VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: mk1vdub on February 21, 2005, 10:49:44 am
-
I've noticed quite a few threads on this and have read some old ones on how to run one from the alternator, and the electronics went over my head pretty much straight away :roll: :lol: I also wasn't too sure about it due to the possibilies of the belt slipping and the readings changing as the belt wears. So I did a little bit of searching and came across this:
http://www.tinytach.com/tinytach/diesel.php
it looks pretty good for the price (which works out about £35 to me, although I haven't looked into the UK distributor, or shipping costs) and looks like it will be much more acurate, and for others like me a very simple soloution :D
I did wonder about making my own using a timing strobe which uses the same sort of transducer cliped over a fuel linebut that would only really be worth it if I could find one second hand for less than the tiny tach...
anyway I just thought I'd share that with you all as it may be of interest to some of you, if I do go ahead and get one I'll be sure to write a little report on how well it works and post it up :D
cheers
Paul
-
hey,
i have a tiny tach on my dirtbike. and even tho it works good to set my idle and to veiw my cruzing rpm's, i wouldnt recomend it for your car. first of all, they arent back-lit, so it would be useless at night. second, its digital so unless you are a math genius, it's hard to tell the rate of acceleration using it. they also have about a 1 second delay in them while it figures out rpm so it realy isn't useful unless you are at a constant rpm.
another idea is taking the transducer and modifying it onto a gas tack somehow. now a gas tach uses 2 pulses a revolution whereas this would only be 1 every 2 revolutions. so you could hook it up to a 1 cylinder motorcycle tach if you could find one, or build a circuit board to multiply the pulses somehow.
hope that helps
Mark
-
cheers for the reply mate,
I did wonder exactly how good it would be. I had already thought of converting it to run a gas tach, I'd definitely prefer an analogue needle and lighting and I'm sure I could make it work with a bit of thought, the second delay is a bit of a bugger though.
-
hey,
does anyone kno how this works?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=42291&item=4359080992&rd=1
do u think there could be useful parts on that to hook up to an analog tack in the car?
Mark
-
thats basically what I was talking about in my first post, the timing strobe - it shold have the same sort of transducer which clips over a fuel line the signal fires the strobe which you point at the flywheel and look at the marks
-
Try:
http://www.4crawler.com/Diesel/CheapTricks/Tachometer/index.shtml
-
The more electronics inclined may wish to check out this DIY page for not only making a non-W tach for a diesel VW, but also integrates a MK1 GTI instrument cluster, with its 7000 RPM tach.
Link. (http://www.4crawler.com/Diesel/CheapTricks/Tachometer/index.shtml)
-
thanks for the link,
couldn't the same idea be used if you took the disk and made 2 - 1/2" bumps on it then used an abs sensor to pick up the signal instead. then you wouldn't have to worry about cleaning the disk and sensor all the time and the whole thing would be protected by the timing belt cover.
Mark
-
I wanted a tach for my 91 GTD (SB Engine), mk2 GTD tachs are like hens teeth, so I fitted the clocks from a mk3 Mechanical TD of a AAV? or 1Z engine.
VDO list a 52mm 5k revcounter that will work with a w terminal, that you could fit in the center console if you remove the blanking plate.
What electrcal system have you used in the SB conversion ce1 or ce2?
-
Try:
http://www.4crawler.com/Diesel/CheapTricks/Tachometer/index.shtml
I`ve tried and it worked well with the factory tach I installed but the trigger set-up is too complicated to suit my tastes. My solution was to use the photo-interuptor from a 1.8L distrubutor and a 2mm notch machined into the crankshaft pully. It`s worked well for 137,000+km despite having road trash tossed up on it and i BELIEVE I still have to circuit some where if anyones` intrested and if they`re handy with this sort of thing,..
N.
-
hey,
does anyone kno how this works?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=42291&item=4359080992&rd=1
do u think there could be useful parts on that to hook up to an analog tack in the car?
Mark
The Snapon Lummy-Mag uses an optical pickup. You remove one of the glowplugs and screw an optical pickup in the hole. The flash from combustion provides a signal to the tach/timing diagnostic device.
On the subject of using a gas tach on the diesel, I've wondered about using a hall effect or magnetic type pickup in the plug at the back of the injection pump. That would get one pulse for each cylinder firing because the plunger in the pump moves once per combustion cycle. That would be analogous to the coil connection on the gas cars. I'm just not sure how easy it would be to get a pickup in there considering the pressure in that chamber behind the plunger.
-
hey,
does anyone kno how this works?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=42291&item=4359080992&rd=1
do u think there could be useful parts on that to hook up to an analog tack in the car?
Mark
The Snapon Lummy-Mag uses an optical pickup. You remove one of the glowplugs and screw an optical pickup in the hole. The flash from combustion provides a signal to the tach/timing diagnostic device.
On the subject of using a gas tach on the diesel, I've wondered about using a hall effect or magnetic type pickup in the plug at the back of the injection pump. That would get one pulse for each cylinder firing because the plunger in the pump moves once per combustion cycle. That would be analogous to the coil connection on the gas cars. I'm just not sure how easy it would be to get a pickup in there considering the pressure in that chamber behind the plunger.
That was my thinking. Rather than go to the troble of mounting the trigger disc on the pump, mounting the sensor in the belt cover, and the rest of it, it occured to me that there might be an easier solution. My fist thought was to use the timing mark on the flywheel but one day while servicing a Canon photocopier it struck me that the way they generate thier own timing signal, which was with a cut-out disc and photointerrutor moted on the main motor, that THAT was close to what I wanted for a trigger circuit for a tach. The end reult was something that reads the crank speed without having to multply up and divide down etc.
I must admit though that taking a signal right from the pump is an intreguing idea though,...
N.
-
That would get one pulse for each cylinder firing because the plunger in the pump moves once per combustion cycle.
The "Tiny Tach" mentioned in the opening post does exactly this, so why try to reinvent the wheel?
-
That would get one pulse for each cylinder firing because the plunger in the pump moves once per combustion cycle.
The "Tiny Tach" mentioned in the opening post does exactly this, so why try to reinvent the wheel?
Actually, the "Tiny Tach" has a transducer that fits on one of the fuel lines to the injectors. It produces a signal every time that injector gets a pulse of fuel, once every two engine revolutions. That's part of why that tach doesn't care how many cylinders the engine has. If it's a 4 stroke diesel, the transducer generates one pulse per 2 engine revolutions.
-
Yes, that's exactly my point. The guys above are talking about using a Hall or magnetic pickup, which, since either produces a small dc pulse which is converted to a tach signal, is functionally identical to what the Tiny Tach does.
Unless the objective of the exercise is to 'reinvent the wheel'...if so, then by all means have at it! :D
-
How about this ?
http://www.logjamelectronics.com/crimdts2.html
-Steve
-
I've been thinking of different ways to get a gas tach to work on a diesel.
Even went so far as to pull a tach apart and draw a schematic of the circuit.
The gas and diesel were basically the same. Gas tach out of a '91 and a diesel tach out of an '85 turbo diesel Jetta. I figured I could probably swap a few resistors and caps and get the gas one to work with the diesel w terminal.
This thread has been very informative. 2 pulses per revolution for the gas tach. I've also concidered using a sensor in the trany timing plug ... was thinking an optical sensor but with 2 pulses I could use a hall effect sensor (doesn't have to be kept as clean as the optical sensor) and have it trigger on the 2 raised metal pieces each side of the timing mark.
I also want to figure out how many volts it takes to make the tack go to 7 grand. Maybe bypass all the circuitry and use a digital to analog converter ... turns number of pulses into a voltage value.
-
This thread has been very informative. 2 pulses per revolution for the gas tach. I've also concidered using a sensor in the trany timing plug ... was thinking an optical sensor but with 2 pulses I could use a hall effect sensor (doesn't have to be kept as clean as the optical sensor) and have it trigger on the 2 raised metal pieces each side of the timing mark.
I also want to figure out how many volts it takes to make the tack go to 7 grand. Maybe bypass all the circuitry and use a digital to analog converter ... turns number of pulses into a voltage value.
Ya, I was kinda thinking the same thing. What would be nice is if one built a module which took the place of the inspection plug on the tranny....Im going to start to collect some info on the mag sensors, and see what I can come up with (Although I would think that you'd want the 180' apart to mimmic the coil firing ?)
-
I've been thinking of different ways to get a gas tach to work on a diesel.
Even went so far as to pull a tach apart and draw a schematic of the circuit.
The gas and diesel were basically the same. Gas tach out of a '91 and a diesel tach out of an '85 turbo diesel Jetta. I figured I could probably swap a few resistors and caps and get the gas one to work with the diesel w terminal.
This thread has been very informative. 2 pulses per revolution for the gas tach. I've also concidered using a sensor in the trany timing plug ... was thinking an optical sensor but with 2 pulses I could use a hall effect sensor (doesn't have to be kept as clean as the optical sensor) and have it trigger on the 2 raised metal pieces each side of the timing mark.
I also want to figure out how many volts it takes to make the tack go to 7 grand. Maybe bypass all the circuitry and use a digital to analog converter ... turns number of pulses into a voltage value.
Funny you should mention the timimg plug as I had originally considered that approach. I had access to a common sensor made by Motorola that set the led and phototransistor at a 90 degree angle to each other: if the sensor could be set close enoughto the rotating flywheel the light from the led would bounce off the notch on the timing wheel to the phototransistor. The trick was building a mount for the sensor that could be adjusted to bring the sensor closer or further from, the flywheel. Some degree of adjustability seemed required. In the end it seemed easier to do it in the manner that I described above.
N.
-
Hrmm....Im really not a fan of any optical approach. Granted, it would work just as well, but with clutch dust, and god-knows-what in there, I believe that magnetic sensors would be the best approach. Affixing them would not be an issue, and dust, dirt would have no affect on performance. I really think that we may be onto something here (as far as the timing plug goes).
-Steve
-
Hrmm....Im really not a fan of any optical approach. Granted, it would work just as well, but with clutch dust, and god-knows-what in there, I believe that magnetic sensors would be the best approach. Affixing them would not be an issue, and dust, dirt would have no affect on performance. I really think that we may be onto something here (as far as the timing plug goes).
-Steve
Air-borne dust isn`t an issue with this sort of set-up. My trigger assy. is mounted on the outside of the lower timing cover to get it`s pulse from a small notch cut into the crank pulley. Water, dust, road trash, etc was tossed ontoit in the first 2 years of use and it functioned without a hitch. The only reason I cleaned it out after 2 years was that I thought it MIGHT need cleaning at some point.
If anything I imagine that the interior of the bell housing in the general area of the timing plug is a much more benigne environment, temperature and vibration aside.
N.
-
hey,
Northern RD, can you post the scematics and more detailed directions on what you did to get a tach working?
And VWRacer, I don't think the point is to "reinvent the wheel", i think it's to make it more usable. the tiny tach is a digital display witch needs some time to think and it causes a delay in the readings vs. actual rpm. I was on my dirt bike the other day and if i reved it it would be back at an idle before it showed my max rpm. witch if you ask me isnt really useful on a "preformance level".
just my 2 cents.
Mark
-
And VWRacer, I don't think the point is to "reinvent the wheel", i think it's to make it more usable. the tiny tach is a digital display witch needs some time to think and it causes a delay in the readings vs. actual rpm. I was on my dirt bike the other day and if i reved it it would be back at an idle before it showed my max rpm. witch if you ask me isnt really useful on a "preformance level". Mark
Quite so, but I thought the point was to have some idea of one's RPM. If it is, then the Tiny Tach is a good way to go. As I said, though, if the point is to have fun building one's own tach, then by all means go for it.
-
hey,
Northern RD, can you post the scematics and more detailed directions on what you did to get a tach working?
And VWRacer, I don't think the point is to "reinvent the wheel", i think it's to make it more usable. the tiny tach is a digital display witch needs some time to think and it causes a delay in the readings vs. actual rpm. I was on my dirt bike the other day and if i reved it it would be back at an idle before it showed my max rpm. witch if you ask me isnt really useful on a "preformance level".
just my 2 cents.
Mark
Sure, I BELIEVE i still have the original diagram around somewhere. Unfortunatly the car has gone to the Great autobahn in the sky so pics are out of the question.
i`ll seee what I can come up with,...
N.
-
ok I have thought a bit more about this, basically my idea behind the 'tiny tach' was to use it for the piezo/transducer, just like the one that is used on the timing strobe which picks up the slight bulging of the pipe when there is an injection pulse. I would basically cuck the LCD display away and use the signal from the transducer to run a gas tacho from a gti, the signal from the transducer should be very similar to that which a gas tach recieves from the coil wire, if only a bit weaker - I can then make up the neccessary amplifying circuit to boost the signal to waht ever the gas tach would normally need to work.
the one second delay on the 'tiny tach' I am fairly sure comes from the display, as if the transucer works in the same way the timing stobe one does then it will produce a signal for every injection pulse which is what I am looking for, I am hopeing this will be an easyier way for me so I don't have to mess around with optical sensors and timing wheels etc.
I hope everyone understands my explanation, if anyone can see any problems, or offerany further advice please do. :D
-
ok I have thought a bit more about this, basically my idea behind the 'tiny tach' was to use it for the piezo/transducer, just like the one that is used on the timing strobe which picks up the slight bulging of the pipe when there is an injection pulse. I would basically cuck the LCD display away and use the signal from the transducer to run a gas tacho from a gti, the signal from the transducer should be very similar to that which a gas tach recieves from the coil wire, if only a bit weaker - I can then make up the neccessary amplifying circuit to boost the signal to waht ever the gas tach would normally need to work.
the one second delay on the 'tiny tach' I am fairly sure comes from the display, as if the transucer works in the same way the timing stobe one does then it will produce a signal for every injection pulse which is what I am looking for, I am hopeing this will be an easyier way for me so I don't have to mess around with optical sensors and timing wheels etc.
I hope everyone understands my explanation, if anyone can see any problems, or offerany further advice please do. :D
Your reasoning is sound, I believe the Snap-on tach works the same way. The only issue I`d have is that piezo`s are fairly sensative and you`d have to figure out a way of using it so that it`s picking up,say, a fulse from one of the injector lines and not all the backround noise with it.
N.
-
You guys are (http://www.vwvortex.com/zeroforum_graphics/screwy.gif) (http://www.vwvortex.com/zeroforum_graphics/screwy.gif) (http://www.vwvortex.com/zeroforum_graphics/screwy.gif)
For as much effort as you are putting into just thinking and posting about this, you could build a tach that runs off the cam/injection pump sprocket. The circuitry and parts have already been figured out for you ~and~ it uses salvaged parts:
http://vwdiesel.net/phpBB/viewtopic.php?t=76
Obviously, no one has yet found a short-cut to installing an accurate tach in a diesel that's any simpler.
Technically sweet but it still has the issue that the other guys set-up has for me: taking the timing cover off, installing the pick-up sensor, etc. Too much work for someone a lazy as me :) :) . The most complicated thing I had to fabricate was the small bracket I used for the Motorola sensor I scrounged and that was simply installed with 2 pop rivets in the timing cover. As well, the debate and ideas thrown around here IS rather intresting!!
Later,
N.
P.S.
Anybody out there guess what the "RD" stands for?
-
Anybody out there guess what the "RD" stands for?
Just a guess, after a clink on your profile and a quick google:
http://www.race-uscra.com/formulard.html ?
-
Anybody out there guess what the "RD" stands for?
Just a guess, after a clink on your profile and a quick google:
http://www.race-uscra.com/formulard.html ?
Bingo!
I have 8 of them, counting my `77 daily ride.
A pint of honey pail ale for guessing if you`re ever up this way and none for the guy who thought 'RD" indicated a location in Rohde Island,... :lol: :lol:
-
HA!! Good ol SEARCH!!
SO...back on topic. Its getting to be a bit of an obsession. I KNOW there is a way.
What I cant seem to find is.. What KIND of pulse does the VW tach need. Or any tach.
-
Hmmmm... then search has let you down... I remember posting oscilloscope pictures of both the gasser and W tach signals... lemme see....
Is this what you're after:
http://www.vwdiesel.net/forum/index.php?topic=13499.0 (http://www.vwdiesel.net/forum/index.php?topic=13499.0)
-
I think I'm going to try going the way of the hall sensor. I have some spare parts from a 90 dist. and I pulled the round window trigger from it and plan to put it onto the end of the cam bolt and set the sensor itself to word just like it did in the distributor. It's going into a 96 and I'm hoping I can hook that directly to the tach....
-
Cam rotates at 1/2 engine speed, and the gasser tach is expecting 2 pulses per rev, so you'll need 4 metal flags on your cam for an accurate tach measurement.
If I did the above math correctly...someone will jump in if not ;)
-
So here is my thought.
Ive mounted a Ford Taurus alternator..and I no longer have AC or PS. I have this spare pulley on the front of my crank. I want to use the 2 mount bolts, towards the firewall that the PS bracket used, to make a sensor mount that would read off my modified unused pulley. If I have to add something or remove it from the pulley I dont really care. What Im looking for is what will my sensor have to put out.
Ive debated tearing into a Ford Duraspark (Ive had alot more experience with the Fords) and taking the distributor pickup out and using that.
I just have NO faith in the W terminal...specially since I dont have one anymore. So..will I just need ANY kind of sine wave?
-
So..will I just need ANY kind of sine wave?
Any documentation I've read indicates that the tachs are not very picky signal-wise... a good clean transition between 0 and something greater than 5V seems to do the trick... 2 pulses per rev... square/sine doesn't seem to matter.
Kinda makes sense... the ignition system is pretty noisy so a picky tach would be problematic.
-
I was wondering if anyone knew of a source for just a normal photosensor that will count say a white dot painted on the crank pulley and output a signal that any standard tach could read?
like say an "aftermarket" tach?
the FAQ doesn't have anything on this and i can't seem to choose the right words for a search to bring up anything useful.
-
So..will I just need ANY kind of sine wave?
Any documentation I've read indicates that the tachs are not very picky signal-wise... a good clean transition between 0 and something greater than 5V seems to do the trick... 2 pulses per rev... square/sine doesn't seem to matter.
Kinda makes sense... the ignition system is pretty noisy so a picky tach would be problematic.
See..thats what I wanted to know. What kind of voltage peak do I need to create to get the tach to work.
-
Just so long as you've noticed all the Vince weasel words: "kinda", "seems to", "should be"... ;)
I've fooled around with this stuff a bit but have never done the definitive test, which would be to use a bench signal generator to play with the tach's mind "mo ha ha ha ha... lets see how you like a triangle wave Mr Gasser Tach". "Oh really... a ha.... yah... you like that, don't ya". ;)
-
I noticed with reference to the link to the ocsilliscope, that optical and flywheel pickup are noted, but not a hall type setup. I have a 90 Jetta 16V I converted to run on megasquirt. The hall is easy to use a pullup to and it will send a clean (depending on size of resistor) 0 - 12v square signal. I could not get this to work with the vw tach in the car. I have an aftermarket autometer in it. I don't want to have to spend big$$ to buy another autometer.
Is there a way to pullup the 12V to a higher voltage as per the link (80V on gasser tach) to get the hall to work nicely with a gasser tach. As I expect the 96' tach will need something similar in order to work properly. I'm a major novice when it comes to electronics. (I tried Rogers optical unit, could not get it to work - I figure the hall unit will be easier to setup)
-
I noticed with reference to the link to the ocsilliscope, that optical and flywheel pickup are noted, but not a hall type setup. I have a 90 Jetta 16V I converted to run on megasquirt. The hall is easy to use a pullup to and it will send a clean (depending on size of resistor) 0 - 12v square signal. I could not get this to work with the vw tach in the car. I have an aftermarket autometer in it. I don't want to have to spend big$$ to buy another autometer.
Is there a way to pullup the 12V to a higher voltage as per the link (80V on gasser tach) to get the hall to work nicely with a gasser tach. As I expect the 96' tach will need something similar in order to work properly. I'm a major novice when it comes to electronics. (I tried Rogers optical unit, could not get it to work - I figure the hall unit will be easier to setup)
yeah i was hoping for something a little easier/less work. like just a normal pickup off of basically any new tdi. I would imagine they would just use some type of photo sensor like that no?
I think i'll try Roger Brown's optical unit.
-
since I am already knee deep into digital gauges, I am tempted to get the Auber tach and hall sender setup, and put four magnets on the cam pulley and call it good.
I agree that analog is better, but the tach would be more a tuning and setup tool for me than something that I look at all the time.
-
since I am already knee deep into digital gauges, I am tempted to get the Auber tach and hall sender setup, and put four magnets on the cam pulley and call it good.
I agree that analog is better, but the tach would be more a tuning and setup tool for me than something that I look at all the time.
I want to use an aftermarket tach. I really dont trust the VW ones...and I like a clock.
My goal is to eliminate as much VW electronics as possible. German wiring is only slightly better then English wiring.
-
My understanding of Roger Brown's little write up there is that it would drive the feed wire of an after market tach...