Speed

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secure
Posts: 230
Joined: Tue Apr 21, 2009 6:38 am

Speed

Post by secure »

I've made TY752 to TY856 transmission swap and having some problems with the radarspeedv. Speedometer(swapped that too) works accurate(GPS tested) but the ecu reads a bit rattling. The VSS sensor is from a later model STI but I think I dont have the right settings for this sensor. Any feedback welcome.

secure
Posts: 230
Joined: Tue Apr 21, 2009 6:38 am

Re: Speed

Post by secure »

Also not sure how to set gear ratios and gear positions.

pat
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Re: Speed

Post by pat »

Do you find that the reading is wobbling a little bit round an average value or very big changes ?

If it's a little bit round and average then the tooth spacing on the pickup is not even. Just try increasing the the number of teeth per sample, 4 should be nice and smooth because that should be a whole revolution. 2 is normally OK, but 1 invariably gives noise.

If it's jumping around all over the place then it's either missing teeth or seeing phantom teeth, both of which are electrical issues. In the first instance check that your speed sensor type is set to Thermistor, this will activate an internal pull up resistor that will damp out some of the noise. The TY856 sender is normally quite good in the MY01- cars, so a little surprised you're having problems.

Setting gear ratios is very easy. Bring up a text gauge for the parameter driveRatio, this will give the current ratio, just enter it into the appropriate gear slot. So if it says 120 in second gear then enter 120 into the second gear ratio etc. You should already have your speed reading correctly before you do this, ie doing 60km/h the ECU should read 60km/h, not 40 or 80, otherwise you'll have to repeat the process! Note that the ratios changes aren't "live", you'll need to flash the ECU before the new ratios are used, but you can check driveRatio for all gears before flashing so that should be fine. Remember to flash after setting the correct tyre diameters to make the speed read correct, or you'll be working with the wrong speed!

Hope this helps,

Pat.

secure
Posts: 230
Joined: Tue Apr 21, 2009 6:38 am

Re: Speed

Post by secure »

Thanks for the inputs. It was wobbling around the avarage speed data but now it is sorted! I tried to correct tyre diameters but made some mistake n the calculation. Pi * Diameter gives the circumstances of the tire. I cant sort out how it comes to 1.484(m) for MY98 stock tires. What does m stand for? Meter? If it is meter than 235/40/18 should be 2.024 which didnt worked for me =) Anyway I'll figure it out .

Cheers

pat
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Re: Speed

Post by pat »

I have seen some oddness in the past with regard to the pulses and the tyre circumference. Like you I ended up with something in the region of 1.5m which is wrong, but it read correctly. I'll have a closer look at it next time I see such a car. And in answer to your question, yes m is metres in this case. You can change the units in SCal if you prefer imperial of course :)

Cheers,

Pat.

Slowie
Posts: 109
Joined: Thu Jan 17, 2013 7:30 am

Re: Speed

Post by Slowie »

Just to add to this old thread.

On my vehicle with 235/40R18 tyres, and 45 tooth trigger wheels with 15 teeth per reading, I need to set circumference to 3.190m, instead of the expected 2.026m that I measured on the ground.

stevieturbo
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Re: Speed

Post by stevieturbo »

Slowie wrote:Just to add to this old thread.

On my vehicle with 235/40R18 tyres, and 45 tooth trigger wheels with 15 teeth per reading, I need to set circumference to 3.190m, instead of the expected 2.026m that I measured on the ground.
Seems very odd ?

I've only 11 teeth and 8 teeth F/R, I use 1 tooth per reading and all numbers make good sense. 1 tooth per reading works very well as it means speed/distance logging is very accurate, and it will pull very good 60ft data etc from datalog information on SView.

When I use more teeth per reading I lose that accuracy in the logs. Although with 45 teeth per revolution you could easily run 3-4 teeth per reading and still keep that ability.

I dont think teeth per reading should affect actual speed readings and relation to circumference though ?

Slowie
Posts: 109
Joined: Thu Jan 17, 2013 7:30 am

Re: Speed

Post by Slowie »

It certainly is strange. I never noticed it when originally configured, simply drove around in the parking lot to check all wheels read the same, not comparing with GPS/Speedo.

Only discovered much later the ECU reading was off. With the new circ, speed in ECU is correct, but now logdistance is wrong by the same ratio I adjusted wheel size, where previously it was perfect. Might ask the support guys for any ideas.

Teeth per reading doesn't change the reading at all.

Slowie
Posts: 109
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Re: Speed

Post by Slowie »

So...turns out you can really confuse yourself if you change the speed unit in SCal to mph, instead of km/h, and forget to change it back :oops:

stevieturbo
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Re: Speed

Post by stevieturbo »

Slowie wrote:So...turns out you can really confuse yourself if you change the speed unit in SCal to mph, instead of km/h, and forget to change it back :oops:
lol.

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