UK-POLOS.NET - THE VW Polo Forum

Thinking about it, good luck finding a place to connect the sensor for a bike computer... unless you've got a set of spoked wheels hidden away somewhere?

reply 1 - ive done far geekier things than that. this is fairly simple; compare various steady readings on the tacho vs the main frequency that the mic is picking up as displayed by my sampler program (i may get it inductively - run a wire parallel to one of the ignition leads), do a little maths on the frequency to get a true RPM reading out of that (eg, if its inductive off a spark lead, then x120)...... simple ah how i love cooledit... good for analysing mp3s and filtering sound files to use on videoCDs.... and for measuring rpms

reply 2 - eh, it's just a magnet. i'll glue it in place last time i heard of someone doing this, they fixed it to the driveshaft somehow (soldered? welded even??*) and somehow affixed the sensor so it would still reliably pick up. same theory as many aftermarket (and some factory fit) cruise control sensors!
what you have to think of as well is the little problem of suspension, so the sensor would either have to be attached so as to go up and down exactly in sync with the magnet, or (i'm guessing is more likely) it was attached at the gearbox side of the first universal joint where that stuff has no effect
after all its not the distance from the wheel centre that matters, only how quickly the shaft rotates and how often the signal goes on/off... im more concerned about getting a wire easily from the outside to the inside

after all, theres nuff people who've done it, cant be so tricky now? (does a caterham have spokey wheels??)

main prob is, it would be out of calibration round corners because of the differential, so maybe not a good way to measure total distance unless all the roads add up to a straight line and of course your main speedo will be the one to rely on when taking a protracted but sharp corner.
(could always fit two of em and split the diff)

good to hear the engines going better now! best of luck putting up with the corsa ...rag that thing, this is your chance to LARP as a chav..

Aye, cooledit is a useful bit of kit.. made good use of it for my AS physics coursework on resonance frequencies etc. Honestly though, you must have far too much spare time if you're going to bother using it to calibrate your speedo

Would have thought the best way to wire it up would be directly to your tacho input, which will be as accurate as you're going to get, far more accurate than using a mic or whatever. I'm also quite sure that you could just wire the bike speedo sensor into the laptop.. wire it to a com port I guess. Would have thought you'd be better getting a GPS tracker with a USB link to connect it to a PC, or a PCMCIA GPS tracker for the laptop, that way you can get it pretty much entirely accurate

Anyway, back on track, it appears that the big end bearings are buggered as well, so I won't be trying to start it up until I get back from wales.

I'd thrash the corsa like a chav scumbag, but it's my sister's, she'd kill me if anything happened to it, I'm taking the p*** somewhat by taking it on a 700-ish mile trip without asking her first, and it's not much of a barrymobile anyway being the most basic 1.2 merit you could possibly imagine.. never mind.

If my opinion of mk1 1.2 corsas is of any use to anyone btw, it is that they are built like a small piece of creaky, squeaky and clonky jelly, the merit is ridiculously basic, the handling is utterly unresponsive and actually quite scary after the polo, but on the plus side the engine is actually quite nice for a 1.2 (feels slightly like it's fitted with a turbo.. nothing special until about 2,500 rpm and then it starts to fly ), it sounds nice apart from the nasty whiney gearbox, and it's fairly refined for such a basic car. Oh yes, and apart from the handbrake locking on after being left for more than 24 hours, the brakes are very impressive for a standard setup.

GroovyCarrot wrote:Anyway, back on track, it appears that the big end bearings are buggered as well, so I won't be trying to start it up until I get back from wales.

Okay lets

So why are the big ends buggered??????? I thought you said you replaced them?

Did you size them up properly or have you used oversize shells without grinding the crank?

I used standard shells, but by process of elimination they must be knackered... with the main bearings that I replaced removed and all pistons disconnected from the crank, it turns reasonably easily. I attached two of the pistons to the crank and tried turning it, rock solid. The pistons all move, if a little stiffly, inside the cylinders, so it must be the connection onto the crankshaft that's siezing it up, surely?

GroovyCarrot wrote:I used standard shells, but by process of elimination they must be knackered... with the main bearings that I replaced removed and all pistons disconnected from the crank, it turns reasonably easily. I attached two of the pistons to the crank and tried turning it, rock solid. The pistons all move, if a little stiffly, inside the cylinders, so it must be the connection onto the crankshaft that's siezing it up, surely?

I don't think you have got std shells - did you keep the old ones?

No I still have the old mains, but not the big ends.. the big end shells are all stamped with 'STD', but they must be the wrong size, it's just solid with them in...

Tahrey1043 wrote: main prob is, it would be out of calibration round corners because of the differential, so maybe not a good way to measure total distance unless all the roads add up to a straight line and of course your main speedo will be the one to rely on when taking a protracted but sharp corner.
(could always fit two of em and split the diff)

How often do you look at your speedo whilst cornering? Eyes on the road dude!

GroovyCarrot wrote:Aye, cooledit is a useful bit of kit.. made good use of it for my AS physics coursework on resonance frequencies etc.

Coolness (so to speak) .... actually using it for some schooly or serious thing rather than just hobbying. But, did you pay for yours?
(i'm still using cool edit 96 and its logged about 2000 hours of use "please register? pretty please?" has been my startup greeting for the last couple years yep, i will, when i have £50 to blow on software rather than something else)

Honestly though, you must have far too much spare time if you're going to bother using it to calibrate your speedo

Well its that or use it to work out a few more ringtones (handy for that as well, if you have a table of rough frequencies vs notes and a bit of time to filter things down to their most basic components). The calibration wins by dint of being far less specky.

Would have thought the best way to wire it up would be directly to your tacho input, which will be as accurate as you're going to get, far more accurate than using a mic or whatever.

If you can tell me how to get at that?? I've got half a feeling it actually goes into the ECU first and then back out to the dial.
I think it would be easy enough to do it inductively - forget using a microphone, just get a loop of wire and stick it near the main ht lead coming off the coil. Wouldn't have to put it *too* close - when the aerial's retracted, it makes enough of a noise thru the radio on the AM band anyway! (thinking more to use the main HT than a single sparker, as that raises the frequency by 4, and anything too low (e.g. 30Hz for one plug at 3600rpm) is hard to easily determine with your average Fast Fourier Transform frequency plot....
</geek>
Anyhow using the mic also allows me to make recordings of the engine sound maybe starting a "whats yours sound like" thread...

I'm also quite sure that you could just wire the bike speedo sensor into the laptop.. wire it to a com port I guess. Would have thought you'd be better getting a GPS tracker with a USB link to connect it to a PC, or a PCMCIA GPS tracker for the laptop, that way you can get it pretty much entirely accurate

whoa nelly, i'm not made of the folding this method uses stuff i already have... one unloved bike speedo, one laptop (borrowed from mum's work), one condenser mic and/or length of random speaker wire jerry-rigged to a 3.5mm plug...

Anyway, back on track, it appears that the big end bearings are buggered as well, so I won't be trying to start it up until I get back from wales.

YOUR BIG END'S GONE always wanted to say that to someone

I'd thrash the corsa like a chav scumbag, but it's my sister's, she'd kill me if anything happened to it,

wellllll..... give it a whizz on a nice straight empty stretch of motorway at least, and light up the tyres at a couple of traffic lights. Gotta keep your arm in.

I'm taking the p*** somewhat by taking it on a 700-ish mile trip without asking her first,

Sis: hey..... bro.... what miles was my car on when i lent it to you again??
GC: um... (hurridly tries to add 500 onto a half-remembered figure)... 180,000?

and it's not much of a barrymobile anyway being the most basic 1.2 merit you could possibly imagine.. never mind.

Dude... it is THE barry mobile!

If my opinion of mk1 1.2 corsas is of any use to anyone btw, it is that they are built like a small piece of creaky, squeaky and clonky jelly, the merit is ridiculously basic, the handling is utterly unresponsive and actually quite scary after the polo,

That was even mum's verdict after having one as a courtesy car
No feel thru the steering at all, you got only the remotest idea that it was going where you told it after a brief period to decide whether to or not, the brakes felt like tinfoil, the whole thing vibrated, bodywork didnt exactly inspire confidence to exceed 30mph, etc

but on the plus side the engine is actually quite nice for a 1.2

only cuz you're used to a 1.0 and the car body is essentially a bit of bacofoil teased into shape around a garden twine scaffold..

(feels slightly like it's fitted with a turbo.. nothing special until about 2,500 rpm and then it starts to fly ),

that sounds like the diesel kangoo i was driving today*... banished my ideas of diesels being torquey right from near-idle revs. It was a 1.9 in a body that couldnt really weigh any more than my own car (stripped out with little cargo), so i expected it to really motor. Once you were moving it was pretty good providing you shifted the gears at the right time to catch the power band (say, maybe like a 1.3 would be), but got badly asthmatic up top...... and below what i'd guess to be 1500-1800 or so, there was NOTHING. Starting off was a darkly humourous affair as there was a 50-40-10 chance i'd not give it quite enough throttle and it would momentarily labour at about 7mph before jetting off, i'd give it a little too much and the tyres would spin crazily, or i'd get it just right and move off nicely with the other traffic. Eventually I figured a way of having the motor spinning quite fast and being very, very, very gentle with the clutch and slipping it until about 15mph.
Splains why van drivers always seem to be revving hard even in traffic i guess..
Did make a fantastic noise however May not have been as pokey as it should be, but sounded like a proper rorty oldskool non-turbo racer.

t'aint that it's got a turbo, its just got rubbish ECU mapping / cam setup for town driving

the brakes are very impressive for a standard setup.

tin foil body again!

</corsabash>



* it was "today" when i started writing, but "yesterday" when i finished as i had to sleep right after that sentence

Gareth_GT_Hatch wrote:
How often do you look at your speedo whilst cornering? Eyes on the road dude!

true, true....

it'd mess up your mileage and average speed figure tho

i hazard a quick glance from time to time if its a sweeping bend just in case of overcooking it or there's plod / plod-o-trons about

Well, you have a tacho input leading to the speedometer, I believe it sends pulses in varying frequencies according to the engine speed. You'll have to figure out the rest though

I think it's just cooledit 96 or something, old and crappy, comes with the software you get when you take the advancing physics A level. Interesting to play about with though.

Anyway, I'm in pembroke now so I may not be around here much, unless I get very bored and steal this laptop again, so, bye for now

GroovyCarrot wrote:Well, you have a tacho input leading to the speedometer, I believe it sends pulses in varying frequencies according to the engine speed. You'll have to figure out the rest though

You mean the entire dash assembly then? It's probably simpler on yours as it's 100% electromechanical and none of this fancy ECU gubbins in which case the signal probably does go direct from the coil (?) to the dash, similar to the cable that runs straight from the gearbox to the speedo on both the mk2 and mk3...
If I'm interpreting the haynes wiring diagrams right, then a lot of stuff on the mk3 instrument console actually goes thru the ECU... so the tacho signal gets decoded into an rpm figure in the chip, used both for engine management purposes and for putting out a pseudo-analogue voltage to the dial, much like the "damper" routine used for the petrol dial someone mentioned (though i'm not sure whether thats just a guage thats physcially very slow to respond).

I think it's just cooledit 96 or something, old and crappy, comes with the software you get when you take the advancing physics A level. Interesting to play about with though.

Owt crappy 'bout cool96, i think i prefer it for my purposes over the demo of 2000 i tried out... missing some of the fancier effects and the multitrackability of course, but it does the job.
and if yours is the fully de-restricted version rather than the shareware 2-functions-per-load thing i've been struggling on with a mass of temp files for over the past 6 years or so, i'll happily take it or a copy of it off your hands on the sly quiet - i doubt syntrillium software will be too happy about rooting out and selling me an 8-year-old product license any more

Have fun.. let us know if the fly-by-string controls get the better of you and you end up rolling it. Particularly if it ends up in a ditch, because, possible injuries notwithstanding, theres something just intrinsically funny about an upside down corsa in a ditch. Fingers crossed for a safe return eh.

I think you'll find that even if the signal does go into the chip, it gets sent to the dash in the same way as in a mk2, because it's possible to wire up a mk3 dashboard for use in a mk2 without any major modifications as would be needed if the signals were sent in a different format.. it's worth thinking about, anyway.

The damper on the petrol guage is just the dial being slow to respond, it's the same on all pre-mk4 polos and early golfs.. I'm realising how useful that is at the moment, as on the corsa the petrol guage is more useful as a G metre than a petrol guage.. accellerate hard and you lose about 5 litres, brake hard and you gain them again

Much as I'd love to put the corsa upside down in a ditch, I think my family might just have words about it Instead I'm being entertained by a mad welsh friend in his 1.3 yaris which he has an interesting habit of powersliding around pembroke country lanes Superb little car that is, really suprisingly powerful..

Toyota worked some insane VVT magic to get 70hp out of the non-turbo 998cc model without *totally* destroying the torque in quite the same way as many japanese minis suffer... so the 1.3 must be a little bit wooo, a little bit waaaah.. in such a rollerskate body (is it my eyes, or does it sit on 12-inch wheels?)
Wouldn't mind getting hold of a 1.4 type of that with a turbo on it

But how the holy heck do you powerslide a FWD car?

No, dont roll it, you'd probably die even if you were to broadside a big bank of cotton wool with the passenger door, let alone roll the thing onto solid earth - remember the construction!
(not like i meant for you to do it on purpose, just to be careful of such.. the suspension probably isnt up for hard cornering down the welsh twisties neither)

K, well, I can probably credit the tacho signal being pulsed rather than analogue as it has *some* circuitry inside it (eg the oil/temp lights*). At least the speedo is still mechanical, because you know... I really, REALLY do not trust the more modern cars where even the speedometer comes off the ECU.. and if you kill the ignition (or, for example, your battery/ECU fails for whatever reason)... bam, no speedo... and for why?? Theres no good godly reason to make it electronic!

*possibly of interest to karl, when jigging about with the clocks with the ignition (but not engine) on, trying to resurrect the indicators.... i found the signal for those lights is likely constant (constant "high" or constant "low", not sure) going into the dash plug, what happens on the actual instruments from thereon in seems to be controlled by the clocks themselves... unplugging it, even slightly so that only those lights went out, then plugging it back in, made them "reset" eg the rhythmic flashing of the oil light would restart no matter where you unplugged it (if you kept tapping it out with your foot to check), and the temp light would come back on even if it had gone out

Well, it's not so much a powerside as a sustained handbrake turn.. whatever it is it's great fun, if a little scary..

Back on topic for a moment, I'm back home and the new big end bearings have arrived, so I'll see if they're alright tomorrow.. fingers crossed, my new deadline is friday when I'm going to a festival in devon, and I don't even have the corsa for backup this time Mind you, my recently deceased neighbour over the road has a pug 205 automatic sitting unused atm, guess I could have words with the relatives if the worst came to the worst