Speedometer/Standard Dash 'Circumference'

[DarthChicken]

All I know is that this probobly saved me from a ticket today.  I got pulled over... for doing 63 in a 55.  I kinda looked at the cop like... umm... ok.. and then he basically just looked at the car, checked to make sure I had insurance and registration, and then didn't even write me a warning, just sent me on my way.

If I would have been doing 70... might have been a different story 

[Alec]

I've just found the copy of the SPA dash manual that someone posted.

The relevant section mentions whether the Trigg points are taken from wheel RPM or from a differential so this is probably where the factor of 8 comes in.

A copy of this section is attached below.

[Karl]

Alec, that's not the issue though.  Say we take a Honda car, we can scale it all we want:

1855mm circumference with 1 trigger point
2710mm circumference with 2 trigger points
5420mm circumference with 3 trigger points

But if we take the theoretical GM F35, which outputs 85 pulses per revolution of the output shaft, it should look like this:

1855mm circumference with 85 trigger points
371mm circumference with 17 trigger points
109mm circumference with 5 trigger points

So unless Brammo modified the speed sensor to spin 8x slower, I'm not sure what's going on here.  Maybe they put the signal into a binary counter and are pulling the 4th bit?  It doesn't make much sense.

[Alec]

I've just found a piece of information on the Toyo Tyre manufacturers page that may explain what is happening.

For a 225/45 ZR16 Tyre it is quoting that 872 is the number of Revs Per Mile.

Toyo R888

As this is only 1 away from the 873 that seems to work, could the setting be the number of revolutions and not the circumference?

[Karl]

If the "Circumference" setting is in revs/distance rather than distance/rev, then Bottoz' factory setting of 800 would have caused the speedometer to read faster than true, not slower.

[Alec]

I'd forgotten the original setting was lower so didn't think it through and when I saw the Revs Per Mile number so close to the final setting that worked I just jumped to a conclusion. 

Next time I'll think before I type.

[maverick1]

I never received any manuals on my SPA dash. Is there anywhere I can download a PDF file for the SPA dash on the Atom?
Cheersâ?¢

[Bottoz]

[quote="maverick1"]
I never received any manuals on my SPA dash. Is there anywhere I can download a PDF file for the SPA dash on the Atom?
Cheersâ?¢
[/quote]

The link is in the first post of this thread on page one.

[bolus]

[quote="maverick1"]
I never received any manuals on my SPA dash. Is there anywhere I can download a PDF file for the SPA dash on the Atom?
Cheersâ?¢
[/quote]


Dude, you need to read all my posts and memorize them 

[maverick1]

[quote="bolus"]
[quote="maverick1"]
I never received any manuals on my SPA dash. Is there anywhere I can download a PDF file for the SPA dash on the Atom?
Cheersâ?¢
[/quote]


Dude, you need to read all my posts and memorize them 
[/quote]
Went to the link (http://bolus.shackspace.com/atom/SPA.pdf) and it will not download for some reason.
cheers

[bolus]

works for me, try right click and save as

[Bruce Fielding]

[quote="maverick1"]
I never received any manuals on my SPA dash. Is there anywhere I can download a PDF file for the SPA dash on the Atom?
Cheersâ?¢
[/quote]

Club members can access it in the guides section of the main atomclub site

[maverick1]

Guys I got a different setting also using a second GPS speedo. My optimal circumference setting is 850 not the 873 Bottoz got. I tried 873 and when the SPA dash showed 40mph the GPS speedo read 38 so I knew I needed to lower the cir setting.
When I plugged in 850 I got a perfect match.
I guess I should also add that I have the Yoko ES-100 tires which might explain the difference in the settings.
cheers

[Bottoz]

Alright! I'm glad some tinkering with the dash produced successful results.