Homemade digital tacho (rev counter).

[68C]

I am thinking of making a digital tacho that I can clip onto the bike when doing engine tuning, the stock item does not seem too accurate.

 

I intend to use an Atmega328 Microcontroller 'Arduino' based project. I will use a 14mm high 4 digit LED display that I can attach to the top of the instrument panel with Velcro.  I have already made a display that shows the throttle position.

 

As the bike has a test lead (wiring diagram item 58) built into the loom connected to the timing sensor I was hoping to use this as my signal.

 

I understand the timing sensor has a 48 tooth wheel with 2 teeth missing, as the timing point, and that it is on the end of the camshaft so rotates at half engine speed.

 

Has anyone tried this before or have any advice on what the nature of the output to the tacho is, I assume it will be digital as it is supplied by the ecu.

 

Why am I doing it, mainly as a hobby interest but also cost.  The microprocessor costs about £4 and the 4 digit display free from an old Sat. TV box. or about £2. 

 

 

[andy york]

sounds very interesting. Would like to have something like that myself but it sounds like there's magic 

smoke involved and i'm allergic to it.    lol

[guzzimeister]

Hi

 

I just love stuff like this, bet you're a long time Guzzi owner. Guzzi owners seem to thrive on stuff like this. I have met a guy who filed down some alternator brushes he had in the garage to fit his G5. These things cost £10, but he did it because he could. Like another guy I met who made a rack and pannier system out of central heating pipe, or the guy in the MGCGB who has sleeved down his engine, fitted a heavier flywheel and a single carb, again BECAUSE HE COULD. All this tells you that Guzzi owners especially V11 owners are special

 

Good luck with it. The standard item overreads badly; at 1000rpm indicated it is actually doing about 750rpm. I would imagine you can take a signal off the diagnostic port as I have a very crude diagnostic system based on a Palm (remember them?) and this is how I know the true rpm differential.

 

All the best

 

Guzz

[emry]

Pretty easy, but why not just count the tach pulse out of your MyECU though or use injector grounding?  The math is alot easier. The correct rpm and TPS angle is available in both the Optimizer and its App, so am I missing the point of this?

[Kiwi_Roy]

Another possibility is to measure the the alternator frequency and divide by 7 

(14 poles, 7 pairs = 7 cycles per revolution)

 

Another possibility is to remove the alternator cover and view the rotor under a flourescent light you should see it stand still at 3000 revs and it will alternate at 1500 revs.  (3600 & 1800 where the line frequency is 60 Hz)

[68C]

Thanks Guzzimeister, yeah I got my first Guzzi, a  T3, in '79.  I just like tinkering.  As an aircraft maintenance engineer I get fed up with having to do things exactly as the manufacturer states, have to keep fitting original bits you know will fail, not allowed to improve the design. The bikes keep me sane, then when my wonderful ideas fail I realise perhaps the aircraft designer is not so daft after all.

 

Thanks emry,  I tend to swap around between the MyEcu and the stock item, particularly since Paul's Guzzidiag software. The Optimiser does have this data displayed and I fitted a larger illuminated screen but still too risky to watch when riding.  The much larger LEDs are brighter and easy to read.  I am just messing around comparing A/F ratios between the two devices whilst I move around the fueling map, can't really explain why I want to do it other than interest and to see if I can.

 

I like the idea of counting the injector pulses, no need to differentiate between the regular 48 tooth pulses and the missing pair.  I believe the ecu output to the Tacho varies the frequency, again not too sure how to handle that.

 

 

Thanks Kiwi_Roy, the intention is to be able to read it while riding, perhaps I could use the street lights and a mirror!  You mention removing the alternator cover, I guess you don't have the front balance pipe.

[Kiwi_Roy]

 

Thanks Kiwi_Roy, the intention is to be able to read it while riding, perhaps I could use the street lights and a mirror!  You mention removing the alternator cover, I guess you don't have the front balance pipe.

Sorry, I missed that.

I;m sure the pulses from the ECU microprocessor to the tach are just a fraction of the pulses from the toothed wheel but I have no idea what the scale factor is.

How about MyECU display, that would be dead accurate I'm sure

I have MyECU also with a fuel mixture meter. I have tried changing the injector timing on the fly by fudging the TPS signal.

Send me a PM if interested.

 

Roy

[emry]

I would setup the ardunio to count interrupts of the falling signal on the ground side of the injector. Easy to program and make a shielding circuit so the input pin doesn't get damaged. Personally I don't like looking while riding, I prefer logs then I can review at my leisure with a beer later. You can get a shield and log to an sd card easily depending on the board you are using.

[Lucky Phil]

I am thinking of making a digital tacho that I can clip onto the bike when doing engine tuning, the stock item does not seem too accurate.

 

I intend to use an Atmega328 Microcontroller 'Arduino' based project. I will use a 14mm high 4 digit LED display that I can attach to the top of the instrument panel with Velcro.  I have already made a display that shows the throttle position.

 

As the bike has a test lead (wiring diagram item 58) built into the loom connected to the timing sensor I was hoping to use this as my signal.

 

I understand the timing sensor has a 48 tooth wheel with 2 teeth missing, as the timing point, and that it is on the end of the camshaft so rotates at half engine speed.

 

Has anyone tried this before or have any advice on what the nature of the output to the tacho is, I assume it will be digital as it is supplied by the ecu.

 

Why am I doing it, mainly as a hobby interest but also cost.  The microprocessor costs about £4 and the 4 digit display free from an old Sat. TV box. or about £2. 

Why are people so obsessed with accurate idle speed? Who cares if the tacho says 1000 when its actually 750?

Unless there is something dramatically wrong with the engine like low compression or an overly rich or week mixture then who cares if its idling at 1000 or 1200 as long as its not ridiculously out of the ball park it doesnt matter.

I set up all my vehicles to idle where the engine seems happiest and most stable and ere on the high side. I can tell if its to high by the way it sounds and if it needs to  be that high to be stable and reliable then there is an  issue and I investigate.

So my 1198 Ducati idles at  1400 rpm because thats where its happy. I could probably set it lower but why bother?

My V11 i havent a clue, but its happy enough where its at and doesnt cause any riding issues and doesnt stall or overheat.

Kind or reminds me of old guys obsession with  how low a speed an engine will  pull top gear or how steep a hill it will pull up in top.

Ciao 

[Kiwi_Roy]

 

Why are people so obsessed with accurate idle speed? Who cares if the tacho says 1000 when its actually 750?

 

 

You have a good point Phil

I have mine set at a point where it gives me good engine braking rather than have to use the brakes all the time just to slow. I have never bothered to verify what the actual speed is at.

[emry]

Its a little hard to make adjustments to fueling when you have to play the "I think thats about right" game. I dont think the OP is to concerned about idle speed.

[68C]

I am not too interested in the idle, just where I am in the fuelling map - throttle position and accurate rpm.

 

I agree idle rpm not important, depends on the ambient conditions, how old the motor is and how much you dislike your neighbours on a cold morning.

[docc]

Yet, on the stock mapping, the TPS position is based on 1050 rpm. I have found that expecting the mapping to function smoothly when actually calibrating at 750 rpm (my tach is off 300), is frustrating at best.

 

I also find that I cannot expect the big Guzzi to idle reliably in traffic circumstances with high ambient temperatures at leas than 1000. Learning the error in the tach helped me better find a suitable idle speed and better fueling.