rather not duplicate someone else's efforts).

If it's three pulses per two revolutions, there are some three-cylinder marine outboard motor tachs that might be good choices -- also available with white faces and bezels.

When an aftermarket tach can be had for under $50 and the smart OEM tach and clock go for $250, it would be worthwhile to identify what (if any) aftermarket tachs could be used in a smart fortwo (451).

P.S. I know about the Scangauge II and plan to get one, but the slow refresh rate and the non-graphical display make it impractical as a tach to be used for shifting.

[chieftmc]

Originally Posted by fmaxwell

I've been considering an aftermarket tach for my smart car and was wondering if anyone knew anything about the tach signal supplied by smart. Specifically, is it one pulse per revolution? Three pulses per two revolution? Is it 12V pulses? 5V pulses? (I could put an o-scope on the connector after taking the dash apart, but I'd rather not duplicate someone else's efforts).

If it's three pulses per two revolutions, there are some three-cylinder marine outboard motor tachs that might be good choices -- also available with white faces and bezels.

When an aftermarket tach can be had for under $50 and the smart OEM tach and clock go for $250, it would be worthwhile to identify what (if any) aftermarket tachs could be used in a smart fortwo (451).

P.S. I know about the Scangauge II and plan to get one, but the slow refresh rate and the non-graphical display make it impractical as a tach to be used for shifting.

The pods are only $120 when you configure your smart!

[fmaxwell]

Originally Posted by chieftmc

The pods are only $120 when you configure your smart!

1. You don't get to configure orphan smart cars, which many of us have.
2. If you don't have a tach, for whatever reason, the cost is about $250 for the tach/clock combo from smart.
3. Some people don't want the clock that comes with the factory tach.
4. Some people want a larger tach, tach with shift light, tach that they can mount into a panel, electronic LED bargraph tach, tach with different color face, etc.

So, do you know what the pulse rate and voltage are?

[BRM42]

I understand that the tach is driven from the LIN network. I was unable to find anyone that had the correct driver. You can drive a tach from the wire from the ECU to one of the coil on plugs. An alternative to a tach and shift light is what I used. Check out this link: Alternative to a Tachometer . I think it is better than an analog tach.

[fmaxwell]

Originally Posted by BRM42

I understand that the tach is driven from the LIN network. I was unable to find anyone that had the correct driver. You can drive a tach from the wire from the ECU to one of the coil on plugs. An alternative to a tach and shift light is what I used. Check out this link: Alternative to a Tachometer . I think it is better than an analog tach.

Thanks! That was exactly the kind of information I was looking for. That you've identified the wire at the ECU for the tach is a tremendous help, whether I do a shift light or a tach (or both).

I was afraid that the tach would be part of a mulitplexed, networked comm bus, meaning that conventional tachs would be worthless for a smart car.

[pitstopautoinc]

fmaxwell, it is 3 pulses per revolution. I hooked an oscillascope ( im sure i spelled that wrong ) on the system when I did mine. Here is a link to how to add an aftermarket tach:

How to add an aftermarket tach to a Smart Car

[webpad]

the tach signal supplied by smart is 25V pulses