Eduardo Santos

Hello everybody.

Can you please tell me if this tachometer works well with our Wankel rotary engines?

Tach Hour Meter For Motorcycle ATV Snowmobile Boat Gas Engine Tachometer Bike | eBay

I'm planning on using this to adjust the idle speed, and idle mixture (amongst other) on my 1987 Mazda RX-7 FC S4 N/A.

Thank you.

PS- Sorry if this isn't the correct thread for this question, but the only thread I could find about tools, is on the classifieds section.

Eduardo Santos

Ham... Nobody knows? I've submitted a question to the seller, but I haven't received any answer so far... :-(

misterstyx69

iTrader: (142)

doesn't that gadget just record RPM and total running time?.
It's unclear what you want to achieve with it.
Can you be more specific and elaborate in how you intend to use it?

dwb87

iTrader: (22)

I believe he may want to use it for some diagnostic testing in the FSM that require a "tachometer" tool. (IF it is to be used that way.)

misterstyx69

iTrader: (142)

I'll have to look that up.
To me "FSM" stands for Fix Stupid Machine.

Eduardo Santos

That tool (or gadget like you wrote) reads instant engine RPM and total running hours.
Like I wrote: I want to use that tool to adjust the idle speed, and idle mixture (amongst other things) on my car (1987 Mazda RX-7 FC S4 N/A), because it's idle speed it's set up too high (around 1000 ~ 1100 RPM), and you need it to be at the correct idle speed to perform other tasks, such as: engine timing, idle mixture...
Like dwb87 wrote, the Factory Service Manual states that you need a tachometer connected to the car's engine, so you can perform these tasks, which makes sense because you need the most accurate RPM reading possible, and you cannot have such a thing while using the car's default tachometer that comes included in the car's dash.


YES!

Eduardo Santos

I really want your help, people. I don't wanna spend my money for nothing...

misterstyx69

iTrader: (142)

I was going to suggest just a regular tach.2 wires to power(Power leads) and a wire to the Trailing coil bullet connector.
BUT I hit the link and saw $10 Bucks for the price of your Item...Heck for that it is worth a shot,providing it reads all the time and doesn't just record and you have to see it by pressing a button.

Eduardo Santos

How much is the one you were thinking about?

Tem120

iTrader: (5)

I believe hes talking about the regular one you can buy from an auto parts store .

Eduardo Santos

Well I think those are a bit expensive for my financial situation, but well... I guess I'm going to buy this one and see if it works...

Eduardo Santos

UPDATE:
I had already sent a message to that eBay seller, a few days ago, asking:
«Dear abeyerr,

Hello.
Can you please tell me if this tachometer works correctly with cars that are equipped with the Wankel Rotary Engine (like the Mazda RX-7, for example)?
Please bear in mind that the Wankel Rotary Engine is not the same engine as the piston engine that comes with 99,9% of the vehicles on the road.

- hk0hunterkiller»

and their reply (about 3 days later), was:

«Dear hk0hunterkiller,

hi,dear friend ,
sorry for the late reply.

yes,the item works correctly with cars that are equipped with the Wankel Rotary Engine.

Best regards,
Li Xiaoqin

- abeyerr»

So it seems that I'm going on the correct way, at least they say it works...
Now it's going to take about 1 month for the item to get here, but as soon as I receive it, I'll test it, and post here to say if it works.

Eduardo Santos

UPDATE:

Hello everybody.
Due to some strikes from the transportation system personnel here in Portugal, my tachometer only arrived today.
So I was reading the tachometer's instruction manual, and I found this:
«TO SET THE TACHOMETER (SPARK PLUG FIRING REVOLUTION):
Press and hold the S1 button for 4 seconds. The LCD will display 01(spark plug fires twice per revolution), 02(once per revolution), 03(every other revolution), 04(hour only, will not display RPM). (...)»

And this got me thinking: "Isn't the rotary engine in this car firing the spark plugs 3 times per revolution?"

Please help!

NOTE: Installation of this Tachometer: Wrap 3 or 4 turns of the wire around the engine's spark plug wire.

misterstyx69

iTrader: (142)

set it to 4 cylinder and try it

Eduardo Santos

I'm not sure if I understood what you mean...
You mean setting it like if it was a 4 cylinder 4 stroke engine? So it's 2 times per revolution, right?

RXSpeed16

iTrader: (41)

Depends on which plug wire you are using.
If you wrap it around a trailing plug wire, it will fire once per revolution. (Mode 02)
If you wrap it around a leading plug wire, it will fire twice per revolution due to the wasted spark control used on the leading coil. (Mode 01)

Eduardo Santos

Yes, you are right!
Because the e-shaft turns 3 times per revolution of the rotor! So the spark plug will fire once per revolution of the e-shaft.
I wasn't remembering that!

Thanks!