BigVWman
Veteran Member
- Joined
- Feb 16, 2007
- TDI
- A1 cabriolet tdi and 01 nb tdi and countless gassers!
How are things going with this idea? I would be interested in plunking down some reasonable cash to get my tach going!
Tachometers for conversions
- Thread starter e*clipse
- Start date
Hi,
I converted my T3 syncro (vanagon) to TDI (AFN code engine).
I tried to use the tacho output of the TDI ecu (pin 2/68), but factory tachometer of the T3 (gas engine) did not work.
I took the tacho out and examined, yes there are resistors (a voltage divider) on input signal.
The chip used in the tacho is SAK215, it is a frequency to current converter. I found the data sheet of SAK215 (googled it) and it says anything between -20 to +20 V is valid as an input signal.
As the TDI output signal is a 0-12V square wave, I just directly conected it to input pin of SAK215 (bypassing all the filters and resistors in tacho), and it worked.
It is accurate as expected!
Eren B.
I converted my T3 syncro (vanagon) to TDI (AFN code engine).
I tried to use the tacho output of the TDI ecu (pin 2/68), but factory tachometer of the T3 (gas engine) did not work.
I took the tacho out and examined, yes there are resistors (a voltage divider) on input signal.
The chip used in the tacho is SAK215, it is a frequency to current converter. I found the data sheet of SAK215 (googled it) and it says anything between -20 to +20 V is valid as an input signal.
As the TDI output signal is a 0-12V square wave, I just directly conected it to input pin of SAK215 (bypassing all the filters and resistors in tacho), and it worked.
It is accurate as expected!
Eren B.
Hi folks!
Sorry I haven't been around here in the last bit.
Right now the tach adapter project is on a bit of a hold, as i'm trying to finish some other projects 1st.
Regarding some of the questions/suggestions:
@ JJordan11: I'm not sure exactly how the VW tach works - it may be very similar to the Toyota's, given Mechano's suggestion. The Toyota circuit has a "fine tuning" loop that includes that potentiometer. On some tachs that may be fixed with a voltage divider. Any chance of finding that, Mechano?
@ CFM: I would also like a 5000 rpm face. Right now I've got things set up to read 2X as fast as it is actually running. Doing that math on the fly isn't too bad. A local laser cutting shop could turn out some sweet faces - problem is the $160 minimum charge. If a few people were interested, perhaps we could do a do a group buy. Making 10 or 20 would most likely drop the price to $10 - $15 per part.
@ Frankendiesel: Right now I have my PCB's made @ Advanced Circuits, in Colorado. Their quality is top notch, and the boards come with a solder mask, which makes surface-mount soldering much easier. I think I can drop the price by making the boards as small as possible, and gridding them. I may be able to cut them apart myself to save that $$.
@ Mechano: Nice work The output of the inductive sensor is considerably less noisy than the alternator signal. If you're eliminating the input protection circuitry, just be careful that intermittent noise doesn't cause long-term failure.
To everyone: Thanks for the inspiration.
Sorry I haven't been around here in the last bit.
Right now the tach adapter project is on a bit of a hold, as i'm trying to finish some other projects 1st.
Regarding some of the questions/suggestions:
@ JJordan11: I'm not sure exactly how the VW tach works - it may be very similar to the Toyota's, given Mechano's suggestion. The Toyota circuit has a "fine tuning" loop that includes that potentiometer. On some tachs that may be fixed with a voltage divider. Any chance of finding that, Mechano?
@ CFM: I would also like a 5000 rpm face. Right now I've got things set up to read 2X as fast as it is actually running. Doing that math on the fly isn't too bad. A local laser cutting shop could turn out some sweet faces - problem is the $160 minimum charge. If a few people were interested, perhaps we could do a do a group buy. Making 10 or 20 would most likely drop the price to $10 - $15 per part.
@ Frankendiesel: Right now I have my PCB's made @ Advanced Circuits, in Colorado. Their quality is top notch, and the boards come with a solder mask, which makes surface-mount soldering much easier. I think I can drop the price by making the boards as small as possible, and gridding them. I may be able to cut them apart myself to save that $$.
@ Mechano: Nice work
The output of the inductive sensor is considerably less noisy than the alternator signal. If you're eliminating the input protection circuitry, just be careful that intermittent noise doesn't cause long-term failure.To everyone: Thanks for the inspiration.
I've made some progress with the pulse translator.
The concept is KISS, and make it easy to operate and bulletproof.
Here's a shot of the proto system:
Right now things are running on a PIC 18F452. It's a lot more capable (and expensive) than the 12 series pic the final system will use. To make sure the prototype matches the final system as closely as possible, I'm running the PIC at 4mhz. I'm also ensuring all functions will be available on the smaller PIC.
The circuit includes a limiter, to ensure the input voltage does not exceed the PIC's 5V limitation. It uses a multiturn potentiometer connected to the pic's 10bit a:d converter for adjustment. The output drives a mosfet that will put out a square wave that matches the input voltage.
In short: The power input is protected, and cannot be connected backwards. The power supply circuit can handle between 5V and 40V. The input circuit can handle 40V as well. In other words, the pulse translator will work on anything from 6V to 36V.
The circuit performs with both sinusoidal and square wave input signals. (two wire or 3 wire sensors) The circuit will put out a 50% duty cycle square wave with an amplitude that matches the power supply voltage.
There are no jumpers or DIP switches necessary to set this up properly. Simply dial in the desired input/output ratio, and lock the ratio by sliding a switch. Once the ratio is locked, it is held in EEPROM and will not be lost due to power-downs.
Here are some shots of it running:
This is a 1:1 ratio. The input pulse is 12V and the output pulse is 12V at the same frequency of the input. The system performs accurately for an output range of 3 to 3khz. (the ratio effects the range) For reference, the Toyota tachometer responds to signals between 15hz and 400hz.
This is a 2:1 ratio. All other parameters are the same.
This is a 1:6 ratio. All other parameters are the same.
All I did to obtain these different settings was adjust the potentiometer. It is adjustible with 1024 settings for any ratio between 1:6 and 2:1.
As previously discussed, this will work equally well for electronic speedometers or any other pulsed data device.
The concept is KISS, and make it easy to operate and bulletproof.
Here's a shot of the proto system:
Right now things are running on a PIC 18F452. It's a lot more capable (and expensive) than the 12 series pic the final system will use. To make sure the prototype matches the final system as closely as possible, I'm running the PIC at 4mhz. I'm also ensuring all functions will be available on the smaller PIC.
The circuit includes a limiter, to ensure the input voltage does not exceed the PIC's 5V limitation. It uses a multiturn potentiometer connected to the pic's 10bit a:d converter for adjustment. The output drives a mosfet that will put out a square wave that matches the input voltage.
In short: The power input is protected, and cannot be connected backwards. The power supply circuit can handle between 5V and 40V. The input circuit can handle 40V as well. In other words, the pulse translator will work on anything from 6V to 36V.
The circuit performs with both sinusoidal and square wave input signals. (two wire or 3 wire sensors) The circuit will put out a 50% duty cycle square wave with an amplitude that matches the power supply voltage.
There are no jumpers or DIP switches necessary to set this up properly. Simply dial in the desired input/output ratio, and lock the ratio by sliding a switch. Once the ratio is locked, it is held in EEPROM and will not be lost due to power-downs.
Here are some shots of it running:
This is a 1:1 ratio. The input pulse is 12V and the output pulse is 12V at the same frequency of the input. The system performs accurately for an output range of 3 to 3khz. (the ratio effects the range) For reference, the Toyota tachometer responds to signals between 15hz and 400hz.
This is a 2:1 ratio. All other parameters are the same.
This is a 1:6 ratio. All other parameters are the same.
All I did to obtain these different settings was adjust the potentiometer. It is adjustible with 1024 settings for any ratio between 1:6 and 2:1.
As previously discussed, this will work equally well for electronic speedometers or any other pulsed data device.
Frankendiesel
Veteran Member
Nice work Eclipse. On my application, I would be driving the input of the factory Chrysler transmission controller. From there, it gets translated to the databus, etc etc... Same principal at work though; it's a frequency converter. <thumbs up>
tongboy
Veteran Member
all the work you guys did... you can buy a 35 dollar converter on ebay and plug it in - works off of a tach signal from the car expecting a coil or an rpm sensor from a crank wheel of some kind - different cylinder conversions - a lot simpler than busting out the oscilloscope and way less expensive than the dakota digital units
Really? Do you have a link? I can't find one.
I've found Dakota ones for $60 - $100 and a used splitter for $31, but nothing as versitile or easy to use as the one I'm developing.
For example: Say you put 33" tires on your truck that originally came with 31's. Could you calibrate your speedometer with one of these inexpensive adapters?
tongboy
Veteran Member
i'll pull the name off of the one I have in the jetta. It was an ebay purchase two years ago I guess now a days.e*clipse said:Really? Do you have a link? I can't find one.
I've found Dakota ones for $60 - $100 and a used splitter for $31, but nothing as versitile or easy to use as the one I'm developing.
For example: Say you put 33" tires on your truck that originally came with 31's. Could you calibrate your speedometer with one of these inexpensive adapters?
It's strictly a tach converter - not a speedo signal converter.
If there is someone making them now, it would be good to know. No need to re-invent things.
If the product has a significant advantage (ease of use, durability, flexibility, etc) it is worth bringing to market. I think this could have advantages over Dakota Digital's product for a number of factors, including price.
However, it's certainly not worth getting in a price war with an existing manufacturer. Whoever has the cheapest manufacturing contacts and prospects for large sales to back it up will win that one. Bin there, done that.
I did find a fairly close product for $50. Perhaps they had a special?
If the product has a significant advantage (ease of use, durability, flexibility, etc) it is worth bringing to market. I think this could have advantages over Dakota Digital's product for a number of factors, including price.
However, it's certainly not worth getting in a price war with an existing manufacturer. Whoever has the cheapest manufacturing contacts and prospects for large sales to back it up will win that one. Bin there, done that.
I did find a fairly close product for $50. Perhaps they had a special?
myke_w
Vendor
I know I'm resurrecting an old thread but it is the "official tach conversion thread" so It ought to live on right?
e*clipse, I think there are still several of us (probably more than before) out here with swaps that would be interested in figuring out how to adapt the ecu tach signal to run older tachs. I'd be willing to drop some coin to get mine straightened out. I also have some junk clusters I'd be willing to donate to research.
e*clipse, I think there are still several of us (probably more than before) out here with swaps that would be interested in figuring out how to adapt the ecu tach signal to run older tachs. I'd be willing to drop some coin to get mine straightened out. I also have some junk clusters I'd be willing to donate to research.
Danielg42
Veteran Member
Just got mine working thanks to this thread/research!
My tach was out of a 1988 Toyota 4runner v6 SR5.
I had a 33k ohm resistor after the input of my tach, that I ended up replacing with a 20k, in order to get the input voltage up to 2.7 volts.
My tach was out of a 1988 Toyota 4runner v6 SR5.
I had a 33k ohm resistor after the input of my tach, that I ended up replacing with a 20k, in order to get the input voltage up to 2.7 volts.
jimbote
Certified Volkswagen Nut
good info ^^ for vanagon users and may also work for toyota?Hi,
I converted my T3 syncro (vanagon) to TDI (AFN code engine).
I tried to use the tacho output of the TDI ecu (pin 2/68), but factory tachometer of the T3 (gas engine) did not work.
I took the tacho out and examined, yes there are resistors (a voltage divider) on input signal.
The chip used in the tacho is SAK215, it is a frequency to current converter. I found the data sheet of SAK215 (googled it) and it says anything between -20 to +20 V is valid as an input signal.
As the TDI output signal is a 0-12V square wave, I just directly conected it to input pin of SAK215 (bypassing all the filters and resistors in tacho), and it worked.
It is accurate as expected!
Eren B.
AndyBees
Top Post Dawg
- Joined
- May 27, 2003
- Location
- Southeast Kentucky
- TDI
- Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
That info ^^ is worth copying and saving!
emus528
Veteran Member
Indeed!!!
emus528
Veteran Member
Pursuant to this, I have never had my tach operating correctly with a Dakota Digital device and will perform Mechano's adaptation this weekend.
Can someone kindly confirm that on my 80 pin, 98 NB ECU, pin 67 is the correct tach output for the input on the SAK215.
Can someone kindly confirm that on my 80 pin, 98 NB ECU, pin 67 is the correct tach output for the input on the SAK215.
emus528
Veteran Member
So I tried to do mechano's adaptation as described here
http://www.brick-yard.co.uk/forum/l...-conversion_topic60315_post527970.html#527970
No joy in mudville. I'm thinking I wired it incorrectly. My engine cuts out when I connect the tach.
Mechano--> Is what you describe in THIS post
"I just directly conected it to input pin of SAK215 (bypassing all the filters and resistors in tacho)..."
exactly what you did in the linked post?
http://www.brick-yard.co.uk/forum/l...-conversion_topic60315_post527970.html#527970
No joy in mudville. I'm thinking I wired it incorrectly. My engine cuts out when I connect the tach.
Mechano--> Is what you describe in THIS post
"I just directly conected it to input pin of SAK215 (bypassing all the filters and resistors in tacho)..."
exactly what you did in the linked post?
emus528
Veteran Member
Well then. I cave. I have another unmolested tach and rather than modify it (perhaps unsuccessfully again) I purchased the needed bits from Rock Auto. If it ever stops raining raining here I will post back with photographic results.
dubmanted
Active member
Hi guys, i have a 90spec 8v gti with a mk3 ahu engine in. Ive installed the correct mk2 gtd clocks with the rev counter and reading from the W pin. It reads about 400rpm too much at idle and at a guess about 700rpm at 70. Ive seen a couple of how to's etc im wondering what is everyone elses solution to having an accurate rpm dial? Can i place a resistor on the W PIN WIRE?
Thanks
Thanks
Vince Waldon
Top Post Dawg
The tach is reading frequency from the W terminal, not voltage, so a resistor won't work unfortunately.
Sounds like your tach is a bit out of calibration for your particular alternator pulley/crank pulley ratio... if I recall correctly the MK2 clocks have a couple of calibration pots on the back of the circuit board.
A little googleing might track them down.... you could also try posting over at www.vwdiesel.net... lots of folks there have done conversions and there are several detailed tach threads.
bbob203
Veteran Member
Sometimes but you need a converter from dakota digital.
dubmanted
Active member
Thanks for the reply, ive seen a couple do it but ive looked for the potentiometer and cant find it on my set of clocks. Mine is a single pin 90 spec VDO unit.
Vince Waldon
Top Post Dawg
If your particular tach has no adjustments then yup you will need to do the adjustment with a digital divider box...Dakota Digital being the gold standard.
Same for adapting a gasser tach to run off a diesel alternator's W terminal.
Same for adapting a gasser tach to run off a diesel alternator's W terminal.
dubmanted
Active member
Heard lots about dakota digital....how does it work and how is it mounted if you dont mind me asking?
jimbote
Certified Volkswagen Nut
i'm not sure anyone understands the question ... could you clarify what you're trying to do ?
Vince Waldon
Top Post Dawg
Specifically...what year injection pump and what year tach?
In general, VW diesel tachs are driven from the alternator (IDI diesels) or the ECU (TDI diesels) rather than directly by the injection pump.
In general, VW diesel tachs are driven from the alternator (IDI diesels) or the ECU (TDI diesels) rather than directly by the injection pump.